EP0247478B1 - Heat-developable colour-photographic recording material - Google Patents

Description

The invention relates to a color photographic recording material which can be developed by heat treatment and has at least one binder layer applied to a layer which contains light-sensitive silver halide and a non-diffusing coloring compound, the recording material furthermore containing a compound which improves the D _min / D _max relationship and the sensitivity.

It is known to produce colored images by heat treatment using suitable color photographic recording materials. Particularly suitable as a color-providing compound are those which can be embedded in the layer of a photographic recording material in non-diffusing form and which, as a result of the development, are able to release a diffusible dye (color releaser). The particular suitability of such color releasers is based on the fact that the imagewise released dyes can be transferred to special image-receiving layers with the formation of a brilliant color image which is not overlaid with disruptive image silver or silver halide and accordingly does not require any aftertreatment. Combining the heat development process with the color diffusion process thus results in an advantageous rapid process for producing colored images. A suitable recording material for this is described, for example, in DE-A-32 15 485.

According to this publication, a recording material having a layer containing a combination of silver halide, silver benzotriazolate, a color releasing agent and guanidine trichloroacetate (base donor) is exposed imagewise and then subjected to heat treatment in contact with an image-receiving sheet, whereby the image-released dye is transferred to the image-receiving sheet . For the production of multicolored images, several such combinations must be present, the silver halide in each of these combinations being sensitive to a different spectral range of the light and, in accordance with its spectral sensitivity, containing a color releaser which releases a dye of a different color, usually a color that is complementary is the color of the light for which the silver halide in question has a predominant sensitivity. Such assignments can be arranged one above the other in different layers.

The color images obtained with the known color photographic recording material which can be developed by heat treatment have rather low maximum color densities and high fog. To remedy this disadvantage, the use of certain mercapto compounds as fog-reducing agents has been described in DE-A-33 45 023. However, the color images obtained using such mercapto compounds also leave something to be desired in terms of the D _mir ! D _max relationship and in terms of sensitivity.

The application is therefore based on the object of specifying a color photographic recording material which can be developed by heat treatment and which is further improved in terms of the D _min / D _max relationship and in terms of sensitivity.

worin bedeuten

• Q den erforderlichen Rest zur Vervollständigung einer heterocyclischen Gruppe mit mindestens einem 5- oder 6-gliedrigen heterocyclischen Ring und
• X eine Carbonsäure- oder Sulfonsäuregruppe oder einen Rest, der eine Carbonsäure- oder Sulfonsäuregruppe enthält, wobei die Carbonsäure- bzw. Sulfonsäuregruppe auch in anionischer Form vorliegen kann, z. B. als Alkali-, Erdalkali- oder Ammoniumsalz, wie auch Salz von organischen Basen wie Tri- oder Tetraalkylammoniumsalz.

The present invention relates to a photographic recording material which can be developed by heat treatment and has at least one binder layer applied to a layer support, the light-sensitive silver halide but essentially no further inorganic silver salts, at least one non-diffusing coloring compound which, as a result of the development by heat treatment, is able to release a diffusible dye , and contains a veil-lowering compound, which is characterized in that the veil-lowering compound corresponds to the following formula I.

in what mean

• Q is the radical required to complete a heterocyclic group with at least one 5- or 6-membered heterocyclic ring and
• X is a carboxylic acid or sulfonic acid group or a radical which contains a carboxylic acid or sulfonic acid group, the carboxylic acid or sulfonic acid group also being able to be in anionic form, e.g. B. as an alkali, alkaline earth or ammonium salt, as well as salt of organic bases such as tri- or tetraalkylammonium salt.

Particularly advantageous fog-lowering compounds according to the present invention are those of the general formula II

worin bedeuten :

• Y ―O―, -S-, -Se- oder -NR3-;
• R¹, R² gleich oder verschieden, Wasserstoff, Alkyl, bevorzugt mit bis zu 6 C-Atomen wie Methyl, Ethyl, Alkenyl wie Allyl, Cycloalkyl wie Cyclohexyl, Aryl wie Phenyl, Aralkyl wie Benzyl, Halogen wie CI oder Br, oder R¹ und R² zusammen einen ankondensierten Benzolring ;
• R³ Wasserstoff, Alkyl bevorzugt mit bis zu 6 C-Atomen wie Methyl, Ethyl, Alkenyl wie Allyl, Cycloalkyl wie Cyclohexyl, Aralkyl wie Benzyl, Aryl wie Phenyl, wobei die genannten Reste weiter substituiert sein können, z. B. durch Hydroxy, Alkoxy oder Halogen.

in which mean:

• Y ―O―, -S-, -Se- or -NR3-;
• R ¹ , R ^{2 are the} same or different, hydrogen, alkyl, preferably with up to 6 carbon atoms such as methyl, ethyl, alkenyl such as allyl, cycloalkyl such as cyclohexyl, aryl such as phenyl, aralkyl such as benzyl, halogen such as CI or Br, or R. ¹ and R ² together form a condensed benzene ring;
• R ^{3 is} hydrogen, alkyl preferably having up to 6 carbon atoms such as methyl, ethyl, alkenyl such as allyl, cycloalkyl such as cyclohexyl, aralkyl such as benzyl, aryl such as phenyl, it being possible for the radicals mentioned to be further substituted, e.g. B. by hydroxy, alkoxy or halogen.

The heterocyclic mercaptoazolecarboxylic acids or sulfonic acids used according to the invention are known compounds, their preparation is described in the relevant literature.

Suitable fog-lowering compounds are, for example, the following compounds:

The fog-lowering compounds used according to the invention are added to the casting solutions for the light-sensitive layers. The amount used can be varied within a wide range and the suitable concentration can easily be determined by a person skilled in the art on the basis of simple routine experiments. Preferably, the fog-lowering compounds are used in an amount of 0.001 to 10.0 g per mol of silver halide. The addition can take place in an aqueous or organic medium. Furthermore, the compounds of the invention can also be added in dispersed form.

The color photographic recording material according to the invention contains, on a dimensionally stable support, at least one binder layer which contains a light-sensitive silver halide, a non-diffusing coloring compound which can produce a diffusible dye due to heat development, and one or more of the fog-lower compounds according to the invention.

An essential component of the heat-developable recording material according to the invention is therefore the silver halide, which consists of silver chloride, silver bromide, silver iodide or mixtures thereof and can have a particle size between 0.02 and 2.0 μm, preferably between 0.1 and 1.0 _f Lm. The silver halide grains can have a regular crystal structure, for example in the form of cubes or octahedra. However, they can also have an irregular crystal structure or be designed in the form of platelets. In the case of mixed crystals, the silver halides can be distributed uniformly over the entire crystal cross section. The silver halide composition can also be different in different areas. Thus, silver halide emulsions with a layered grain structure can be used, in which there are at least two layers with a different silver halide composition. Negative working silver halide emulsions are generally used; In other embodiments, however, directly positive-working silver halide emulsions can also be used, as described, for example, in DE-A-23 32 802, DE-A-23 08 239 and DE-A-2211728. The light-sensitive emulsion can be present as an unsensitized silver halide or chemically and / or spectrally by suitable additives be sensitized, the spectral sensitizer being added before, during and after chemical ripening.

The amount of light-sensitive silver halide in the respective layer can be between 0.01 and 3.0 g per m ² , the actual amount of silver halide used depending on the requirements of the reactants used and the desired effects.

It is known that in photographic recording materials which can be developed by heat treatment, in addition to the photosensitive silver halide, it is often possible to use further essentially non-photosensitive or at least much less photosensitive silver salts. Such additional silver salts, which can likewise be silver halides as well as other inorganic silver salts such as silver cyanide, silver thiocyanate, silver sulfite or silver sulfate, have a photosensitivity that is at least about 10 times lower and a significantly higher solubility.

Although such additional silver salts generally do not contribute to sensitivity, they are often advantageous because they can be used to increase the available color density. However, since this effect is frequently accompanied by a considerable increase in fog, particularly in the case of the silver halide emulsions used in the present case, only those recording materials are used according to the invention in which the proportion of the essentially non-photosensitive silver salt in the total amount of the silver salts is 4 mol%, preferably Does not exceed 2 mol%. Recording materials according to the present invention which contain no inorganic silver salt in the light-sensitive layers apart from the light-sensitive silver halide of the desired sensitivity are very useful.

On the other hand, it is advantageous to add organic silver salts which are about the same or less soluble than the light-sensitive silver halide. Silver salts of compounds with an imino group are suitable. In preferred examples, these include silver salts of benzotriazole and its derivatives, e.g. B. silver salts of alkyl, hydroxy, sulfo and / or halogen substituted benzotriazoles.

Another essential component of the recording material according to the invention is a non-diffusing coloring compound. As a result of a redox reaction that occurs during development, this can release a diffusible dye. In the following, it is referred to as a paint splitter.

The color separators used according to the invention can be a variety of connection types, all of which are distinguished by a link which is redox-dependent in terms of their binding strength and which links a dye residue to a carrier residue containing a ballast residue.

In this context, a summary of the subject area in Angew. Chem. Lnt. Ed. Engl. 22 (1983), 191-209, in which the most important of the known systems are described.

Redox-active color releasers of the formula have proven to be particularly advantageous

Ballast redox dye, in what mean Ballast a ballast remnant

Redox is a redox active group, i. H. a group which is oxidizable or reducible under the conditions of alkaline development and, depending on whether it is in the oxidized or in the reduced state, is subject to different degrees to an elimination reaction, a nucleophilic displacement reaction, a hydrolysis or another cleavage reaction, with the result that the Residual dye is split off, and

Dye the rest of a diffusible dye, e.g. B. a yellow, purple or cyan dye, or the rest of a dye precursor.

Such residues are to be regarded as ballast residues which make it possible to store the color releasers according to the invention in a diffusion-resistant manner in the hydrophilic colloids usually used in photographic materials. Organic radicals which generally contain straight-chain or branched aliphatic groups with generally 8 to 20 C atoms and optionally also carbocyclic or heterocyclic optionally aromatic groups are preferably suitable for this purpose. With the rest of the molecule, these residues are either directly or indirectly, e.g. B. connected via one of the following groups: -NHCO-, -NHSO _z -, -NR-, where R is hydrogen or alkyl, -O- or ―S―. In addition, the ballast residue can also contain water-solubilizing groups, such as. B. sulfo groups or carboxyl groups, which may also be in anionic form. Since the diffusion properties depend on the molecular size of the total compound used, it is sufficient in certain cases, e.g. B. if the total molecule used is large enough to use short-chain residues as ballast residues.

Redox-active carrier residues of the structure ballast-redox and corresponding color releasers are known in a wide variety of embodiments. A detailed description can be omitted here with regard to the overview article in the app. Chem. Lnt. Ed. Engl. 22 (1983) 191-209.

For the sake of explanation only, a few examples of redox-active carrier residues are listed below, from which a dye residue is split off in accordance with an image-related oxidation or reduction:

(Continuation)

The groups enclosed in brackets are functional groups of the dye residue and are separated together with this from the remaining part of the carrier residue. The functional group can be a substituent which can have a direct influence on the absorption and, if appropriate, complex formation properties of the released dye. On the other hand, the functional group can also be separated from the chromophore of the dye by an intermediate link or a link. Finally, the functional group together with the intermediate member may also be of importance for the diffusion and pickling behavior of the released dye. Suitable intermediate members are, for example, alkylene or aryl groups.

In principle, the residues of dyes of all dye classes are suitable as dye residues insofar as they are sufficiently diffusible to be able to diffuse from the light-sensitive layer of the light-sensitive material into an image-receiving layer. For this purpose, the dye residues can be provided with one or more alkali-solubilizing groups. Suitable alkali-solubilizing groups include carboxyl groups, sulfo groups, sulfonamide groups and aromatic hydroxyl groups. Such alkali-solubilizing groups can already be pre-formed in the dye releasers used according to the invention or can only result from the cleavage of the dye residue from the carrier residue which contains ballast groups. The following are mentioned as dyes which are particularly suitable for the process according to the invention: azo dyes, azomethine dyes, anthraquinone dyes, phthalocyanine dyes, indigo dyes, triphenylmethane dyes, including those dyes which are complexed or complexable with metal ions.

The residues of dye precursors are to be understood as the residues of those compounds which, in the course of photographic processing, in particular under the conditions of heat development, be it by oxidation, be it by coupling, by complex formation or by exposure of a auxochrome groups in a chromophoric system, for example by saponification, are converted into dyes. Dye precursors in this sense can be leuco dyes, couplers or dyes that are converted into other dyes during processing. Unless a distinction between dye residues and the residues of dye precursors is essential, the latter should also be understood below as dye residues.

• US-A-3 227 550, US-A-3 443 939, USA-A-3 443 940,
• DE-A-19 30 215, DE-A-22 42 762, DE-A-24 02 900,
• DE-A-24 06 664, DE-A-25 05 248, DE-A-25 43 902,
• DE-A-2613 005, DE-A-26 45 656, DE-A-28 09 716,
• DE-A-28 23 159, BE-A-861 241, EP-A-0 004 399,
• EP-A-0 004 400, DE-A-30 08 588, DE-A-30 14 669,
• GB-A-80 12 242.

Suitable color releasing agents are described, for example, in:

• US-A-3 227 550, US-A-3 443 939, USA-A-3 443 940,
• DE-A-19 30 215, DE-A-22 42 762, DE-A-24 02 900,
• DE-A-24 06 664, DE-A-25 05 248, DE-A-25 43 902,
• DE-A-2613 005, DE-A-26 45 656, DE-A-28 09 716,
• DE-A-28 23 159, BE-A-861 241, EP-A-0 004 399,
• EP-A-0 004 400, DE-A-30 08 588, DE-A-30 14 669,
• GB-A-80 12 242.

In some embodiments of the heat development method according to the invention, the color releasers can be present as oxidisable or couplable color releasers, in others as reducible color releasers. Depending on whether the dye is released from the oxidized or from the reduced form of the color releasing agent, negative or positive illumination is obtained from the original when conventional negative-working silver halide emulsions are used. You can therefore create positive or negative images by selecting suitable color releasing systems.

DE-A-26 45 656 is described, for example, in DE-A-26 45 656 which is particularly suitable for the heat-developable recording materials according to the invention.

If the color splitter can be oxidized, then it is itself a reducing agent which is oxidized directly or indirectly with the aid of electron transfer agents (electron transfer agent, ETA) through the imagewise exposed silver halide. This creates a pictorial differentiation in terms of the ability to release the diffusible dye. If, on the other hand, the color releaser is reducible, then it is expediently used in combination with a reducing agent present in a limited amount, a so-called electron donor compound or an electron donor precursor compound, which in this case is contained in the same binder layer in addition to the color releaser and the photosensitive silver halide. The use of electron transfer agents can also prove to be advantageous in the case of the use of reducible color separators in combination with electron donor compounds.

worin bedeuten

• R¹ Alkyl oder Aryl ;
• R² Alkyl, Aryl oder eine Gruppierung, die zusammen mit R³ einen ankondensierten Ring vervollständigt ;
• R³ Wasserstoff, Alkyl, Aryl, Hydroxyl,. Halogen wie Chlor oder Brom, Amino, Alkylamino, Dialkylamino einschließlich cyclischer Aminogruppen (wie Piperidino, Morpholino), Acylamino, Alkylthio, Alkoxy, Aroxy, Sulfo, oder eine Gruppierung, die zusammen mit R² einen ankondensierten Ring vervollständigt ;
• R⁴ Alkyl ;
• R⁵ Alkyl oder vorzugsweise Wasserstoff, und wobei mindestens einer der Reste R¹ bis R⁴ einen Ballastrest enthält.

A recording material according to the invention, which contains reducible color releasers of the following formula, is suitable, for example, for producing positive color images of positive originals (original) when using negative working silver halide emulsions:

in what mean

• R ^{1 is} alkyl or aryl;
• R ^{2 is} alkyl, aryl or a group which together with R ^{3 completes} a fused ring;
• R ^{3 is} hydrogen, alkyl, aryl, hydroxyl ,. Halogen such as chlorine or bromine, amino, alkylamino, dialkylamino including cyclic amino groups (such as piperidino, morpholino), acylamino, alkylthio, alkoxy, aroxy, sulfo, or a group which together with R ^{2 completes} a fused ring;
• R ⁴ alkyl;
• R ^{5 is} alkyl or preferably hydrogen, and at least one of the radicals R ¹ to R ⁴ contains a ballast radical.

The electron donor compound used in combination with a reducible dye releasing agent serves equally as a reducing agent for the silver halide and the color releasing agent. Due to the fact that the silver halide and the color releaser compete with each other to a certain extent in the oxidation of the electron donor compound, but is superior to the latter, the silver halide present becomes determinant for the image areas within which the color releaser through the electron donor compound in its reduced form is transferred.

The electron donor compound, which is present in a limited amount, is developed under the conditions of development, e.g. B. when heating the imagewise exposed color photographic recording material, oxidized in accordance with the extent of the exposure and is consequently no longer available for a reaction with the color splitter. This creates an image-like distribution of unused electron donor compound.

Derivatives of hydroquinone, benzisoxazolone, p-aminophenol or ascorbic acid (e.g. ascorbyl palmitate) which have not or only little diffusing have been described as electron donor compounds (DE-A-28 09 716).

Further examples of electron donor compounds are known from DE-A-29 47 425, DE-A-30 06 268, DE-A-31 30 842, DE-A-31 44 037, DE-A-32 17 877 and EP-A- 0 124 915 and Research Disclosure 24 305 (July 1984). It has been shown that the electron donor compounds mentioned also meet the requirements placed on them under the conditions of heat development and are therefore also suitable as electron donor compounds in the context of the present invention. Particularly suitable are those electron donor compounds that are formed in the layer from corresponding electron donor precursor compounds only under the conditions of heat development, i. H. Electron donor compounds that are only in a masked form in the recording material before development, in which they are practically ineffective. The initially inactive electron donor compounds are then converted into their effective form under the conditions of heat development, for example by hydrolytically cleaving certain protective groups. In the present case, the electron donor precursor compounds mentioned are also understood as electron donor compounds.

In a further embodiment it is also possible to use color releasers which can be coupled and which can release a diffusible dye as a result of a coupling reaction. There are two options. In the first case, the dye is only formed by chromogenic coupling, whereby a diffusion-inhibiting ballast group is split off from the coupling position. In the other case, there are non-diffusing couplers which contain an already formed dye residue as an escape group in the coupling point, which is split off by coupling and thus becomes diffusible. Such systems are described, for example, in US-A-3,227,550. The dye cleavers can also be polymeric couplers of the dye-releasing type, as described, for example, in DE-A-34 22 455.

The above-mentioned essential constituents of the recording material according to the invention, namely the light-sensitive silver halide and the color releaser, optionally in combination with an electron donor compound, and the fog-reducing compound used according to the invention are dispersed in a binder. These can be hydrophobic as well as hydrophilic binders, but the latter are preferred. Gelatin is preferably used as the binder for the light-sensitive layer. However, this can be replaced in whole or in part by other natural or synthetic binders. On natural binders such. B. alginic acid and its derivatives such as salts, esters or amides, cellulose derivatives such as carboxymethyl cellulose, alkyl cellulose such as hydroxyethyl cellulose, starch and its derivatives and caragenates are suitable. Synthetic binders include polyvinyl alcohol, partially saponified polyvinyl acetate and polyvinyl pyrrolidone.

Examples of hydrophobic binders are polymers made from polymerizable ethylenically unsaturated monomers such as alkyl acrylates, alkyl metharylates, styrene, vinyl chloride, vinyl acetate, acrylonitrile and acrylamides. Furthermore, polyester, polyurethane compounds and waxes can be used. Such polymers can be used in latex form, for example.

For the production of monochrome color images, the light-sensitive binder layer contains one or more color releasers associated with the light-sensitive silver halide, from which dyes of a specific color are released. The overall resulting color can be obtained by mixing several dyes. In this way, it is also possible to produce black and white images by precisely coordinating the mixing of several color separators of different colors. For the production of multicolored color images, the color photographic recording material of the present invention contains several, that is to say three, assignments of color releasers and silver halide which has been sensitized differently in each case, preferably the absorption range of the dye released from the color releaser with the range of the spectral sensitivity of the assigned silver halide essentially coincides. The various assignments of color releaser and assigned silver halide can be accommodated in different binder layers of the color photographic recording material, with separating layers of a water-permeable binder, eg. B. gelatin, which contain, for example, a scavenger for developer oxidation products, which essentially have the function of separating the different assignments from one another and in this way counteracting color distortion. In such a case, the color photographic recording material of the present invention contains, for example, a light-sensitive binder layer in which the silver halide contained therein is predominantly red-sensitive due to spectral sensitization and in which a cyan color releaser is contained, a further light-sensitive binder layer in which the silver halide contained therein is spectrally sensitive Sensitization is predominantly green-sensitive, and in which a purple dye releasing agent is contained, and a third light-sensitive binder layer in which the silver halide contained therein due to its own nature sensitivity or predominantly blue-sensitive due to spectral sensitization, and which contains a yellow dye releaser.

In a further embodiment of the present invention, each of the cited combinations of photosensitive silver halide and color releaser is used in the form of a so-called complex coacervate.

A complex coacervate is understood to mean a form of dispersion in which a mixture of the essential constituents is enclosed in a common covering made of a hardened binder. Such dispersions are also called packet emulsions. They are obtained through complex coacervation.

The term `` complex coacervation '' means the occurrence of two phases when each mixing an aqueous solution of a polycationic colloid and a polyanionic colloid, a concentrated colloid phase (hereinafter referred to as a complex coacervate) and a dilute colloid phase (hereinafter referred to as an equilibrium solution) ) are formed due to an electrical interaction. The complex coacervate is separated from the equilibrium solution in the form of droplets and appears as a white turbidity. When complex coacervation is carried out in the presence of a solid such as silver halide or fine oil droplets, it is generally believed that the complex coacervate includes the solid or the droplets inside colloidal particles. As a result, a dispersion of coacervate particles is obtained, in which the solid (in the present case the light-sensitive silver halide) and oily droplets of a solution of the organic constituents (in the present case the color releasing agent and optionally further auxiliaries) are included. It is then hardened with a hardening agent so that the original shape of the particles is not destroyed in the following steps for producing the photographic recording material, such as producing the casting solution and coating. The dispersion is expediently cooled to a temperature of 25 ° C. or below, preferably 10 ° C. or below, before curing, whereby a good quality packet emulsion is obtained.

Methods for producing a packet emulsion in which a color-forming substance is incorporated by complex coacervation are described, for example, in US Pat. Nos. 3,276,869 and 3,396,026.

Examples of hardening agents which can be used to prepare the packet emulsion according to the invention include chromium salts (for example chromium alum, chromium acetate), aldehydes (for example formaldehyde, glyoxal, glutaraldehyde), N-methylol compounds (for example dimethylolurea, methyloldimethylhydantoin), dioxane derivatives (for example 2,3- Dihydroxydioxane), active vinyl compounds (e.g. 1,3,5-triacryloylhexahydro-s-triazine, 1,3-vinylsulfonyl-2-propanol), active halogen compounds (e.g. 2,4-dichloro-6-hydroxy-s-triazine), and Mucohalogenic acids (e.g. mucochloric acid, mucophenoxychloric acid). The curing agents can be used individually or as a mixture.

The use of packet emulsions enables, according to the invention, the combination of several emulsion components of different spectral sensitivity, including the relevant color releasers, in a single binder layer without the spectral assignment being lost and thereby a color falsification occurring. This is possible because the degree of exposure of a particular silver halide particle becomes almost exclusively decisive for the degree of dye release from the color releaser which is in the same coacervate particle (packet) as the silver halide. The use of packet emulsions thus enables a blue-sensitive, a green-sensitive and a red-sensitive silver halide emulsion and spectrally assigned color separators to be accommodated in the same binder layer without fear of serious color falsification.

In addition to the constituents already mentioned, the color photographic recording material according to the invention may contain further constituents and auxiliaries which are beneficial, for example, for carrying out the heat treatment and the color transfer which takes place here. These further constituents or auxiliary substances can be contained in a light-sensitive layer or in a non-sensitive layer.

Such auxiliaries are, for example, auxiliary developers. These auxiliary developers generally have developing properties for exposed silver halide; In the present case, they primarily have a beneficial effect on the reactions taking place between the exposed silver halide and the reducing agent, the reducing agent being identical to the latter if oxidizable color releasers are used, or reacting with the color releasers if reducible color releasers are used . Since this reaction consists mainly of electron transfer, the auxiliary developers are also referred to as electron transfer agents (ETA).

Examples of suitable auxiliary developers include hydroquinone, pyrocatechol, pyrogallol, hydroxylamine, ascorbic acid, 1-phenyl-3-pyrazolidone and their derivatives, e.g. B. 4-methyl-1-phenyl-3-pyrazolidone, 4,4-dimethyl-1-phenyl-3-pyrazolidone, 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone, 4-hydroxymethyl-4- methyl-1-tolyl-3-pyrazolidone and 4,4-dihydroxymethyl-1-phenyl-3-pyrazolidone. In certain cases it is advantageous to use them in masked form with a protective group that can be split off under alkaline conditions. Since the auxiliary developers have a catalytic function, so to speak, it is not necessary Lich that they are present in stoichiometric amounts. In general, it is sufficient if they are present in the layer in amounts of up to 1/2 mole per mole of color releaser. The incorporation into the layer can take place, for example, from solutions in water-soluble solvents or in the form of aqueous dispersions which have been obtained using oil formers.

Color developers are required for coupling color systems. Reference is made here to the customary phenylenediamine developers and also to aminophenols. For reasons of stability, it is advantageous to use the developer additives in masked form, the protective group then being split off under the process conditions.

Other auxiliaries are compounds that activate development. Bases or base precursors, ie compounds with a pka value of 8 and more, are suitable. Examples of suitable inorganic bases are hydroxides, tertiary phosphates, borates, carbonates of alkali or alkaline earth metals, or ammonium hydroxide. Suitable organic bases are, for example, aliphatic amines, heterocyclic amines, amidines, cyclic amidines, guanidines or cyclic guanidines.

Base precursors are compounds that are capable of releasing a base component when heated. Salts of the above-mentioned bases with heat-decomposable organic acids such as trichloroacetic acid, acetoacetic acid, cyanoacetic acid, sulfonylacetic acid or acetylenecarboxylic acids are suitable. Also advantageous are base precursors with covalent binding of the base, which release the base in the heat, for example via a fractionation reaction. In this connection, reference is made to hydroxamic acid carbamates in EP-A-0 120 402 or to aldoxime carbamates in EP-A-0 118 078.

Other auxiliaries are, for example, compounds which are able to release water under the action of heat. In particular, inorganic salts containing water of crystallization are suitable, e.g. B. Na:, S04-10H20, NH ₄ Fe (SO ₄ ) ₂ . 12H20.

The water released during heating favors the development and diffusion processes required for image formation.

Other auxiliaries are, for example, the so-called thermal solvents, which are generally understood to mean non-hydrolyzable organic compounds which are solid under normal conditions but melt when heated up to the temperature of the heat treatment and thereby provide a liquid medium in which the development processes can take place more quickly. Such thermal solvents can act as diffusion accelerators, for example. Preferred examples of the thermal solvents include polyglycols as described, for example, in US-A-3,347,675, e.g. B. polyethylene glycol with an average molecular weight of 1,500 to 20,000, derivatives of polyethylene oxide, such as its oleic acid ester, beeswax, monostearin. For example, compounds with a high dielectric constant are suitable, which have an -SO _z - or -CO group.

In this connection, reference is also made to the thermal solvents listed in the patent EP-A-0 119 615, ureas, pyridines, pyridine-N-oxides, carboxamides, imides, sulfonamides, polyhydric alcohols, oximes, pyrazoles and imidazoles.

Other suitable auxiliaries are development accelerators. Mention should be made here, for example, of sulfonamides which are described in EP-A-0160 313 and DE-A-33 39 810.

Furthermore, certain pH-lowering agents can be added, which above all help to stabilize the minimum densities. Suitable compounds are acid precursor compounds as described, for example, in DE-A-34 42 018 and DE-A-3515 176.

The development of the imagewise exposed color photographic recording material according to the invention is initiated by subjecting it to a heat treatment in which the light-sensitive binder layer is heated to an elevated temperature, e.g. B. is brought in the range of 80 to 250 ° C. This creates suitable conditions for the development processes, including dye diffusion, in the recording material.

This can be completely dry, i.e. H. only with the moisture content present in the layered structure or also, if necessary, for example with water. During development, dyes capable of diffusion are released imagewise from the color separators and transferred to an image-receiving layer which is either an integral part of the color photographic recording material according to the invention or is at least brought into contact with it during development.

The image-receiving layer can accordingly be arranged on the same layer support as the light-sensitive element (single sheet material) or on a separate layer support (two-sheet material). It essentially consists of a binding agent which contains mordants for the determination of the diffusible dyes released from the non-diffusing color separators. Long-chain quaternary ammonium or phosphonium compounds, e.g. B. As described in US-A-3,271,147 and US-A-3,271,148.

Furthermore, certain metal salts and their hydroxides, which form poorly soluble compounds with the acid dyes, can also be used. Polymeric mordants should also be mentioned here, such as those described in DE-A-23 15 304, DE-A-26 31 521 or DE-A-29 41 818. Preferred stains are also polyvinylimidazole stains which are partially quaternized, for example with benzyl, hydroxyethyl, alkyl, epoxypropyl, propyl, methyl and ethyl halides, the degree of quaternization being between 1 and 50%. The dye mordants are in the mordant layer dispersed in one of the usual hydrophilic binders, e.g. B. in gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, completely or partially hydrolyzed cellulose esters. Of course, some binders can also act as mordants, e.g. B. Polymers of nitrogen-containing, optionally quaternary bases, such as N-methyl-4-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, as described, for example, in US Pat. No. 2,484,430. Other useful binding agents are, for example, guanylhydrazone derivatives of alkylvinyl ketone polymers, as described, for example, in US Pat. No. 2,882,156, or guanylhydrazone derivatives of acylstyrene polymers, as described, for example, in DE-A-20 09 498. In general, however, other binders, e.g. B. add gelatin.

If the image-receiving layer remains in layer contact with the light-sensitive element even after development is complete, there is usually an alkali-permeable, pigment-containing, light-reflecting binder layer between them, which serves for the optical separation between negative and positive and as an aesthetically pleasing background for the transferred positive color image.

If the image-receiving layer is arranged between the support and the photosensitive element and is separated from the latter by a pre-formed light-reflecting layer, either the support must be transparent so that the color transfer image produced can be viewed through it, or the photosensitive element together with the light-reflecting layer of the image-receiving layer are removed to expose the latter. However, the image-receiving layer can also be present as the uppermost layer in an integral color photographic recording material, in which case the exposure is expediently carried out through the transparent layer support.

In the case of integral layer units comprising a photosensitive element and an image receiving element, stripping layers can also be included, which enable the two layer elements to be separated.

The supports for the light-sensitive element and, if appropriate, for the image-receiving element must remain dimensionally stable at the process temperature. Standard film or paper documents are eligible. Polyester materials are preferably used.

The conventional hardening agents, as well as rapid and instant hardeners, which are customary for photographic materials, can be used as hardening agents for both the light-sensitive element and for the image receiving element.

example 1

A photosensitive member of a photothermographic recording material for the diffusion transfer process was prepared by coating the layers described below on a transparent substrate made of polyethylene terephthalate. The quantities given relate in each case to 1 m ² .

Layer 1

A layer with a green-sensitized silver halide emulsion of 0.5 g AgN0 ₃ (4 mol% AgCl; 88.7 mol% AgBr, 7.3 mol% Agl; average grain diameter 0.3 wm) with 0.3 g color releaser A.

(emulgiert in 0,15 g Diethyllauramid) ; 0,05 g Kaliumbromid ; 1 g Polyesterurethan folgender Zusammensetzung :

• 84,1 % Polyester, aus Adipinsäure, 1,6-Hexandiol und Neopentylglykol
• 13,1 % Hexamethylendiisocyanat, und
• 2,7 % N-Aminoethyltaurin; und
• 1,5 g Gelatine.

Paint releaser A:

(emulsified in 0.15 g diethyl lauramide); 0.05 g potassium bromide; 1 g polyester urethane of the following composition:

• 84.1% polyester, from adipic acid, 1,6-hexanediol and neopentyl glycol
• 13.1% hexamethylene diisocyanate, and
• 2.7% N-aminoethyl taurine; and
• 1.5 g gelatin.

Layer 2

A layer with 1.5 g guanidine trichloroacetate; 0.035 g acetylation product of 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone; 0.3 g of compound B,

Compound B

(emulgiert in Trikresylphosphat) 0,03 g der Verbindung C,

(emulsified in tricresyl phosphate) 0.03 g of compound C,

Compound C

und 1,5 g Gelatine.

and 1.5 g gelatin.

Layer 3

A protective layer with 0.5 g gelatin. The hardening agent is also applied with this protective layer.

The photosensitive member thus produced is referred to as Sample 1 and serves as a comparative sample.

Further samples 2 to 23 were prepared in an analogous manner, compounds of the invention or comparison compounds according to the invention being added in the amount indicated in each case to the silver halide emulsion in layer 1, as can be seen from Table 1 below. The following comparison compounds were used.

• 1. Eine Beizschicht mit 2 g Polyurethanbeize aus 4,4'-Diphenylmethandiisocyanat und N-Ethyldiethanolamin, quaterniert mit Epichlorhydrin gemäß DE-A-26 31 521, Beispiel 1 ; 0,035 g der Verbindung C und 2 g Gelatine.
• 2. Eine Schutzschicht aus 0,8 g Gelatine. Mit dieser Schutzschicht wurde gleichzeitig Härtungsmittel aufgetragen.

An image receiving part for the photothermographic recording material was produced in that the following layers were applied successively to a support made of paper coated with polyethylene. The quantities given relate in each case to 1 m ² .

• 1. A pickling layer with 2 g of polyurethane pickling from 4,4'-diphenylmethane diisocyanate and N-ethyldiethanolamine, quaternized with epichlorohydrin according to DE-A-26 31 521, Example 1; 0.035 g of compound C and 2 g of gelatin.
• 2. A protective layer of 0.8 g gelatin. Hardening agent was applied simultaneously with this protective layer.

processing

A sample of the photosensitive element (samples 1 to 23) was exposed through a step wedge. The development took place in two steps; in the first, the photosensitive element was heated at 120 ° C for 60 s. This was done with the help of a heating plate, the sample being placed on the layer on the heating plate and covered with another plate. In the second step, the sample was brought into contact with the image-receiving element on the layer side, the image-receiving element having previously been soaked with water. The set formed in this way was treated for 2 minutes at 70 ° C. using the same procedure as in the first step. During this time the color transfer from the photosensitive element to the image receiving element took place. The two layer elements were then separated from one another. A purple negative image of the exposure original was obtained on the image receiving element.

The development results obtained with Samples 1 to 23 are summarized in Table 1.

As can be seen from Table 1, the minimum densities are very clearly improved by the compounds according to the invention. However, an activating effect can also be observed. Despite lowering the minimum densities, both the maximum densities are increased and the sensitivity is improved. In contrast, the comparison substances show no or only a slight fog-lowering effect or even a strong fog-increasing effect, such as the compound V-2, which differs from the compound St-6 according to the invention only in the absence of the solubilizing group.

Example 2

As in Example 1, a photothermographic recording material was produced with the following layers:

Layer 1

A layer like layer 1 from example 1 but with additional silver benzotriazolate from 0.5 g AgN0 ₃ .

Layer 2

• 1,5 g Guanidin-trichloracetat,
• 0;035 g 4-Methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidon
• 0,008 g Natriumsulfit
• 0,5 g Verbindung B
• 0,03 g Verbindung C und
• 1,5 g Gelatine.

A layer with

• 1.5 g guanidine trichloroacetate,
• 0.035 g of 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone
• 0.008 g sodium sulfite
• 0.5 g of compound B
• 0.03 g of compound C and
• 1.5 g gelatin.

Layer 3

A layer like layer 3 from example 1.

The photosensitive element thus produced is referred to as sample 24 and serves as a comparison sample.

A further sample 25 was prepared in an analogous manner, 1.7 g of the compound St-6 according to the invention being added to the silver halide emulsion in layer 1 per mol of silver halide.

Both samples were processed as described in Example 1. The results are summarized in Table 2.

This example again shows very clearly the strongly fog-reducing effect of the compound according to the invention.

Example 3 Layer 1

(emulgiert in 0,15 g Diethyllauramid), 0,05 g Kaliumbromid, 1 g Polyesterurethan aus Beispiel 1 ; und 1,5 g Gelatine.A layer with a blue-sensitized silver halide emulsion consisting of 0.5 g AgN0 ₃ (95.5 mol% AgBr, 4.5 mol% Agl, average grain diameter 0.4 µm) with 0.3 g color releaser D.

(emulsified in 0.15 g diethyl lauramide), 0.05 g potassium bromide, 1 g polyester urethane from Example 1; and 1.5 g gelatin.

Layers 2 and 3 were identical to layers 2 and 3 from Example 2.

The photosensitive member thus produced is referred to as sample 26 and serves as a comparative sample.

A further sample 27 was produced in an analogous manner, with the silver halide emulsion in layer 1 per mol of AgNO ₃ , 1.7 g of the compound St-6 according to the invention being added.

Both samples were processed as described in Example 1. A yellow negative image of the original was obtained. The results are summarized in Table 3.

Example 4 Layer 1

A layer with a red-sensitized silver halide emulsion of 0.5 g AgN0 ₃ (4 mol% AgCl, 88.7 mol% AgBr, 7.3 mol% Agl, average grain diameter 0.36 µm), with 0.16 g of color releaser E

Compound E

(emulgiert mit 0,08 g Diethyllauramid), 0,05 g Kaliumbromid, 1 g Polyesterurethan aus Beispiel 1 und 1,5 g Gelatine.

(emulsified with 0.08 g diethyl lauramide), 0.05 g potassium bromide, 1 g polyester urethane from Example 1 and 1.5 g gelatin.

Layers 2 and 3 were identical to layers 2 and 3 from Example 2.

The photosensitive member thus produced is referred to as sample 28 and serves as a comparative sample.

A further sample 29 was prepared in an analogous manner, 1.7 g of the compound St-6 according to the invention being added to the silver halide emulsion in layer 1 per mole of AgNO ₃ .

Both samples were processed as described in Example 1. A blue-green negative image of the original was obtained. The results are summarized in Table 3.

As can be seen from Table 3, sample 27 from example 3, when the compound according to the invention was added, showed both an improvement in the fog and an improvement in sensitivity, while in the case of sample 29 from example 4, above all a significant improvement in the fog was evident.

The following layer structure was drawn as the image receiving element on the same base as in Example 1.

Layer 1

A pickling layer with 3 g of compound F and 3 g of gelatin.

Connection F

Layer 2

A cover layer, which is also a hardening layer, with 0.5 g gelatin and 0.35 g dimethylol urea.

The photosensitive samples 1, 3, 5, 6 from example 1 (sample 1 is a comparative sample) were processed with the image receiving element of example 5 as described in example 1. Purple images of the template were obtained. The results are summarized in Table 4.

As can be seen from Table 4, the compounds according to the invention show a significantly improved D _min / D _max relationship.

Example 6 Layer 1

A layer with a green-sensitized platelet-shaped silver halide emulsion of 0.5 g AgN0 ₃ (95 mol% AgBr, 5 mol% Agl; average aspect ratio about 10; average grain diameter when assigned to a volume-equal sphere 0.61 µm); with 0.005 g of the compound St-6 according to the invention; 0.3 g of paint releasing agent A, 0.02 g of potassium bromide; 1 g polyester urethane from Example 1 and 1.0 g gelatin.

Layer 2

A layer with 1.5 g guanidine trichloroacetate; 0.035 g of 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone; 0.008 g sodium sulfite; 0.3 g of compound B; 0.03 g of compound C and 1.8 g of gelatin.

Layer 3

Layer 3 is identical to layer 3 from example 1.

The material was processed as described in Example 1. The D _min / D _max relationship was 0.17 / 2.11, while a material without the additive according to the invention had a noticeably higher fog in layer 1 with a D _min / D _max relationship of 0.31 / 2.04.

After storage of the unprocessed material at normal temperature for two months, the increase in fog in the sample with the compound St-6 according to the invention was half less than in the sample without additive.

Example 7

According to the instructions in Example 1, further samples 30-37 were produced and processed, which differed only in the addition of the fog-reducing compound added to layer 1 (1.7 g per mol AgN0 _{3 in} each case). The results are shown in Table 5. The compounds according to the invention bring about a significant improvement in the image whiteness and in some cases also an increase in the maximum color density.

Example 8

A photosensitive member of a photothermographic recording material for the diffusion transfer process was prepared by coating the layers described below on a transparent substrate made of polyethylene terephthalate. The quantities given relate in each case to 1 m ² .

Layer 1

A layer with a green-sensitized silver halide emulsion composed of 0.5 g AgN0 ₃ (4 mol% AgCl; 88.7 mol% AgBr, 7.3 mol% Agl; average grain diameter 0.3 µm) with 0.3 g color releaser G

(emulgiert in 0,15 g Diethyllauramid) ; 0,05 g Kaliumbromid ; 1 g Polyesterurethan aus Beispiel 1 und 1,5 g Gelatine.Paint splitter G:

(emulsified in 0.15 g diethyl lauramide); 0.05 g potassium bromide; 1 g polyester urethane from Example 1 and 1.5 g gelatin.

Layer 2

A layer with 2.0 g guanidine trichloroacetate, 0.035 g 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone, 0.5 g compound B, 0.03 g compound C and 1.5 g gelatin.

Layer 3

A layer like Layer 3 in Example 1

The photosensitive member thus produced is referred to as sample 38 and serves as a comparative sample. A further sample 39 was prepared in an analogous manner, 6.8 g of the compound St-6 according to the invention being added to the silver halide emulsion in layer 1 per mole of AgNO ₃ . As can be seen from Table 6, sample 39 showed a significantly lower haze value after processing than sample 38.

Example 9

A photosensitive member of a photothermographic recording material for the diffusion transfer process was prepared by coating the layers described below on a transparent substrate made of polyethylene terephthalate. The quantities given relate in each case to 1 m ² .

Layer 1

A layer with a green-sensitized silver halide emulsion made from 1.0 g AgN0 ₃ (4 mol% AgCl; 88.7 mol% AgBr, 7.3 mol% Agl; average grain diameter 0.3 µm) and silver benzotriazolate from 0.5 g AgNO ₃ , with 0.3 g paint releasing agent H,

0,05 g Kaliumbromid ; 1 g Polyesterurethan aus Beispiel 1 und 1,8 g Gelatine.Paint splitter H:

0.05 g potassium bromide; 1 g polyester urethane from Example 1 and 1.8 g gelatin.

Layer 2

• A layer with
• 1.5 g guanidine trichloroacetate,
• 0.24 g of 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone
• 0.06 g sodium sulfite
• 0.03 g of compound C and
• 1.5 g gelatin.

Layer 3

A layer like layer 3 from example 1

The photosensitive member thus produced is referred to as sample 40 and serves as a comparative sample. A further sample 41 was prepared in an analogous manner, 6.8 g of the compound St-6 according to the invention being added to the silver halide emulsion in layer 1 g per mole of AgNO ₃ . The samples were processed as described in Example 1. In the present example it is a positive color process. In the areas where silver is exposed and developed, no dye is split off, and in the areas where silver is not developed, color is released. Accordingly, in this case the haze-lowering effect of the compound according to the invention primarily affects an increase in the maximum densities. Accordingly, the density of the comparison sample was 1.58, while the maximum density with the compound according to the invention was 2.07.

Claims (10)

1. A photographic recording material developable by heat treatment comprising at least one binder layer which is applied to a layer support and which contains photosensitive silver halide, but essentially no other inorganic silver salts, at least one non-diffusing dye-producing compound, which is capable of releasing a diffusible dye in consequence of development by heat treatment, and a fog-reducing compound, characterized in that the fog-reducing compound corresponds to the following formula I

in which

Q represents the radical required to complete a heterocyclic group containing at least one 5- or 6- membered heterocyclic ring and, optionally, rings fused thereto ;

X represents a carboxylic acid or sulfonic acid group or a radical containing a carboxylic acid or sulfonic acid group, it also being possible for the carboxylic acid or sulfonic acid group to be present in anionic form.

2. Recording material according to Claim 1, characterized in that the fog-reducing compounds correspond to the following general formula II

in which

Y represents -O-, -S-, -Se- or -NR^3- ;

R¹ and R² may be the same or different and represent hydrogen, alkyl, alkenyl, cycloalkyl, aryl, phenyl, aralkyl, halogen or R¹ and R² together represent a fused benzene ring ;

R³ represents hydrogen, alkyl, alkenyl, cycloalkyl, aralkyl, aryl.

3. Recording material according to one of Claims 1 and 2, characterized in that the binder layer containing the silver halide contains the fog-reducing compound in a quantity of from 0.001 to 10.0 g per mole of silver halide.

4. Recording material according to one of Claims 1 and 2, characterized in that the binder layer containing the photosensitive silver halide contains at most 4 mole %, based on the total quantity of silver salts, of substantially non-photosensitive inorganic silver salts.

5. Recording material according to Claim 4, characterized in that the binder layer containing the photosensitive silver salt contains no substantially non-photosensitive inorganic silver salt.

6. Recording material according to Claim 1, characterized in that the binder layer containing the photosensitive silver halide additionally contains a silver salt of an organic imino compound.

7. Recording material according to Claim 6, characterized in that the organic imino compound is benzotriazole or a benzotriazole derivative.

8. Recording material according to one of Claims 1 and 2, characterized in that it contains as dye-producing compound an oxidizable dye-producing compound which is capable of releasing a diffusible dye in consequence of oxidation.

9. Recording material according to one of Claims 1 and 2, characterized in that it contains as dye-producing compound a reducible dye-producing compound, which is capable of releasing a diffusible dye in consequence of reduction, in combination with an electron donor compound.

10. Recording material according to one of Claims 1 and 2, characterized in that it contains three combinations of, in each case, a photosensitive silver halide and a non-diffusing dye-producing compound which is capable of releasing a diffusible dye, the silver halide having a different spectral sensitivity in each of the three combinations and the dye-producing compound associated in each case with the silver halide providing a dye of which the absorption range largely corresponds with the spectral sensitivity range of the associated silver halide.