EP0215356A2 - Heat development process and suitable image-receiving sheet therefor - Google Patents

Abstract

The heat development process using a photographic material and a separate image-receiving sheet results in stain-free transfer images if either the photothermographic material or the image-receiving sheet or both contain a mixture of gelatin and sodium alginate in a surface contact layer.

Description

The invention relates to a heat development process in which an imagewise exposed color photographic recording material which contains a binder layer with silver halide and at least one coloring compound on a common substrate is heated in contact with an image-receiving sheet and in which the image-receiving sheet with the color image generated therein is subsequently heated by the latter Recording material is separated.

It is known to produce colored images by heat treatment using suitable color photographic recording materials. Particularly suitable as color-imparting compounds are those which can be embedded in the layer of a photographic recording material in a non-diffusing form and which, as a result of the development, can 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. By combining the heat development process with the diffusion process, this 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 with a layer which contains a combination of silver halide, silver benzotriazole, a color releaser and guanidine trichloroacetate (base donor) is exposed imagewise and then subjected to heat treatment in contact with an image-receiving sheet, the imagewise released dye being applied to the image-receiving sheet is transmitted. For the production of multi-colored 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, according to 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 separation of the image-receiving sheet from the photosensitive part of the recording material is carried out in the usual embodiments of the color diffusion transfer process, i.e. when using liquid or paste-like treatment materials, smooth from place. However, it is difficult in the heat development process, especially if the supply of moisture from the outside is dispensed with. In this case, it is observed that at the higher temperatures of heat generation, the photosensitive member and the image-receiving sheet are bonded. Separation is only possible through the use of force, which usually results in damage to the surfaces, or only after soaking in warm water for a long time, as a result of which the advantage of the heat development process as a quick process is lost. It is also observed that it is apparently difficult to make full and perfect surface contact between the light-sensitive part of the recording material and the image-receiving sheet: the color transfer image obtained often has numerous spots and irregularities in color density, which indicate poor contact between the materials involved leaves.

The invention has for its object to design the heat development process based on the color diffusion process using a color photographic recording material with a separate image receiving sheet so that a perfect color transfer is achieved and that finally a smooth separation of the image-receiving sheet from the color photographic recording material is made possible even without the action of a treatment bath.

The invention relates to a heat development process for producing colored images, in which an imagewise exposed color photographic recording material with at least one binder layer arranged on a layer support contains the light-sensitive silver halide, optionally in combination with an essentially non-light-sensitive silver salt, and at least one non-diffusing coloring compound , which is able to release a diffusible dye as a result of the development, is developed by heat treatment, and in which the dye released imagewise from the non-diffusing coloring compound by heat treatment onto an image-receiving sheet brought into surface contact with the recording material on the coating side with an image-diffusible layer arranged on a support Dyestuffs are transferred to the image-receiving layer, whereupon the image-receiving sheet is removed from the recording material runs, characterized in that either the light-sensitive material or the image-receiving sheet or both contain an alkali alginate, in particular sodium alginate, in a surface contact layer.

The color photographic recording material in the process according to the invention contains, on a dimensionally stable support, at least one binder layer which contains a light-sensitive silver halide, optionally in combination with an essentially non-light-sensitive silver salt and a non-diffusing coloring compound which can give a diffusible dye through heat development.

An essential component of the heat-developable recording material is the silver halide, which consists of silver chloride, silver bromide, silver iodide or mixtures thereof and can have a particle size between 0.01 and 2.0 μm, preferably between 0.1 and 1.0 μm. It can be in the form of an unsensitized silver halide or it can also be chemically and / or spectrally sensitized by suitable additives.

The amount of light-sensitive silver halide in the respective layer can be between 0.01 and 2.0 g per m 2, the actual amount of silver halide used due to its catalytic function (as exposed silver halide) in some embodiments mainly in the lower part of the range given emotional.

The essentially non-light-sensitive silver salt can be, for example, a silver salt which is comparatively stable to light, e.g. trade an organic silver salt. Suitable examples of this include the silver salts of aliphatic or aromatic carboxylic acids and the silver salts of nitrogen-containing heterocycles: also silver salts of organic mercapto compounds.

Preferred examples of silver salts of aliphatic carboxylic acids are silver behenate, silver starch, silver oleate, silver laurate, silver caprate, silver myristate, silver palmitate, silver maleate, silver fumarate, silver tartrate, silver furoate, silver linolate, silver adipate, silver sebacate, silver succinate, silver acetate or silver butyrate. The carboxylic acids on which these silver salts are based can be substituted, for example, by halogen atoms, hydroxyl groups or thioether groups.

Examples of silver salts of aromatic carboxylic acids and other compounds containing carboxyl groups include silver benzoate, silver 3,5-dihydroxybenzoate, silver o-methylbenzoate, silver m-methylbenzoate, silver p-methylbenzoate, silver 2, -4-dichlorobenzoate, silver acetamidobenzoate, Silver gallate, silver tannate, silver phthalate, silver terephthalate, silver salicylate, silver phenylacetate, silver pyromellitate, silver salts of 3-carboxymethyl-4-methyl-4-thiazolin-2-thione or similar heterocyclic compounds. Silver salts of organic mercaptans, for example those, are also suitable Silver salts of 3-mercapto-4-phenyl-1,2,4-triazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptooxadiazole, mercaptotriazine, thioglycolic acid, as well as the silver salts of dithiocarboxylic acids, such as, for example, the silver acid salt, such as dithiocarboxylic acid salt .

The silver salts of compounds having an imino group are also suitable. Preferred examples include the silver salts of benzotriazole and its derivatives, e.g. Silver salts of alkyl and / or halogen substituted benzotriazoles, e.g. the silver salts of methylbenzotriazole, 5-chlorobenzotriazole, and also the silver salts of 1,2,4-triazole, 1-H-tetrazole, carbazole, saccharin and silver salts of imidazole and its derivatives.

The application amount of essentially non-light-sensitive silver salt according to the present invention is in the respective layer between 0.05 and 5 g per m². The substantially non-light-sensitive silver salt and the light-sensitive silver halide can be present side by side as separate particles or in a combined form, which can be produced, for example, by treating a substantially non-light-sensitive silver salt in the presence of halide ions, the surface of which Particles from the essentially non-photosensitive Lichen silver salt by double conversion (conversion) form light-sensitive centers from light-sensitive silver halide. For this purpose, reference is made to US-A-3 457 075.

The essentially non-light-sensitive silver salt serves as a reservoir for metal ions, which are reduced to elemental silver when heat is developed in the presence of a reducing agent under the catalytic influence of the imagewise exposed silver halide and thereby serve as an oxidizing agent (for the reducing agent present).

Another essential constituent of the recording material according to the invention is a non-diffusing coloring compound which, as a result of a redox reaction taking place during development, is able to release a diffusible dye and which is referred to below as a color releasing agent.

The dye releasers 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 bond 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. Int. 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.e. a group that can be oxidized or reduced 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 rest of DYE is split off, and
DYE the rest of a diffusible dye, for example 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. For this purpose, organic radicals are preferred, which in all contain generally straight-chain or branched aliphatic groups with generally 8 to 20 carbon atoms and optionally also carbocyclic or heterocyclic optionally aromatic groups. With the remaining part of the molecule, these radicals are either directly or indirectly, for example connected via one of the following groups: -NHCO-, -NHSO₂-, -NR-, where R is hydrogen or alkyl, -O- or -S-. In addition, the ballast residue can also contain water-solubilizing groups, such as sulfo groups or carboxyl groups, which can 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, for example if the total molecule used is large enough, to use shorter-chain residues as ballast residues.

Redox-active carrier residues of the BALLAST-REDOX structure 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. Int. 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:

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 arylene groups.

In principle, the residues of dyes of all classes of dyes are suitable as dye residues insofar as they are sufficiently diffusible 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 or can only result from the cleavage of the dye residue from the carrier residue containing ballast groups. Suitable dyes, to be mentioned: azo dyes, azomethine dyes, anthraquinone dyes, phthalocyanine dyes, indigoid dyes, triphenylmethane dyes, including those dyes that 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, either by oxidation, by coupling, by complex formation or by exposure of an auxochromic group in a chromophoric system, for example by saponification, can be 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 is made between dye residues and the residues of dye precursors, the latter should also be understood below as dye residues.

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- 26 13 005, 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 process 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.

Oxidizable color releasers which are particularly suitable for the heat-developable recording materials according to the invention are, for example, in DE-A-22 42 762, DE-A-25 05 248, DE-A-26 13 005, DE-A-26 45 656 and GB-A-80 12 242.

If the color splitter can be oxidized, then it is itself a reducing agent which, directly or indirectly, with the participation of electron transfer agents (electron transfer agent, ETA) through the imagewise exposed silver halide or through the essentially non-photosensitive silver salt under the catalytic action of the imagewise exposed Silver halides is oxidized. This creates a pictorial differentiation in terms of the ability to release the diffusible dye. If, on the other hand, the paint releaser is reducible, then it is expediently used in combination with a reducing agent present in a limited amount, a so-called ten 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, the light-sensitive silver halide and optionally the substantially non-light-sensitive silver salt. The use of electron transfer agents can also prove to be advantageous in the case of the use of reducible color releasers 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 eine Ballastrest enthält.A recording material according to the invention which contains reducible color releasers with a carrier residue 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

• R1 alkyl or aryl;
• R² is alkyl, aryl or a group which together with R³ completes a fused ring;
• R³ 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 R² fused one Ring completed;
• R⁴ alkyl;
• R⁵ alkyl or preferably hydrogen;

and wherein at least one of the radicals R¹ to R⁴ contains a ballast radical.

Such reducible dye releasers and others which are also suitable in the context of the present invention are described, for example, in DE-A-28 09 716, EP-A-0 004 399, DE-A-30 08 588, DE-A-30 14 669.

The electron donor compound used in combination with a reducible color releasing agent also serves as a reducing agent for the silver halide, the essentially non-photosensitive silver salt and the color releasing agent. Because the essentially non-light-sensitive silver salt and the color releaser compete with each other to a certain extent in the oxidation of the electron donor compound, but the latter is in any case superior to the latter in the presence of exposed silver halide, the silver halide present becomes determinant for that in accordance with a previous imagewise exposure Image areas, within which the color releaser is converted into its reduced form by the electron donor compound.

The electron donor compound, which is present in a limited amount, is subjected to under the conditions of development, in the present case when the imagewise exposed color photographic recording material is heated in contact with the auxiliary sheet used in accordance with the invention, in accordance with the extent of the exposure under the catalytic effect of the latent image nuclei produced by exposure in the silver halide the essentially non-photosensitive silver salt and the photosensitive silver halide oxidize and are consequently no longer available for reaction with the color releaser. 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, 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 which are formed from the corresponding electron donor precursor compounds only under the conditions of heat development in the layer, i.e. Electron donor compounds that are only in a masked form in the recording material before development, in which they are practically ineffective. Under the conditions of heat development, the electron donor compounds, which are initially ineffective, are then converted into their effective form, 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.

The above-mentioned essential constituents of the recording material used in the process according to the invention, namely the light-sensitive silver halide, the possibly non-light-sensitive reducible silver salt and the color releaser, optionally in combination with an electron donor compound, are dispersed next to one another in a binder. These can be hydrophobic as well as hydrophilic binders, but the latter are preferred and gelatin is preferably used, but it can also be replaced in whole or in part by other natural or synthetic binders.

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 and optionally the non-light-sensitive silver salt, 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. To produce multicolored color images, the color photographic recording material used in the method according to the invention contains several, ie generally three, assignments of color releasers and in each case differently spectrally sensitized silver halide, 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 different assignments of color releaser and assigned silver halide can be accommodated in different binder layers of the color photographic recording material, preferably between these different binder layers there are separating layers made of a water-permeable binder, for example gelatin, which essentially have the function of separating the different assignments from one another and counteract color distortion in this way. In such a case, this includes use in the method according to the invention The color photographic recording material includes, for example, a light-sensitive binder layer in which the silver halide contained therein is predominantly red-sensitive due to spectral sensitization, a further light-sensitive binder layer in which the silver halide contained therein is predominantly green-sensitive due to spectral sensitization, and a third light-sensitive binder layer in which the contained therein Silver halide is predominantly blue-sensitive due to its inherent sensitivity or due to spectral sensitization. The electron donor compounds optionally contained in the three light-sensitive layers can be the same or different.

Each of the above-mentioned assignments of light-sensitive silver halide, essentially non-light-sensitive silver salt (if present) and color releasers can also be 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 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 performed 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 optionally the essentially non-light-sensitive silver salt) and oily droplets of a solution of the organic constituents (in the present case the color releasing agent and optionally further auxiliaries) are included are. 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.

The use of packet emulsions makes it possible to combine several emulsion components of different spectral sensitivity, including the relevant color releasers, in a single binder layer, without losing the spectral assignment and thereby causing color falsification. This is possible because the degree of exposure of a particular silver halide particle becomes almost exclusively the determining factor for the degree of dye release from the color releaser which is in the same coacervate particle (package) as the silver halide. The use of packet emulsions thus enables the accommodation of a blue-sensitive, a green-sensitive and a red-sensitive silver halide emulsion with any additional, essentially non-light-sensitive silver salt and spectrally assigned color separators in the same binder layer, without fear of serious color falsification.

In addition to the constituents already mentioned, the color photographic recording material used in the method according to the invention can contain further constituents and auxiliary substances which are used, for example, for carrying out the heat treatment and the process taking place here Color transfer are beneficial. These further constituents or auxiliary substances can be contained in a light-sensitive layer or in a non-sensitive layer. However, they can also be contained in whole or in part in the image-receiving sheet used according to the invention.

Such auxiliary substances 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 salt (= silver salt in the presence of exposed silver halide) and the reducing agent, the reducing agent being used oxidizable color releaser is identical to the latter, or in the case of using reducible color releasers in turn reacts with the color releaser. Since these reactions consist mainly of electron transfer, the auxiliary developers are also known as electron transfer agents (ETA). Examples of suitable auxiliary developers include hydroquinone, pyrocatechol, pyrogallol, hydroxylamine, ascorbic acid, 1-phenyl-3-pyrazolinone and their derivatives. Since the auxiliary developers have a catalytic function, it is not necessary for them to be 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. Familiarization with the The layer can be processed, for example, from solutions in water-soluble solvents or in the form of aqueous dispersions which have been obtained using oil formers.

Other auxiliaries are, for example, basic substances or compounds which are able to provide basic substances under the influence of the heat treatment. Sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, sodium acetate and organic bases, in particular amines such as trialkylamines, hydroxyalkylamines, piperidine, morpholine, dialkylaniline, p-toluidine, 2-picoline, guanidine and their salts, in particular salts with aliphatic carboxylic acids, are to be mentioned here, for example. By providing the basic substances, a suitable medium is created during the heat treatment in the light-sensitive layer and the adjacent layers in order to ensure the release of the diffusible dyes from the dye releasers and their transfer to the image-receiving sheet.

Further auxiliaries are, for example, the so-called thermal solvents or thermal development and diffusion promotion agents, which are described, for example, in DE-A-32 15 485, EP-A-0 122 512, and German patent application P 35 23 361.3. These are non-hydrolyzable organic compounds, which are in any case liquid at the temperature of the heat and form a medium suitable for the development and diffusion processes.

In the method according to the invention, a separate image-receiving sheet is used, the most important component of which is an image-receiving layer which can be colored by diffusible dyes and is arranged on a transparent or opaque layer support.

In the method according to the invention, the image receiving layer is therefore not arranged on the same layer support as the color photographic recording material. The image-receiving layer essentially consists of a binder which contains mordants for the determination of the diffusible dyes released from the non-diffusing color releasers. Long-chain quaternary ammonium or phosphonium compounds, e.g. those 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. The dye mordants are dispersed in the mordant layer in one of the usual hydrophilic binders, for example in gelatin, polyvinylpyrrolidone, completely or partially hydrolyzed cellulose esters. Of course, some binders can also act as mordants, for example polymers of nitrogen-containing, optionally quaternary bases, such as, for example, of N-methyl-4-vinylpyridine and 4-vinylpyri din, 1-vinylimidazole, as described, for example, in US Pat. No. 2,484,430. Further usable binders are, for example, guanylhydrazone derivatives of alkyl vinyl 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, for example gelatin, will be added to the last-mentioned pickling binders.

Said image-receiving layer can have a structured layer structure, as described, for example, in DE-A-30 18 644 or DE-A-33 45 070; it can also contain a mixture of different mordants, as described, for example, in DE-A-33 42 629. The image-receiving layer mentioned or an adjacent binder layer can finally also contain metal ions or metal complexes as metallizing agents for complexable dyes, as described, for example, in DE-A-27 40 719, US-A-4 282 305, DE-A-31 05 777, DE-A-31 32 333, DE-A-32 02 127, DE-A-32 20 435 and EP-A-0 009 411 is.

The heat development process according to the invention is characterized in that either the photothermographic recording material used or the image-receiving sheet or both contain an alkali alginate in a surface contact layer. A surface contact layer is a layer which, owing to its composition, its properties, in particular its mechanical properties, and not least because of their specific arrangement in the image-receiving sheet or in the photographic recording material is able to exert a significant influence on the layer contact that occurs between the two. The surface contact layer is usually the outermost or one of the outermost layers in the respective sheet material; it is usually arranged above the other essential layers in the respective material. On the other hand, it does not necessarily have to be the outermost layer, but can also be covered, for example, by an alginate-free gelatin layer which contains a hardening agent for the layer structure of the respective sheet material.

For example, an image-receiving sheet according to the present invention is advantageously used, which contains an image-receiving layer on a layer support, which may be opaque or transparent, and above that a surface contact layer which contains alginate, a comparatively thin binder layer which can also be arranged above the surface contact layer Purpose of curing the laminate of the image-receiving sheet was applied. However, the uppermost alginate-free binder layer can also be dispensed with, especially if a hardening agent for the laminate has itself been added to the alginate-containing surface contact layer.

The surface contact layer contains alkali alginate, preferably dispersed in a hydrophilic binder. The usual binders come in Photography conventional layer binder, preferably gelatin. Surface contact layers in which the weight ratio of sodium alginate to gelatin is between 1: 4 and 4: 1, preferably between 2: 3 and 3: 2, have proven very successful.

The image-receiving sheet of the present invention may contain other additives, optionally in additional layers, e.g. dye stabilizing agents or opacifying agents. For example, a layer can contain a white pigment, especially if the substrate used is transparent. Such a layer, which can be located between the layer support and the image-receiving layer or else above the image-receiving layer, generally serves as a white image background for the color transfer image generated. This layer serving as a white image background is preferably deposited with a layer containing soot (in relation to the viewing direction) in order to prevent transparency phenomena due to the transillumination through the back of the image. However, the image-receiving sheet can also contain one of the auxiliary substances already mentioned in one of its layers, e.g. an auxiliary developer, a base donor or a so-called development and diffusion aid.

The development of the imagewise exposed color photographic recording material is initiated according to the invention by subjecting it, optionally in contact with the image-receiving sheet according to the invention, to a heat treatment in which the layers for a time of about 0.5 to 300 s to an elevated temperature, for example in the range from 80 to 250 ° C. Suitable conditions for the development processes, including dye diffusion, are created in the layers of the recording material without the need for the supply of a liquid medium, for example in the form of a developer bath. During development, dyes that are diffusible in terms of image are released from the color releasers and transferred to the image-receiving layer of the image-receiving sheet. The process can be carried out in such a way that imagewise silver development, dye release and color transfer take place synchronously in a one-step development process.

Color image formation according to the invention can also be carried out in a two-step development process, the silver halide development and dye release taking place in a first step by heating the photothermographic recording material in the absence of the image-receiving sheet according to the invention, whereupon in a second step the color image transfer from the photographic recording material to that brought into contact with it Image receiving sheet is carried out, for example, by heating to a temperature between 50 and 150 ° C, preferably to 70 to 90 ° C, in which case diffusion aids (solvents) can be applied externally before the lamination of the recording material and image receiving sheet, for example by the recording material or the image-receiving sheet or both are briefly soaked in water.

After color transfer has taken place, the image-receiving sheet can be smoothly separated from the recording material. Here, the surface contact layer according to the invention performs well. Completely stain-free brilliant color images with smooth surfaces are obtained. Adhesion, as is observed when heating laminated sheet materials with alginate-free gelatin layers, and the resulting damage to the surface during violent separation, does not occur in the present case.

example 1 Preparation of the silver salt emulsions Emulsion 1

17.0 g of AgNO₃, dissolved in 200 ml of water at 45 ° C., became a 45 ° C. solution of 20.0 g of gelatin in 1000 ml of water which contained 13.0 g of benzotriazole (BTA) within 2 minutes, metered in with stirring. The mixture was then stirred for 5 minutes. With 5% Na₂CO₃ solution pH 5.0 was adjusted. The mixture was flocculated by adding 20 ml of a 10% polystyrene sulfonic acid solution, cooling to 25 ° C. and adding 10% sulfuric acid (up to pH 3.0 to 3.5) and then washing three times with 1000 ml of water each time. The flocculate was heated to 45 ° C, adjusted to pH 6.0 with 5% Na₂CO₃ solution, mixed with 5 ml of 1% aqueous phenol solution and brought to a final weight of 435 g by adding water.

Emulsion 2

34.0 g of AgNO₃ dissolved in 200 ml of water were metered in over 10 minutes to a 50 ° warm solution of 40.0 g of gelatin, 23.7 g of KBr and 1.66 g of KI. The mixture was then stirred at 50 ° C for 20 min and then cooled to 35 ° C. 40 ml of a 10% polystyrene sulfonic acid solution was added dropwise and then it was cooled to 20 ° C. The mixture was flocculated by adding 10% strength sulfuric acid (up to pH 3.0 to 3.5) and washed three times with 700 ml of water each time. The mixture was then heated to 40 ° C. and adjusted to pH 6.0 with 10% sodium hydroxide solution. Final weight 1171 g.

For spectral sensitization, parts of emulsion 2 (crude emulsion) were melted at 40 ° C., per mol of Ag with 4 × 10⁻⁴ mol red sensitizer, 4 × 10⁻⁴ mol green sensitizer or 8 × 10⁻⁴ mol blue sensitizer, each in methanolic solution or slurry , added and digested in a closed vessel for about 70 min.

The following spectral sensitizers were used.

Example 2 Manufacture of the Dispergate Dispersant 1 (paint releasing agent C-1)

50 g of color releaser C-1 were dissolved in a mixture of 50 g of tricresyl phosphate, 50 g of tetrahydrofuran, 200 ml of ethyl acetate with 50 g of 20% aqueous solution of KHCO₃ and in the presence of 2.6 g of sodium dodecylbenzenesulfonate in 330 g of 10% aqueous gelatin solution dispersed, and then the auxiliary solvents were removed in a vacuum apparatus with relaxed steam. Yield: 1060 g of dispersant 1

Dispersant 2 (paint releasing agent M1)

50 g of color releasing agent M-1 were dissolved in 25 g of diethyl laurylamide and 150 ml of ethyl acetate and further treated as disperse 1. Yield: 834 g of dispersant 2

Dispersant 3 (paint releasing agent Y-1)

50 g of color releasing agent Y-1 were dissolved in 25 g of diethyl laurylamide and 150 ml of ethyl acetate and then treated further as disperse 1. Yield: 821 g of dispersant 3

Dispersant 4 (auxiliary developer precursor compound)

62 g of auxiliary developer precursor compound were dissolved in 120 g of diethyl laurylamide and 150 ml of ethyl acetate and in The presence of 3.5 sodium dodecylbenzenesulfonate dispersed in 612 g of 10% aqueous gelatin solution: and then, as in the case of disperse 1, the auxiliary solvent was removed. Yield: 997 g of dispersant 4

The following connections were used:

Example 3 Image receiving part A

• 1. Eine Gelatineschicht mit 1,25 g Ruß und 1,5 g Gelatine.
• 2. Eine lichtreflektierende Schicht mit 13 g TiO₂ und 1,3 g Gelatine.
• 3. Eine Beizschicht mit 2 g Polyurethanbeize aus 4,4'-Diphenylmethandiisocyanat und N-Ethyldi­ethanolamin, quaterniert mit Epichlorhydrin gemäß DE-A-26 31 521, Beispiel 1, und 2 g Gelatine.
• 4. Eine Schicht aus 0,6 g Gelatine und 0,6 g Natriumalginat, der ein Härtungsmittel zugesetzt war.

The image-receiving part of a photographic recording material for the color diffusion transfer process was produced by successively applying the following layers on a transparent substrate made of polyethylene terephthalate. The quantities given relate to 1 m².

• 1. A layer of gelatin with 1.25 g of carbon black and 1.5 g of gelatin.
• 2. A light reflecting layer with 13 g TiO₂ and 1.3 g gelatin.
• 3. A pickling layer with 2 g of polyurethane pickle made from 4,4'-diphenylmethane diisocyanate and N-ethyldiethanolamine, quaternized with epichlorohydrin according to DE-A-26 31 521, example 1, and 2 g of gelatin.
• 4. A layer of 0.6 g gelatin and 0.6 g sodium alginate to which a hardening agent was added.

Further image receiving parts B to F (according to the invention) and V (comparison) were produced as follows.

Image receiving part B

Production as for image receiving part A, but with an additional layer 5 of 0.5 g of gelatin, to which the hardener (instead of layer 4) was added.

Image receiving part C

Production as for image receiving part A, but in the reverse order of layers 1, 2 and 3.

Image receiving part D

Production as for image receiving part B, but in the reverse order of layers 1, 2 and 3.

Image receiving part E

Production by applying the layers 3 and 4 of the image receiving part A (no layers 1 and 2) on a layer of baryta paper.

Image receiving part F

Production by applying the layers 3 to 5 of the image receiving part B (no layers 1 and 2) on a layer support made of barite paper.

Image receiving part V (not according to the invention)

 Production as for image receiving part B, but without layers 1, 2 and 4 (only layers 3 and 5).

Example 4

Photosensitive parts of color photographic materials for the color diffusion transfer process were prepared as follows.

Sample 1

24.0 g of 2.5% aqueous solution of hydroxyethyl cellulose were homogenized with 108 ml water and 8 ml of a 4% aqueous solution of Triton® X 100.

Triton X 100
Manufacturer: Rohm & Haas Company, Philadelphia

Then 6.7 g of disperse 4, 18.5 g of dispersant 1 (color releasing agent C-1), 45.6 g of emulsion 1 and 32.0 g Emulsion 2, red-sensitized, added and melted. Then 3.2 g of guanidine trichloroacetate in 30 ml of water were added slowly, and finally 44.0 g of the 30% polyurethane solution described below, whereupon the whole was homogenized. The finished casting solution was applied with a wet layer thickness of 100 μm to a layer support made from polyethylene terephthalate and dried at 35 ° C. With a 1% aqueous gelatin solution, which contained a hardening agent, was overlaid (wet layer thickness 40 microns) and dried.

The polyurethane used is a 30% aqueous wetting agent-free dispersion of an anionic polyester polyurethane, which consists of
84.1% polyester, from adipic acid, 1,6-hexanediol and neopentyl glycol (molar ratio 30:22:12) OH number: 66.6: molecular weight 1600-1700
13.1% hexamethylene diisocyanate, and
2.7% N-aminoethyl taurine
was obtained: content of -SO₃Na groups 1.93%.

Sample 2

Preparation in the same way as sample 1, but using 32.0 g of emulsion 2, green-sensitized, and 17.2 g of dispersant 2 (color releaser M-1).

Sample 3

Manufactured in the same way as sample 1 but below Use of 32.0 g of emulsion 2, blue-sensitized, and 15.3 g of disperse 4 (color releasing agent Y-1).

Example 5

The samples produced according to Example 4 were exposed with a tungsten lamp (1000 lx, 5 s), the exposure in the case of samples 1 and 2 being carried out behind a transparent yellow filter with a density of 1.25. The samples were then heated to 110 ° C. dry for 60 s; The samples were then swollen in water for 10 s and laminated together with the image-receiving sheets (from Example 3) which had been swollen in water for 30-60 s and heated to 75 ° C. for 2-3 minutes on a regulated heating bench, then separated and then dried immediately. Complete, spot-free, brilliant, sharp color images were obtained on the image-receiving sheets AF. The reference image-receiving sheet V, on the other hand, reproducibly shows a strong color stain in the color transfer, presumably caused by poor lamination properties, which strongly hinder the dye diffusion at the relevant points. The surface contact layer according to the invention does a good job of avoiding such errors. In addition, it can be seen from the values in Table 1 that the surface contact layer according to the invention has virtually no influence on the diffusion of the different chromophores. In addition, when using the image-receiving materials according to the invention, an adhesive bond, as is generally observed when heating laminated sheet materials with alginate-free gelatin layers, avoided. Perfect surface qualities are obtained with immediate separation immediately after processing.

Claims (5)

1. Heat development process for the production of colored images, in which an imagewise exposed color photographic recording material with at least one binder layer arranged on a support contains the light-sensitive silver halide, optionally in combination with a substantially non-light-sensitive silver salt, and at least one non-diffusing color-providing compound, which as As a result of the development, a diffusible dye can be released, developed by heat treatment, and in which the dye released imagewise from the non-diffusing coloring compound by heat treatment on an image-receiving sheet brought into surface contact with the recording material on the coating side with an image-receiving layer arranged on a support and capable of being colored by diffusible dyes is transferred, whereupon the image-receiving sheet is separated from the recording material, thereby g indicates that either the light-sensitive material or the image-receiving sheet or both contain an alkali alginate, especially sodium alginate, in a surface contact layer. 2. Heat development process according to claim 1, characterized in that either the recording material or the image-receiving sheet or both contains sodium alginate, dispersed in a hydrophilic binder, in particular gelatin. 3. Heat development process according to claim 2, characterized in that the weight ratio of sodium alginate to gelatin is between 1: 4 and 4: 1. 4. Image-receiving sheet with a binder layer (image-receiving layer) arranged on a layer support by diffusible dyes, characterized in that a layer is arranged over the dyeable binder layer which contains sodium alginate and gelatin in a weight ratio of between 1: 4 and 4: 1. 5. Image receiving sheet according to claim 4, characterized in that the weight ratio of sodium alginate to gelatin is between 2: 3 and 3: 2.