EP0017025B1 - Photographic film unit for the production of coloured transfer images - Google Patents

Description

The invention relates to a photographic film unit for the production of color photographic images by the color diffusion transfer process and in particular to a neutralization element consisting of an acidic polymer layer and a brake layer for such a film unit, in which the acidic polymer layer contains a copolymer with at least 5 moi-0 / o carboxyalkyl (meth) acrylate units.

To carry out the color diffusion transfer process, a photosensitive member containing coloring compounds is usually used, and a. Image receiving element, in which the desired color image is generated by image-wise diffusing dyes. For this purpose, it is necessary that there is firm contact between the photosensitive element and the image-receiving element for at least a finite period within the development time, so that the imagewise distribution of diffusing dyes produced in the photosensitive element as a result of the development can be transferred to the image-receiving element . The contact can be made after development has started or it can have been made before development begins. The latter is the case, for example, if a material is used to carry out the color diffusion transfer process in which the light-sensitive element and the image-receiving element form an integral unit. Embodiments of the color diffusion transfer method are known in which such an integral unit continues to exist even after the development process has ended; d. that is, a separation of the photosensitive element from the image receiving element is not provided even after color transfer. Such an embodiment is described, for example, in DE-A-2019430. However, according to another embodiment, the image-receiving element, which carries the finished image after the color transfer, can be separated from the photosensitive element, e.g. B. be separated by means of a stripping layer arranged between the two elements. With regard to such an embodiment, reference is made, for example, to DE-A-2 049 688.

The imagewise exposed photosensitive element is treated with an alkaline developer preparation to develop the silver halide and to produce an imagewise distribution of diffusing dyes which is transferred to the image receiving element. A subsequent washing treatment is generally not intended. However, it is necessary to reduce the high pH set in the image-receiving layer during development in order to finally fix the image dyes in the image-receiving layer and to effectively complete the development. The latter is particularly important if the image receiving element forms an integral unit or a so-called mono sheet with the light-sensitive element. Known measures for lowering the pH are, for example, that a so-called neutralization system is arranged in close spatial relationship with the image-receiving layer, which consists of a neutralization layer containing a polymer with free acid groups and a neutralization-retarding brake layer containing a polymer which offers a certain resistance to the diffusing hydroxyl ions. Such a neutralization system is described for example in DE-C-1 285 310.

It is known to use polymeric organic acids, preferably in partially esterified form, for the preparation of the neutralization layers, the polymers being used as organic solutions (FR-A-2 290 699) or as aqueous dispersions (BE-A-860 771) can. A disadvantage of the acidic polymers described so far is either the low acid number, defined by the number of acid equivalents per unit weight of copolymer, or, in the case of a high acid number, the brittleness of the acidic polymer layers, characterized by a high glass transition temperature (Tg) of the polymers. Pure polyacrylic acid, for example, has a high acid number, but is not suitable at room temperature because of the likewise very high glass transition temperature and the associated brittleness and brittleness of the neutralization layers produced therefrom.

It is also known to lower the glass transition temperature of acidic homopolymers by using copolymers which, as comonomer, softening monomers such as, for example, those which lower the glass transition temperature. B. butyl acrylate, 2-ethylhexyl acrylate. The incorporation of comonomers of this type leads to the fact that the polymers have a lower Tg value, but at the same time also to a high undesired decrease in the acid number. If these copolymers are used as a neutralization layer, large amounts of polymer must be applied due to the low acid number in order to achieve a sufficient neutralization capacity of the neutralization layer.

The present invention is based on the object of specifying polymers containing acid groups which have both a high neutralization capacity and a low Tg value and thus have a neutralization capacity which is sufficient for the color diffusion process in thin layers.

It has now been found that copolymers of polymerizable acids with at least 5% by weight carboxyalkyl (meth) acrylate units are particularly suitable.

worin bedeuten

• R¹ Wasserstoff oder Methyl,
• R² eine gegebenenfalls verzweigte Alkylengruppe mit 1 bis 3 C-Atomen.

The present invention relates to a photographic film unit for producing colored transfer images, comprising an image-receiving layer, a light-sensitive element with at least one light-sensitive silver halide emulsion layer and an associated non-diffusing coloring compound, and a neutration element, on a dimensionally stable support. consisting of a neutralization layer and a neutralization-retarding brake layer, the neutralization layer mainly consisting of a copolymer containing essentially polymerized units of acid group-containing copolymerizable monomers and optionally up to 10% by weight polymerized units of acid group-free copolymerizable monomers, characterized in that the copolymer contains 5-50% by weight of polymerized units of copolymerizable monomers of the following formula (1):

in what mean

• R ^{1 is} hydrogen or methyl,
• R ^{2 is} an optionally branched alkylene group with 1 to 3 carbon atoms.

Suitable monomers of the above formula are e.g. B. ß-acryloyloxypropionic acid, methacryloyloxyacetic acid, methacryloyloxybutyric acid. ·

Such compounds can be produced according to generally applicable principles, as described in the literature. For example, acrylic acid or methacrylic acid chloride with hydroxyalkyl carboxylic acid derivatives, such as. B. esters, implement and convert into the desired compounds by subsequent selective hydrolysis. However, it is also possible to react acrylic acid or methacrylic acid alkali metal salts with haloalkyl carboxylic acid salts or their esters and then optionally hydrolyze them selectively. Another method, especially for the preparation of ß-acryloyloxypropionic acid, has been described by Sherlin et al. in J. Gen. Chem. (USSR), 8, No. 7 (1938).

erhalten, in der n eine ganze Zahl von 1 bis 6 bedeutet. Die nicht umgesetzte Acrylsäure kann aus dem Reaktionsgemisch leicht destillativ entfernt werden. Ebenso kann die dimere Acrylsäure (n=1) durch Destillation isoliert werden. Letzteres ist jedoch für die Herstellung. der erfindungsgemäßen Mischpolymerisate nicht erforderlich; vielmehr kann auch das Oligomerengemisch für die Mischpolymerisation eingesetzt werden.The last-mentioned compound, which is also referred to as carboxyethyl acrylate or dimeric acrylic acid and is particularly preferably suitable for the preparation of the copolymers according to the invention, can furthermore be prepared by heating acrylic acid in the presence of a polymerization inhibitor by a process described in DE-A-2,800 357 is described. In this process, depending on the conditions selected, a mixture of oligomeric acrylic acids of the formula (II)

obtained, in which n is an integer from 1 to 6. The unreacted acrylic acid can easily be removed from the reaction mixture by distillation. The dimeric acrylic acid (n = 1) can also be isolated by distillation. However, the latter is for manufacturing. the copolymers according to the invention not required; rather, the oligomer mixture can also be used for the mixed polymerization.

worin R¹ und R² die bereits angegebene Bedeutung haben und worin bedeuten

• M¹ polymerisierte Einheiten von säuregruppenhaltigen copolymerisierbaren Monomeren, soweit sie nicht durch die Formel (1) erfaßt werden; Beispiele sind Acrylsäure, Methacrylsäure, Maleinsäure, Itaconsäure, Acrylamidoglykolsäure, 2-Acrylamido-2-methyl-propansulfonsäu- re, Sulfoethylacrylat, Vinylphosphonsäure,
• M² polymerisierte Einheiten von säuregruppenfreien copolymerisierbaren Monomeren; Beispiele sind Vinylaromaten (Styroi, Vinyltoluol, Methylstyrol), Vinylether, Vinylester, N-Vinylverbindungen (Vinylcarbazol, Vinylpyrrolidon, Vinylamide), Vinylhalogenide, Ester, Amide und Nitrile von α,β-ungesättigten Carbonsäuren (Acrylsäureester, Methacrylsäureester, Acrylsäureamide, Acrylnitril), Olefine (Ethylen, Propylen, Butylen), Allylverbindungen (Allylacetat). Besonders werden hier solche Monomeren in Betracht gezogen, die eine weichmachende Wirkung auf das Mischpolymerisat ausüben, z. B. Butylacrylat. Zu erwähnen sind auch Monomere mit zwei oder mehr copolymerisierbaren C-C-Doppelbindungen, die in geringer Konzentration, vorzugsweise weniger als 3 Gew.-% bei der Copolymerisation verwendet werden und dabei einer Vernetzung des Mischpolymerisates bewirken. Weiterhin sind hier Monomere zu erwähnen, die eine copolymerisierbare Doppelbindung und eine aktive Methylengruppe enthalten; durch Reaktion dieser Methylengruppe mit Härtungsmitteln ergibt sich die Möglichkeit einer nachträglichen Vernetzung.
• x, y, z die prozentualen Anteile der polymerisierten Monomeren am Mischpolymerisat (in Gew.-%) und zwar im einzelnen:
  

^* The copolymer used according to the invention for the production of the neutralization layer can be represented by the following formula (III):

wherein R ¹ and R ^{2 have} the meaning already given and where mean

• M ¹ polymerized units of acid group-containing copolymerizable monomers, insofar as they are not covered by the formula (1); Examples are acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamidoglycolic acid, 2-acrylamido-2-methyl-propanesulfonic acid, sulfoethylacrylate, vinylphosphonic acid,
• M ² polymerized units of acid group-free copolymerizable monomers; Examples are vinyl aromatics (styroi, vinyl toluene, methyl styrene), vinyl ethers, vinyl esters, N-vinylver bonds (vinyl carbazole, vinyl pyrrolidone, vinyl amides), vinyl halides, esters, amides and nitriles of α, β-unsaturated carboxylic acids (acrylic acid esters, methacrylic acid esters, acrylic acid amides, acrylonitrile), olefins (ethylene, propylene, butylene), allyl compounds (allyl acetate). In particular, those monomers are considered here that have a plasticizing effect on the copolymer, for. B. butyl acrylate. Also to be mentioned are monomers with two or more copolymerizable CC double bonds, which are used in a low concentration, preferably less than 3% by weight, in the copolymerization and thereby cause the copolymer to crosslink. Also worth mentioning here are monomers which contain a copolymerizable double bond and an active methylene group; By reacting this methylene group with hardening agents there is the possibility of subsequent crosslinking.
• x, y, z the percentage of the polymerized monomers in the copolymer (in% by weight), specifically:
  

In the above formula (III), each of the symbols M ¹ and M ^{2 can represent} a single monomer or a mixture of the corresponding monomers. If the copolymer contains higher oligomers of acrylic acid (formula II; n ≥ 2), these are included in M ¹ . However, they never make up the bulk of the acid group-containing copolymerizable monomers represented by M ¹ .

Examples of copolymers suitable according to the invention for producing the neutralization layer are listed below.

The polymers according to the invention are solid substances. They can be applied from organic solution or as an aqueous dispersion.

The copolymers can be prepared by the processes of solution, precipitation or emulsion polymerization known to the person skilled in the art. A purification of the polymers is necessary if the polymerization conditions are chosen so that after the end of the polymerization process a considerable amount of residual monomers remain in the polymer. The removal of the residual monomers can e.g. B. by distillation, reprecipitation, dialysis or membrane filtration. The polymerization is expediently carried out in such a way that the unpolymerized proportion of monomers remains low.

The copolymers according to the invention have a glass transition temperature (Tg) of less than or equal to 80 ° C. and an acid number of at least 545 mg KOH / g polymer. The glass transition temperature is determined using differential thermal analysis, a method known to the person skilled in the art. The acid number can be determined by calculation or in a known manner by titration.

The neutralization layers produced from the polymers according to the invention can be crosslinked to improve cohesion. All bifunctional or polyfunctional compounds which react at elevated temperature with carboxylic acid groups, such as, for. B. bi- or polyfunctional oxiranes, bi- or polyfunctional activated vinyl compounds.

However, as already mentioned, the crosslinking of the copolymers according to the invention can also be achieved by carrying out the copolymerization under crosslinking conditions, ie. H. in the presence of crosslinking monomers. These are understood to mean monomeric compounds with at least two copolymerizable C-C double bonds which, owing to the multiplicity of copolymerizable double bonds, are incorporated in different copolymer chains and thereby bring about crosslinking of the copolymers. Examples of suitable crosslinking compounds are: tetraallyloxyethane, trivinylcyclohexane, divinylbenzene, 1,7-octadiene or other crosslinking agents as described in Houben-Weyl, Methods of Organic Chemistry, Macromolecular Substances, Part 1, Georg Thieme Verlag, Stuttgart, 1961, p. 32, 33. As a rule, only weak crosslinking of the copolymers will be sought and therefore the proportion of crosslinking monomers in the copolymer will have less than 3% by weight.

The crosslinking can also be brought about by using, as already mentioned, copolymerizable compounds with active methylene groups as monomers M ² , which react in a known manner with gelatin hardeners such as dialdehydes, triacryl formal, bisvinyisuifones to form polymeric networks. Such monomers are described for example in DE-A-1 547 765 and DE-A-2 442 165, e.g. B. acetoacetoxyethyl methacrylate, 2-cyanoacetoxyethyl methacrylate, vinylphenyl-2,4-hexanedione.

The neutralization element consisting of the neutralization layer according to the invention and the brake layer can be used in an image-receiving sheet for the color diffusion transfer process if a separation of the image-receiving sheet and the light-sensitive element is provided after the development. The preferred and main application, however, is in use in integral type color diffusion transfer materials, i. H. in monosheet materials in which a separation of the image receiving element and the photosensitive element is not provided.

• 1 ) einen transparenten Schichtträger,
• 2) eine Bildempfangsschicht,
• 3) eine lichtundurchlässige Schicht,
• 4) ein lichtempfindliches Element mit mindestens einer lichtempfindlichen Silberhalogenidemulsionsschicht und mindestens einer dieser zugeordneten farbgebenden Verbindung,
• 5) eine Bremsschicht,
• 6) eine saure Polymerschicht (Neutralisationsschicht),
• 7) einen transparenten Schichtträger.

A monosheet material suitable for carrying out the color diffusion transfer method according to the present invention has, for example, the following layer elements:

• 1) a transparent layer support,
• 2) an image receiving layer,
• 3) an opaque layer,
• 4) a light-sensitive element with at least one light-sensitive silver halide emulsion layer and at least one coloring compound assigned to it,
• 5) a brake layer,
• 6) an acidic polymer layer (neutralization layer),
• 7) a transparent substrate.

The film unit can be assembled in such a way that two different parts are produced separately from one another, namely the light-sensitive part (layer elements 1-4) and the cover sheet (layer elements 5-7), which are then placed on one another on the layer side and connected to one another, optionally under Use of spacer strips so that a space is formed between the two parts for a precisely measured amount of a developer liquid or paste. The layer elements 5 and 6, which together form the neutralization element, can also be arranged additionally or alternatively, but in reversed order, between the layer support 1 and the image-receiving layer 2 of the light-sensitive part.

Means may be provided to introduce a working fluid between two adjacent layers of the monosheet material, e.g. B. in the form of a laterally arranged, splitable container, which pours its contents between two adjacent layers of mono-sheet material, in the present case between the light-sensitive part and the cover sheet, when subjected to mechanical forces.

The alkaline developer liquid sets a relatively high pH (about 11 to 14) in the light-sensitive material, which triggers the development and the imagewise dye diffusion. It has been shown that at this high pH the dyes and layer dressings and thus the images obtained are not particularly stable. It is therefore necessary that the material is made almost neutral or slightly acidic after development is complete. This is achieved in a known manner in that the material additionally contains an acidic polymer layer (neutralization layer) which is only gradually accessible to the alkaline developer liquid in the course of development. According to the invention, a neutralization layer is understood to be a layer which is composed of a copolymer, an ethylenically unsaturated copolymerizable acid and a copolymerizable compound of the formula (I). The acidic groups react with the hydroxyl groups of the processing mass to form water and lower the pH of the mass.

The acidic polymerization layer (neutralization layer) according to the invention contains enough acid groups even at low layer thicknesses to lower the pH value of the developer liquid from the beginning 11-14 to the extent that the material is finally almost neutral or slightly acidic (pH value 5-8 ).

The time delay of the lowering of the pH value is achieved in a known manner in that the acidic polymer layer is coated with a so-called brake layer. This contains a polymer with a delayed permeability to diffusing alkali, as a result of which the pH drop occurs only with a delay, and together with the acidic polymer layer forms the neutralizing element of the present invention. It is obvious that the brake layer must be arranged within the layer structure between the acidic polymer layer and the image receiving layer. The brake layer according to the invention is preferably produced by casting the corresponding polymers from an aqueous solution and then drying them. The thickness of the brake layer depends on the desired braking time (development time) and is generally between 2 and 20 itm.

An essential part of the photographic material according to the present invention is the photosensitive element which, in the case of a single dye transfer process, contains a photosensitive silver halide emulsion layer and associated with this a coloring compound. The coloring compound can be in a layer adjacent to the silver halide emulsion layer or in the silver halide emulsion layer itself, in the latter case the color of the image dye is preferably selected so that the predominant absorption range of the coloring compound does not match the predominant sensitivity range of the silver halide emulsion layer. In order to produce multicolored transfer images in true-to-life colors, however, the light-sensitive element contains three such assignments of coloring compound and light-sensitive silver halide emulsion layer, the absorption range of the coloring compound generally matching the range of spectral sensitivity of the assigned silver halide emulsion layer substantially. A prerequisite for the highest possible sensitivity is, however, that the color-providing compound is arranged in a separate binder layer (viewed in the direction of the light incident during the exposure) behind the silver halide emulsion layer.

The developer oxidation products formed during the development of a silver halide emulsion may of course only have an effect on the assigned coloring compound. Separating layers are therefore generally present in the photosensitive element, which effectively prevent the diffusion of the developer oxidation products into other unassigned layers. These separating layers can e.g. B. contain suitable substances which react with the developer oxidation products, for example non-diffusing hydroquinone derivatives or, if the developer compound is a color developer compound, non-diffusing color couplers.

The light-sensitive element contains substances in the silver halide emulsion layers or in adjacent layers which are capable of developing an imagewise distribution of a diffusible image dye during development. Such substances are referred to below as coloring compounds. In principle, compounds of any kind are suitable for this purpose, which provide diffusing dyes during the development of the light-sensitive element. These can be colored compounds which are themselves diffusible and which begin to diffuse when the layers are treated with an alkaline working fluid and are only determined by the development at the exposed areas. However, the coloring compounds can also be diffusion-resistant and release a diffusing dye in the course of development.

Coloring compounds that are a priori diffusible are known, for example, from German patents 1,036,640, 1,111,936 and 1,196,075. The so-called dye developers described therein contain in the same molecule a dye residue and a group which is capable of exposed silver halide to develop.

Among the processes known to date for producing colored photographic images using the color diffusion transfer process, those based on the use of diffusion-resistant, color-imparting compounds from which diffusing dyes or dye precursor products are cleaved during development and transferred to an image-receiving layer are becoming increasingly important .

The color-providing compounds suitable for this purpose include, for example, the non-diffusing color couplers described in DE-C-1 095 115, which produce a pre-formed color coupling during development as a result of a reaction with the oxidation product of a color developer compound consisting of a primary aromatic amine Release dye in diffusing form. The selection of the developer compounds required is naturally limited to color developers.

- Furthermore, reference is made to the non-diffusing coloring compounds described in DE-A-1 930215, which contain a pre-formed latent diffusible dye residue linked to a diffusion-proofing residue via a cleavable hydrazone group. These compounds are not to be referred to as color couplers, and it has also been found that the selection of developer compounds which are required to release the diffusing dye residue is in no way limited to the customary color developers, but that black and white developers, e.g. B. catechins are very useful.

DE-A-1 772 929 also describes non-diffusing colored compounds with a special grouping which undergo an oxidative ring closure reaction during development and thereby release a pre-formed dye residue in diffusing form. The connections presented there can be divided into two groups. The compounds of the one group require a customary color developer compound for development, with whose oxidation product they couple and in a subsequent ring closure reaction release the pre-formed dye residue in diffusing form. The compounds of the other group are themselves silver halide developing agents and are therefore able, even in the absence of further developer compounds in the oxidized form, to undergo the aforementioned ring closure reaction with the release of the diffusing dyes.

At this point, reference should also be made to the non-diffusing coloring compounds of DE-A-2 242 762. These are sulfonamidophenols and sulfonamidoanilines which, after oxidation during development, are cleaved under the influence of developer alkali with the release of diffusing dyes. The non-diffusing color compounds described in DE-A-2 505 248 and DE-A-2 645 656 also react in a similar manner, e.g. B. 3-sulfonamidoindole derivatives. Research Disclosure Publication No. 15 654 (1977) should also be remembered in this context.

The non-diffusing coloring compounds mentioned above work without exception negative, i. that is, the imagewise distribution of the diffusing dye released arises when conventional (negative working) silver halide emulsions are used in accordance with the negative silver image produced during development. In order to generate positive dye images, it is therefore necessary to use direct-positive silver halide emulsions or else to use a suitable reversal process.

Such a reversal process is available in the silver salt diffusion process. Photographic reversal using the silver seed diffusion process to produce positive color images using conventional color couplers is described, for example, in US-A-2,763,800. By exchanging the color couplers for the coloring compounds mentioned, a light-sensitive element is obtained which is suitable for the dye diffusion transfer process. Such a light-sensitive element has, for example, at least one combination of a light-sensitive silver halide emulsion layer and a binder layer associated therewith, which contains development nuclei for physical development and a coloring compound.

During development, the light is exposed in the light-sensitive silicon shark halide layer Proportion of silver halide chemically developed; the unexposed portion is transferred by means of a silver halide solvent into the binder layer containing the associated development nuclei and is physically developed there. If a developer is used for the physical development, which is able to release a diffusing dye in oxidized form as a result of a reaction with the coloring compound present in this layer, then an image-wise distribution of diffusing dyes, which are due to a Image receiving layer can be transferred and form a positive colored image there.

When reversed using compounds which release development inhibitors imagewise, the photosensitive element consists of at least one layer combination of a photosensitive silver halide emulsion layer and a second, unexposed, developable emulsion layer which contains the coloring compound. The light-sensitive silver halide emulsion layer is developed, for example, with color developers in the presence of certain compounds which, when reacted with oxidized color developers, release development-inhibiting substances. The development-inhibiting substances released imagewise in the light-sensitive layer diffuse into the neighboring, unexposed, developable emulsion layer and inhibit development there. The uninhibited (positive) portions of the unexposed developable emulsion layer are developed by the remaining developer, whose oxidation products then react with the non-diffusing coloring compounds to release diffusing dyes, which are transferred imagewise to the image receiving element. Suitable compounds which release development-inhibiting substances when reacting with color developer oxidation products are, for example, the known DIR couplers (DIR = development inhibitor releasing), which are color couplers which contain a releasable inhibitor residue in the coupling point. Such DIR couplers are described, for example, in US-A-3,227,554.

Another group of compounds which release development-inhibiting substances on reaction with color developer oxidation products is described in US Pat. No. 3,632,345. These are not color couplers. Accordingly, no dyes are formed when the development-inhibiting substances are released. Very similar compounds are also described in DE-A-2 359 295. According to DE-C-1 229389, suitable substituted, non-diffusing hydroquinone compounds can finally be used in such a process, which are oxidized to the corresponding quinones during the reaction with developer oxidation products and thereby release development-inhibiting mercaptans.

In principle, all directly positive silver halide emulsions are suitable as directly positive silver halide emulsions which, with simple development, produce a positive silver image and a corresponding image-wise distribution of developer oxidation products. For example, those silver halide emulsions are suitable in which a veil which can be developed has been produced by exposure or by chemical treatment and which is imagewise destroyed when the image-wise exposure is observed under certain conditions. The fog remains in the unexposed areas, so that a directly positive silver image is obtained in the subsequent development, and accordingly an imagewise distribution of diffusing dye if a color-imparting compound is associated with the directly positive silver halide emulsion.

vorzugsweise kein Silberbild oder nur eines mit sehr geringer Dichte ergeben, während bei Verwendung eines fnnenkeimentwickfers der folgenden Zusammensetzung:

ein Silberbild mit ausreichender Dichte entsteht.Another group of direct positive silver halide emulsions which are preferably used according to the present invention comprises the so-called unveiled direct positive silver halide emulsions which have a photosensitivity predominantly inside the silver halide grains. When these emulsions are exposed imagewise, a latent image is formed predominantly inside the silver halide grains. However, the development of such unveiled, directly positive silver halide emulsions is carried out under hazing conditions, a veil being produced predominantly at the unexposed areas and a positive silver image being developed during the development. The unveiled, directly positive silver halide emulsions are characterized in that exposed samples are developed using a typical surface developer of the following composition:

preferably does not produce a silver image or only one with a very low density, while when using an internal seed developer of the following composition:

a silver image with sufficient density is created.

The selective fogging of the imagewise exposed, unveiled direct positive emulsions can be carried out before or during development by treatment with a fogging agent. Suitable fogging agents are reducing agents, such as hydrazine or substituted hydrazines. See, for example, US-A-3,227,552.

Unveiled, direct positive emulsions are, for example, those which have defects in the interior of the silver halide grains (US Pat. No. 2,592,250) or silver halide emulsions with a layered grain structure (DE-A-2 308 239).

However, positive color transfer images can also be produced using conventional negative emulsions without the need for a reversal process of the type described above, namely, for example, when the color-imparting compounds used are those with a non-diffusing oxidizable carrier residue which is only present in the non-oxidized form under the Influence of the developer alkali is split off, while it is converted by oxidation into a form in which the split-off is prevented or is made considerably more difficult. Such non-diffusing coloring compounds are described for example in DE-A-2 402 900, DE-A-2 543 902 and DE-A-2 823 159.6.

The opaque layer arranged under the photosensitive element is permeable to aqueous alkaline treatment solutions and thus to the diffusing dyes. It has two main functions. Firstly, it serves to cover the image silver remaining in the originally light-sensitive element after development and the color-providing compounds remaining as color negatives, so that when viewed through the transparent support of the light-sensitive part, only the positive color transfer image is visible. Secondly, it closes the light-sensitive element in a light-tight manner on the side of the image-receiving layer (downward). The latter is particularly important if, after exposure, the mono-sheet material is still brought into contact with the alkaline processing compound in the camera, then is to be pulled out of the camera and developed outside the camera.

Layers with sufficient opacity, but sufficient permeability for diffusing dyes can, for example, with suspensions of inorganic or organic dark, preferably black pigments, for example with suspensions of carbon black in suitable binders, for. B. in gelatin solutions. In general, 0.5 to 2 μm thick layers containing 10 to 90% by weight (based on the total dry weight) of carbon black in gelatin are sufficient in order to ensure sufficient exclusion of light during development. The particle size of the pigments used is relatively uncritical as long as they do not significantly exceed 0.5 μm.

In addition to the black pigment layer, the opaque layer preferably also comprises a white pigment layer arranged underneath. This has the task of covering the black layer and creating a white background for the picture. All white pigments are suitable for this, provided that their opacity is sufficiently high for layers that are not too large. Examples include barium sulfate, oxides of zinc, titanium, silicon, aluminum and zircon, and also barium stearate or kaolin. Titanium dioxide is preferred as the white pigment. The same information applies to the binder, the concentration and the particle size as for the black pigments. The thickness of the white pigment layer can be varied depending on the desired whiteness of the substrate. Thicknesses between 2 and 20 μm are preferably used.

Instead of the opaque layer, means for producing such an opaque layer can also be arranged in the film unit according to the present invention between the light-sensitive element and the image-receiving layer, e.g. B. in the form of a laterally arranged container with an opacifying agent (pigment) containing working liquid which pours its contents between the layers mentioned under the action of mechanical forces, so that such a pigment layer forms there.

The image-receiving layer essentially consists of a binder which contains dye mordants for the determination of the diffusing acid dyes.

Long-chain quaternary ammonium or phosphonium compounds or tertiary sulfonium compounds, e.g. B. those as described in US Pat. Nos. 3,271,147, 3,371,148, or polymers containing quaternary ammonium groups, e.g. B. according to DE-A-2631 521. Furthermore, certain metal salts and their hydroxides, which form poorly soluble compounds with the acid dyes, can also be used. The dye mordants are in the receiving layer in one of the usual hydrophilic binders dispersed, e.g. B. in gelatin, polyvinylpyrrolidone, fully or partially hydrolyzed cellulose esters and the like. Of course, some binders can also act as mordants, for. B. copolymers or polymer mixture of vinyl alcohol and N-vinylpyrrolidone, as described for example in DE-B-1 130 284, furthermore those which are polymers of nitrogen-containing quaternary bases, for. B. Polymers of N-methyl-2-vinylpyridine, as described, for example, in US Pat. No. 2,484,430. Further pickling binders which can be used are, for example, guanylhydrazone derivatives of alkylvinyl ketone polymers, as described, for example, in US Pat. No. 2,882,156 or guanyihydrazone derivatives of acylstyrene polymers, as described, for example, in DE-A-2 009 498. In general, however, other binders, e.g. B. add gelatin.

As the transparent layer support for the monosheet material according to the invention, the usual transparent support materials used in photographic practice, e.g. B. films made of cellulose esters, polyethylene terephthalate, polycarbonate or other film-forming polymers are used.

For processing, the photosensitive element is treated after the imagewise exposure with an aqueous alkaline developer preparation and brought into contact with the image receiving element. In the case of monosheet materials, the developer preparation is pressed between two layers of the monosheet. In addition to the aqueous alkali, the developer preparation can also contain developer compounds which, however, have to be matched to the type of color-providing compounds. Other possible components of the developer preparation are thickeners to increase the viscosity, for. B. hydroxyethyl cellulose, silver halide solvent, e.g. As sodium thiosulfate or one of the bissulfonylalkane compounds described in DE-A-2 126 661, opacifiers for producing opaque layers, for. B. pigments of Ti0 ₂ , ZnO, barium stearate or kaolin. Alternatively or additionally, some of these components can also be embedded in one or more layers of monosheet materials. For example, according to a particularly preferred embodiment, non-diffusing developer compounds are embedded in layers of the light-sensitive element, while the developer preparation itself contains only small amounts of a diffusing auxiliary developer compound. For this purpose, reference is made to DE-A-2 327 963 and DE-A-2 335 179.

The following are examples of the preparation of some polymers according to the invention and a comparative example.

example 1

A mixture of 500 ml of toluene and 100 ml of cyclohexane is heated to 65 ° C. while introducing nitrogen. A solution of 2 g of benzoyl peroxide in 100 ml of toluene and a mixture of 50 g of dimeric acrylic acid and 50 g of acrylic acid are simultaneously added dropwise over the course of 1 hour. After a further 4 h stirring time at 65 ° C, the resulting precipitate is filtered off, washed with 200 ml of cyclohexane and dried. The polymer is clearly soluble in methanol. To determine the glass transition temperature, a polymer sample is purified by reprecipitation from methanol in methylene chloride.

Examples 2-5

The procedure is as in Example 1, with the difference that the monomers listed in Table 1 are used. In Example 5, the monomer mixture contains 40 ml of methanol.

The comparison shows that all polymers produced with dimeric acrylic acid as comonomer have a higher acid capacity than the comparative polymer and at the same time have a lower glass transition temperature.

Application example 1 (Comparative example)

• 1) Beizschichtaus
  
• 2) Weiße Pigmentschicht aus
  
• 3) Schwarze Pigmentschicht aus
  
• 4) Blaugrünfarbstoffschicht aus
  
• 5) Rotsensibilisierte Silberhalogenidemulsionsschicht mit einer unverschleierten, direkt positiv arbeitenden Silberchloridbromidemulsion aus
  
• 6) Sperrschicht aus
  
• 7) Purpurfarbstoffschichtaus
  
• 8) Grünsensibilisierte Silberhalogenidemulsionsschicht mit einer unverschleierten, direkt positiv arbeitenden Silberchloridbromidemulsion aus
  
• 9) Sperrschicht (identisch mit Schicht Nr. 6).
• 10) Gelbfarbstoffschicht aus
  
• 11) Blauempfindliche Silberhalogenidemulsionsschicht mit einer unverschleierten direkt positiv arbeitenden Silberchloridbromidemulsion aus
  
• 12) Schutzschicht aus
  
• 13) Härteschicht aus
  
• 14) Haftschicht aus
  • 1,0 g eines Terpolymer Latex aus Vinylidenchlorid, Methylacrylat und Itaconsäure im Verhältnis 55/39/6.
  • B. Das Abdeckblatt mit dem Neutralisationselement wurde hergestellt, indem auf einen transparenten Träger aus 100 um dicker Polyesterfolie nacheinander folgende 3 Schichten aufgetragen wurden:
    • 1. Neutralisationsschicht aus 19 g Mischpolymerisat aus 70 Teilen Acrylsäure und 30 Teilen Acrylsäurebutylester (vgl. FR-A-2 290 699).
    • 2. Erste Bremsschicht aus 4,5 g, aufgetragen aus einer Mischung aus:
      
    • 3. Zweite Bremsschicht aus 2,2 g Terpolymer aus Vinylidenchlorid/Methacrylat/ltaconsäure im Mischungsverhältnis 55/39/6, aufgetragen als Latex.

A. The light-sensitive part of a photographic film unit according to the invention was produced by successively applying the following layers on a transparent support made of polyester film 150 μm thick. The quantities given relate in each case to 1 m ² . For structural formulas of compounds A to D, see Appendix.

• 1) Pickling layer
  
• 2) White pigment layer
  
• 3) Black pigment layer
  
• 4) cyan dye layer
  
• 5) Red-sensitized silver halide emulsion layer with an unveiled, directly positive working silver chloride bromide emulsion
  
• 6) barrier layer off
  
• 7) Purple dye layer
  
• 8) Green-sensitized silver halide emulsion layer with an unveiled, directly positive working silver chloride bromide emulsion
  
• 9) Barrier layer (identical to layer No. 6).
• 10) Yellow dye layer
  
• 11) Blue-sensitive silver halide emulsion layer with an unveiled, directly positive working silver chloride bromide emulsion
  
• 12) protective layer
  
• 13) hardness layer
  
• 14) adhesive layer
  • 1.0 g of a terpolymer latex made of vinylidene chloride, methyl acrylate and itaconic acid in a ratio of 55/39/6.
  • B. The cover sheet with the neutralizing element was produced by successively applying the following 3 layers on a transparent support made of 100 μm thick polyester film:
    • 1. Neutralization layer of 19 g of copolymer from 70 parts of acrylic acid and 30 parts of butyl acrylate (cf. FR-A-2 290 699).
    • 2. First brake layer of 4.5 g, applied from a mixture of:
      
    • 3. Second brake layer made of 2.2 g terpolymer of vinylidene chloride / methacrylate / itaconic acid in a 55/39/6 mixing ratio, applied as a latex.

One sheet each of the photosensitive part A and the cover sheet B were connected to one another on the side of the layer by means of two spacer strips of 100 .mu.m in thickness, a bag containing developer paste being attached to one end and a trap for excess developer attached to the other end. The set thus formed was exposed through an exposure original (gray wedge and color separations), then passed through a pair of squeeze rollers, the developer paste being distributed between the photosensitive part and the cover sheet. The developer paste had the following composition:

After the development period, a positive image of the original was visible through the transparent support on the TiO _z layer as the background.

Example of use 2

A film unit was constructed and processed analogously to application example 1, but with the change that a copolymer of 90 parts of acrylic acid and 10 parts of dimeric acrylic acid (example 3) was used for the neutralization layer. In accordance with the higher neutralization capacity of the polymer (see SZ in Table 1), this time only 12.5 g were applied per m ² . The image sheet processed with this cover sheet and the above paste according to Example 1 provided a positive image of the original with very good color quality and excellent durability. ' The thickness of the neutralization layer was considerably reduced compared to application example 1.

Example of use 3

Results as good as in Application Example 2 were obtained using a neutralization layer consisting of 13 g of a copolymer of 10 parts of dimeric acrylic acid, 70 parts of acrylic acid and 20 parts of methacrylic acid (Example 4).

Formula attachment

Claims (5)

1. A photographic film unit for producing coloured transfer images containing, on a dimensionally stable support layer, an image-receiving layer, a photosensitive element containing at least one photosensitive silver halide emulsion layer, and, associated therewith, a non-diffusing colour-providing compound and a neutralising element consisting of a neutralising layer and a retarding layer which delays neutralisation, the neutralising layer consisting of a copolymer, which essentially contains polymerised units of acid-groupcontaining copolymerisable monomers and optionally up to 10% by weight of polymerised units of copolymerisable monomers free from acid groups, characterised in that the copolymer contains 5-50% by weight of polymerised units of copolymerisable monomers of the following formula (I)

wherein

R^I denotes hydrogen or methyl and

R² denotes an optionally branched alkylene group containing 1 to 3 carbon atoms.

2. A film unit according to Claim 1, characterised in that the copolymer used in the neutralising layer corresponds to the following formula:

wherein

R' denotes hydrogen or methyl;

R² denotes an optionally branched alkylene group containing 1 to 3 carbon atoms;

M¹ denotes polymerised units of copolymerisable monomers containing acid groups;

M² denotes polymerised units of copolymerisable monomers free from acid groups; x, y

and z denote the percentage contents of the polymerised monomers in the copolymer (in % by weight); more particularly

x 50-95% by weight,

y 0-10% by weight, and

z 5-50% by weight.

3. A film unit according to Claim 2, characterised in that M¹ denotes polymerised units of one or more of the following monomers; acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamidoglycolic acid, 2-acrylamido-2-methyl propane sulphonic acid, sulphoethyl acrylate and vinyl phosphonic acid.

4. A film unit according to Claim 2, characterised in that M² denotes polymerised units of acetoacetoxy ethyl methacrylate.

5. A film unit according to Claim 1, characterised in that the copolymer contains 5-50% by weight of polymerised units of dimeric acrylic acid.