US3340058A - Photographic stratum transfer process and elements therefor - Google Patents

Description

United States Patent 9 Claims. (61. 9s-2s The invention relates to the production of photographic transfer images by means of silver halide emulsion layers which are developed by means of a tanning silver halide developing substance to produce tanned and non-tanned areas in said layers, which non-tanned areas are transferred to a non-light-sensitive transfer material and transformed into a positive image by tanning development under heat, using special light-sensitive materials and transfer materials.

United States Patent No. 3,080,230 describes the production of positive transfer images which are not laterally reversed by a process employing silver halide emulsion layers (negative layers) containing tanning silver halide developer substances which layers after imagewise exposure are developed by the application of heat. The de' veloper substances employed in this process so modify the gelatin of the negative layer during reduction of the exposed silver halide, that the gelatin becomes infusible and unswellable. The gelatin at the unexposed areas is not influenced and can be used for the formation of a positive image. This can be carried out by bringing the exposed material, during or after development, into contact with a non-light-sensitive transfer material (positive material) to which the gelatin of the unexposed areas becomes firmly bonded, so that when the two materials are separated, these gelatin sections are stripped out of the light-sensitive material. As a result, a gelatin relief, which is a non-reversed positive of the original, is obtained on the transfer material. This relief layer still contains unused silver halide and developer substances and can be blackened after exposure to difiused light and heat development. Generally, in order to save the second exposure, transfer materials are used which contain compounds which either reduce the silver halide or transform it into black compounds during the transfer process. Prepared or untreated papers, synthetic plastic supports, fabrics or metal foils can be used as transfer materials in the known process. Substances containing sulphur such as thiosemicarbazides or guanidine derivatives, have beenv described for producing the blackening effect.

The known processes are particularly advantageous because they avoid the use of aqueous processing baths. The methods used for blackening the transferred gelatin relief are, however, still unsatisfactory. Chemical blackening is indeed already simpler than diffused light exposure and separate development, but other disadvantages arise in this process, for example, insufiicient depth of color and deterioration in the quality of the image due to yellowing of the image whites. In addition, many materials which behave satisfactorily chemically have an unpleasant natural odour which prevents their use in practice.

Chemical blackening only leads to deep black images of good density if the silver coating is at least 1.4 g./m. and if temperatures of at least 75 C. are used during the transfer. At lower temperatures, the sulphur-containing substances do not react with the silver halide. Most reducing agents, such as potassium borohydride, sodium hyposulphite, formamidine-sulphinic acid, hydrazone, hydroxylamine or its salts and particularly the known photographic developer substances do not reduce the ice transferred unexposed silver halide in the positive or only produce images which are light to dark brown in color. Some reducing agents fog the negative, so that the transfer of the unexposed image portions, which will then also be developed and tanned, is disturbed or completely prevented.

According to the present invention, black to bluishblack positive transfer images of good density are obtained by subjecting an imagewise exposed light-sensitive silver halide emulsion layer containing a leuco-phthalocyanine to tanning developement to cause the emulsion layer to be tanned in its exposed areas, pressing said emulsion layer against a transfer layer containing a reducing agent which is capable of reducing said leucophthalocyanines to colored phthalocyanines, subjecting said combined silver halide emulsion layer and transfer layer to the action of heat to transfer the unexposed portions of the silver halide emulsion layer to the transfer layer and reduce at the same time in said portions of the emulsion layer the leuco-phthalocyanines to a phthalocyanine dyestuif and the silver halide to silver. The reduction of the leucophthalocyanines in the transferred portion of the silver halide layer apparently catalyses at the same time the reduction of the unexposed silver halide to silver. Therefore the formed transfer image consists of silver and the very light-fast phthalocyanine dyestufI. It is consequently necessary to use less silver than with the known processes, to produce images of dense color, since the phthalocyanine dyestuffs contribute to the depth of color and the density.

According to one modification of the present invention the tanning development of the negative layer and the production of the transfer image may be carried out according to the method disclosed in United States Patent 3,080,230 while using a negative layer which in addition to the leucophthalocyanines contains a tanning developing agent. This negative layer can now be brought into contact during or after the tanning heat development with the above positive material, which has the capacity of becoming firmly bonded to the unchanged emulsion layer that are thus stripped out of the negative layer and are made bluish-black in color. According to another modification of the invention, the negative material can also be developed in a conventional manner with the aid of an aqueous bath, it being possible to use an aqueous alkaline solution which may contain pyrocatechol or another tanning silver halide developing substance. Furthermore, negative layers may be used which do not contain a tanning developing substance. In this case the development is carried out he means of an alkaline aqueous solution containing a tanning developer substance. The negative is then brought into contact with the transfer material according to the invention and subjected to the action of heat.

By the term leuco-phthalocyanines" is to be understood in this connection colorless or only slightly colored compounds which are composed of four isoindolenine units arranged in a true phthalocyanine structure and which produce on reduction a phthalocyanine dye. The leuco-phthalocyanines according to the foregoing definition can be used in the metal-free form or in the form of complexes with metals that form phthalocyanine complexes, such as cobalt, nickel, copper or zinc. The metal complexes in particular those with cobalt are preferred. This term includes compounds which are known as phthalocyanine-precursors, a term which has been used by B. R. A. Brooks, J. G. Burt, B. F. Skiles and M. S. Whelen, J. Org. Chem., vol. 24, page 383 (1959), for those leucophthalocyanines which are not prepared from phthalocyanines. In Ullmanns Encyklopaedie der Technischen C-hemi, Third edition, vol. 13, the term phthalocyanine-metal-complexes is used to designate the same 3 compounds which are referred to herein as leucophthalocyanines. In US. Patent No. 2,772,285, R. A. Brooks uses the term leucophthalocyanine to refer in a restricted sense to the copper complexes of leucophthalocyanines, which are described therein.

The leuco-phthalocyanines can be produced, for example, by first preparing a phthalocyanine, e.g., a phthalocyanine containing no metal or containing cobalt, nickel, copper or zinc, and then attaching additional groups thereto under oxidizing conditions or by heating a reactlon mixture which is suitable for the preparation of a phthalocyanine to a temperature below that required for forming the phthalocyanine, or by eliminating the reduction potential required for the formation of a phtha'locyanine.

Combined processes have also been described, in which a phthalocyanine is first formed and then further converted, within the same reaction mixture, to the leuco stage. Alternatively, a complex-forming metal atom can be introduced into a leuco-.phthalocyanine containing no metal, or a metallic leuco-phthalocyanine can be prepared from a phthalocyanine free from metal. The leucophthalocyanines can be modified in their structure or solubility by subsequent treatments without thereby losing their essential property of being convertible into a phthalocyanine by reduction. In principle, all leucophthalo'cyanines, regardless of the method by which they have been .prepared, are suitable for the copying process according to the invention.

Cobalt leuco-phthalocyanines are particularly suitable because they are only very slightly colored. Copper or nickel leuco-phthalocyanines have a yellowish or brownish tinge. Particularly to be mentioned are cobalt leucophthalocyanines of the type Phthalogen Blue IB (tradename of the Farbenfabriken Bayer AG) which has been described in the Zeitschrift fiir Angewandte Chemie, vol. 68, page '145 (1956), and which is regarded as a leucophthalocyanine-cobalt-ethylenediamine complex.

Other suitable amines or polyamines such as 1,2 propylenediamine, 1,3-propylenediamine, N-monoethyl-l,3-propylenediamine,

N- 2-hydroxyethyl) ethylenediamine, N,N-di (2-arninoethyl) ethylenediamine, or NH n-Propylamine n-B utyl amine Iso-butyl amine n-Dodecylamine n-Tetradecylamine n-Hexadecylamine n-Octadecylamine N, N-diethylste arylamine Allyl amine Diallylamine Diethylamine Di-n-propylarnine Di-n-butyl amine N,N-dimethyl-ethylendiamine N,N-diethyl-ethylendiamine N,N'- di 2-aminoethyl-) -ethylendiamine N,N-di- (Z-(Z-aminoethyl) -aminoethyl) amine Tetramethylethylenediamine l-amino-3 -methylaminoprop an Di- (2-aminoethyl-) -amine 3-dimethylaminopropylamine 3 -diethylaminop ropylamine Tetramethylendiamine Hexamethylendiamine Tetraethylenpentamine Di 3-amino-propyl-) -amine 1-diethylamino-4-amino-n-pentane Di( 3-amino-propyl-) -methylamine N-methyl-N- 2-hydroxy-ethy'l) propylendiamine 1,3 3-'( 2-ethylhexoxy) -propylamine- (1 Z-ami'noethanol N-methyl-aminoethanol Diethanolamine 3-methoxypropylamine-(1 3-butoxypropylamine- 1 N-( 2-hydroxyethyl-) -ethylendiamine l-aminobutanol-( 3) l -aminobutar1ol-(4) 2-amino-Z-methyl-propandiol-( 1,3)

may be used as ligands instead of ethylenediamine. Especially suitable are, for example,

Stearylamine N-methyl-N (Z-hydroxyethyl) -1,3 epropylenediamine n-Dodecylamine n-Tetradecylamine n-Hexadecylamine n-Octadec'ylamine:

3-(2'-ethylhexoxy)-propylamine-'(l) 1-an1inobutanol-(4) The solubility of the metal leuco-pht-halocyanine, for

instance, of cobalt leuco-phthalocyanine, depends on the type of amine used.

"In the reduction of the leuco-phthalocyanine constituents, for example, the constituents referred to hereinbefore can be split oif.

Suitable solvents for the leuco-phthalocyanines are: inorganic and organic acids as amidosulphonic acid, orthophosphoric acid, acetic acid, propionic acid, lactic acid, succinic acid, tartaric acid and p-toluene sulphonic acid, acid amides as dimethylformamide, pyrrolidone and N- methyl pyrrolidone, alcohols as methanol, p'ropanol, benzyl alcohol, ethylene glycol, ethylene glycol ethyl ether and polyglycols, esters as the ethoxyethyl ester of acetic acid and hydrocarbons asbenzene, toluene, chlorobenzene, cyclohexane and n-hexane. Mixtures of these solvents can also be used.

The solutions can be added to the silver halide emulsion, alternatively, the leuco-phthalocyanines can be emulsified in aqueous solutions of gelatin or other colloids known as additives to silver halide emulsions, with the aid of emulsifiers and using mixing apparatus, such as vibratory mills. The emulsions can, for example, contain 0.5 to '10 g. per liter of the leuco-phthalocyanine compound, which amount corresponds to a concentration in the dried emulsion layer of about 0.05 to 1 gram per square meter.

Silver chloride, silver bromide or mixtures thereof, possi'bly with a small content of silver iodide, can be used as light-sensitive silver salts for the negative material. If necessary, the layers can also be optically sensitized. As binding agents there are to be considered all known layerforming hydrophili-c colloids which are hardened by the oxidation products of tanning silver halide developer substance, more especially gelatin and zein, which can partially be replaced by other layer-forming substances, e.g., such cellulose derivatives as carboxymethyl cellulose or methyl hydroxyethyl cellulose, polyvinyl alcohol, polyviny acetal, polyvinyl acetate, partially hydrolyzed'polyvinyl acetates, such alginic acid derivatives as alginates, the propylene glycol ester of alginic acid, polyvinyl pyrrolidone or other natural or synthetic substances. In addition, the additives usual in the emulsion art can be used, such as anti-fogging agents, e.g., benztriazole, l-phenyl-S- mercapto-tetrazole or 4-hydroxy-6-methyl-1,2,3a,7-tetraazaindene, mating agents as starch,starch ether or dextrin, colloidal silica, finely dispersed SiO A1 0 or TiO developer preservatives as aldehyde and ketone bisulphites, cyclohexanedione and dimethyl-cyclohexanedione, substances which evolve water on heating, such as urea, caprolactam or salts which contain water of crystallization, more especially sodium acetate, sodium citrate or the 1-aryl-2-n'itroethanols and 1-aryl-2-cyanoethanols described in the copendin-g applicationSer. No. 342,528,

filed Feb. 4, 1964, and substances which increase the residual moisture of the layer, such as polyhydric alcohols, e.g., sorbitol, glycerol or polyethylene glycols.

Suitable tanning developer substances are polyhydroxy compounds of benzene, naphthalene or diphenyl, for example, pyrocatechol, 2,3-dihydroxydiphenyl, 2,6-d1- hydroxy naphthalene, 3,4-dihydroxydiphenyl, cyclohexyl pyrocatechol and benzyl catechol. Non-tanning auxiliary developers such as p-methyl-aminophenol, 1-hydroxy-4- methoxy naphthalene or 8-hydroxy naphthol, can be added in small quantity to accelerate development. The pH of the layers is to be approximately 4.5 to 6.5, advantageously 4.9 to 5.6, and the layer coating 0.8 to 2.0 g./m. of silver, advantageously 1 to 1.3 g./m.

The transfer material according to the invention contains, in a separate layer or in the support itself, a reducing agent which reduces the leuoo-phtha'locyanines to phthalocyanine dyestuffs. As support, it is possible to use paper, various plastic foils, for example of cellulose ester, polystyrene, polycarbonate or polyesters, and also fabrics or metal foils.

The following are suitable reducing agents:

(1) Hydroxylamine salts or organically substituted hydroxylamines such as hydroxylamine hydrochloride or 2 5)2 (2) Alkali metal borohyd-r'ides such as that of potassium,

'(3) Formamidine sulphinic acid,

(4) Hydroxytetronic acid and its derivatives, particularly those of the following general formula wherein R represents an oxygen atom or an imine group and R represents a hydrogen atom or an alkyl or aryl group for example phenyl, which can be optionally substituted, or the group CH(OH)CH In detail, these include:

Ascorbic acid Ascorbic acid palmitate Ascorbic acid stearate Ascorbic acid laurate Ascorbic acid myristate Hydroxytetronic acid 4-phenyl-2-hydroxytetronic acid 4-phenyl-2-hydroxytetronimide the 3-pyrazolidone series, having where R represents a hydrogen atom or an alkyl or aryl group which can for example be sustituted by alkyl groups, alkoxy groups or halogen atoms, R represents a hydrogen atom or an acyl group, advantageously a low aliphatic acyl group and R R R and R represent hydrogen atoms or alkyl, aryl, substituted alkyl, or substituted aryl groups.

The following are, for example, suitable:

1-phenyl-3 -pyr azolidone 1-m-tolyl-3 -pyr azolidone 1-p-tolyl-3 -pyrazolidone 1-phenyl-4-methyl-3-pyrazolidone l-phenyl-5-rnethyl-3 -pyrazolidone 1,4-dimethyl-3-pyrazolidone 4methyl-3 -pyrazolidone 4,4-dimethyl-3 -pyrazolidone 1-phenyl-2-acetyl-3 -pyrazolidone 1-phenyl-4,4-dirnethyl-3 -pyr azolidone 1- (4'-bromophenyl) -3 -pyrazolidone 1-phenyl-2-carbop henoxy-3 -pyraz olidone 1, 5-diphenyl-3 -pyrazolidone 1- 3 '-chlorophenyl -4-methyl3 -pyrazolidone 1- (4'-chlorophenyl -4-methyl-3 -pyrazolidone 1- (3 -chlorophenyl) -3 -pyrazolidone 1- (4'-chlorophenyl) -3 -pyrazolidone 1-(4-to1yl) -4-methyl-3 -pyrazolidone 1- (2-tolyl) -4-methyl-3 -pyrazolidone 1- (4-tolyl) -3 -pyrazolidone 1- (3'-tolyl) -3 -pyrazolidone 1- (3 -tolyl) -4,4 dimethyl-3 -pyrazolidone 1- phenyl) -2-carb ethyl amino-3 -pyrazolidone These compounds can be prepared by the processes described in British patent specifications Nos. 679,677 and 679,678, the phenimines available by reaction of acrylonitrile derivatives with the corresponding hydrazine compounds being hydrolysed to the 3-pyrazolidones. Furthermore, 3-pyrazolidones can be prepared by the process described in British patent specification No. 703,669, the final products being obtained by direct condensation of esters of acrylic acid or derivatives thereof with hydrazines. This process is particularly suitable for reactions with hydrazine itself. The 3-pyrazolid0nes of oily consistency which are formed can be obtained as crystalline compounds by conversion into salts, e.g. hydrochlorides, sulphates or 1,5-naphthalene disulphonates. The preparation of 4,4 dialkyl-3 -pyrazolidones is described in US. Patent 2,772,282. In this connection, 2,2- dialkyl-fl-chloropropionyl chlorides are reacted with hydrazines. Acetyl-1-phenyl-3-pyrazolidone is prepared by the process described in Beilstein, vol. 26, page 2, by reacting 1-phenyl-3-pyrazolidone with acetic anhydride. To prepare 1-phenyl-2-carbophenoxy-3-pyrazolidone, 31.3 g. of phenyl chloroformate can be added dropwise, while stirring, to a mixture of 32.4 g. of l-phenyl-S-pyrazolidone in 150 ml. of pyridine cooled to 0 C., and heating the mixture under reflux for 2 hours. After concentrating to dryness in vacuo, the residue is re-crystallised from alcohol with addition of active carbon; M.P. 142 C. 1- phenyl-2-carbethylamino-3-pyrazolid0ne is prepared by boiling 16.2 g. of 1-phenyl-3-pyrazolidone, 8 g. of ethyl isocyanate and 200 ml. of benzine under reflux for 3 hours. The product which crystallises on cooling is recrystallised from alcohol; M.P. -92 C.

The 3-pyrazolidones can be used as free bases or in the form of their salts.

In one preferred embodiment of the invention, the reducing agents described above are used in combination with other compounds, which do not by themselves reduce either the leuco-phthalocyanine or silver halide, but cause a further deepening of the colour in the presence of the reducing agents. These additional compounds include:

(1) Hydrazine derivatives such as amino guanidine and its derivatives, monohydrazides or dihydrazides of aliphatic or aromatic monocarboxylic or polycarboxylic acids or monosulphonic or disulphonic acids, substituted hydrazines, advantageously aliphatically substituted hydrazines or semicarbazides. These compounds have the following general formula Rn /H N-N H R wherein:

R represents an acyl, aryl sulphonyl, alkyl, aryl, carbonamide or amidine group, and

R represents a hydrogen atom or an acyl or aryl sulphonyl group The following compounds are mentioned by way of example:

Amino guanidine nitrate Diamino guanidine nitrate Triamino guanidine nitrate l-methyloctylidene amino guanidine l-methyloctadecylidene amino guanidine l-methyl dodecylidene amino guanidine Formic hydrazide Acetic hydrazide Oxalic dihydrazide Malonic dihydrazide Succinic, dihydr azide, N,N-dibenzoic acid hydrazide Glutaric, dihydrazide, terepthalic acid dihydrazide Adipic dihydrazide Benzoic hydrazide Salicylic hydrazide. Tartaric dihydrazide, malic dihydrazide Benzene-sulphonic hydrazide, nitric trihydrazide N ,N'-di-benzene-sulphonic acid hydrazide p-Toluenesulphonic hydrazide Octadecyl hydrazine hydrochloride Semicarbazide l-phenyl semicarbazide (2)' 4-aminotriazole and its derivatives and (3) Hydroxyalkoxy naphthalenes such as 1-hydroxy-4-methoxy naphthalene 1-hydroxy-5-methoxy naphthalene 2-hydroxy-3 -methoxy naphthalene 2-hydroxy-7-methoxy naphthalene These additional compounds can be used in any desired concentrations, related to the reducing agents, but the materials which are preferred are those in which the reducing agents and these additional compounds are contained in approximately equal quantities. The optimum concentration of each of the additional compounds will depend on the properties of the paper and the requirements of the reproduction process being used. It can easily be determined by means of a few exploratory experiments.

The reducing agents and the additional compounds are added to the transfer material. They can on the one hand be incorporated in a separate layer, the binding agent of which is a hydrophilic film-forming colloid, such as polyvinylalcohol, polyvinyl acetates, polyvinyl acetal, partially hydrolyzed polyvinyl acetate, carboxymethyl cellulose, hydroxyethyl cellulose, gallactomannans (guar), alginic acid and its derivatives, such as esters, gelatin, zein, starch and starch derivatives,'e.g., starch ethers, or mixtures of binders. On the other hand, the transfer materials may be prepared by impregnating paper with a solution of the substances, or by adding the substances to the paper pulp during manufacture. In the last-mentioned processes, the casting of a separate layer is superfluous, so they are preferred on account of the more simple manufacture. The concentration in which the compounds are used is from 0.2 to 20 g./m. advantageously 1 to 5 g./m. of the transfer material. r

According to onepreferred form of the invention,- the transfer papers also contain compounds which guarantee the presence of some residualmoisture in the transfer material. Examples of such compounds include polyglycols, such as triethylene glycol, glycerol, glycol and sorbitol, as well as compounds which contain water of crystallization, such as sodium acetate, sodium sulphate, furthermore the l-aryl-Z-nitroethanols and the l-aryl-2-cyanoethanols, which are described in copending application S.N. 342,528.

The substances or combinations of substances which are suitable for the transfer process can be established by simple tests. It may sometimes be advantageous to combine more than one compound of a type with one or more compounds of the other type.

The development of the negative material and/ or the transfer of the unchanged portions of the negative layer to the positive material takes place at temperatures from to 200 C., advantageously in the range from to 150 C. in about 0.5 to 30 seconds and advantegeously 0.5 to 5 seconds. Alternatively, the negative material is developed at temperatures from90 to 200 C. and is then brought into contact with the positive material at temper- .atures from 50 to 180 C. It is favourable if a trace of Water is present during the transfer. This is obtained either by adding to the negative or positive layer, substances which give off water on heating, or by a slight moistening of the negative or positive. Moistening the back of the paper has a particular advantage in that it stops the processed material from curling since complete drying out of the paper is prevented by the moisture.

EXAMPLE 1 Positive material 1 liter of a silver chloride emulsion containing 0.3 mole of silver chloride per liter is mixed with Benzotriazole (1% in alcohol) Crystalline sodium acetate Cyclohexanone bisulphite Pyrocatechol 30 Colloidal silica A 3 Saponin 30% 1 5 Positive material A hard post paper is immersed in a 1% alcoholic solution of 1-(4-chlorophenyl)-4-methyl-3-pyrazolidone for 3 to 5 seconds and dried.

Processing After exposure, the negative is brought into contact with the positive. Depending upon the developing apparatus to be used, either the back or the front of the positive or the back of the negative or the backs of both papers are slightly moistened and the papers are subjected for 0.5 to 30 seconds to a temperature of 90 to C. by means of a heatable press, drying cylinder, rollers or a heat-developing apparatus according to French Patent 1,346,705. The positive can be heated to a lower temperature. After separating the two layers, a bluish-black positive image of the copied original with a White back-ground is obtained on the positive paper.

The leuco-phthalocyanine employed was prepared as follows: 50 g. of a crude product, prepared according to German Patent 855,710, Example 1, were converted into the nitrate. described in German Patent No. 839,939.

16 g. of the dried nitrate were boiled for 20 minutes in 50 ml. of benzine with 15 g. of stearylamine, the mixture was diluted with 750 ml. of benzine, forming a solution which was filtered at 100 C. and stirred to some hours in the cold. The product (27 g.) which crystallized was suction-filtered, dried and dissolved in boiling methanol. The resulting solution was stirred when cold, the crystallisate was suction-filtered and dried. 12 g. of an orange-colored substance were obtained.

Instead of the aforementioned cobalt-leuco-phthalocyam'ne, the emulsion can contain cobalt-leuco-phthalocyanines which have been reacted with propylamine, isobutylamine, di-n-propylamine, n-butylarnine, dodecylamine, hexadecylamine or ethylamine instead of with stearylamine.

Instead of using l-(4-chlorophenyl)-4-methyl-3-pyrazolidone, the positive paper can be immersed in a 1.3% alcoholic solution of l-(3-chlorophenyl)-3-pyrazolidone or a 1% alcoholic solution of 4-benzoylamino-5-phenyl-3- pyrazolidone or a mixture of a 1% alcoholic solution of 1-pheny1-3-pyrazolidone and a 1% alcoholic solution of 2-hydroxy-3-methoxynaphthalene.

EXAMPLE 2 Negative material 1 liter of a suitable silver chloride emulsion is mixed with:

Benzotriazole g 0.05 4-hydroxy-6-methy1-1,2,3a,7-tetraazaindene (1% in alcohol) g 0.2 Crystallised sodium acetate g 150 Terephthalaldehyde bisulphite g 10 Pyrocatechol g 30 Colloidal silica g 3 Saponin, (30%) cc 5 and 2 g. of a cobalt-leuco-phthalocyanine, the production of which is described at the end of this example, dissolved in 20 cc. of polyethylene glycol (molecular weight 400) and 20 cc. of acetic acid.

The pH is adjusted to 4.9. The emulsion is cast on to a support as in Example 1 and dried.

Positive material 5 g. of ascorbic acid, 1 g. of l-phenyl-3-pyrazolidone and l g. of cyclopentanone bisulphite or 5 g. of l-phenyl-4- dimethyl-3-pyrazolidone and 2 g. of N,N'-dibenzenesulphonic hydrazide.

The leuco-phthalocyanine used was prepared as follows:

20 g. of the leuco-cobalt-phtha1o-cyanine obtained according to Example 1 of German Patent 855,710, were heated with 20 g. of N,N-bis- (2-aminoethyl)-ethylene diamine in 50 ml. of methanol and boiled for 30 minutes.

The reaction product, forming as irregular crystals which are dark brown externally, was separated by suction-filtering at 20 C. from the greenish mother liquor, washed with a little methanol and dried. The yield was 10 20 g. The product is light yellow and soluble in 1% acetic acid.

EXAMPLE 3 Negative material 1 litre of a suitable silver halide emulsion are mixed with:

Benzotriazole (1% in alcohol) g 0.03 1-phenyl-5-mercaptotetrazole (1% in alcohol) g 0.02 Sodium acetate g 110 Cyclopentanone bisulphite g 3 Pyrocatechol g 35 Saponin cc 5 Positive material Typewriter or hard post paper, fabric or other suitable papers are immersed for 5 minutes in a mixture of a 10% aqueous solution of hydroxylamine hydrochloride and a 2% aqueous solution of tartaric hydrazide and dried.

Processing is carried out as described in Example 1, or the negative, after exposure, is developed at 100 to 180 C. and brought immediately or after some time into contact with the moistened positive paper at 50 to 180 C. After separating the two layers, a black image is obtained.

The cobalt-leuco-phthalocyanine used was prepared by heating 12 g. of the nitrate referred to in Example 1, to boiling in 100 ml. of methanol with 10 ml. of N-methyl- N-(2-hydroxyethyl)-propylene-1,3-diamine, for 15 minutes until the reaction product was homogeneously crystallised. 12 g. of orange-yellow crystals were obtained by suction-filtering, washing with methanol and drying.

Instead of using the cobalt-leuco-phthalocyanine indicated above, the emulsion can contain cobalt leucophthalocyanines which have been reacted with 3-(2'-ethylhexoxy)-l-propylamine, diethanolamine, 1-amino-3-methylaminopropane, 3-methoxypropylamine, butoxypropylamine, or amino ethanol instead of with N-methyl-N-(Z- hydroxyethyl)-propylene diamine alternatively there can be used the cobalt leuco-phthalocyanine of Example 6 of German Patent 839,939.

Instead of being immersed in the aforementioned mixture, the positive paper can be immersed in a mixture of:

A 1% alcoholic solution of 1 phenyl 5 methyl-3- pyrazolidone and a 1% alcoholic solution of l-me-thyloctylidene amino guanidine or a 1% aqueous solution of 4-phenyl oxytetronimide and a 1% aqueous solution of amino guanidine nitrate or a 1.2% alcoholic solution of l phenyl 2 carbophenoxy-3-pyrazolidone and a 1% alcoholic solution of succinic dihydrazide or in a 10% alcoholic solution of ascorbyl palmitate and a 2% alcoholic solution of salicylic hydrazide.

We claim:

1. A process for producing photographic transfer images which comprise subjecting an imagewise exposed light-sensitive silver halide emulsion layer containing a leuco-phthalocyanine to tanning development to cause the emulsion layer to be tanned in its exposed areas, pressing said emulsion layer against a transfer layer containing a reducing agent which is capable of reducing said leucophthalocyanine to phthalocyanine dyestuffs, subjecting said combined silver halide and transfer layer to the action of heat to transfer unexposed parts of the silver halide emulsion layer to the transfer layer and to reduce at the same time in said transferred parts of the emulsion 1 1 layer the vleuco-phthalocyanine to-phthalocyanine dyestuff and the silver halide to silver to thereby produce a black to bluish-black positive image of the original.

2. A process as claimed in claim 1, wherein the transfer material contains a reducing agent selected from the group consisting of a hydroxylamine, an alkali metal borohydride, formamidine-sulphinic acid, a hydroxytetronic acid, and a 3-pyrazolidone.

3. A process as claimed in claim 1, wherein the transfer material reducing agent, has the formula in which R represents a member selected from the group consisting of an oxygen atom and an imine group and R represents a member of the group consisting of a hydrogen atom, an alkyl and an aryl group.

4. A process as claimed in claim 3, wherein the reducing agent in the transfer material is an ascorbic acid.

5. A process as claimed in claim 2, wherein the transfer material reducing agent is a 3-pyrazolidone of the formula in which R R R R and R represent members of the group consisting of hydrogen atoms, alkyl, and aryl groups, and, R represents a member of the group consisting of a hydrogen atom and an acyl group.

6. A process as claimed in claim 1, wherein the transfer material contains, apart from the reducing agent, a compound selected from the group consisting of aminoguanidines, hydrazides or carboxylic acids, hydrazides of sulfonic acids, hydrazines, ser'nicarbazides, 4-aminotriazoles and hydroxyalkoxy naphthalenes.

7. In a layer of light-sensitive silver halide emulsion in untanned gelatine for selective tanning by a tanning developer and transfer of the unhardened portions to a transfer support for reduction of the silver halide in these portions, the improvement according to which the emulsion contains a leuco-phthalocyanine that is reduced to form a phthalocyanine dye intensifying the reduced silver halide image in the transferred portions.

8. In a layer of light-sensitive silver halide emulsion in unt-anned gelatine for selective tanning by a tanning developer and including a moistening compound that improves transfer of the unhardened portions to a transfer support for reduction of the silver halide in these portions, the improvement according to which the emulsion contains a leuco-phthalocyanine that is reduced to form a phthalocyanine dye'intensifying the reduced silver halide image in the transferred portions.

9. The combination of claim 1, wherein said leucophthalocyanine is a cobalt leuco phthalocyanine.

No references cited NORMAN G. TORCHIN, Primary Examiner. 'J. RAUBITSCHEK, Assistant Examiner.

Claims (1)

1. A PROCESS FOR PRODUCING PHOTOGRAPHIC TRANSFER IMAGES WHICH COMPRISE SUBJECTING AN IMAGEWISE EXPOSED LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER CONTAINING A LEUCO-PHTHALOCYANINE TO TANNING DEVELOPMENT TO CAUSE THE EMULSION LAYER TO BE TANNED IN ITS EXPOSED AREAS, PRESSING SAID EMULSION LAYER AGAINST A TRANSFER LAYER CONTAINING A REDUCING AGENT WHICH IS CAPABLE OF REDUCING SAID LEUCOPHTHALOCYANINE TO PHTHALOCYANINE DYESTUFFS, SUBJECTING SAID COMBINED SILVER HALIDE AND TRANSFER LAYER TO THE ACTION OF HEAT TO TRANSFER UNEXPOSED PARTS OF THE SILVER HALIDE EMULSION LAYER TO THE TRANSFER LAYER AND TO REDUCE AT THE SAME TIME IN SAID TRANSFERRED PARTS OF THE EMULSION LAYER THE LEUCO-PHTHALOCYANINE TO PHTHALOCYANINE DYESTUFF AND THE SILVER HALIDE TO SILVER TO THEREBY PRODUCE A BLACK TO BLUISH-BLACK POSITIVE IMAGE OF THE ORIGINAL.