Willems, Jozef Frans (Wilrijk, BE)
Poot, Albert Lucien (Kontich, BE)
Heugebaert, Frans Clement (Kontich, BE)
Vandenberghe, Anton Leon (Hove, BE)
Von Konig, Anita (Leverkusen, DT)

05/319604

10/29/1974

12/29/1972

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Agfa-gevaert (Mortsel, BE)

430/495.100

430/570, 430/965, 430/619, 430/617

G03C1/498; G03C1/02

96/114.1,36.8,67,64,94,48HD

3589903

June 1971

Birkeland

Smith, Ronald H.

Goodrow, John L.

Daniel, William J.

1. In a photographic recording material having a lightsensitive layer comprising a substantially non-light-sensitive silver salt, a reducing agent, a toning agent and in admixture therewith a light-sensitive heavy metal compound and/or a polymethine sensitizing agent for the spectral sensitization of the non-light-sensitive silver compound, the improvement wherein the light-sensitive layer comprises a phthalazinone toning agent according to the following general formula: ##SPC4##

2. Photographic recording material according to claim 1, wherein the light-sensitive layer comprises a silver salt of a long chain fatty acid

3. Photographic recording material according to claim 1, wherein said

4. Photographic recording material according to claim 1, wherein the light-sensitive layer comprises a silver halide as said light-sensitive

5. Photographic recording material according to claim 1, wherein the light-sensitive layer contains 0.05 to 0.02 percent by weight of light-sensitive heavy metal compound calculated on the weight of

6. Photographic recording material according to claim 1, wherein the phthalazinone toning agent is present in a molar proportion of at least

7. Photographic recording material according to claim 1, wherein the light-sensitive layer comprises as the sole silver compound therein a non-light-sensitive silver salt, a reducing agent, and a polymethine sensitizing agent for the spectral sensitization of the non-light-sensitive silver salt.

The invention relates to a photographic material for the production of photographic copies in a dry manner, the photographic material comprising toning agents for the formation of black silver images. The invention also relates to a photographic heat-copying process, wherein the formation of the silver image is performed in the presence of toning agents that shift the image tone from yellow to black-brown and black.

In the copying process described in the German Pat. No. 1,300,014 filed Apr. 23, 1964 by Minnesota Mining and Manufacturing Co. recording materials are used, which comprise an oxidizing agent, a reducing agent, and a small amount of a light-sensitive compound. At the exposed areas, upon supply of heat, a coloured image is formed by a redox reaction. As oxidizing agents organic silver salts are used, whereas aminophenols, hydroxylamines, pyrazolidones, phenols, phenylene-diamines or etherified naphthols, e.g. 4-methoxynaphthol-1 are used as reducing agents. Heavy metal salts, which during exposure form traces of the free metal, are suitable light-sensitive compounds. More particularly light-sensitive silver salts such as silver halides are considered, which form photolytic silver during exposure. The redox reaction is initiated by these photolytically formed heavy metal nuclei.

For the practical use of such materials it is essential to utilize non-light-sensitive silver salts as oxidizing agents, e.g. silver saccharide or silver salts of long chain fatty acids.

An especially high light-sensitivity is attained when the necessary silver halide is formed at the surface of the non-light-sensitive silver salt by reaction with halide ions or with a compound forming halide ions e.g. according to the process described in the published German Pat. Application No. 1,572,203 filed Apr. 23, 1965 by Minnesota Mining & Manufacturing Co. These materials have a sensitivity in the short wave region of the spectrum in accordance with the inherent sensitivity of the silver halides used and can be spectrally sensitized to light of longer wavelengths by the addition of spectral sensitizing dyes.

In the Belgian Pat. No. 787,340 filed Aug. 9, 1972 by Agfa-Gevaert N.V. a process is described for the production of photographic copies in a dry manner wherein a photographic material comprising a silver salt and a reducing agent for this silver salt is exposed image-wise and then heated to a temperature, at which the reducing agent reduces the silver compound at the exposed areas to form a visible silver image. In this process use is made of a photographic material comprising a layer, which contains a substantially non-light-sensitive silver compound, a reducing agent, and a polymethine sensitizing agent for the spectral sensitization of the non-light-sensitive silver compound. According to the examples of said Belgian Patent the recording layer(s) contain(s) as sole silver compound non-light-sensitive silver compounds.

In these processes only yellow to light-brown silver images of low contrast are obtained, unless suitable measures have been taken. A better contrast can be obtained with increasing amounts of reducing agent in the materials used. However, this measure has the following drawbacks:

The amount of the reducing agent present in the light-sensitive material has to be restricted to a minimum to avoid any undesired darkening of the coating solution or of the layer, i.e., to avoid the reduction of the organic silver salts during the manufacture and storage of the material. Therefore, weak reducing agents of the type of the o-alkyl-substituted phenols as described, e.g. in the published German Patent Application No. 1,908,761 filed Feb. 18, 1969 by Minnesota Mining & manufacturing Co. are added.

It is known to add so-called toning agents shifting the image tone to brown and black to the light-sensitive layers in order to obtain images having a sufficient optical density and a sufficient contrast in the finished copy. Such a compound is, e.g. 2H-phthalazinone(1). This toning agent, when combined with various silver salts and reducing agents causes a darkening of the coating solution or of the materials obtained, so that it has but a limited utility.

It is the object of the present invention to provide toning agents for the photographic processes described above, which toning agents shift the image tone of the silver image to black without impairing the stability of the material as a result of darkening during the manufacture or the storage of this material.

There has been found now a photographic material for the production of photographic copies in a dry manner with a light-sensitive layer containing a substantially non-light-sensitive reducible silver salt and in admixture therewith a light-sensitive heavy metal compound and/or a polymethine sensitizing agent for the spectral sensitization of the non-light-sensitive silver compound, as well as a reducing agent and a phthalazinone compound corresponding to the following general formula: ##SPC2##

wherein:

R represents

1. an aliphatic group including a cycloaliphatic group and such groups in substituted form, e.g. an alkyl group having a straight carbon chain or branched chain structure including a substituted alkyl group, e.g. an alkoxy-substituted alkyl group, an alkoxycarbonyl-substituted alkyl group e.g. a carbethoxymethyl group, preferably a C ₁ --C ₁₈ alkyl group, e.g. methyl, ethyl, n-propyl, isopropyl, hexyl, dodecyl, or octadecyl, an alkenyl group including a substituted alkenyl group, e.g. an allyl group, a cycloalkyl group including a substituted cycloalkyl group, e.g. a cyclopentyl, cyclohexyl, or methylcyclohexyl group, an aralkyl group including a substituted aralkyl group, e.g. a benzyl group or phenethyl group,

2. an aryl group including a substituted aryl group, e.g. a phenyl group, a naphthyl group, or a biphenyl group including these groups in substituted form, e.g. a halogen-substituted phenyl group, e.g. 4-chlorophenyl and 3,4-chlorophenyl, alkyl-substituted phenyl, e.g. a tolyl group, alkoxy-substituted phenyl, in which the alkyl group in the alkoxy group is, e.g. a C ₁ --C ₁₈ alkyl group, a carboxy-substituted phenyl group, an esterified carboxy-substituted phenyl group, e.g. a methoxycarbonyl-substituted phenyl group, a cyano-substituted phenyl group, or a fluorosulfonyl-substituted phenyl group,

3. a heterocyclic group including a substituted heterocyclic group,

4. an acyl group, e.g. an aliphatic or aromatic acyl group derived from a carboxylic or sulphonic acid, e.g. acetyl, methylsulphonyl, benzoyl, or phenylsulphonyl.

Suitable examples of such compounds are the following: ##SPC3##

For example, compounds corresponding to the above general formula and containing 2-phthalazinone nuclei, which in the 2-position are linked by a --CO--NH--X--NH--CO-- group, can be used, X being a bivalent organic group, e.g. alkylene or arylene. The phthalazinone derivatives of the above general formula are prepared according to known methods, e.g. by reaction of phthalazinone with an isocyanate. The preparation of the compounds 1 and 2 is described hereinafter. Other phthalazinones that can be used according to the invention are prepared in an analogous way.

Preparation of compound 1

A mixture of 146 g (1 mole) of phthalazinone and 138 g (1.1 mole) of phenylisocyanate in 1 l of dry benzene are boiled 4 hours with stirring. The resulting solution is then cooled and the precipitate formed is filtered with suction. The precipitate is then washed with dry diethyl ether.

Yield: 93 percent.

Melting point: 154°-156° C (decomposition).

Preparation of compound 2

Within 15 minutes 147 g (1 mole) of benzoylisocyanate are added to 147 g(1 mole) of phthalazinone dissolved in 2 litres of boiling dry toluene. The reaction product precipitates in the boiling solution. This reaction mixture is kept boiling for 1 hour with stirring. Subsequently, the mixture is cooled, whereupon the resulting precipitate is filtered with suction and washed with toluene.

Yield: 85 percent.

Melting point: 179° C.

The photographic materials of the invention containing a phthalazinone derivative are used in the above described processes for the production of copies in a dry manner.

As a result of the addition of phthalazinone-derivatives the image tone of the silver images is shifted as desired from yellowish-brownish to black and blue-black. The stability of the coating solution for these layers and the stability of the layers themselves is not impaired by the addition of these toning agents. The coating solutions and the layers themselves do not turn brown. Moreover, the photographic properties such as the developability are stabilized surprisingly thereby as compared with the properties of materials comprising no such toning agent. This surprising advantage is observed especially in unfavourable conditions such as increased temperature and relative humidity, i.e., in tropical conditions.

In the first process use is made of a photographic material having a layer that contains a non-light-sensitive silver salt and usually small amounts of a light-sensitive heavy metal salt, more particularly a silver salt, as well as a reducing agent for the reduction of the silver salt at the exposed areas.

In the second process use is made of a photographic material having a layer that contains a silver compound, which in the conditions of the process of the invention is substantially non-light-sensitive as well as a reducing agent and usually a small amount of polymethine sensitizing agent for the spectral sensitization of the non-light-sensitive silver salt. Usually the sensitizing agents are dissolved in organic solvents and added to the solutions ready for coating. They may also be added in solid form to the silver salt before the grinding or a short time before the application of the coating solution to the support. The concentration of the sensitizing agent in the layer may vary within wide limites. It depends on the desired effect and on the nature of the sensitizing agent used in combination with the silver salt. In general, concentrations of 0.1 to 2 g of sensitizing dye, preferably of 0.2 to 0.6 per mole of silver salt, appeared to be sufficient. In certain cases amounts of sensitizing agents beneath or beyond this range may be added.

The toning agents of the invention are added preferably to the light-sensitive layer. However, they may be added partially to an adjacent layer.

Varying amounts of the compounds used according to the invention can be added to the layers. The optimum amount depends on the desired effect and on the composition of the layer. It can easily be established by the average technician skilled in the art by making some tests. In general, additions of 0.5 to 6 mole, preferably of 1 to 4 mole of the phthalazinone derivative per mole of non-light-sensitive silver compound, preferably an organic silver salt, appeared to be sufficient.

The phthalazinone derivatives used according to the invention can also be used in combination with known toning agents. The concentration of the additional toning agents is preferably lower than that of the toning agents used according to the invention. Suitable additional toning agents are, e.g. the unsubstituted phthalazinone, phthalimide, and phthalimide derivatives.

The toning agents of the invention can be used in combination with substances and compounds known for the heat transfer process and for the light-sensitive copying material. Such substances and compounds are, e.g. reducing agents, binders, silver salts, and other heavy metal salts, white pigments, and stabilizing agents. Such materials are generally known and they have been described e.g. in the published German Patent Application Nos. 1,300,014 filed Apr. 23, 1964 by Minnesota Mining & Manufacturing Co., 1,547,878 filed June 6, 1967 by Fuji Co., 1,572,203 filed Apr. 23, 1965 by Minnesota Mining & Manufacturing Co. and 1,908,761 filed Feb. 18, 1969 by Minnesota Mining & Manufacturing Co.

Organic reducing agents known for these processes comprise an active hydrogen atom linked to an oxygen, nitrogen or carbon atom, e.g. o-alkyl-substituted phenol derivatives, di- and trihydroxyaryl-derivatives, aminophenol derivatives, aminonaphthol derivatives, p-phenylenediamine derivatives, and hydroxylamine derivatives, alkoxy-naphthols and derivattives of acetoacetonitrile, pyrazolidin-3-one, pyrazolidin-5-one, indanedione-1,3, ascorbic acid and hydroxychroman or hydrocumaran. Preferred examples are e.g. o-alkyl-substituted phenols, hydroquinone, aminophenol derivatives, and methoxy-naphthol derivatives.

According to an embodiment of the material according to the invention wherein light-sensitive heavy metal salts, more particularly silver salts, are present as light-sensitive compounds, the layers can be sensitized optically by the addition of dyes. Suitable sensitizing agents are preferably compounds, which are used customarily for the optical sensitization of conventional silver halide emulsion layers, e.g. cyanine dyes, merocyanine, oxonols, or rhodacyanides, of varying types as described e.g. in "The Cyanine Dyes and Related Compounds" (1964) of F. M. Hamer.

For the manufacture of the materials according to the invention the components for the redox reaction and the light-sensitive heavy metal are used together with an appropriate binder. Suitable binders are the usual natural or synthetic film-forming polymers e.g. proteins, e.g. gelatin, cellulose derivatives, such as cellulose ethers, cellulose esters or carboxymethylcellulose, alginic acid and derivatives thereof, starch ether or gallactomannan. Preferred binders are the organic polymers such as copolymers of vinyl chloride and vinyl acetate, or of butadiene and styrene, polyethylene, polyamide, polyisobutylene, polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, or wholly or partially saponified polyvinyl acetate, polyvinyl-idene chloride, polyvinylpyrrolidone, polystyrene, chlorinated rubber, polyvinyl butyral, polymers of acrylates or methacrylates, acrylamide, or copolymers of the derivatives of acrylic acid and methacrylic acid, cellulose derivatives such as cellulose nitrate, cellulose acetate, cellulose propionate, or mixtures thereof, such as cellulose acetobutyrate, etc.

The light-sensitive layer can be used in the form of a self-supporting layer though it is preferably applied to an appropriate support. The support has to be stable at processing temperatures between 60° and 200° C. Suitable supports are, e.g. sheets or foils of paper, cellulose acetate, polyethylene terephthalate, fabric, metal foils, and glass. In the case of paper supports the paper may carry the usual auxiliary layers such as baryta coatings, polyethylene coatings, etc.

Preferably used silver compounds are substantially non-light-sensitive in the conditions of the process of the invention. Such silver compounds are, e.g. the silver salts of aliphatic carboxylic acids with a thioether group or silver salts of long chain fatty acids such as silver behenate, silver palmitate, silver stearate, etc., described in the U.K. Pat. No. 1,111,492 filed Aug. 13, 1965 by Agfa AG.

Light-sensitive heavy metal salts suited for the first process and forming metal nuclei upon exposure, which metal nuclei are capable of initiating the image-forming redox reaction, are e.g. inorganic or organic salts of silver, mercury, or gold. Heavy metals of group Ib of the periodic table of the elements, more particularly silver salts and especially silver halides are preferred.

The light-sensitive heavy metal salt that is best for the redox system used can be found by making some simple tests. E.g. the metal salt in the form of an aqueous suspension can be mixed with the components of the redox reaction: no change at all must occur in the dark. When this mixture is exposed to ultraviolet radiation, it should change colour rather quickly. If a particular heavy metal salt behaves in this way, it is suited for the redox system.

Relatively small amounts of approximately 0.05 to 0.2 percent by weight of light-sensitive heavy metal salt calculated on the amount of the oxidizing agent are used. This concentration of light-sensitive salt suffices for most systems. Accidentally lower or high amounts can be used, of course.

The light-sensitive heavy metal salt, e.g. the silver halide should be used in such small amounts that the photolytically formed heavy metal nuclei can initiate the redox reaction. The concentration of the silver halide should, however, be so low that the metal nuclei formed do not colour the copying material or do so in a neglegible way only.

Some of the silver salts that are non-light-sensitive by nature and can be used according to the invention, show a certain inherent sensitivity, however low it may be, when precipitated in the presence of a protective colloid such as proteins, e.g. gelatin, as is generally done for the preparation of conventional gelatin silver halide emulsions. The precipitation of the silver salts for the manufacture of the material according to the invention should thus be performed in such a way that the silver salts formed are non-light-sensitive. Usually the silver salts are non-light-sensitive when they are formed by precipitation in the absence of a protective colloid.

The dried silver salts are then incorporated in the solutions or dispersions of the desired binding agent. The concentration of the silver salt in the binder solutions or dispersions may vary within wide limits depending on the desired silver content of the photographic layers. In general, amounts of 0.1 to 0.01 mole of silver salt per kg of coating solution, will do. Preferably amounts of 0.02 to 0.04 mole of silver salt are used per kg of solution or dispersion. The same applies to the silver content of the finished photographic layer. The concentration therof also varies within wide limits depending on the desired effect and the intended use. Usually the coating ratio will be of 0.1 to 1 g of silver in the form of the silver salt per sq.m., preferably of 0.3 to 0.6 g per sq.m. It is obvious that also mixtures of different non-light-sensitive silver compounds can be used in the material used according to the invention.

In order to improve the photographic properties of the material according to the invention other non-light-sensitive heavy metal compounds can be added to the material, preferably to the layer containing the non-light-sensitive silver salt. In this way, e.g. a lowering of the fog, an increase of the density, or a shift of the image tone to desired colour tones, e.g. to neutral black, can be attained.

Suitable heavy metal compounds are, e.g. salts or compounds of mercury, cadmium, lead, uranium, gold, platinum, palladium, or rhodium. The heavy metal compounds can be added already during the precipitation of the silver salt. Preferably solutions of the heavy metal salts and of the silver salts are added to the precipitation component in question according to the double jet method and precipitated at the same time. Although the simultaneous precipitation of the silver salt and the heavy metal salt is of particular advantage and gives rise to especially favourable effects depending on the nature of the heavy metal salt, these heavy metal salts, can, however, be added also in solid or dissolved form to the coating solutions for the photographic layer, which already contain the silver salt. The heavy metal salts can also be mixed with the dried silver salts by grinding or they can be added prior to the coating of the coating solution for the photographic layer. Obviously, combinations of different heavy metal salts can be used likewise. The added amount of the heavy metal salts or heavy metal compounds may vary within wide limits.

The concentration depends upon the nature of the heavy metal salt and the silver salt as well as on the desired effect. The optimum amount can be established easily by the average technician skilled in the art by making some tests. In the case of simultaneous precipitation, the heavy metal salts show a higher activity. In order to obtain the desired effect concentrations of 0.001 to 10 mole percent or preferably of 0.01 to 5 mole percent will do mostly. When the heavy metal salts are added during a subsequent step of the manufacture of the photographic material but prior to the coating, concentrations of 0.001 to 0.2, preferably of 0.005 to 0.07 mole of heavy metal salt, e.g. mercury(II)-acetate per mole of silver salt suffice.

These layers may comprise white pigments such as zinc oxide, silica, or titanium dioxide as filling agents for the improvement of the whiteness of the image background and for influencing the stickiness of the layers. Further terpene resins and organic acids can be added to the layers for improving the keeping properties. Such layers have been described in the U.S. Pat. Nos. 3,074,809 of Richard Owen, issued Jan. 22, 1963, and 3,107,174 of Thomas G. Wartman, issued Oct. 15, 1963.

For the exposure of the light-sensitive layers according to the invention the light sources known in the reproduction technique can be used, e.g. halogen lamps, iodine-quartz lamps, and incandescent lamps. The type of light source used depends on the spectral sensitivity of the heavy metal salt or sensitizing dye used. The exposure lasts a few seconds.

The development of the light-sensitive copying materials containing a silver salt is performed at temperatures between 80° and 200° C. The heating can be carried out, e.g. by conducting the exposed light-sensitive layer over heated plates or rollers or by exposing the layer to ultraviolet radiation. In order to spare the layer and to obtain an image with high gloss the light-sensitive material containing a silver salt can be heat-developed in contact with a foil, e.g. a polyester foil. The optimum temperature and heating period depend, of course, on the composition of the light-sensitive material containing the silver salt. They can be established by some simple tests.

EXAMPLE 1

Light-sensitive material:

A mixture of the following ingredients was ground for several hours: silver behenate-behenic acid (molar proportion 1:1) 1.8 g toning agent in the amount given in the table hereinafter mercury(II)-acetate 50 mg celluloseacetobutyrate 1.5 g copolymer of vinyl chloride and vinyl acetate (weight proportion 60:40) 0.75 g methyl ethyl ketone 26 g

Prior to the coating 0.5 mg of the sensitizing agent 5-[(3-ethylthiazolidin-2-ylidine)-ethylidene]-3-allyl-2-thio -oxazolidin-2, 4-dione dissolved in 0.5 ml of methyl ethyl ketone, and 1 g of bis-(2-hydroxy-3-tert.butyl-5-methylphenyl)-methane were added to this suspension with stirring.

The coating solution was applied to a paper support and dried. 0.5 to 0.6 g of silver in the form of the silver compound was present per sq.m.

Processing:

The light-sensitive material was exposed through a transparent original by means of tungsten lamps for 3 to 30 sec. depending on the intensity and the desired gradation. Subsequently, the material was heat-developed. Depending on the temperature used (60° to 160° C) and on the equipment used the development time varied from 3 to 80 sec. The development equipment includes heatable presses, drying drums, rollers, the contrivances described in the Belgian Pat. No. 628,174 filed Feb. 8, 1963 by Agfa AG or the French Pat. Nos. 1,419,101 filed Dec. 4, 1964; 1,416,752 filed Dec. 2, 1964; and 1,512,332 filed Sept. 18, 1964 all by Agfa AG as well as commercial devices.

Whereas in the absence of toning agents only yellow image silver of poor density was obtained, black images having a favourable density were obtained in the presence of the following toning agents. In order to spare the layer and to produce an image showing a high gloss the side of the material showing the layer could be heat-developed in contact with a polyester foil.

For comparison of the stability of the materials according to the invention with materials comprising the known toning agents, e.g. the unsubstituted phthalazinone, test strips of the material containing the toning agent to be tested were examined in the following way. The unexposed strips were developed for 20 sec. at increasing temperature with rising intervals of 5° C. Subsequently, the temperature was established, at which the unexposed material showed a development to a fog value of 0.15-0.2. The higher this temperature, the more stable was the light-sensitive layer. The results of these tests are represented in the following table.

Table ______________________________________ g per Toning agent Image tone Fogging develop- preparation ment temperature ______________________________________ 1.9 1 black 110° C 1.9 2 black 100° C 2.2 3 black 110° C 2 4 black 105° C 2.5 5 black 105° C 1 comparison black 85° C compound ______________________________________

The light-sensitive material comprising the toning agents according to the invention was more stable in consequence of the fogging temperature being 15° to 25° C higher than that of the material containing phthalazinone. The material comprising the toning agents according to the invention also had a greater processing latitude. An amount of 0.1 to 0.2 g of phthalazinone could be added to the layers for the purpose of accelerating the development without any adverse effect on the stability.

EXAMPLE 2

A baryta-coated paper support was covered with the following layers:

1. Light-sensitive layer having the following composition: silver behenate/behenic acid (molar proportion 1:1) 1.8 g cellulose acetate 3.0 g 1 % calcium bromide solution in methanol 4.5 ml 1 % solution of mercury(II) acetate in methanol, acidified with glacial acetic acid 5.7 ml a 0.01 % solution of 1-methyl-3-allyl-5- [2(3-ethylbenzoxazolylidene-(2)ethylidene] 2-thiohydantoin in chloroform 3.0 ml silica 0.15 g acetone 55.0 g 1.0 g of a copolymer of vinyl chloride and vinyl acetate (weight proportion 88:12) dissolved in 20 g of acetic butyl ester, 3 g of compound 1, and 0.2 g of phthalazinone

2. Covering layer having the following composition:

polyvinylbutyral 10.0 g hydroquinone 4 g methanol 100 ml compound 1 1.5 g

The coating solution for the light-sensitive layer was ground for 16 h in a ball-mill prior to the coating. The light-sensitive layer comprised 0.7 to 0.9 g of silver in the form of the silver salt per sq.m.

The dried light-sensitive layer was coated with the covering layer. The concentration of the reducing agent in the covering layer varied from 0.5 to 1.5 g per sq.m. The exposed material was then heat-developed as described in example 1 so that a black image was obtained.

EXAMPLE 3

Light-sensitive material:

An equimolar mixture of silver behenate and behenic acid was prepared by precipitation of silver nitrate with a solution of sodium behenate and behenic acid in alcohol and water. The precipitate was washed carefully and dried.

The suspension for the layer was prepared by grinding the following ingredients for 12 h in a ball-mill:

methanol 240 ml a 10 % solution of polyvinylbutyral in methanol 125 ml a 10 % solution of poly-N-vinylpyrro- lidone in methanol 20 ml equimolar mixture of silver behenate and behenic acid 30 g a 1 % solution of ammonium bromide in methanol 10 ml toning agent nr. 3 1.5 g 1-phenyl-3-methylpyrazolon-(5) 15 g

The suspension was applied to a common paper support at a ratio of 100 g per sq.m and dried at room temperature.

Processing:

The light-sensitive layer was exposed through a transparent original by means of an ultraviolet lamp of 750 watt placed at a distance of 5 cm. The exposure time was 2 sec. Subsequently, the layer was heated for 5 sec. to 120° C. A black negative image was obtained from the original.