US3721559A

US3721559A - Photographic material for the preparation of printing plates

Info

Publication number: US3721559A
Application number: US00174140A
Authority: US
Inventors: Haes L De; H Gevers; J Vanheertum
Original assignee: Agfa Gevaert NV
Current assignee: Agfa Gevaert NV
Priority date: 1967-06-19
Filing date: 1971-08-23
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20
Also published as: FR1582133A; CH518577A; DE1771627A1; DE1772677C3; NL161591B; NL161591C; BE716778A; CH517324A; SE359938B; DE1772677B2; DE1772677A1; AT294135B; NL6808599A; FR1583235A; GB1241661A

Abstract

A planographic printing plate is prepared from a photographic sheet material comprising a support, a light-sensitive silver halide emulsion layer and an exterior hydrophilic colloid stratum having at its free surface a pattern of finely divided silver particles, by contacting the same with an aqueous alkaline fixer composition containing an oxidizing agent for metallic silver and an organic thione, or mercapto tautomer thereof, for converting the pattern of silver particles into a hydrophobic ink-receptive pattern, the colloid stratum being hardened before the material is used for printing and preferably before or at least concurrently with its contact with said fixer composition, the extent of the hardening being at least that necessary to prevent removal of the colloid material during printing. The pattern of silver particles is produced by means of the silver complex diffusion transfer process in which insoluble development nuclei are applied to the free layer surface either from the diffusion transfer developing liquid or a separate liquid applied prior to the developing liquid. Preferably the colloid stratum is hardened by means of a latent hardener released during the course of the diffusion transfer process. The colloid stratum can be an external stratum of the emulsion layer or a separate colloid layer applied to the emulsion layer.

Description

United States Patent De Haes et al.

1 1] 3,721,559 1March 20,1973

PREPARATION OF PRINTING PLATES [75] Inventors: Louis Maria De Haes; Hugo Karel Gevers, both of Edegern; Johannes Josephus Vanheertum, l-lalle-Zandhoven, all of Belgium I [73] Assignee: Ag fa Gevaert N.V., M0rtsel, Belgi- [22] Filed: Aug. 23, 1971 [21] Appl.No.: 174,140

. Related [1.8. Application Data [63] Continuation of Ser. No. 738,097, June 19, 1968,

abandoned.

[30] l I Foreign Application Priority Data June 19, 1967 Great Britain..'. ..28,237/67 April 26, 1968 Great Britain ..l9,887/68 [52] U,S.'Cl. ..,....96/33, 96/29, 96/48, 97/76 51] Int. Cl .....G03f 7/02 [58] Field of Search ..96/33, 29, 48, 76

[56] References Cited UNITED STATES PATENTS 3,490,905 7/l970 Blake "96/33 3,083,097 3/1963 Lassig et al ..96/ 29 2,725,298 11/1955 Yutzyetalm, .....96/ 76 2,843,485 7/1958 Yutzy et al. ..96/29 PHOTOGRAPHIC MATERIAL FOR THE.

Primary Examiner-J. Travis Brown Assistant Examiner-Edward C. Kimlin Attorney-William J. Daniel [57] ABSTRACT A planographic printing plate is prepared from a photographic sheet material comprising a support, a light-sensitive silver halide emulsion layer and an exterior hydrophilic colloid stratum having at its free surface a pattern of finely divided silver particles, by contacting the same with an aqueous alkaline fixer composition containing an oxidizing agent for metallic silver and an organic thione, or mercapto tautomer thereof, for converting the pattern of silver particles into a hydrophobic ink-receptive pattern, the colloid stratum being hardened beforethe material is used for printing and preferably before or at least concurrently with its contact with said fixer composition, the extent of the hardening being at least that necessary to prevent removal of the colloid material during print ing. The pattern of silver particles is produced by means of the silver complex diffusion transfer process in which insoluble development nuclei are applied to the free layer surface either from the diffusion transfer developing liquid or a separate liquid applied prior to the developing liquid. Preferably the colloid stratum is hardened by means of a latent hardener released during the course of the diffusion transfer process. The

'colloid stratum can be an external stratum of the emulsion layer or a separate colloid layer applied to the emulsion layer.

12 Claims, No Drawings PI-IOTOGRAPIIIC MATERIAL FOR THE PREPARATION OF PRINTING PLATES This application is a continuation of Ser. No.

738,097, filed 6/19/68, and now abandoned.

.stances for promoting the silver deposition from the diffusing complexed silver halide, further on called development nuclei, at the surface of the material, the development nuclei being present either on top of the said emulsion layer or on top of a hardenable hydrophilic colloid layer applied to said emulsion layer.

The diffusion transfer silver image produced in the photographic material according to the present invention is substantially situated at the surface of the material. According to a preferred embodiment of this invention a planographic printing plate can be prepared very simply from the diffusion transfer copy obtained by one single treatment as will be described detailedly hereinafter.

The support sheet of the photographic material according to the invention maybe any usual flexible support sheet, e.g., a paper sheet or a transparent hydrophobic usual film support such as a support of cellulose triacetate or of a polyester, e.g., polyethylene terephthalate.

Any silver halide emulsion of the negative or direct positive type preferably a gelatin silver halide emulsion, may be used dependent on the nature of the original to be reproduced. Preferably, however, emulsions of the negative type having a rather high sensibitiy of the order as normally required for camera exposure are used. As a matter of fact, although the exposure of the silver halide emulsion layer can be carried out according to any usual technique, e.g., in contact, reflectographically, by transmission or episco'pically, mostly an episcopic exposure in a camera is carried out. The silver halide emulsion layer preferably has a sensitivity of the order as normally required for camera exposure. The silver halide emulsion layer generally comprises an amount of silver halide equivalent to from about 0.5 g to about 1.5 g of silver nitrate and preferably amounting only to the equivalent of about 1 g of silver nitrate. This means a considerable economy of silver halide with respect to the silver halide content of emulsion layers commonly used in the production of diffusion transfer copies. If necessary a suitable subbing layer is provided for strongly adhering the silverhalide emulsion layer to the support sheet.

The development nuclei may be provided directly on top of the silver halide emulsion layer. In that case it should be a hardenable one and preferably a gelatin silver halide emulsion layer. Preferably, however, one and sometimes even more other water-permeable layer(s) is (are) applied on top of the silver halide emulsion layer, the outer layer always being a hardenable hydrophilic colloid layer preferably a gelatin layer, on which the development nuclei have to be present.

According to a preferred embodiment the development nuclei are applied on top of the photographic material at the preparation stage by means of a specific after-treatment of the material with a liquid composition containing such nuclei. In order to keep the development nuclei in dispersion a minor amount of a hydrophilic protective colloid, e.g., gelatin, may be added to the dispersion. This amount of colloid does not suffice to form a layer and in most cases .is hardened at the hardening stage'of the hydrophilic colloid layer or by diffusion of hardener from said layer.

The development nuclei may also be supplied by a specific processing liquid with which the photographic material is wetted after the image-wise exposure and before the alkaline processing liquid for carrying out the diffusion transfer image formation is applied, or they may be incorporated into the said alkaline processing liquid itself.

Suitable development nuclei for being applied to the photographic material according to the present invention are sulphides of heavy metals such as the sulphides, of antimony, bismuth, cadmium, cobalt, lead, nickel, silver and zinc. Other suitable salts are the selenides, polysulphides, polyselenides, mercaptans and tin(ll)halides. Heavy metals or their salts and fogged silver halides are suitabletoo. The complexed salts of lead and zinc sulphides are active alone as wellas mixed with thioacetamide, dithiobiuret, and dithiooxamide. Heavy metals, preferably silver, gold, platina, palladium, and mercury may be used in their colloidal form. From these metals the noble metals are the most active ones. Thedevelopment nuclei may be applied on top of the photographic material at the preparation stage or they may be incorporated into a processing liquid in the usual concentrations as generally known in the art. a I

For the preparation of the hydrophilic colloid outer layer any hardenable hydrophilic colloid is suitable. Although gelatin is favored, as already mentioned above, other hardenable hydrophilic colloids such as polyvinyl alcohol, casein, carboxymethylcellulose and sodium alginate can be used too. If gelatin is used for forming the hydrophilic colloid outer layer, it may be submitted to a treatment as described in the United Kingdom Pat. specification No. 883,843 filed Sept. 2,

' 1959 by Agfa AG in order to improve the printing characteristics of the planographic printing plate.

The outer hydrophilic colloid layer, i.e., the silver halide emulsion layer or an outer layer on top thereof, has to be hardened at the printing stage.

Hardening of the hydrophilic colloid binder of the outer layer may occur before, during or after the treatment of the diffusion transfer copy produced with the fixer composition for preparing the planographic printing plate and must occur at least to such an extent that no substantial amount of colloid is transferred on printing neither to the rollers for applying water and ink to the printing plate nor to the material to be printed. In other words hardening, i.e., insolubilizing in water and strengthening against mechanical damage must occur at least to such an extent that the material obtained can be used as a planographic printing plate. This explanation in our opinion will suffice for one skilled in the art.

The said hardening mostly occurs before the said treatment with fixer. In that case the said hardening may occur by addition of the generally known hardening agents for gelatin and similar colloids such as fordevelopment nuclei in dispersion is applied on top of the said outer layer the hardeners can also be incorporated-into said coating composition. Hardening of the hydrophilic colloid binder of the outer layer may also occur during the production of the diffusion transfer silver pattern by incorporating hardeners into at least one of the processing liquids and/or by incorporating latent hardeners into the photographic materi-- al to be hardened. These latent hardeners are active only in a well defined pH-range, mostly the pH-range of the usual alkaline processing liquid for carrying out the diffusion transfer image formation. For more details on the useof latent hardeners in photographic material there can be referred to United Kingdom Pat. specification No. 962,483 filed Jan. 1, 1962 by Agfa AG and German Pat. specification No. 1,203,604 filed Jan. 15, 1964 by Agfa AG. Finally hardening of the outer hydrophilic colloid layer may also occur after the production of the silver pattern, viz. by treatment with a hardening liquid. This liquid may be an aqueous hardening composition applied before the treatment with the fixer, the fixer composition itself or an aqueous hardening composition applied after the treatment with the fixer.

' The exposure latitude of the photographic material according to the present invention in most cases can be prolonged considerably. Also the image sharpness of the silver pattern can be increased and, as a consequence thereof, the sharpness of the final result of printing can be improved by applying antihalation dyes or pigments. These dyes or. pigments may be present in the .silver halide emulsion layer or in the support, but preferably are incorporated into a layer situated between the silver halide emulsion layerand the support. If a transparent support is used the antihalation dyes or pigments may be applied to the rear side of the material or on top of the emulsion layer dependent on the manner inwhich the exposure is carried out, viz. atv

the front side or through the support. Preferably a red or black antihalation dye or pigment is used. If the antihalation layer is gray the correctness of the exposure can easily be controlled 1 by judging the diffusion transfer image in transmittance before carrying out the fixing step.

The photographlcmaterial according to the present invention may comprise at least partof the compounds that are essential or useful for carrying out the diffusion transfer image formation such as developing. agents, preservatives for these developing agents, complexing agents, stabilizers, alkaline substances, black-toning agents, hardeners and softening agents in the materials used, whereby the aqueous processing liquid can be reduced to an aqueous solution of alkaline substances described in the United Kingdom Pat. specification No. 1,013,343 filed Dec. 29, 1961 by Gevaert Photo Producten N.V.. For silver complex diffusion transfer processes in which the developing agents and preservatives for these developing agents are incorporated into the light-sensitive and/or image-receiving material, there can be referred to United Kingdom Pat. specifications Nos. 1,000,115 filed Aug. 4, 1961, 1,012,476 filed Dec. 18, 1961, 1,042,477 filed June 17, 1963, 1,054,253 filed Aug. 6, 1963, 1,057,273 filed Feb. 3,

1964 and 1,093,177 filed Dec. 16, 1964 all by Gevaert Photo-Producten N.V. I

It is a preferred embodiment of the present invention to incorporate at least part and preferably even the total amount of developing agent(s), mostly hydroquinone and a 3-pyrazolidinone developing compound used together, into the photographic material whereby the developing liquid becomes reduced to an aqueous alkaline liquid that is substantially free from developing agent(s) and consequently shows excellent keeping qualities.

The presence of certain hydrophilic colloid binders,

e.g., carboxymethylcellulose, gum arabic, sodium alginate, propylene glycol ester of alginic acid, hydroxyethyl starch, dextrine, hydroxyethylcellulose, polyvinylpyrrolidone, polystyrene sulphonic acid and polyvinyl alcohol in the outer hydrophilic colloid layer of the photographic material often improves the hydrophilic, ink-repellent properties of the non-printing areas of the printing plate finally obtained. Also hygroscopic substances, likewise called hydrophilic softening agents, e.g. sorbitol, glycerol,trihydroxyethyl ether of glycerol and turkish red oil, and certain wetting agents,

i.e., those mentioned hereinafter incorporated in atleast one hydrophilic colloid layer will improve the hydrophilic properties of the non-printing areas.

The hydrophilic colloid outer layer also may advantageously comprise a considerable amount of pigment particles that will prevent the so-called scumming (i.e., ink-acceptance that arises in the non-printing areas of the printing plate after a certain number of copies has been printed). The usual inorganic pigments, e.g., barium sulphate, titanium dioxide, china clay and silica applied from a colloidal solution, have proved to be particularly suitable for this purpose. The pigment particles are generally homogeneously applied in such an amount that about 5-20 g thereof are present per sq.m. of the hydrophilic colloid outer layer. A similar anti-scumming effect may also be obtained by addingat least one mern'ber selected of colloidal silica, an inorganic acid, e.g., o-phosphoric acid, a hydrophilic softening agentas those mentioned above and a suitable wetting agent to the fountain solution used during the printing process. Suitable wetting agents are,

;-(C :)1 r- )s 'sodium dodecylsulphatesodium tetradecylsulphatev R--CH, SO,Na wherein R represents an alkyl group comprising from 14 to 18 carbon atoms R hexadecyl 90 percent octadecyl 6 percent octadecenyl 4 percent A very suitable fountain solution comprises water, glycerol, o-phosphoric acid and colloidal silica. v

For the production of the diffusion transfer silver image on top of the photographic material according to the present invention, the material is first image-wise exposed to an original. This may occur according to any usual technique as detailedly described above. The material is then treated with an aqueous alkaline processing liquid for carrying out the diffusion transfer image formation in the presence of a developing agent, a complexing agent for silver halide and development nuclei on top of the outer hardenable hydrophilic colloid layer. The said aqueous alkaline processing liquid may be applied in different ways, e.g., by spraying, by rubbing, with a lick roller, or by dipping the photographic material in the liquid composition. In order to obtain a diffusion transfer silver deposition that will be sufficiently dense, the photographic material has to be kept for a short while, e.g., for about 10 seconds, in the dark afterit has been wetted with the alkaline processing liquid for carrying out the diffusion transfer image formation. The application of the fixer composition may already take place during the period the multilayermaterial is kept in the dark. However, this application of fixer may also occur thereafter.

For the production of the diffusion transfer silver image the photographic material comprising development nuclei on top of the silver halide emulsion layermay be provided in roller form. After image-wise exposure, e.g., an episcopic exposure in a camera or an exposure through a transparent original in contact with the photographic material, the latter may be guided automatically through a usual processing unit containing the alkaline processing liquid and comprising guiding and driving means as generally known in the art. In order to overcome processing irregularities during the cutting stage of the multilayer material, an empty tray with loose roller, which is lifted by the material during cutting, may be provided between the exposure unit and the processing unit.

The production of a planographic printing plate from the photographic material carrying at its surface a diffusion transfer silver pattern may occur according to any technique for producing a planographic printing plate from a sheet material having'a hardenable hydrophilic colloid outer layer carrying at its surface a pattern of silver particles. In this respect reference is made to German Pat. specifications Nos. 1,011,280 filed Apr. l8, l956, 1,058,844 filed Apr. 27, 1957, 1,064,343 filed Aug. 16, 1957, 1,128,296 filed Apr. 22,

1959 and 1,146,367 filed Apr. 22, 1959a" by Agfa AG. A specific technique especially suitable for being applied in order to convert the diffusion transfer copy produced from a photographic material according to the present invention into a planographic printing plate and according to which only one treatment (fixing) has to be carried out for making the plate ready for printing will be described in detail hereinafter.

According to this preferred technique the photographic material carrying the diffusion transfer silver image at its surface is treated with a fixer being an aqueous treating composition buffered at a pH value from 7 to 12 and to which have been added potassium cyanoferrateflll) and an organic compound that converts the pattern of silver particles in a hydrophobic ink-receptive pattern.

Potassium cyanoferrateglll) mostly is incorporated into the fixer in a concentration of from 25 to 300 g'per liter and may simply be added by dissolving it in the aqueous fixer composition. The effect of the present invention may also be obtained by using other generally known oxidizing agents for silver particles instead of potassium cyanoferrateflll) even by using such agents that only in a very minor amount produce silver ions at the surface of the silver pattern such as water-soluble cadmium, strontium or calcium salts. However, the good results obtained by using potassium cyanoferrate(III) as an oxidizing agent cannot be obtained by using other oxidizing agents. This is very unexpected since there exist many oxidizing agents having a better oxidizing power than potassium cyanoferrate(IlI).

In addition to the potassium cyanoferrate(III) an organic compound that converts the silverimage parts in hydrophobic ink-receptive parts is added to the fixer.

Examples of such organic compounds that have proved to be especially suitable for this purpose are thioxo compounds, including the tautomeric structures thereof, making the silver image ink-receptive, e.g.

- imidazoline-Z-thiones and imidazolidine-Z-thiones including the N-substit'uted derivatives such as imidazolidine-4-on-2-thiones including substituted derivatives such as phenyltetrazoline-thiones including derivatives such as tetrahydro pyrimidine-Z-thiones including substituted derivatives such as tetrahydroand -dihydro-oxazine-2 -thiones and thiazine-Z-thiones including substituted derivatives such as l,3,4-dihydro thiadiazine-Z-thiones including sub- ,7

stituted derivatives such as thiourea compounds including substituted derivatives preferably N-phenyl thiourea compounds such (ll) CH: S

(12)}. Nos

substituted The compounds that convert the silver image parts in hydrophobic ink-receptive parts may be added directly to the fixer, but are often added from an aqueous alkaline solution or from a solution in a suitable organic, water-miscible solvent such as ethanol, isopropanol,

ethylene glycolmonomethyl ether and dimethylformamide. They must be at leastpartially soluble in the fixer composition. They are mostly applied in an' amount of from 0.5to 5 g per liter of fixer. it is remarkable that most of the suitable compounds for converting the silver image parts in ink-receptive parts are black-toning agents generally known in the silver complex diffusion transfer process. A

An explanation of the reaction mechanism according to which the silver image parts are converted into hydrophobic ink-receptive parts cannot be given with certainty. Indeed, it might be a chemical transformation that takes place or more likely a physical adsorption to the silver image parts. In any event the fact remains that at least a superficial oxidation of the silver pattern is necessary. With certain thioxo compounds it is possible that oxidation products of these compounds are present in the fixer and it is not beyond possibility that precisely these oxidation products are responsible for the hydrophobising effect obtained in carrying ou the method of the invention.

The fixer composition is buffered at a pH value from 7 to 12. Very often it is buffered at a pH of about 8-9. Hereby its stability is considerably improved. Any compound or-combination of compounds having a buffering action in the indicated pl-l region is suitable.-

Sodium' hydrogen carbonate and sodium tetraborate have proved to be especially suited for this purpose as well as the following combinations of compounds sodium carbonate and sodium hydrogen carbonate, sodium carbonate and citric acid, sodium carbonate, sodium hydrogen carbonate and citric acid, boric acid and sodium tetraborate, and trisodium phosphate and oleic acid.

The compound or compounds for buffering the fixer may be applied in the usual concentrations generally known to those skilled in the art.

The fixer may comprise some further compounds'for improving the hydrophilic ink-repellent properties of the non-printing areas. Suitable such compounds are colloidal silica and hydrophilic colloid binders, hydro philic softening agents, inorganic acids and wetting agents already mentioned and exemplified above.

These compounds mostly are added to the fixer in a concentration ranging from about 5 to about 200g'per liter.

, The fixer may also contain compounds for improving the ink-receptive character of the printing areas such as higher fatty acids, e.g. oleic acid, and hydrophobic softening agents, e.g., dimethyl phthalate, dibutyl phthalate, the phthalic acid ester with the following formula The fixer composition used in carrying out the method of the present invention is very stable to aerial oxidation and to temperature fluctuations and it may be used for the production of many printing plates without having to frequently adjust the processing time. Many printing plates (about 100 plates of 21 cm X 29.7 cm size per liter of fixer) can be produced before the fixer composition is fully exhausted.

At the moment the treatment with the aqueous fixer starts, the outer colloid layer showing the silver pattern may be in dry as well as in wet condition. A superficial oxidationof the silver pattern suffices; generally, however, a more penetrating oxidation is advantageous. Generally, the treatment with the fixer does not last long, mostly no longer than about seconds and can be accelerated by increasing the concentration of the components present in the fixer. The plate may be stored for a long time before being fixed and even thereafter it may be stored for a long time before being used in the printing process. Preferably, however, the fixing step is carried out just before printing.

Just as the development or activator liquid for the production of the diffusion transfer image the fixer can be applied in different ways, e.g., by spraying, by rubbing, with a lick roller, or by dipping the material to be treated in the liquid composition.

Also the fixing step of the printing plate may occur automatically by conducting the plate through a device having a narrow channel filled with the fixer composition and at the end thereof between two squeezing rollers. In order to reduce the risk for aerial oxidation of the fixer to a minimum, funnel-shaped inand outlet openings may be provided at the ends of the narrow channel and an upperlying plastic bag containing the fixer liquid may be used. If the apparatus is not used, the bag is moved downwards and the fixer runs back from the channel into the bag.

aqueous phase are suitable too. In that case the aqueous phase may contain thickeners or other usual compounds for improving the hydrophilic character of the non-printing areas of the lithographic printing plate as described above. Suitable lacquers are described in the United Kingdom Pat. specifications No. 967,598 filed Feb. 6, 1961 by Kalle, 968,706 filed June 2, 1961 by Geva ert Photo-Producten N.V., 1,0,04,342 filed July 17, 1962 by Kalle, 1,071,163 and 1,071,164 both filed Apr. 30, 1964 by Gevaert Photo-Producten N.V. Resins that have proved to be especially suitable for improving the ink-receptive character of the printing areas and strengthening them are phenol-formaldehyde acid esters, epoxy resins e.g. condensation products of a poly aryl ethylene oxide) with an acid anhydride, an amine or another suitable compound and epoxidized polyesters.

The resin, wax or oil used mostly is present in a concentration of from about 100 to about 500 g per liter of liquid lacquer composition. The liquid lacquer composition may be applied after the aqueous composition containing. the oxidizing agent has been applied and while the printing plate is still wet. Only when an emulsion lacquer is used the plate need not necessarily to be wet at the stage the lacquer is applied. The lacquer may be applied by dipping, spraying, spreading or by means of a material soaked therewith. The lacquer is rubbed out, e.g., with a plug of wadding. The hydrophobic solid 1 substances settle on the image areas and improve the The production of the diffusion transfer silver image on top of the photographic material (occasionally including the image-wise exposure of the silver halide emulsion layer) and the treatment with the fixer may occur automatically, e.g., in processing stations as described above, and occasionally can be carried out both in a compact processing unitcomprising both processing stations.

After the application of the fixer the sheet material is ready for use as a printing plate. This means that no further treatment with a lacquer composition for strengthening the printing parts is necessary.

This is an important advantage over most of the conventional methods hitherto used for the production of a planographic printing plate that require the application of a lacquer as an essential feature.

Nevertheless, in some cases the hydrophobic character of the ink-receptive parts may still be improved and their mechanical strength may be reinforcedby applying a lacquer thereon. Suitable lacquer compositions are solutions of oils, waxes and resins in organic solvents. Suitable organic solvents are cyclohexanone, acetone, butanol, monomethyl ether of ethylene glycol, monethyl ether of diethylene glycol, tetrahydrothiophene-l,l-dioxide, diacetone, dioxane, 1,2-dichloroethane, ethyl acetate, trichloroethylene, butyl butyrate, diethanolamine and dimethylformamide. Mixtures of such organic solutions with an aqueous phase or dispersions of such organic solutions in an hydrophobic ink-receptive character thereof. At the same time the mechanical strength .of the printing areas is improved. The adherence of the lacquer to the printing areas may still be improved by heating the plate.

Instead of being applied by means of a separate aftertreatment of the printing plate, the liquid lacquer composition may also be mixed with in the aqueous composition containing potassium cyanoferrateflll') and the organic compound for converting the silver image in a hydrophobic ink-receptive pattern. The ratio of the organic phase that contains the hydrophobic solid substances to the aqueous phase then mostly is comprised between H1 and H10.

The printing plate has to be wet at the stage the fatt printing ink is applied. This is generally known in the art and it is usualto apply an aqueous liquid before applying the printing ink. This mayoccur by means of a wet sponge or by means of the fountain arrangement of the printing machine This wetting has to be more intensive as the printing plate is more dry, e.g. when it has been stored for a long time after its fixation and occasional lacquering.

The following examples illustrate the photographic material according to the present invention-and the method of preparing a planographic printing plate therewith.

EXAMPLE 1 To a paper support of g per .sq.m. a common high-sensitive, negative silver chlorobromide gelatin emulsion layer, hardened by means of formaldehyde, was applied in such a way that an amount of silver halide equivalent to 1 g of silver nitrate is'present per sq.m. After drying of the silver halide gelatin emulsion layer, said layer was overcoated at a rate of 20 g per sq.m with the following development nuclei composition water 890 ccs 12.5 aqueous saponin ccs aqueous colloidal nickel sulphide dispersion comprising per 100 ccs 0.2 g of nickel sulphide and 10 g of gelatin 7 100 ccs.

The photographic material thus obtained was exposed to an original and treated for 30 sec. in the following processing composition sodium hydroxide to g anhydrous sodium sulphite 75 g potassium bromide l g hydroquinone 16 g l-phenyl-3-pyrazolidinone 1 g water up to 1,000 ccs anhydrous sodium thiosulphate 10 g.

A diffusion transfer silver image was produced on top of the material. Y

The material was then rubbed for somev 20 seconds with a plug of wadding saturated with the following fixer composition:

10% aqueous sodium carbonate 30 ccs 5 I: aqueous sodium hydrogen carbonate 30 ccs 10 1) aqueous citric acid 20 ccs potassium cyanoferrateflll) 10.75 g 10 solution of compound (3) (l-ally) imidazolidine-Z-thione) in ethylene glycol monomethyl ether) 4 ccs distilled water up to 100 ccs water 90 ccs glycerol 10 ccs colloidal silica 2 ccs phosphoric acid 2 ccs EXAMPLE 2 To a paper support of 250 g per sq.m. a common high sensitive negative silver chlorobromide gelatin emulsion layer, hardened by means of formaldehyde and comprising hydroquinone and 1 phenyl-3- pyrazolidone, was applied in such a way that per sq.m

were present an amount of silver halide equivalent to 1 g of silver nitrate, 0.5 g of hydroquinone and 0.25 g of 1-phenyl-3-pyrazolidinone.

The light-sensitive material obtained was exposed image-wise and for 10 sec. dipped. in the following processing liquid water 1,000 ccs sodium phosphate-ll-water 75 g anhydrous sodium sulphite 40 g potassium bromide 0.5 g anhydrous sodium thiosulphate 10 g aqueous colloidal nickel sulphide dispersion of example 1 In this way, a positive diffusion transfer silver image was produced at the surface of the silver halide emul-. sion layer.

The material was then rubbed for some 15 seconds with a plug of wadding saturated with the fixer described in example 1, wherein, however, compound (3) had been replaced by a same amount of compound (2). The printing plate thus prepared could be used for printing in the same manner as described in example 1 and about the same good results were obtained.

EXAMPLE 3 To a paper support of 135 g per sq.m a common high-sensitive silver chlorobromide. gelatin emulsion layer comprising hydroquinone and l-phenyl-3- pyrazolidinone was applied in such away that per sq. m were present, an amount of silver halide equivalent to 1 g of silver nitrate, 1 g of hydroquinone and 0.5 g of 1- phenyl-S-pyrazolidinone.

After drying of the silver halide gelatin emulsion layer, said layer was overcoated at arate of g per sq.m with the followingcomposition water 926 ccs gelatin 10 g 12.5 aqueous saponin 8 ccs 20 aqueous formaldehyde 56 ccs Thenthe following liquid was applied in a proportion of 22 g per sq.m

water 890 ccs 12.5 aqueous saponin 10 ccs aqueous colloidal nickel sulphide dispersion of example 1 100 ccs.

The photographic light-sensitive material obtained was exposed image-wise and then guided through an automatic two-bath processing device, thehaths, of which had the following compositions respectively l activating liquid) water a 1,000 ccs sodium phosphate-12-water 75 'g anhydrous sodium sulphite 40 g potassium bromide 0.5 g anhydrous sodium thiosulphate 10 g H. The fixer described in example 1, wherein, however, compound (3) had been replaced by a same amount of compound (10).

The material obtained after this treatment was ready for use as planographic printing plate with positive image values in respect of the original. More than 1,000 copies could be printed therewith. The fountain solution might be mere water or thefspecific fountain composition of example 1.

EXAMPLE 4 To an extra strong paper support of g per sq.m a thin gray antihalation layer was applied by pouring a dispersion of 3 g of lamp black in 1 liter of a 4'percent aqueous solution of gelatin at a rate of 1 liter per 40 sq.m.

To this antihalation layer a common high-sensitive silver chlorobromide gelatin emulsion layer comprising hydroquinone and l-phenyl-3-pyrazolidinone was applied in such'a way that per sq.m there were present an 20 ccs y al was guided through a processing amount of silver halide equivalent to 1 g of silver nitrate, l g of hydroquinone and 0.5 g of l-phenyl-3- pyrazolidinone.

After drying, the silver halide gelatin emulsion layer was overcoated at a rate of 100 g per sq.m with the following composition water 926 ccs gelatin 10 g 12.5 aqueous saponin 8 ccs 20 aqueous formaldehyde 56 ccs Then the following liquid was applied at a rate of 22 g per sq.m

water 890 ccs 12.5 aqueous saponin 10 cos aqueous colloidal nickel sulphide 'nuclei dispersion comprising per 100 ccs 0.2 g of nickel sulphide and 10 g of gelatin 100 ccs.

water 1,000 ccs sodium phosphate-lZ-water 75 g anhydrous sodium sulphite 40 g potassium bromide 0.5 g anhydrous sodium thiosulphate 10 g Thereafter the multilayer material was kept for some 10 seconds in the dark in order to permit an intense diffusion transfer silver deposition to take place. A sharp bronzed legible diffusion transfer image became visible on a gray background. I

The plate was then moistened (e.g., by means of a plug of wadding) for some 20 seconds with the following fixer composition:

16 aqueous sodium hydrogen carbonate 30 ccs potassium cyanoferrateflll) 10.75 g solution of l-allyl-imidazolidine- 2-thione in ethylene glycol monomethyl ether 4 ccs distilled water up to 100 ccs The pH-value of this buffered fixer composition amounted to 8.7. This fixer composition was very stable to aerial oxidation and to temperature fluctuations. With lliter thereof about 100 printing plates (21 cm X 29.7 cm size) could be prepared.

The preparation of the printing plate might occur automatically in a compact processing unit comprising the successive treating stations and wherein the plate was transported automatically from one unit to the other. v

The printing plate thus obtained was ready for use as a planographic printing plate with positive image values in respect of the original. It was braced on a usual offset apparatus and after having been we'tted with water or another usual fountain solution (e .g., a liquid composed of 90 ccs of water, 10 ccs of glycerol, 2 ccs of colloidal silica and 2 cos of phosphoric acid), the fatty printing ink was applied and printing started. More than 1,000 copies were printed with the plate thus prepared.

About the same good results could be obtained by replacing the fixer composition described above by one of the following fixer compositions 10 aqueous sodium carbonate 30 cos 5 aqueous sodium hydrogen carbonate 30 ccs potassium cyanoferrateflll) 10.75 g 10 I: solution of l-allyl-imidazolidine- 2-thione in ethylene glycol monomethyl ether 4 ccs distilled water up to 100 ccs The pH-value of this buffered fixer composition amounted to 10.2. I

10 aqueous sodium carbonate 30 ccs 10 aqueous citric acid 30 ccs potassium cyanoferrateflll) 10.75 g 10 solution of l-allyl-imidazolidine- 2-thione in ethylene glycol monomethyl ether 4 cos distilled water up to 100 ccs The pH-value of this buffered fixer composition amounted to 7.9.

' lll.

10 aqueous boric acid 30 cos l0 aqueous sodium tetraborate 30 ccs potassium cyanoferrateflll) 10.75 g 10 solution of l-allyl-imidazolidine- 2 -thione in ethylene glycol monomethyl ether 4 cos distilled water up to ccs The pl'l-.value of this buffered fixer composition amounted to 8.1.

10 aqueous sodium tetraborate 30 ccs potassium cyanoferrateflll) 10.75 g 10 solution of l-allyl-imidazolidine- Z-thione in ethylene glycol monomethyl ether 4 cos distilled water up to 100 ccs The pl-l-value of this buffered fixer composition amounted to 9.5.

water 50 ccs trisodium phosphate 4 g potassium cyanoferrateflll) 9.8 g ethanol 26.2 ccs oleic acid 6.5 ccs 10 17 solution of l-allyl-imidazolidine- 2-thione in ethylene glycol monomethyl ether 5.2 ccs distilled water up to 100 ccs The pl-l-value of this buffered fixer composition amounted to 7.3. V1. Same as V but the amount of oleic acid was reduced to only 1 cc.

The pH-value of this buffered fixer composition amounted to l 1.2.

In case fixer V or V] is applied, the additional advantage of a still improved ink-receptivity of the printing parts of the printing plate is taken.

7 EXAM PLE 5 To a usual flexible film support of cellulose triacetate an antihalation backing was applied by pouring the following coating composition at a rate of 1 liter per 20 sq.m

water 570 ccs gelatin 40 g 50 g of a red pigment dye (C.l. 15.865

Lake) in 300 ccs of water 12.5 1: aqueous saponin l ccs 20 aqueous formaldehyde l0 ccs EXAMPLE 6 A printing plate was prepared as described in example 4, with the difference, however, that the gelatin layer directly on the silver halide emulsion layer was applied from the following coating composition water 926 ccs gelatin 5.6 g 12 1: aqueous saponin 8 ccs 20 k aqueous formaldehyde 56 ccs propylene glycol ester of alginic acid 20 g A printing plate was still improved printing characteristics was obtained.

We claim:

1. A method of preparing a planographic printing plate from a photographic sheet material comprising a light-sensitive silver halide emulsion layer and an exterior hardenable hydrophilic colloid stratum which comprises:

l. forming a pattern of finely divided silver particles at the exterior surface of said stratum by the steps of:

a. image-wise exposing said emulsion layer to light according to the image to be printed,

b. contacting said stratum'with a liquid dispersion of insoluble development nuclei for precipitating complexed silver halide as metallic silver, to

deposit said nuclei at said surface of saidstratum, and c. photographically developing the exposed emulsion layer with an aqueous alkaline liquid in the presence of a photographic developing agent for silver halide and a complexing agent for silver halide to form said silver particles at the free surface of said stratum by the precipitation by said nuclei of migrating undeveloped complexed silver halide;

2. contacting the developed material with an aqueous fixer composition containing an oxidizing agent for metallic silver and an organic thione or mercapto tautomer thereof for converting the pattern of silver particles into a hydrophobic inkrecept ive' attern;and 3. chemical y hardening said colloid stratum at the latest before said material is used for printing, said hardening being at least sufficient. to prevent transfer of any substantial amount of such colloid during printing.

2. The process of claim 1 wherein said colloid stratum is hardened prior to contacting the same with said fixer composition.

3. The process of claim 1 wherein said colloid stratum is constituted by the external surface stratum of said emulsion layer.

4. The process of claim 1 wherein said colloid stratum is a separate layer arranged in superposed rela tion to said emulsion layer.

5. The process of claim 1 wherein said insoluble development nuclei are dispersed in said aqueous alkaline liquid for developing said light-sensitive emulsion layer. v

6. The process of claim 1 wherein said development nuclei aredispersed in a liquid applied to said colloid stratum prior to developing the emulsion layer with said aqueous alkaline liquid.

7. The process of claim 1 wherein said oxidizing agent is a metal salt.

8. In a method for the preparation of a planographic printing plate according to claim 1, wherein an antihalation dye or pigment layer is provided for said emulsion layer.

9. In a method for the preparation of a planographic printing plate according to claim 1, wherein the support of the sheet material is a transparent hydrophobic film support.

10. In a method for the preparation of a planographic printing plate according to claim 4 wherein the 'hardenable hydrophilic colloid layer present on top of the silver halide emulsion layer is a gelatin layer.

1 1. In a method for the preparation of a planographic printing plate according to claim 1, wherein the hardening of the colloid stratum, is achieved by a hardener released by the application of the aqueous alkaline liquid. l

12. In a method for the preparation of a planographic printing plate according to claim 4, wherein the outer hydrophilic colloid layer contains a substantial amount of pigment particles homogeneously dispersed therein.

Claims

2. The process of claim 1 wherein said colloid stratum is hardened prior to contacting the same with said fixer composition.
2. contacting the developed material with an aqueous fixer composition containing an oxidizing agent for metallic silver and an organic thione or mercapto tautomer thereof for converting the pattern of silver particles into a hydrophobic ink-receptive pattern; and
3. chemically hardening said colloid stratum at the latest before said material is used for printing, said hardening being at least sufficient to prevent transfer of any substantial amount of such colloid during printing.
3. The process of claim 1 wherein said colloid stratum is constituted by the external surface stratum of said emulsion layer.
4. The process of claim 1 wherein said colloid stratum is a separate layer arranged in superposed relation to said emulsion layer.
5. The process of claim 1 wherein said insoluble development nuclei are dispersed in said aqueous alkaline liquid for developing said light-sensitive emulsion layer.
6. The process of claim 1 wherein said development nuclei are dispersed in a liquid applied to said colloid stratum prior to developing the emulsion layer with said aqueous alkaline liquid.
7. The process of claim 1 wherein said oxidizing agent is a metal salt.
8. In a method for the preparation of a planographic printing plate according to claim 1, wherein an antihalation dye or pigment layer is provided for said emulsion layer.
9. In a method for the preparation of a planographic printing plate according to claim 1, wherein the support of the sheet material is a transparent hydrophobic film support.
10. In a method for the preparation of a planographic printing plate according to claim 4 wherein the hardenable hydrophilic colloid layer present on top of the silver halide emulsion layer is a gelatin layer.
11. In a method for the preparation of a planographic printing plate according to claim 1, wherein the hardening of the colloid stratum is achieved by a hardener released by the application of the aqueous alkaline liquid.
12. In a method for the preparation of a planographic printing plate according to claim 4, wherein the outer hydrophilic colloid layer contains a substantial amount of pigment particles homogeneously dispersed therein.