Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/06—Silver salts
  • G03F7/063—Additives or means to improve the lithographic properties; Processing solutions characterised by such additives; Treatment after development or transfer, e.g. finishing, washing; Correction or deletion fluids

Definitions

• a photographic printing plate is prepared from a sheet material carrying an exterior hydrophilic colloid layer having substantially concentrated at its free surface a pattern of finely divided silver particles, by contacting the same with an aqueous alkaline liquid fixer composition containing an oxidizing agent for said silver particles, e.g.
• cyanoferrate(HI)-ions an organic thioxo compound or tautomer thereof for converting the pattern of silver particles into a hydrophobic ink-receptive pattern, a higher fatty acid, e.g., oleic acid, for improving the ink-receptivity of said pattern, and a water-soluble nitrite, such as alkali metal nitrite or an ammonium nitrite, for stabilizing the dispersion of the higher fatty acid in the fixed liquid.
• a higher fatty acid e.g., oleic acid
• a water-soluble nitrite such as alkali metal nitrite or an ammonium nitrite
• the present invention relates to a method of producing a planographic printing plate by converting a silver image into a hydrophobic ink-receptive pattern.
• the preparation of a printing plate according to the present invention comprises treating a sheet material having an outer hydrophilic colloid layer carrying at its surface a pattern of finely divided silver particles, with an aqueous fixer comprising an oxidizing agent for said silver particles, an organic compound that converts the pattern of silver particles in a hydrophobic ink-receptive pattern, a higher fatty acid having from 12 to 22 carbon atoms, and a water-soluble nitrite, the said outer hydrophilic colloid layer having been hardened before, during or after said treatment at least to such an extent that no substantial amounts of colloid are transfered during printing.
• an aqueous fixer comprising an oxidizing agent for said silver particles, an organic compound that converts the pattern of silver particles in a hydrophobic ink-receptive pattern, a higher fatty acid having from 12 to 22 carbon atoms, and a water-soluble nitrite
• the present invention also relates to an aqueous fixer as described above.
• the presence of the higher fatty acid in the aqueous fixer results in an improvement of the hydrophobic inkreceptive characteristics of the printing portions.
• This effeet is especially pronounced when the sheet material to be treated with the fixer for the production of the printing plate is a photographic material comprising at its surface a silver pattern, which has been formed according to the silver complex diffusion transfer process from silver complexes diffusing image-wise distributed from an underlying image-wise exposed silver halide emulsion layer. Consequently, the method of the present invention is particularly suited for application in connection with this specific embodiment.
• the higher fatty acid does not remain homogeneously distributed in the fixer and easily tends to unmix during aging. This tendency is fully overcome by the addition of the water-soluble nitrite.
• an aqueous fixer having excellent keeping qualities is obtained.
• the water-soluble nitrite exerts a further favourable effect in preventing an undesirable yellow, brownish, and even bluish colouring of the fixer during aging. Although such a colour change has no substantial effect on the very fixing properties, it might confuse the operator as to the nature as well as to the quality of the liquid.
• All water-soluble nitrites i.e. all organic and inorganic compounds releasing nitrite ions in an aqueous medium are suited for use according to the present invention.
• simple water-soluble inorganic nitrites e.g. sodium nitrite, potassium nitrite, or ammonium nitrite.
• the nitrites are generally applied in an amount comprised between 2 and 20 g. per litre of fixer.
• the higher fatty acids to be incorporated into the fixer include saturated as well as unsaturated acids, e.g. lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid.
• unsaturated higher fatty acids and especially oleic acid have proved to be the most suited ones for the purpose of the present invention.
• These higher fatty acids may be incorporated into the fixer from a solution in a water-miscible organic solvent, e.g. a lower aliphatic alcohol such as propanol, or in the form of a water-soluble salt (soap), e.g. the sodium or potassium salt.
• a watersoluble salt of the higher fatty acid may also be produced in situ by the presence of suitable alkaline substances such as trisodium phosphate or sodium hydroxide, in the fixer.
• suitable alkaline substances such as trisodium phosphate or sodium hydroxide
• the expression higher fatty acids also includes the water-soluble salts thereof.
• the higher fatty acids are preferably applied in an amount comprised between 5 and g. per litre of fixer.
• the oxidizing agent present in the fixer liquid preferably is a water-soluble cyanoferratefl'll), and the fixer is then preferably buffered at a pH value between 7 and 12.
• Suitable organic compounds for converting the pattern of silver particles into a hydrophobic ink-receptive pattern are thioxo compounds, including the tautomeric structures thereof.
• a paper support or ahydrophobic synthetic film support including a paper sheet provided with a thin layer of a hydrophobic synthetic polymeric material, e.g. polyethylene.
• the preparation of printing plates according to the subject matter of such applications comprises treating a sheet material having an outer hydrophilic colloid layer carrying at its surface a pattern of finely divided silver particles, which pattern has been produced in a photographic way by the application of the silver complex diffusion transfer process being carried out with a single photographic material comprising both the silver halide emulsion layer and the substance or substances for promoting the silver deposition from the diffusing complexed silver halide, i.e., the so-called development nuclei, with an aqueous fixer composition containing an oxidizing agent for the silver particles and an organic thioxo compound or tautomer thereof that converts the pattern of silver particles to a hydrophobic ink-receptive pattern, said outer hydrophilic colloid layer being hardened before, during or after the said treatment, and at least to such an extent that no substantial amount of colloid is transferred on printing.
• the silver complex diffusion transfer process is especially suited for producing the pattern of silver particles
• the silver deposition mainly occurs at the outer surface of the layer provided with the substance or substances for promoting the silver deposition from the diffusing complexed silver halide, i.e., the so-called development nuclei.
• the development nuclei can be supplied to the light-sensitive material by the processing liquid for carrying out the diffusion transfer process. In this case it is sufficient to dispose of a light-sensitive material only, which is provided either or not with a colloid layer on top of the silver halide emulsion layer.
• the development nuclei will deposit from the processing liquid onto the surface of the light-sensitive material at the development stage and as a result the diffusion transfer silver deposition Will also occur at this outer surface of the light-sensitive material. It is the latter diffusion transfer silver image that will be converted into the ink-receptive printing areas of a planographic printing plate and not the silver image resulting from the primary development of the image-wise exposed silver halide.
• the development nuclei are supplied by the processing liquid and preferably according to said embodiment wherein also a colloid layer is provided on top of the silver halide emulsion layer it is also possible to transfer a diffusion transfer silver image containing stratum to a suitable support and to use the resulting material as starting material for the preparation of a planographic printing plate according to the method of the invention.
• a colloid layer is provided on top of the silver halide emulsion layer
• the development nuclei for the diffusion transfer image formation instead of being supplied by the alkaline processing liquid can also be supplied to the light-sensitive material by a special treatment with a separate liquid com position containing such nuclei.
• This treatment may be the last step in the preparation of the material or a treatment that is carried out after the exposure of the lightsensitive material and before wetting with the alkaline processing liquid for carrying out the diffusion transfer image formation.
• the development nuclei may be provided in a colloid layer on top of the silver halide emulsion layer at the preparation stage; in this way a multilayer material is obtained.
• a multilayer material is known among others from the United States patent specifications 2,725,298 and 2,843,485 and from the United Kingdom patent specification 758,627.
• This transfer to another sheet may be avoided by substantially or completely concentrating the development nuclei at the free surface of the outer colloid layer of the multilayer material, whereby the diffusion transfer silver deposition substantially takes place at this outer free surface.
• the French patent specification 1,569,398 there may be referred to the French patent specification 1,569,398.
• the development nuclei instead of being present in the said colloid layer on top of the silver halide emulsion layer, may also be provided between the light-sensitive emulsion layer and the said colloid layer. After the diffusion transfer image formation the said colloid layer is transferred to another sheet material and carries the diffusion transfer silver image on its free surface.
• Such a multilayer material is described i.a. in United Kingdom patent specification 654,631 and to the United States patent specifications 3,020,155, 3,203,796 and 3,325,284. .
• the lightsensitive emulsion layer may be removed by detaching in an aqueous rinsing bath as a coherent membrane or in flakes, by dissolving or by stripping off either or not by means of an auxiliary sheet, whereupon the colloid imagereceiving layer with the silver pattern formed on its surface becomes visible.
• the development nuclei are very often substantially or completely concentrated at the imagereceiving side of that layer.
• This can be very advantageously effected by the application of the development nuclei through an after-treatment of the colloid layer with a liquid composition containing such nuclei.
• this liquid composition may be the processing liquid itself for carrying out the diffusion transfer image formation or another aqueous dispersion or solution of said nuclei, which is provided on top of the hydrophilic colloid layer before the diffusion transfer image formation takes place.
• a minor amount of a hydrophilic protective colloid is often 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 sheet material carrying the silver pattern generally has a rather simple composition and comprises a suitable support such as a usual hydrophobic flexible film support, e.g. a sheet of cellulose triacetate or of polyethylene terephthalate, or a paper sheet provided either directly or indirectly, e.g., by means of a suitable subbing layer, with a hydrophilic colloid outer layer having at its surface a pattern of finely divided silver particles.
• a silver halide emulsion layer is present between the colloid outer layer and the support and antihalation dyes or pigments are provided.
• a photographic material which in order comprises a support sheet, preferably a paper support or a hydrophobic film support, an antihalation layer, a silver halide emulsion layer and development nuclei on top thereof.
• the antihalation layer is gray the correctness of the exposure can be controlled by judging the diffusion transfer image in transmittance before carrying out the fixing step.
• the said photographic material has to be kept for a short while, e.g. for about 10 seconds, in the dark after it has been wetted with the alkaline processing liquid for carrying out the diffusion transfer image formation.
• the application of the fixer composition may already occur during the period the multilayer material is kept in the dark. However, this application of fixer may also occur thereafter.
• a photographic material comprising development nuclei on top of the silver halide emulsion layer may be provided in roller form.
• image-wise exposure e.g. an episcopic exposure in a camera or an exposure through a trans parent 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.
• a usual processing unit containing the alkaline processing liquid and comprising guiding and driving means as generally known in the art.
• 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.
• At least part of the compounds that are essential or useful for carrying out said process may be provided in the sheet material(s) used.
• these compounds there may be mentioned developing agents, preservatives for these developing agents, complexing agents, stabilizers, alkaline substances, blacktoning agents, hardeners, including latent hardeners, and softening agents.
• Suitable substances for promoting the silver deposition from the diffusing complexed silver halide 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 thin(II) halides.
• Heavy metals or their salts and fogged silver halides are suitable too.
• the complexed salts of lead and zinc sulphides are active alone as well as 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.
• the support of the photographic material comprising the silver halide emulsion layer may be 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.
• the exposure latitude of the photographic material in most cases can be increased considerably and also the image sharpness of the silver pattern 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 layer and the support. If a transparent support is used the antihalation dyes or pigments may be applied at the rear side of the material or on top of the emulsion layer dependent on the manner in which the exposure is carried out, viz at the front side or through the support. Preferably a red or black antihalation dye or pigment is used.
• any silver halide emulsion of the negative or direct positive type may be used dependent on the nature of the original to be reproduced.
• emulsions of the negative type having a rather high sensitivity of the order as normally required for camera exposure are used.
• the exposure of the silver halide emulsion layer may be carried out according to any usual technique e.g. in contact, reflectographically, by transmission or episcopically, mostly an episcopic exposure in a camera is carried out, particularly when the development nuclei are provided on top of the silver halide emulsion layer as detailedly described hereinbefore.
• the silver halide emulsion layer generally comprises an amount of silver halide equivalent to form about 0.5 g. to about 1.5 g.
• hydrophilic colloid outer layer any hardenable hydrophilic colloid may be used.
• Suitable hydrophilic colloids include gelatin polyvinyl alcohol, casein, carboxymethylcellulose and sodium alginate.
• the nature of the hardener used is dependent on the type of hydrophilic colloid to be hardened.
• the hydrophilic colloid binder of said outer layer comprises a mixture of a proteinaceous hydrophilic colloid, preferably gelatin, and a hydrophilic colloid that is a latent hardener for said proteinaceous colloid, i.e. that in the alkaline medium wherein the production of the diffusion transfer image takes place hardens said proteinaceous colloid.
• Suitable hydrophilic colloids of this type are addition products of high molecular weight hydroxyl group-containing compounds With acrolein, described in the United States patent specification 3,382,077 and especially water-soluble hydroxy alkyl esters of alginic acid, particularly propylene glycol esters of algininc acid, described in the United States patent specification 3,378,373. If gelatin is used in the hydrophilic colloid outer layer, it may be submitted to a treatment as described in the United States patent specification 3,089,770 in order to improve the printing characteristics of the planographic printing plate.
• Hardening of the hydrophilic colloid binder of the outer layer may occur before, during or after the treatment with the fixer composition 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.
• 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 planographic printing plate.
• the said hardening is carried out before the treatment with fixer, it may occur by adding generally known hardening agents for the hydrophilic colloid(s) of the outer layer such as formaldehyde, glyoxal, mucochloric acid and chrome alum to the coating composition of the outer layer, at the surface of which the silver pattern will be produced, and/ or to the coating composition of another layer, with which the said outer layer is in water-permeable relationship whereby hardening of the said outer layer takes place by diffusion of hardener from said other layer to said outer layer.
• hardening agents for the hydrophilic colloid(s) of the outer layer such as formaldehyde, glyoxal, mucochloric acid and chrome alum
• a coating composition comprising development nuclei, either or not together with a minor amount of a hydrophilic colloid to keep the development nuclei in dispersion is applied on top of the said outer layer the hardeners can be 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 silver pattern according to the silver complex diffusion transfer process. Said hardening may occur by incorporatmg hardeners in at least one of the processing liquids and/ or by incorporating latent hardeners, as already referred to above, into the photographic material to be hardened.
• hardening of the outer hydrophilic colloid layer can also occur after the production of the silver pattern namely 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.
• hydrophilic colloid binders e.g. carboxymethylcellulose, gum arabic, sodium alginate, propyleneglycol ester of alginic acid, hydroxyethyl starch, dextrine, hydroxyethylcellulose, polyvinylpyrrolidone, polystyrene sulphonic acid and polyvinyl alcohol in the outer hydrophilic colloid layer carrying at its surface the pattern of silver particles often improves the hydrophilic, ink-repellent properties of the non-printing areas of the printing plate finally obtained.
• hydrophilic colloid binders e.g. carboxymethylcellulose, gum arabic, sodium alginate, propyleneglycol ester of alginic acid, hydroxyethyl starch, dextrine, hydroxyethylcellulose, polyvinylpyrrolidone, polystyrene sulphonic acid and polyvinyl alcohol in the outer hydrophilic colloid layer carrying at its surface the pattern of silver particles often improves the hydro
• sorbitol, glycerol, trihydroxyethyl ether of glycerol and turkish red oil, and certain wetting agents, i.e. those mentioned hereinafter incorporated in at least one hydrophilic colloid layer of the sheet material carrying the silver image at its surface 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. inkacceptance 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 -20 g. thereof are present per sq. m. of the hydrophilic colloid outer layer.
• a similar anti-scumming etfect may also be obtained by adding at least one member selected of colloidal silica, an inorganic acid e.g. o-phosphoric acid, a hydrophilic softening agent as those mentioned above and a suitable wetting agent to the fountain solution used during the printing process. Suitable wetting agents are i.a.
• a very suitable fountain solution comprises water, glycerol, o-phosphoric acid and colloidal silica.
• the sheet material comprising an outer hydrophilic colloid layer having at its surface a pattern of finely divided silver particles is treated with an aqueous fixed composition as described above.
• oxidizing agents are available for oxidizing the finely divided silver particles in the surface pattern including the Water-soluble cyanoferrate(III) compounds mentioned above.
• Other oxidizing agents include Water-soluble Cr salts, e.g., sodium or potassium dichromate (application S.N. 887,- 323), Water-soluble iron(III) salts, e.g., iron(III) chloride (application Ser. No.
• the oxidizing agent is selected from the later groups, the pH of the composition is desirably made acidic by means of a suitable acidic compound e.g., acetic acid or boric acid.
• a pH of not more than 4.0 is preferable for iron(III) salts and less than 3.5 is preferably for the Cr salts.
• the oxidizing agent mostly is incorporated into the fixer composition in a concentration of from 10 to 300 g. per liter.
• the presence of halide ions often has a favorable effect on the action of the fixer composition.
• water-soluble chlorides, bromides or iodides, such as potassium bromide are often incorporated into the fixer.
• the oxidizing agent used in carrying out the present method may be used in combination with at least one other oxidizing agent, e.g., a lead(II) ion-releasing compound,
• a compound of another type and that also converts the sllver image parts in hydrophobic ink-receptive parts is (12) IIICS
• 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 solution or from a solution in a suitable organic, water-miscible solvent such as ethanol, isopropanol, ethylene glycolmonomethyl ether and dirnethylformamide. They must be at least partially soluble in the fixer composition. They are mostly applied in an amount of from 0.5 to 5 g. per litre fixer. It is remarkable that most of the suitable compounds for converting the silver image parts in ink-receptive parts are generally known black-toning agents in the silver complex diffusion transfer process.
• 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, hydrophilic 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 200 g. per litre.
• 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, which often are applied together with a water-soluble nitrite in order to keep them homogeneously distributed in the fixer, and hydrophobic softening agents, e.g. dimethyl phthalate, dibutyl phthalate, the phthalic acid ester with the following formula:
• the hydrophobic softening agents mostly are added to the fixer in an amount of from about 5 to about g. per litre. It is also possible to apply at least one of these compounds in about the same concentrations after the treatment with the fixer composition.
• 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 litre of fixer) can be produced before the fixer composition is fully exhausted.
• 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.
• the treatment with the fixer does not last long, mostly not longer than about 20 seconds and can be accelerated by increasing the concentration of the components 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.
• the fixing step is carried out just before printing.
• the fixer as well as the development or activating liquid for the production of the difiusion transfer image 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.
• 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.
• 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.
• the production of a silver image on top of the outer hydrophilic colloid layer (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 may be carried out both in a compact processing unit comprising both processing stations.
• the sheet material 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.
• 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, monoethyl ether of diethylene glycol, tetrahydrothiophene-1,1 dioxide, diacetone, dioxane, 1,2-dichloroethane, ethyl acetate, trichloroethylene, butyl butyrate, diethanolamine and dimethylformamide.
• 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.
• lacquers are described in the United Kingdom patent specifications 967,598,
• Resins that have proved to be especially suitable for improving the ink-receptive character of the printing areas and strengthening them are phenol-formaldehyde resins e.g. the usual phenol-formaldehyde resins, o-cresol formaldehyde resins and p-tert.- butylphenol formaldehyde resins, alkyd resins e.g. rosin maleic 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.
• phenol-formaldehyde resins e.g. the usual phenol-formaldehyde resins, o-cresol formaldehyde resins and p-tert.- butylphenol formaldehyde resins
• alkyd resins e.g. rosin maleic acid esters
• epoxy resins e.g. condensation products of a poly(ary
• the resin, wax or oil used mostly is present in a concentration of from about 100 to about 500 g. per litre 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 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 substances settle on the image areas and improve the 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.
• the liquid lacquer composition may also be mixed with the aqueous fixer composition.
• the ratio of the organic phase that contains the hydrophobic solid substances to the aqueous phase then mostly is comprised between 1:1 and 1:10.
• the printing plate has to be wet at the stage the fatty printing ink is applied. This is generally known in the art and it is usual to apply an aqueous liquid before applying the printing ink. This may occur 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 drier, e.g., when it has been stored for a long time after its fixation and occasional lacquering.
• EXAMPLE 1 A thin grey antihalation layer was applied to an extra strong paper support of 135 g. per sq. m. at a ratio of 1 litre per 40 sq. m. with a dispersion of 3 g. of lamp black in l litre,,of.a ,4% aqueous solution of gelatin.
• antihalatiqn layer a common high-sensitive silver chlorobromidegelatin emulsion layer comprising hydroquinone and 1-phenyl-3-pyrazolidinone was applied in such a way 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 l-phenyl-3-pyrazolidinone.
• the following coating composition was applied to the dry silver halide gelatin emulsion layer in a ratio of 100 g. per sq. m.:
• Aqueous dispersion of colloidal nickel sulphide nuclei comprising per 100 ml. 0.2 g. of nickel sulphide and 10 g. of gelatin-4 ml.
• the light-sensitive multilayer material thus obtained was image-wise exposed to an original.
• the multilayer material was kept for approximately -l0 seconds in the dark to make possible an intense silver deposition by diffusion transfer.
• a sharp bronzed legible diffusion transfer image became visible on a gray background.
• the plate was then rubbed for approximately 20 seconds with the following fixer:
• the pH of this buffered fixer composition was 7.6.
• a high-quality planographic printing plate having positive image values in respect of the original was obtained.
• the fixer described above has excellent keeping qualities.
• the colour of the fixer does not change during aging and the oleic acid remains homogeneously distributed throughout the fixer.
• a similar fixer containing, however, no sodium nitrite becomes brownish and bluish after about one week, and the oleic acid unmixes from the aqueous phase. Said unmixing is of course highly unwanted since it impairs the fixing properties.
• Example 1 was repeated with the diflerence, however, that trisodium phosphate-lZ-Water was omitted from the fixer and oleic acid was replaced by 3 g. of the sodium salt of oleic acid.
• the fixer thus obtained has a pH-value of 8.8 and shows good keeping properties which are similar to those of the fixer described in Example 1.
• Aqueous fixer liquid composition for use in the productionof a planographic printing plate from a sheet support having an outer hydrophilic colloid layer carrying substantially concentrated at its free surface a pattern of finely divided silver particles, said fixer comprising an oxidizing agent for said silver particles, an organic thioxo compound or tautomer thereof adapted to convert the pattern of silver particles into a hydrophobic ink-receptive pattern, a higher fatty acid having about 12-22 carbons in the fatty chain dispersed in said aqueous liquid in an amount sufficient to improve the hydrophobic characteristics of said ink-receptive pattern, and a water-soluble nitrite in sufiicient amount to significantly improve the stability of the fatty acid dispersion.
• planographic printing plates which comprises contacting a sheet support having an exterior hydrophilic colloid layer carrying substantially concentrated at its free surface a pattern of finely divided silver particles, with an aqueous alkaline fixer composition containing an oxidizing agent for said silver particles, and an organic thioxo compounds or a tautomer thereof adapted to convert the pattern of the oxidized silver particles into a.
• the sheet support is a paper support, hydrophobic synthetic film sup port, or a paper sheet provided with a thin layer of a hydrophobic synthetic polymeric material.
• the higher fatty acid is an unsaturated higher fatty acid selected from the group consisting of lauric acid, myristic acid, palmitic acid.

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• Photosensitive Polymer And Photoresist Processing (AREA)

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• 1969
  • 1969-04-25 GB GB21279/69A patent/GB1300418A/en not_active Expired
• 1970
  • 1970-04-23 CH CH600470A patent/CH527448A/de not_active IP Right Cessation
  • 1970-04-23 FR FR7014959A patent/FR2046459A5/fr not_active Expired
  • 1970-04-24 DE DE2019995A patent/DE2019995C3/de not_active Expired
  • 1970-04-24 BE BE749462D patent/BE749462A/nl unknown
  • 1970-04-24 US US31787A patent/US3676125A/en not_active Expired - Lifetime

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