EP0908779B1 - Méthode pour la production de plaques d'impression positives à partir d'un élément thermosensible - Google Patents

Méthode pour la production de plaques d'impression positives à partir d'un élément thermosensible Download PDF

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Publication number
EP0908779B1
EP0908779B1 EP19980203118 EP98203118A EP0908779B1 EP 0908779 B1 EP0908779 B1 EP 0908779B1 EP 19980203118 EP19980203118 EP 19980203118 EP 98203118 A EP98203118 A EP 98203118A EP 0908779 B1 EP0908779 B1 EP 0908779B1
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EP
European Patent Office
Prior art keywords
printing plates
layer
lithographic printing
plates according
imaging element
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EP19980203118
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German (de)
English (en)
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EP0908779A1 (fr
Inventor
Joan Vermeersch
Marc Van Damme
Guy Hauquier
Eric Verschueren
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Agfa Gevaert NV
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Agfa Gevaert NV
Agfa Gevaert AG
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C1/00—Forme preparation
    • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
    • B41C1/1008—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials
    • B41C1/1016—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials characterised by structural details, e.g. protective layers, backcoat layers or several imaging layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/02—Positive working, i.e. the exposed (imaged) areas are removed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/06—Developable by an alkaline solution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/14—Multiple imaging layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/22—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by organic non-macromolecular additives, e.g. dyes, UV-absorbers, plasticisers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/24—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by a macromolecular compound or binder obtained by reactions involving carbon-to-carbon unsaturated bonds, e.g. acrylics, vinyl polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2210/00—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation
    • B41C2210/26—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by a macromolecular compound or binder obtained by reactions not involving carbon-to-carbon unsaturated bonds
    • B41C2210/262—Phenolic condensation polymers, e.g. novolacs, resols

Definitions

  • the present invention relates to a method for preparing a lithographic printing plate using a heat mode imaging element.
  • the invention is related to a method for preparing a lithographic printing plate using a heat mode imaging element whereby the capacity of the top layer of being penetrated and/or solubilised by an aqueous developer is changed upon exposure.
  • Lithography is the process of printing from specially prepared surfaces, some areas of which are capable of accepting lithographic ink, whereas other areas, when moistened with water, will not accept the ink.
  • the areas which accept ink form the printing image areas and the ink-rejecting areas form the background areas.
  • a photographic material is made imagewise receptive to oily or greasy inks in the photo-exposed (negative-working) or in the non-exposed areas (positive-working) on a hydrophilic background.
  • lithographic printing plates also called surface litho plates or planographic printing plates
  • a support that has affinity to water or obtains such affinity by chemical treatment is coated with a thin layer of a photosensitive composition.
  • Coatings for that purpose include light-sensitive polymer layers containing diazo compounds, dichromate-sensitized hydrophilic colloids and a large variety of synthetic photopolymers. Particularly diazo-sensitized systems are widely used.
  • the exposed image areas become insoluble and the unexposed areas remain soluble.
  • the plate is then developed with a suitable liquid to remove the diazonium salt or diazo resin in the unexposed areas.
  • printing plates are known that include a photosensitive coating that upon image-wise exposure is rendered soluble at the exposed areas. Subsequent development then removes the exposed areas.
  • a typical example of such photosensitive coating is a quinone-diazide based coating.
  • the above described photographic materials from which the printing plates are made are camera-exposed through a photographic film that contains the image that is to be reproduced in a lithographic printing process.
  • Such method of working is cumbersome and labor intensive.
  • the printing plates thus obtained are of superior lithographic quality.
  • GB-1 492 070 discloses a method wherein a metal layer or a layer containing carbon black is provided on a photosensitive coating. This metal layer is then ablated by means of a laser so that an image mask on the photosensitive layer is obtained. The photosensitive layer is then overall exposed by UV-light through the image mask. After removal of the image mask, the photosensitive layer is developed to obtain a printing plate.
  • This method however still has the disadvantage that the image mask has to be removed prior to development of the photosensitive layer by a cumbersome processing.
  • thermoplastic polymer particles By image-wise exposure to an infrared laser, the thermoplastic polymer particles are image-wise coagulated thereby rendering the surface of the imaging element at these areas ink-acceptant without any further development.
  • a disadvantage of this method is that the printing plate obtained is easily damaged since the non-printing areas may become ink accepting when some pressure is applied thereto. Moreover, under critical conditions, the lithographic performance of such a printing plate may be poor and accordingly such printing plate has little lithographic printing latitude.
  • US-P- 4 708 925 discloses imaging elements including a photosensitive composition comprising an alkali-soluble novolac resin and an onium-salt. This composition can optionally contain an IR-sensitizer. After image-wise exposing said imaging element to UV - visible - or IR-radiation followed by a development step with an aqueous alkali liquid there is obtained a positive or negative working printing plate. The printing results of a lithographic plate obtained by irradiating and developing said imaging element are poor.
  • EP-A- 625 728 discloses an imaging element comprising a layer which is sensitive to UV- and IR-irradiation and which can be positive or negative working.
  • This layer comprises a resole resin, a novolac resin, a latent Bronsted acid and an IR-absorbing substance.
  • the printing results of a lithographic plate obtained by irradiating and developing said imaging element are poor.
  • US-P- 5 340 699 is almost identical with EP-A- 625 728 but discloses the method for obtaining a negative working IR-laser recording imaging element.
  • the IR-sensitive layer comprises a resole resin, a novolac resin, a latent Bronsted acid and an IR-absorbing substance.
  • the printing results of a lithographic plate obtained by irradiating and developing said imaging element are poor.
  • EP-A- 678 380 discloses a method wherein a protective layer is provided on a grained metal support underlying a laser-ablatable surface layer. Upon image-wise exposure the surface layer is fully ablated as well as some parts of the protective layer. The printing plate is then treated with a cleaning solution to remove the residu of the protective layer and thereby exposing the hydrophilic surface layer.
  • EP-A- 97 200 588.8 discloses a heat mode imaging element for making lithographic printing plates comprising on a lithographic base having a hydrophilic surface an intermediate layer comprising a polymer, soluble in an aqueous alkaline solution and a top layer that is sensitive to IR-radiation wherein said top layer upon exposure to IR-radiation has a decreased or increased capacity for being penetrated and/or solubilised by an aqueous alkaline solution.
  • This material does not give a selective dissolution of the exposed or unexposed parts of the top and intermediate layer.
  • EP-A- 703 499 discloses a photosensitive article comprising a substrate having on at least one surface thereof a photosensitive composition which upon irradiation provides surface areas which are, or on press become, more hydrophilic in one area and less hydrophilic in a second area, said one area and said second area being differentiated by being exposed or not exposed to radiation, and having over said photosensitive composition a hydrophilic, non-photosensitive protective layer, said protective layer having a contact angle with water which is less than the contact angle of the photoactive layer with water.
  • EP-A- 160 395 discloses a laser-imageable assembly comprising a transparent substrate having on a surface thereof an energy absorbent transfer layer characterized in that the transfer layer comprises particles which absorb laser energy dispersed in a heterogeneous resin layer.
  • US-P- 4 946 758 discloses a photosensitive recording material comprising
  • lithographic printing plates including the following steps:
  • lithographic printing plates including the following steps:
  • the top layer in accordance with the present invention comprises an organic quaternary ammonium salt.
  • a mixture of organic quaternary ammonium salts may be used, but it is preferred to use only one organic quaternary ammonium salt.
  • Said organic quaternary ammonium salt can be a low molecular compound, preferably containing at least a C 6 carbon chain, more preferably containing at least a C 12 carbon groep, still more preferably at least a C 12 aliphatic group.
  • Most preferable said organic quaternary ammonium salt is a polymer, particularly preferable a poly-p-vinylbenzyltrimethylammonium salt.
  • the top layer can comprise as binder a water insoluble polymer such as a cellulose ester, a copolymer of vinylidene chloride and acrylonitrile, poly(meth)acrylates, polyvinyl chloride, silicone resins, etc.
  • a water insoluble polymer such as a cellulose ester, a copolymer of vinylidene chloride and acrylonitrile, poly(meth)acrylates, polyvinyl chloride, silicone resins, etc.
  • the top layer may comprises as a binder resin in accordance with the present invention preferably a water soluble polymer.
  • a water soluble polymer a protein, preferably gelatin may be used.
  • synthetic, semi-synthetic, or natural water soluble polymers may be used.
  • Synthetic polymers are e.g. polyvinyl alcohol, poly-N-vinyl pyrrolidone, polyvinyl imidazole, polyvinyl pyrazole, polyacrylamide, polyacrylic acid, and derivatives thereof, in particular copolymers thereof.
  • Natural substitutes for gelatin are e.g. other proteins such as zein, albumin and casein, cellulose, saccharides, starch, and alginates.
  • the semi-synthetic substitutes for gelatin are modified natural products e.g. gelatin derivatives obtained by conversion of gelatin with alkylating or acylating agents or by grafting of polymerizable monomers on gelatin, and cellulose derivatives such as hydroxyalkyl cellulose, carboxymethyl cellulose, phthaloyl cellulose, and cellulose sulphates.
  • modified natural products e.g. gelatin derivatives obtained by conversion of gelatin with alkylating or acylating agents or by grafting of polymerizable monomers on gelatin
  • cellulose derivatives such as hydroxyalkyl cellulose, carboxymethyl cellulose, phthaloyl cellulose, and cellulose sulphates.
  • the total amount of the top layer preferably ranges from 0.1 to 10 g/m 2 more preferably from 0.3 to 2 g/m 2 .
  • top layer a difference in the capacity of being penetrated and/or solubilised by the aqueous alkaline solution is generated upon image-wise exposure for an alkaline developer according to the invention.
  • the said capacity is increased upon image-wise exposure to actinic light to such degree that the imaged parts will be cleaned out during development without solubilising and/or damaging the non-imaged parts.
  • the development with the aqueous alkaline solution is preferably done within an interval of 5 to 120 seconds.
  • the top layer or the layer just underlying said top layer includes a compound capable of converting light to heat.
  • Suitable compounds capable of converting light into heat are preferably infrared absorbing components although the wavelength of absorption is not of particular importance as long as the absorption of the compound used is in the wavelength range of the light source used for image-wise exposure.
  • Particularly useful compounds are for example dyes and in particular infrared dyes, carbon black, metal carbides, borides, nitrides, carbonitrides, bronze-structured oxides and oxides structurally related to the bronze family but lacking the A component e.g. WO 2.9 .
  • conductive polymer dispersion such as polypyrrole or polyaniline-based conductive polymer dispersions.
  • the lithographic performance and in particular the print endurance obtained depends on the heat-sensitivity of the imaging element. In this respect it has been found that carbon black yields very good and favorable results.
  • IR-cyanine dyes are IR-cyanine dyes.
  • a mixture of IR-cyanine dyes may be used, but it is preferred to use only one IR-cyanine dye.
  • Particularly useful IR-cyanine dyes are cyanines dyes with two acid groups, more preferably with two sulphonic groups . Still more preferably are cyanines dyes with two indolenine and two sulphonic acid groups. Most preferably is compound I with the structure as indicated
  • the ratio in weight between the organic quaternary ammonium salt and the compound capable of converting light into heat is preferably between 98:2 to 20:80, more preferably between 95:5 to 50:50.
  • the present invention comprises a first layer soluble in an aqueous developing solution, more preferably an aqueous alkaline developing solution with preferentially a pH between 7.5 and 14.
  • Said layer is preferably contiguous to the top layer but other hydrophilic layers can be present between the top layer and the first layer.
  • the alkali soluble binders used in this layer are preferably hydrophobic binders as used in conventional positive or negative working PS-plates e.g. novolac, polyvinyl phenols, carboxy substituted polymers etc. Typical examples of these polymers are descibed in DE-A- 4 007 428, DE-A- 4 027 301 and DE-A- 4 445 820.
  • the hydrophobic binder used in connection with the present invention is further characterised by insolubility in water and partial solubility/swellability in an alkaline solution and/or partial solubility in water when combined with a cosolvent.
  • this aqueous alkali soluble layer is preferably a visible light- or UV-light desensitised layer.
  • Still further said layer is preferably thermally hardenable.
  • This preferably visible light- or UV-light desensitised layer does not comprise photosensitive ingredients such as diazo compounds, photoacids, photoinitiators, quinone diazides, sensitisers etc. which absorb in the wavelength range of 250nm to 650nm. In this way a daylight stable printing plate can be obtained.
  • Said first layer preferably also includes a low molecular acid, preferably a carboxylic acid, still more preferably a benzoic acid, most preferably 3,4,5-trimethoxybenzoic acid.
  • a low molecular acid preferably a carboxylic acid, still more preferably a benzoic acid, most preferably 3,4,5-trimethoxybenzoic acid.
  • the weight ratio between the total amount of low molecular acid and polymer in the first layer preferably ranges from 2:98 to 40:60, more preferably from 5:95 to 20:80.
  • the total amount of said first layer preferably ranges from 0.1 to 10 g/m 2 , more preferably from 0.3 to 2 g/m 2 .
  • the lithographic base can be an anodised aluminum.
  • a particularly preferred lithographic base is an electrochemically grained and anodised aluminum support.
  • the anodised aluminum support may be treated to improve the hydrophilic properties of its surface.
  • the aluminum support may be silicated by treating its surface with sodium silicate solution at elevated temperature, e.g. 95°C.
  • a phosphate treatment may be applied which involves treating the aluminum oxide surface with a phosphate solution that may further contain an inorganic fluoride.
  • the aluminum oxide surface may be rinsed with a citric acid or citrate solution. This treatment may be carried out at room temperature or can be carried out at a slightly elevated temperature of about 30 to 50°C.
  • a further interesting treatment involves rinsing the aluminum oxide surface with a bicarbonate solution.
  • the aluminum oxide surface may be treated with polyvinylphosphonic acid, polyvinylmethylphosphonic acid, phosphoric acid esters of polyvinyl alcohol, polyvinylsulphonic acid, polyvinylbenzenesulphonic acid, sulphuric acid esters of polyvinyl alcohol, and acetals of polyvinyl alcohols formed by reaction with a sulphonated aliphatic aldehyde It is further evident that one or more of these post treatments may be carried out alone or in combination.
  • the lithographic base having a hydrophilic surface comprises a flexible support, such as e.g. paper or plastic film, provided with a cross-linked hydrophilic layer.
  • a particularly suitable cross-linked hydrophilic layer may be obtained from a hydrophilic binder cross-linked with a cross-linking agent such as formaldehyde, glyoxal, polyisocyanate or a hydrolysed tetraalkylorthosilicate. The latter is particularly preferred.
  • hydrophilic binder there may be used hydrophilic (co)polymers such as for example, homopolymers and copolymers of vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate or maleic anhydride/vinylmethylether copolymers.
  • the hydrophilicity of the (co)polymer or (co)polymer mixture used is preferably the same as or higher than the hydrophilicity of polyvinyl acetate hydrolyzed to at least an extent of 60 percent by weight, preferably 80 percent by weight.
  • the amount of crosslinking agent, in particular of tetraalkyl orthosilicate, is preferably at least 0.2 parts by weight per part by weight of hydrophilic binder, more preferably between 0.5 and 5 parts by weight, most preferably between 1.0 parts by weight and 3 parts by weight.
  • a cross-linked hydrophilic layer in a lithographic base used in accordance with the present embodiment preferably also contains substances that increase the mechanical strength and the porosity of the layer.
  • colloidal silica may be used.
  • the colloidal silica employed may be in the form of any commercially available water-dispersion of colloidal silica for example having an average particle size up to 40 nm, e.g. 20 nm.
  • inert particles of larger size than the colloidal silica can be added e.g. silica prepared according to Stöber as described in J. Colloid and Interface Sci., Vol.
  • alumina particles or particles having an average diameter of at least 100 nm which are particles of titanium dioxide or other heavy metal oxides.
  • the thickness of a cross-linked hydrophilic layer in a lithographic base in accordance with this embodiment may vary in the range of 0.2 to 25 ⁇ m and is preferably 1 to 10 ⁇ m.
  • plastic film e.g. substrated polyethylene terephthalate film, cellulose acetate film, polystyrene film, polycarbonate film etc.
  • the plastic film support may be opaque or transparent.
  • the amount of silica in the adhesion improving layer is between 200 mg per m 2 and 750 mg per m 2 .
  • the ratio of silica to hydrophilic binder is preferably more than 1 and the surface area of the colloidal silica is preferably at least 300 m 2 per gram, more preferably at least 500 m 2 per gram.
  • the heat mode imaging element according to the invention is first image-wise exposed to actinic light and then developed in an aqueous solution.
  • Actinic light is light that is absorbed by the compound converting light into heat.
  • Image-wise exposure in connection with the present invention is preferably an image-wise scanning exposure involving the use of a laser that operates in the infrared or near-infrared, i.e. wavelength range of 700-1500 nm. Most preferred are laser diodes emitting in the near-infrared. Exposure of the imaging element can be performed with lasers with a short as well as with lasers with a long pixel dwell time. Preferred are lasers with a pixel dwell time between 0.005 ⁇ s and 20 ⁇ s.
  • the heat mode imaging element is developed by rinsing it with an aqueous alkaline solution.
  • aqueous alkaline solutions used in the present invention are those that are used for developing conventional positive working presensitised printing plates and have preferably a pH between 11.5 and 14.
  • the imaged parts of the top layer that were rendered more penetrable for the aqueous alkaline solution upon exposure and the corresponding parts of the underlying layer are cleaned-out whereby a positive working printing plate is obtained.
  • the composition of the developer used is also very important.
  • the developers and replenishers for developer used in the invention are preferably aqueous solutions mainly composed of alkali metal silicates and alkali metal hydroxides represented by MOH or their oxyde, represented by M 2 O, wherein said developer comprises SiO 2 and M 2 O in a molar ratio of 0.5 to 1.5 and a concentration of SiO 2 of 0.5 to 5% by weight.
  • alkali metal silicates preferably used are, for instance, sodium silicate, potassium silicate, lithium silicate and sodium metasilicate.
  • alkali metal hydroxides preferred are sodium hydroxide, potassium hydroxide and lithium hydroxide.
  • the developers used in the invention may simultaneously contain other alkaline agents.
  • other alkaline agents include such inorganic alkaline agents as ammonium hydroxide, sodium tertiary phosphate, sodium secondary phosphate, potassium tertiary phosphate, potassium secondary phosphate, ammonium tertiary phosphate, ammonium secondary phosphate, sodium bicarbonate, sodium carbonate, potassium carbonate and ammonium carbonate; and such organic alkaline agents as mono-, di- or triethanolamine, mono-di- or trimethylamine, mono-, di- or triethylamine, mono- or di-isopropylamine, n-butylamine, mono-, di- or triisopropanolamine, ethyleneimine, ethylenediimine and tetramethylammonium hydroxide.
  • the concentration of SiO 2 in the developer and replenisher preferably ranges from 1 to 4 % by weight. Such limitation of the concentration of SiO 2 makes it possible to stably provide lithographic printing plates having good finishing qualities even when a large amount of plates according to the invention are processed for a long time period.
  • an aqueous solution of an alkali metal silicate having a molar ratio [SiO 2 ] / [M 2 O], which ranges from 1.0 to 1.5 and a concentration of SiO 2 of 1 to 4 % by weight is used as a developer.
  • a replenisher having alkali strength equal to or more than that of the developer is employed.
  • a molar ratio, [SiO 2 ] / [M 2 O] of the replenisher is equal to or smaller than that of the developer, or that a concentration of SiO 2 is high if the molar ratio of the developer is equal to that of the replenisher.
  • organic solvents having solubility in water at 20 °C of not more than 10 % by weight according to need.
  • organic solvents are such carboxilic acid esters as ethyl acetate, propyl acetate, butyl acetate, amyl acetate, benzyl acetate, ethylene glycol monobutyl acetate, butyl lactate and butyl levulinate; such ketones as ethyl butyl ketone, methyl isobutyl ketone and cyclohexanone; such alcohols as ethylene glycol monobutyl ether, ethylene glycol benzyl ether, ethylene glycol monophenyl ether, benzyl alcohol, methylphenylcarbinol, n-amyl alcohol and methylamyl alcohol; such alkyl-substituted aromatic hydrocarbons as xylene; and such halogenated hydrocarbons
  • organic solvents may be used alone or in combination. Particularly preferred is benzyl alcohol in the invention. These organic solvents are added to the developer or replenisher therefor generally in an amount of not more than 5 % by weight and preferably not more than 4 % by weight.
  • the developers and replenishers used in the present invention may simultaneously contain a surfactant for the purpose of improving developing properties thereof.
  • surfactants include salts of higher alcohol (C8 - C22) sulfuric acid esters such as sodium salt of lauryl alcohol sulfate, sodium salt of octyl alcohol sulfate, ammonium salt of lauryl alcohol sulfate, Teepol B-81 (trade mark, available from Shell Chemicals Co., Ltd.) and disodium alkyl sulfates; salts of aliphatic alcohol phosphoric acid esters such as sodium salt of cetyl alcohol phosphate; alkyl aryl sulfonic acid salts such as sodium salt of dodecylbenzene sulfonate, sodium salt of isopropylnaphthalene sulfonate,sodium salt of dinaphthalene disulfonate and sodium salt of metanitrobenzene sulfonate; sulfonic acid salts of alkyl
  • Examples of such compounds are neutral salts such as NaCl, KCl and KBr as disclosed in JN-A- 58- 75 152; chelating agents such as EDTA and NTA as disclosed in JN-A- 58- 190 952 (U.S-A- 4 469 776), complexes such as [Co(NH3)6]Cl3 as disclosed in JN-A- 59- 121 336 (US-A- 4 606 995); ionizable compounds of elements of the group IIa, IIIa or IIIb of the Periodic Table such as those disclosed in JN-A- 55- 25 100; anionic or amphoteric surfactants such as sodium alkyl naphthalene sulfonate and N-tetradecyl-N,N-dihydroxythyl betaine as disclosed in JN-A- 50- 51 324; tetramethyldecyne diol as disclosed in US-A- 4 374 920; non-ionic surfactants as
  • any known means of supplementing a replenisher for developer may be employed.
  • Examples of such methods preferably used are a method for intermittently or continuously supplementing a replenisher as a function of the amount of PS plates processed and time as disclosed in JN-A- 55- 115 039 (GB-A- 2 046 931), a method comprising disposing a sensor for detecting the degree of light-sensitive layer dissolved out in the middle portion of a developing zone and supplementing the replenisher in proportion to the detected degree of the light-sensitive layer dissolved out as disclosed in JN-A- 58- 95 349 (US-A- 4 537 496); a method comprising determining the impedance value of a developer and processing the detected impedance value by a computer to perform supplementation of a replenisher as disclosed in GB-A- 2 208 249.
  • the printing plate of the present invention can also be used in the printing process as a seamless sleeve printing plate.
  • the printing plate is soldered in a cylindrical form by means of a laser.
  • This cylindrical printing plate which has as diameter the diameter of the print cylinder is slided on the print cylinder instead of applying in a classical way a classically formed printing plate. More details on sleeves are given in "Grafisch Nieuws" ed. Keesing, 15, 1995, page 4 to 6.
  • the obtained plate After the development of an image-wise exposed imaging element with an aqueous alkaline solution and drying, the obtained plate can be used as a printing plate as such. However, to improve durability it is still possible to bake said plate at a temperature between 200°C and 300°C for a period of 30 seconds to 5 minutes. Also the imaging element can be subjected to an overall post-exposure to UV-radiation to harden the image in order to increase the run length of the printing plate.
  • EXAMPLE 1 Positive working thermal plate based on an alkalisoluble binder.
  • a 0.20 mm thick aluminum foil was degreased by immersing the foil in an aqueous solution containing 5 g/l of sodium hydroxide at 50°C and rinsed with demineralized water.
  • the foil was then electrochemically grained using an alternating current in an aqueous solution containing 4 g/l of hydrochloric acid, 4 g/l of hydroboric acid and 5 g/l of aluminum ions at a temperature of 35°C and a current density of 1200 A/m 2 to form a surface topography with an average center-line roughness Ra of 0.5 ⁇ m.
  • the aluminum foil was then etched with an aqueous solution containing 300 g/l of sulfuric acid at 60°C for 180 seconds and rinsed with demineralized water at 25°C for 30 seconds.
  • the foil was subsequently subjected to anodic oxidation in an aqueous solution containing 200 g/l of sulfuric acid at a temperature of 45°C, a voltage of about 10 V and a current density of 150 A/m 2 for about 300 seconds to form an anodic oxidation film of 3.00 g/m 2 of Al 2 O 3 then washed with demineralized water, posttreated with a solution containing polyvinylphosphonic acid and then with a solution containing aluminum trichloride, subsequently rinsed with demineralized water at 20°C during 120 seconds and dried.
  • aqueous dispersion containing 0.10 g/m 2 of carbon black (trade name Printex L6) and 0.90 g/m 2 poly-p-vinylbenzyltrimethylammonium chloride (trade name DowECR77 from Dow Chemicals).
  • This material was imaged with an external drum IR-laser imaging apparatus (diode laser 830 nm, drumspeed 3.2 m/s, addressability 3600 dpi, power level in image plane 80-120 mW), and developed in an alkaline silicate containing developing solution (75% EP 26 developer commercially available from Agfa), containing 1.16 weight percent of SiO 2 and a molar ratio of [SiO 2 ] to [Na 2 O] of 0.59.,dissolving very rapidly the exposed parts
  • EXAMPLE 2 Positive working thermal plate based on an alkalisoluble binder.
  • a heat mode material was prepared in an identical way as the material described above except that the top layer contained 0.15 g/m 2 of carbon black (trade name Printex L6) and 0.85 g/m 2 poly-p-vinylbenzyltrimethylammonium chloride (trade name DowECR77 from Dow Chemicals).
  • This material was imaged with an external drum IR-laser imaging apparatus (diode laser 830 nm, drumspeed 3.2 m/s, addressability 3600 dpi, power level in image plane 80-120 mW), and developed in an alkaline silicate containing developing solution (75% EP 26 developer commercially available from Agfa), containing 1.16 weight percent of SiO 2 and a molar ratio of [SiO 2 ] to [Na 2 O] of 0.59.dissolving very rapidly the exposed parts.
  • an external drum IR-laser imaging apparatus diode laser 830 nm, drumspeed 3.2 m/s, addressability 3600 dpi, power level in image plane 80-120 mW
  • an alkaline silicate containing developing solution (75% EP 26 developer commercially available from Agfa), containing 1.16 weight percent of SiO 2 and a molar ratio of [SiO 2 ] to [Na 2 O] of 0.59.dissolving very rapidly the exposed parts.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Photosensitive Polymer And Photoresist Processing (AREA)
  • Printing Plates And Materials Therefor (AREA)

Claims (13)

  1. Procédé pour préparer des clichés d'impression lithographique englobant les étapes ci-après consistant à :
    a) préparer un élément de formation d'image thermosensible possédant, sur une base lithographique comprenant une surface hydrophile, une première couche englobant un polymère soluble dans une solution alcaline aqueuse, un composé capable de transformer la lumière en chaleur et une couche de protection du même côté de la base lithographique que celui où est située la première couche, ladite couche de protection étant impénétrable à un révélateur alcalin contenant du SiO2 à titre de silicate ;
    b) exposer en forme d'image ledit élément de formation d'image thermosensible à de la lumière actinique ;
    c) développer ledit élément de formation d'image thermosensible exposé en forme d'image avec ledit révélateur alcalin, de telle sorte que les zones exposées de la couche de protection et les zones sous-jacentes de la première couche sont dissoutes et les zones non exposées de la première couche restent non dissoutes, caractérisé en ce que ladite couche de protection englobe un sel d'ammonium quaternaire organique.
  2. Procédé pour préparer un cliché d'impression lithographique selon la revendication 1, dans lequel ledit sel d'ammonium quaternaire organique est un composé à bas poids moléculaire dont la chaíne carbonée contient au moins 6 atomes de carbone.
  3. Procédé pour préparer un cliché d'impression lithographique selon la revendication 2, dans lequel ledit sel d'ammonium quaternaire organique est un composé à bas poids moléculaire dont la chaíne carbonée contient au moins 12 atomes de carbone.
  4. Procédé pour préparer un cliché d'impression lithographique selon la revendication 3, dans lequel ledit sel d'ammonium quaternaire organique est un composé à bas poids moléculaire dont la chaíne aliphatique contient au moins 12 atomes de carbone.
  5. Procédé pour préparer un cliché d'impression lithographique selon l'une quelconque des revendications 1 à 4, dans lequel ledit sel d'ammonium quaternaire organique est un polymère.
  6. Procédé pour préparer un cliché d'impression lithographique selon la revendication 5, dans lequel ledit sel d'ammonium quaternaire organique est un sel de poly-p-vinylbenzyltriméthylammonium.
  7. Procédé pour préparer un cliché d'impression lithographique selon l'une quelconque des revendications 1 à 6, dans lequel le rapport en poids entre le sel d'ammonium quaternaire organique et le composé capable de transformer la lumière en chaleur se situe entre 98 : 2 et 20 : 80.
  8. Procédé pour préparer un cliché d'impression lithographique selon l'une quelconque des revendications 1 à 7, dans lequel le composé capable de transformer la lumière en chaleur est le noir de carbone.
  9. Procédé pour préparer un cliché d'impression lithographique selon l'une quelconque des revendications 1 à 7, dans lequel le composé capable de transformer la lumière en chaleur est un colorant de cyanine absorbant l'infrarouge.
  10. Procédé pour préparer un cliché d'impression lithographique selon l'une quelconque des revendications 1 à 9, dans lequel ledit révélateur alcalin contient du SiO2 et du M2O dans le rapport molaire de 0,5 à 1,5 et à une concentration du SiO2 de 0,5 à 5 % en poids.
  11. Procédé pour préparer un cliché d'impression lithographique selon la revendication 10, dans lequel ledit élément de formation d'image thermosensible exposé en forme d'image est développé avec un révélateur alcalin contenant du SiO2 dans le domaine de 1 à 4 % en poids.
  12. Procédé pour préparer un cliché d'impression lithographique selon la revendication 10 ou 11, dans lequel ledit élément de formation d'image thermosensible exposé en forme d'image est développé avec un révélateur alcalin contenant du SiO2 et du M2O dans un rapport molaire de 0,7 à 1,3.
  13. Procédé pour préparer un cliché d'impression lithographique selon l'une quelconque des revendications 1 à 12, dans lequel le liant de la première couche est une résine novolaque.
EP19980203118 1997-10-08 1998-09-16 Méthode pour la production de plaques d'impression positives à partir d'un élément thermosensible Expired - Lifetime EP0908779B1 (fr)

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EP97203127 1997-10-08
EP97203127 1997-10-08
EP19980203118 EP0908779B1 (fr) 1997-10-08 1998-09-16 Méthode pour la production de plaques d'impression positives à partir d'un élément thermosensible

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US6358669B1 (en) 1998-06-23 2002-03-19 Kodak Polychrome Graphics Llc Thermal digital lithographic printing plate
US6472119B1 (en) 1999-01-26 2002-10-29 Agfa-Gavaert Heat mode sensitive imaging element for making positive working printing plates
EP1023994B1 (fr) * 1999-01-26 2004-04-28 Agfa-Gevaert Un élément pour l'enregistrement de l'image thermosensible pour la fabrication de plaques lithographiques positives
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JP2001166462A (ja) 1999-12-10 2001-06-22 Fuji Photo Film Co Ltd 平版印刷版原版
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