EP1440797A2 - Wärmeempfindlicher Flachdruckplattenvorläufer - Google Patents

Wärmeempfindlicher Flachdruckplattenvorläufer Download PDF

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Publication number
EP1440797A2
EP1440797A2 EP04100163A EP04100163A EP1440797A2 EP 1440797 A2 EP1440797 A2 EP 1440797A2 EP 04100163 A EP04100163 A EP 04100163A EP 04100163 A EP04100163 A EP 04100163A EP 1440797 A2 EP1440797 A2 EP 1440797A2
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EP
European Patent Office
Prior art keywords
group
product
printing plate
plate precursor
independently represent
Prior art date
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EP04100163A
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English (en)
French (fr)
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EP1440797A3 (de
EP1440797B1 (de
Inventor
Marc AGFA-GEVAERT Van Damme
Geert AGFA-GEVAERT Deroover
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Agfa NV
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Agfa Gevaert NV
Agfa Gevaert AG
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Priority to EP20040100163 priority Critical patent/EP1440797B1/de
Publication of EP1440797A2 publication Critical patent/EP1440797A2/de
Publication of EP1440797A3 publication Critical patent/EP1440797A3/de
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Publication of EP1440797B1 publication Critical patent/EP1440797B1/de
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/46—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography characterised by the light-to-heat converting means; characterised by the heat or radiation filtering or absorbing means or layers
    • B41M5/465—Infrared radiation-absorbing materials, e.g. dyes, metals, silicates, C black

Definitions

  • the present invention relates to a positive working lithographic printing plate precursor that requires aqueous alkaline processing and comprises an infrared absorbing dye containing a polysiloxane group.
  • Lithographic printing presses use a so-called printing master such as a printing plate which is mounted on a cylinder of the printing press.
  • the master carries a lithographic image on its surface and a print is obtained by applying ink to said image and then transferring the ink from the master onto a receiver material, which is typically paper.
  • ink as well as an aqueous fountain solution also called dampening liquid
  • the lithographic image which consists of oleophilic (or hydrophobic, i.e. ink-accepting, water-repelling) areas as well as hydrophilic (or oleophobic, i.e. water-accepting, ink-repelling) areas.
  • so-called driographic printing the lithographic image consists of ink-accepting and ink-abhesive (ink-repelling) areas and during driographic printing, only ink is supplied to the master.
  • Printing masters are generally obtained by the so-called computer-to-film method wherein various pre-press steps such as typeface selection, scanning, color separation, screening, trapping, layout and imposition are accomplished digitally and each color selection is transferred to graphic arts film using an image-setter.
  • the film can be used as a mask for the exposure of an imaging material called plate precursor and after plate processing, a printing plate is obtained which can be used as a master.
  • a typical printing plate precursor for computer-to-film methods comprise a hydrophilic support and an image-recording layer of a photosensitive polymer layers which include UV-sensitive diazo compounds, dichromate-sensitized hydrophilic colloids and a large variety of synthetic photopolymers. Particularly diazo-sensitized systems are widely used.
  • Upon image-wise exposure typically by means of a film mask in a UV contact frame, the exposed image areas become insoluble and the unexposed areas remain soluble in an aqueous alkaline developer.
  • the plate is then processed with the developer to remove the diazonium salt or diazo resin in the unexposed areas.
  • the exposed areas define the image areas (printing areas) of the printing master, and such printing plate precursors are therefore called 'negative-working'.
  • positive-working materials wherein the exposed areas define the non-printing areas, are known, e.g. plates having a novolac/naphtoquinone-diazide coating which dissolves in the developer only at exposed areas.
  • heat-sensitive printing plate precursors are known. Such materials offer the advantage of daylight stability and are especially used in the so-called computer-to-plate method wherein the plate precursor is directly exposed, i.e. without the use of a film mask.
  • the material is exposed to heat or to infrared light and the generated heat triggers a (physico-)chemical process, such as ablation, polymerization, insolubilization by cross-linking of a polymer or by particle coagulation of a thermoplastic polymer latex, and solubilization by the destruction of intermolecular interactions.
  • a (physico-)chemical process such as ablation, polymerization, insolubilization by cross-linking of a polymer or by particle coagulation of a thermoplastic polymer latex, and solubilization by the destruction of intermolecular interactions.
  • US 5,466,557 describes a positive-working printing plate precursor which is sensitive to both ultraviolet (UV) and infrared (IR) light but not to visible light, comprising a support and a coating comprising an oleophilic polymer that is soluble in an aqueous alkaline developer and a latent Bronsted acid.
  • UV ultraviolet
  • IR infrared
  • EP-A 864420 describes a positive-working heat-sensitive printing plate precursor comprising a support, a first layer containing an oleophilic polymer that is soluble in an aqueous alkaline developer and an IR-sensitive top layer of which the penetrability by or solubility in the aqueous alkaline developer is changed upon exposure to IR light.
  • WO 97/39894 describes a positive-working heat-sensitive printing plate precursor which is sensitive to IR light but not to UV light comprising a support and an IR-sensitive coating comprising an oleophilic polymer that is soluble in an aqueous alkaline developer and a dissolution inhibitor which reduces the solubility of the polymer in the developer.
  • WO99/21725 and WO99/21715 describe a positive-working heat sensitive printing plate precursor of which the coating comprises a compound which increases the developer resistance thereof.
  • Said compound is selected from the group of poly(alkylene oxide), siloxanes and esters or amides of polyhydric alcohols.
  • US 5 491 046 describes a method for imaging a positive and/or negative lithographic printing plate precursor wherein the imaging layer comprises a resole resin, a novolac resin, a latent Bronsted acid and an IR absorber.
  • EP 1 162 078 describes an image formation material comprising a substrate and an image formation layer on the substrate which contains an infrared absorption dye having at least one surface orientation group as substituent for the purpose of improving sensitivity and/or image forming property of the image formation material.
  • the major problems associated with the prior art materials is (i) the low differentiation between the development kinetics of exposed and non-exposed areas - i.e. the dissolution of the exposed coating in the developer is not completely finished before the unexposed coating also starts dissolving in the developer - and (ii) thermal diffusion of heat into the substrate resulting in a reduced sensitivity of the printing plate precursor. This leads to low quality prints showing unsharp edges and toning (ink-acceptance in exposed areas) and narrow development latitude.
  • the lithographic printing plate precursor of the present invention contains a support having a hydrophilic surface and a coating provided thereon.
  • the coating comprises at least two layers, designated herein as first and second layer, the first layer being closest to the support, i.e. located between the support and the second layer.
  • the printing plate precursor is positive-working, i.e. after exposure by light and development the exposed areas of the coating are removed from the support and define hydrophilic (non-printing) areas, whereas the unexposed coating is not removed from the support and defines an oleophilic (printing) area.
  • the second layer is believed to act as a barrier that prevents penetration of the aqueous alkaline developer into the oleophilic resin of the first layer at unexposed areas.
  • the barrier function of the second layer can be reduced due to the exposure and dissolution of the coating at those areas can be increased upon immersion in an aqueous alkaline developer.
  • This reduction of the barrier function of the second layer upon exposure can be tested e.g. by measuring the water uptake, due to swelling of the oleophilic resin, of an exposed and a non-exposed sample: typically, the exposed sample absorbs a small amount of water whereas the average water-uptake of non-exposed samples is within statistical error not different from zero.
  • the barrier function of the second layer arises from the presence of a water-repellent compound.
  • a water-repellent compound Suitable examples thereof are polymers comprising siloxane and/or perfluoroalkyl units or block- or graft-copolymers comprising a poly- or oligo(alkylene oxide) block and a block of poly- or oligosiloxane and/or perfluoroalkyl units.
  • the water-repellent polymer may be present in an amount of e.g. between 0.5 and 15 mg/m 2 , preferably between 0.5 and 10 mg/m 2 , more preferably between 0.5 and 5 mg/m 2 and most preferably between 0.5 and 2 mg/m 2 .
  • the block comprising the siloxane and/or perfluoroalkyl units may be a linear, branched, cyclic or complex cross-linked polymer or copolymer.
  • the perfluoroalkyl unit is e.g. a -(CF 2 )- unit.
  • the number of such units may be larger than 10, preferably larger than 20.
  • the term polysiloxane compound shall include any compound which contains more than one siloxane group -Si(R,R')-O-, wherein R and R' are optionally substituted alkyl or aryl groups.
  • Preferred siloxanes are phenylalkylsiloxanes and dialkylsiloxanes, e.g.
  • the number of siloxane groups -Si(R,R')-O- in the (co-)polymer is at least 2, preferably at least 10, more preferably at least 20. It may be less than 100, preferably less than 60.
  • the alkylene-oxide block preferably includes units of the formula -C n H 2 n-O- wherein n is preferably an integer in the range 2 to 5.
  • the moiety - C n H 2 n- may include straight or branched chains.
  • the alkylene-oxide block moiety may also comprise optional substituents. Preferred embodiments and explicit examples of such polymers have been disclosed in WO99/21725.
  • a suitable water-repellent polysiloxane compound is preferably a random or block-copolymer comprising siloxane and alkyleneoxide groups, suitably comprising about 15 to 25 siloxane units and 50 to 70 alkyleneoxide groups.
  • Preferred polysiloxanes include a copolymer of dimethyldichlorosilane, ethylene oxide and propylene oxide. Specific compounds are the following: wherein o, p, q, r and s are integers >1.
  • a poly(alkylene oxide) block consisting of ethylene oxide and propylene oxide units is grafted to a polysiloxane block.
  • long chain alcohols consisting of ethylene oxide and propylene oxide units are grafted to a trisiloxane group.
  • the second layer may contain the oleophilic resin as well as the water-repellent compound.
  • block- or graft-copolymers comprising a poly- or oligo(alkylene oxide) block and a block of poly- or oligosiloxane and/or perfluoroalkyl units due to their bifunctional structure, position themselves during coating at the interface between the coating solution and air and thereby automatically form a separate layer, corresponding to the second layer of the present invention, even when applied as an ingredient of the coating solution of the oleophilic layer.
  • the water-repellent compound can be applied in a second solution, coated on top of the first layer.
  • a solvent in the second coating solution that is not capable of dissolving in the ingredients present in the first layer so that a phase of highly concentrated water-repellent polymer is obtained at the top of the material.
  • the oleophilic resin is preferably a polymer that is soluble in an aqueous developer, more preferably an aqueous alkaline developing solution with a pH between 7.5 and 14.
  • Preferred polymers are phenolic resins e.g. novolac, resoles, polyvinyl phenols and carboxy substituted polymers. Typical examples of these polymers are described in DE-A-4007428, DE-A-4027301 and DE-A-4445820.
  • the coating comprises an IR dye containing a polysiloxane group, which sensitizes the material to the IR light used during the exposure.
  • the polysiloxane group can be linear, branched, cyclic or complex cross-linked.
  • the number of silicium atoms in the polysiloxane group may be greater than 2, preferably 4 or greater than 4.
  • Preferred siloxane groups -Si(R,R')-O- are groups wherein R and R' are optionally substituted alkyl or aryl groups.
  • Preferred siloxane groups are phenylalkylsiloxanes and dialkylsiloxanes, e.g. phenylmethylsiloxanes and dimethylsiloxanes.
  • the IR dye is preferably a compound having an absorption maximum in the wavelength range between 750 and 1500 nm, so that a daylight stable material is obtained which can be handled without the need for darkroom conditions.
  • Daylight stable material means that no substantial dissolution in the developer is induced by exposure to visible light.
  • the sensitizing dye may be present in the first layer, in the second layer discussed above or in an optional other layer. It is believed that the high hydrophobicity of the polysiloxane group comprised in the IR light absorbing dye makes the dye more compatible with the water-repellent compound and thereby promotes the tendency of the dye to position itself preferentially in the second layer, i.e. further away from the support. As a result, the heat generated by the exposure is concentrated in the second layer and a high sensitivity is observed.
  • the concentration of the IR absorbing compound in the coating is typically between 0.25 and 10.0 wt %, more preferably between 0.5 and 7.5 wt %.
  • Preferred IR absorbing compounds for use in this invention are represented by the general formula III: wherein
  • a counter ion X with opposite charge is required to neutralize the compound.
  • the dye can be anionic or cationic as the chromophore and/or polysiloxane containing substituents on the chromophore and/or other substituents on the chromophore can have a charge.
  • the unit of charge of the dye is determined by the sum of the positive and/or negative charges of the substituents on the dye and one or more counter ions with equal sum of opposite charge is present to neutralize the dye.
  • the unit of charge of the counter ions can be mono or multiple and/or positive or negative.
  • -E 1 and -E 2 represent a neutral terminal group such as alkyl, -H, -OH,-F or -SiR a R b R c (and no other charged groups are present on the IR light absorbing dye)
  • a counter ion X carrying a negative charge is present to neutralise the positively charged IR light absorbing dye.
  • one of the terminal groups is represented by an anionic group such as -SO 3 - , -SO 4 - , or -COO - (and the other terminal group is represented by a neutral group and no other charged groups are present on the IR light absorbing dye) no counter ion is required.
  • One of the terminal groups can be a cationic group such as -[NR a R b R c ] + , than one counter ion carrying two negative charges (e.g. D-PO 4 2- , D-PO 3 2- ) or two counter ions each carrying one negative charge (e.g. Cl - , Br - , I - , F - , D-SO 3 -, D-SO 4 - , D-COO - , ClO 4 - or BF 4 - ) are present.
  • two counter ions each carrying one negative charge
  • none, one or more counter ions are necessary to neutralise the IR light absorbing dye.
  • R 3 represents a substituent carrying a negative charge, e.g. a negatively charged barbituric group, and no other substituents carrying a positive or negative charge are present on the IR light absorbing dye, a Zwitterion where the sum of charge of the dye is zero is obtained and no counter ion is present.
  • Negatively charged barbituric group wherein R 4 and R 5 independently represent an optionally substituted alkyl, alkenyl, cycloalkyl, aryl or aralkyl group, a perfluoroalkyl group or a polysiloxane group; each of said groups may optionally comprise a terminal group E defined above as -E 1 and -E 2 .
  • the negatively charged barbituric group is bonded to the heptamethine group by *.
  • Suitable subclasses of the above IR light absorbing dyes are represented by the following formulae:
  • p 1 , p 2 , a, b, -L 1 -, -L 2 -, -A 1 -, -A 2 -, -E 1 , -E 2 , R 1 , R 2 , R 3 , -Y 1 -, -Y 2 -, -Z 1 , -Z 2 and X have the same meaning as in formula III above;
  • R 4 and R 5 have the same meaning as defined above, with the proviso that at least one of the following substituents is represented by a polysiloxane group: -A 1 -, -A 2 -, R 1 , R 2 , R 3 , R 4 , R 5 or X.
  • IR light absorbing dyes are represented by formulae wherein two adjacent R 1 groups or two adjacent R 2 groups form an optionally substituted phenyl group, annelated with another phenyl group of the dye. So any of the formulae III to XIV wherein such phenyl group is present also represent dyes that are suitable for a precursor of the present invention. Two preferred embodiments of such dyes are represented by formulae XV and XVI: wherein
  • two adjacent R 1 groups and/or two adjacent R 2 groups can form an optionally substituted annelated phenyl group and such subclasses also are part of the present invention.
  • IR light absorbing dyes are represented by formula III in which the polysiloxane group is covalently linked to the dye and/or comprised in the counter ion X, if a counter ion X is present.
  • the indices/substituents p 1 , p 2 , -L 1 -, -L 2 -, -E 1 , -E 2 , -A 1 -, -A 2 -, -Y 1 -, -Y 2 -, R 1 , R 2 , R 3 , -Z 1 , -Z 2 and X have the same meaning as in formula III above.
  • IR light absorbing dyes are represented by formula III in which the polysiloxane group is not covalently linked to the dye but comprised in the counter ion X.
  • the indices/substituents p 1 , p 2 , -L 1 -, -L 2 -, -E 1 , -E 2 , -A 1 -, -A 2 -, -Y 1 -, -Y 2 -, R 1 , R 2 , R 3 , -Z 1 , -Z 2 and X have the same meaning as in formula III above with the proviso that:
  • IR absorbing dyes that are preferred for use in this invention include the following compounds:
  • the coating can contain additional infrared absorbing dyes such as cyanine dyes or pigments such as carbon black.
  • additional infrared absorbing dyes such as cyanine dyes or pigments such as carbon black.
  • suitable IR absorbers are described in e.g. EP-A 823327, EP-A 978376, EP-A 1029667, EP-A 1053868, EP-A 1093934; WO 97/39894 and WO 00/29214.
  • the first layer may further contain other ingredients such as additional binders to improve the run length of the plate, colorants, development inhibitors as disclosed in WO 97/39894 and EP-A 823 327 or accelerators such as 3,4,5-trimethoxybenzoic acid.
  • Said colorants are preferably dyes which during development remain in the coating at non-exposed areas and which are washed out at exposed areas, thereby producing a visible image.
  • Such indicator dyes preferably do not sensitize the coating to visible light.
  • Suitable development accelerators are described in e.g. EP-A933682.
  • Such compounds act as dissolution promoters because they are capable of reducing the dissolution time of the first layer.
  • cyclic acid anhydrides, phenols or organic acids can be used a lineair, branched, cyclic or cross-linked polysiloxane group in order to improve the aqueous developability.
  • Example of the cyclic acid anhydride include phtalic anhydride, tetrahydrophtalic anhydride, hexahydrophtalic anhydride, 3,6-endoxy 4-tertrahydrophalic anhydride, tetrachlorophtalic anhydride, maleic anhydride, chloromaleic anhydride, alpha-phenylmaleic anhydride, succinic anhydride, alpha-phenylmaleic anhydride, succinic anhydride, and pyromellitic anhydride, as described in U.S. Patent No. 4,115,128.
  • phenols examples include bisphenol A, p-nitrophenol, p-ethoxyphenol, 2,4,4'-trihydroxybenzophenone, 2,3,4-trihydroxy-benzophenone, 4-hydroxyphenone, 4,4',4"-trihydroxy-triphenylmethane, and 4,4',3",4"-tetrahydroxy-3,5,3',5'-tetramethyltriphenyl-methane, and the like.
  • organic acids include sulfonic acids, sulfinic acids, alkylsulfuric acids, phosphonic acids, phosphates, and carboxylic acids, as described in, for example, JP-A Nos. 60-888,942 and 2-96,755.
  • organic acids include p-toluenesulfonic acid, dodecylbenzenesylfonic acid, p-tolenesulfinic acid, ethylsulfuric acid, phenylphosphonic acid, phenylphosphinic acid, phenyl phosphate, diphenyl phosphate, benzoic acid, isophtalic acid, adipic acid, p-toluic acid, 3,4-dimethylmethoxybenzoic acid, phtalic acid, terephtalic acid, 4-cyclohexene-1,2-dicarboxylic acid, erucic acid, lauric acid, n-undecanoic acid, and ascorbic acid.
  • the amount of the cyclic acid anhydride, phenol, or organic acid contained in the image forming composition is preferably in the range of 0.05 to 20% by weight.
  • the support has a hydrophilic surface or is provided with a hydrophilic layer.
  • the support may be a sheet-like material such as a plate or it may be a cylindrical element such as a sleeve which can be slid around a print cylinder of a printing press.
  • the support is a metal support such as aluminum or stainless steel.
  • a particularly preferred lithographic support is an electrochemically grained and anodized aluminum support.
  • the anodized aluminum support may be treated to improve the hydrophilic properties of its surface.
  • the aluminum support may be silicated by treating its surface with a 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 may 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, polyvinylsulfonic acid, polyvinylbenzenesulfonic acid, sulfuric acid esters of polyvinyl alcohol, and acetals of polyvinyl alcohols formed by reaction with a sulfonated aliphatic aldehyde. It is further evident that one or more of these post treatments may be carried out alone or in combination.
  • the support can also be a flexible support, which is provided with a hydrophilic layer, hereinafter called 'base layer'.
  • the flexible support is e.g. paper, plastic film, thin aluminum or a laminate thereof.
  • Preferred examples of plastic film are polyethylene terephthalate film, polyethylene naphthalate film, cellulose acetate film, polystyrene film, polycarbonate film, etc.
  • the plastic film support may be opaque or transparent.
  • the base layer is preferably a cross-linked hydrophilic layer obtained from a hydrophilic binder cross-linked with a hardening agent such as formaldehyde, glyoxal, polyisocyanate or a hydrolyzed tetra-alkylorthosilicate.
  • a hardening agent such as formaldehyde, glyoxal, polyisocyanate or a hydrolyzed tetra-alkylorthosilicate.
  • the thickness of the hydrophilic base layer may vary in the range of 0.2 to 25 ⁇ m and is preferably 1 to 10 ⁇ m.
  • the hydrophilic binder for use in the base layer is e.g. a hydrophilic (co)polymer such as homopolymers and copolymers of vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylate acid, methacrylate 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% by weight, preferably 80% by weight.
  • the amount of hardening agent, in particular tetraalkyl orthosilicate, is preferably at least 0.2 parts per part by weight of hydrophilic binder, more preferably between 0.5 and 5 parts by weight, most preferably between 1 parts and 3 parts by weight.
  • the hydrophilic base layer may also contain 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 may be added e.g. silica prepared according to Stöber as described in J. Colloid and Interface Sci., Vol. 26, 1968, pages 62 to 69 or 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 surface of the hydrophilic base layer is given a uniform rough texture consisting of microscopic hills and valleys, which serve as storage places for water in background areas.
  • hydrophilic base layers for use in accordance with the present invention are disclosed in EP-A- 601 240, GB-P- 1 419 512, FR-P- 2 300 354, US-P- 3 971 660, and US-P- 4 284 705.
  • the amount of silica in the adhesion improving layer is between 200 mg/m 2 and 750 mg/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 /gram, more preferably at least 500 m 2 / gram.
  • the printing plate precursor of the present invention can be exposed to light, e.g. by means of LEDs or a laser head.
  • one or more lasers or a laser diode are used.
  • the light used for the exposure is infrared light having a wavelength in the range from about 750 to about 1500 nm and preferably a laser such as a semiconductor laser diode, a Nd:YAG or a Nd:YLF laser is used.
  • the required laser power depends on the sensitivity of the image-recording layer, the pixel dwell time of the laser beam, which is determined by the spot diameter (typical value of modern plate-setters at 1/e 2 of maximum intensity: 10-25 ⁇ m), the scan speed and the resolution of the exposure apparatus (i.e. the number of addressable pixels per unit of linear distance, often expressed in dots per inch or dpi; typical value: 1000-4000 dpi).
  • ITD plate-setters for thermal plates are typically characterized by a very high scan speed up to 1500 m/sec and may require a laser power of several Watts.
  • the Agfa Galileo T (trademark of Agfa Gevaert N.V.) is a typical example of a plate-setter using the ITD-technology.
  • XTD plate-setters operate at a lower scan speed typically from 0.1 m/sec to 20 m/sec and have a typical laser-output-power per beam from 20 mW up to 500 mW.
  • the Creo Trendsetter plate-setter family (trademark of Creo) and the Agfa Excalibur plate-setter family (trademark of Agfa Gevaert N.V.) both make use of the XTD-technology.
  • the known plate-setters can be used as an off-press exposure apparatus, which offers the benefit of reduced press down-time.
  • XTD plate-setter configurations can also be used for on-press exposure, offering the benefit of immediate registration in a multi-color press. More technical details of on-press exposure apparatuses are described in e.g. US 5,174,205 and US 5,163,368.
  • the non-exposed areas of the coating are removed by immersion in an aqueous alkaline developer, which may be combined with mechanical rubbing, e.g. by a rotating brush.
  • the development step may be followed by a drying step, a rinsing step, a gumming step, and/or a post-baking step.
  • the printing plate thus obtained can be used for conventional, so-called wet offset printing, in which ink and an aqueous dampening liquid are supplied to the plate.
  • Another suitable printing method uses so-called single-fluid ink without a dampening liquid.
  • Single-fluid inks which are suitable for use in the method of the present invention have been described in US 4,045,232 and US 4,981,517.
  • the single-fluid ink comprises an ink phase, also called the hydrophobic or oleophilic phase, and a polyol phase as described in WO 00/32705.
  • a 0.30 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, post-treated with a solution containing polyvinylphosphonic acid and subsequently with a solution containing aluminum trichloride, rinsed with demineralized water at 20°C during 120 seconds and dried.
  • the IR-sensitivity of the different compositions corresponds to the minimum energy density setting that is required to obtain a 50% reduction of the light absorption of the coating, measured on the developed plate at the wavelength maximum of the contrast dye, in areas which have been exposed with a dot area of a 50% screen (@200 lpi).
  • the support was prepared as described in examples 1 and 2.
  • the IR-sensitivity of the different compositions corresponds to the minimum energy density setting that is required to obtain a 50% reduction of the light absorption of the coating, measured on the developed plate at the wavelength maximum of the contrast dye, in areas which have been exposed with a dot area of a 50% screen (@200 lpi).

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials For Photolithography (AREA)
EP20040100163 2003-01-27 2004-01-20 Wärmeempfindlicher Flachdruckplattenvorläufer Expired - Fee Related EP1440797B1 (de)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1767353A3 (de) * 2005-09-27 2007-07-25 FUJIFILM Corporation Lithographischer Druckplattenvorläufer, lithographisches Druckverfahren und Cyaninfarbstoff

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1080884A1 (de) * 1999-08-31 2001-03-07 Agfa-Gevaert N.V. Verarbeitungsfreie thermische Flackdruckplatte mit einer genau definierten Nanostruktur
EP1249341A1 (de) * 2001-04-09 2002-10-16 Agfa-Gevaert Flachdruckplattenvorläufer
EP1256444A1 (de) * 2001-04-09 2002-11-13 Agfa-Gevaert Positivarbeitende lithographische Druckplattenvorläufer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1080884A1 (de) * 1999-08-31 2001-03-07 Agfa-Gevaert N.V. Verarbeitungsfreie thermische Flackdruckplatte mit einer genau definierten Nanostruktur
EP1249341A1 (de) * 2001-04-09 2002-10-16 Agfa-Gevaert Flachdruckplattenvorläufer
EP1256444A1 (de) * 2001-04-09 2002-11-13 Agfa-Gevaert Positivarbeitende lithographische Druckplattenvorläufer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1767353A3 (de) * 2005-09-27 2007-07-25 FUJIFILM Corporation Lithographischer Druckplattenvorläufer, lithographisches Druckverfahren und Cyaninfarbstoff
US7833689B2 (en) 2005-09-27 2010-11-16 Fujifilm Corporation Lithographic printing plate precursor and lithographic printing method

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EP1440797B1 (de) 2007-10-03

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