EP0649374B1 - Formation d'images - Google Patents

Formation d'images Download PDF

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Publication number
EP0649374B1
EP0649374B1 EP93914890A EP93914890A EP0649374B1 EP 0649374 B1 EP0649374 B1 EP 0649374B1 EP 93914890 A EP93914890 A EP 93914890A EP 93914890 A EP93914890 A EP 93914890A EP 0649374 B1 EP0649374 B1 EP 0649374B1
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EP
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Prior art keywords
coating
infra
ink
ablatable
layer
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EP93914890A
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German (de)
English (en)
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EP0649374A1 (fr
Inventor
Allen Peter Gates
Thomas Clark Felder
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Agfa Gevaert NV
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Du Pont UK Ltd
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    • 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
    • B41C1/1033—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 by laser or spark ablation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
    • B41N1/00—Printing plates or foils; Materials therefor
    • B41N1/003—Printing plates or foils; Materials therefor with ink abhesive means or abhesive forming means, such as abhesive siloxane or fluoro compounds, e.g. for dry lithographic printing
    • 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
    • B41C2210/16—Waterless working, i.e. ink repelling exposed (imaged) or non-exposed (non-imaged) areas, not requiring fountain solution or water, e.g. dry lithography or driography

Definitions

  • This invention relates to the formation of images directly from electronically composed digital sources and is concerned with the formation of images in this way in dry planography in which there is used a planographic printing plate having background or non-image surface areas which, although not moistened by water or other liquid, will not accept ink.
  • Imaging systems are also available which involve a sandwich structure which, on exposure to a heat generating infra-red laser beam, undergoes selective (imagewise) delamination and subsequent transfer of materials.
  • peel-apart systems are generally used as replacements for silver halide films.
  • planographic printing plates which do not require a dampening of the printing plate with an aqueous fountain solution to effectively wet the non-image areas.
  • diographic plates are typically derived from radiation sensitive plates comprising a substrate coated with a photosensitive layer, said layer being overlaid with a coating of a low surface energy material, which is repellant to printing ink.
  • the ink-repellant layer may be applied directly to the substrate, with the photosensitive layer being coated over the ink-repellant layer.
  • a single photosensitive, ink-repellant layer containing, for example, a photosensitive silicone polymer may be coated on a suitable substrate.
  • Radiation sensitive plates for driography as described in the prior art are imaged, in general, by selective removal of areas of the ink-repellant coating to reveal an oleophilic surface which readily accepts printing ink.
  • This may be accomplished in the case of two layer systems, for example, by photochemically changing the adhesion of the ink-repellant layer by exposing the plate to ultraviolet radiation though a photographic positive or negative transparency; the photosensitive layer may be either positive-working, in which case the adhesion of the ink-repellant layer will be strengthened, or negative-working, in which case adhesion will be weakened. In either case, the most weakly adhered coating may subsequently be removed by development with a processing solution.
  • plates having a single photosensitive, ink-repellant layer may be imagewise exposed to harden the image areas and then be developed with a processing solution to remove unhardened coating.
  • Such plates may be used to produce high quality images, but the required imagewise exposure via a photographic transparency detracts from the efficiency of the process. Similar disadvantages are associated with the attendant development step using a processing solution.
  • a digital imaging technique has been described in US Patent No. 4,911,075 whereby a driographic plate is produced by means of a spark discharge.
  • a plate precursor comprising an ink-repellant coating containing electrically conductive particles coated on a conductive substrate is used and the coating is ablatively removed from the substrate.
  • the ablative spark discharge provides images having relatively poor resolution.
  • Coatings which may be imaged by means of ablation with infra-red radiation have previously been proposed.
  • a proofing film in which an image is formed by imagewise ablation of a coloured layer on to a receiver sheet is described in PCT Application No. 90/12342.
  • This system is, however, disadvantageous in requiring a physical transfer of material in the imaging step, and such methods tend to give rise to inferior image resolution.
  • a driographic plate precursor comprising a base substrate carrying an infra-red radiation ablatable ink repellant coating, the coating being covered with a transparent cover sheet.
  • the infrared radiation ablatable ink repellant coating may be in the form of a single layer including an infra-red radiation ablatable moiety and an ink repellant moiety. Generally, however, the coating is in the form of at least two layers, viz one or more layers providing the coating with its ablatable properties and a further outer layer providing the coating with its ink repellant properties.
  • the ablatable properties may be provided by a layer including an ablatable polymer which also absorbs infra-red radiation.
  • an ablatable polymer which does not significantly absorb infrared radiation can be used in combination with a material which absorbs infra-red radiation.
  • the infra-red radiation absorbing material may be present in the same layer as the ablatable polymer or in another layer adjacent thereto.
  • up to 60% of infra-red absorbing material may be present and typical coating weights for the ablatable layer(s) are from 0.1 to 5.0 g/m2.
  • At least one of the base substrate and the ablatable layer or layers should have ink-receptive properties so that the image produced an exposure is ink-receptive.
  • the coating may be a simple mixture of an ink repellant component and an infra-red radiation ablatable component or an interpenetrating polymeric network formed in situ on the substrate.
  • Another alternative comprises a random block on graft copolymer of an ink repellant monomer units and ablatable monomer units containing infra-red absorbing material.
  • the plate precursor may contain one or more additional layers so as to increase adhesion of the coating to the substrate or to increase adhesion between layers, improve resistance to abrasion, or enhance the performance of the system in other respects.
  • the base substrate employed in the present invention can be any substrate suitable for the preparation of printing plates.
  • substrates are paper, plastics materials, metals, or plastics materials or paper coated with metal by lamination or by any other suitable method. It is advantageous to employ substrates with good rigidity to preserve dimensional stability.
  • Preferred substrates are metals, or plastics, or metallised plastics where there is a need for high reflectivity for infra-red radiation so as to 'trap' the radiation in the overlying coating.
  • Suitable polymers for the ablatable layer(s) are those which thermally decompose to products which are volatile at ambient temperature.
  • a wide variety of polymers has been found to function acceptably. Suitable examples include self-oxidising binders such as nitrocellulose and modified nitrocellulose as described in, for example, Cellulose and its Derivatives , by Ister and Flegien; non-self-oxidising binders, for example ethylcellulose, (meth)acrylic polymers and copolymers, such as poly(methyl methacrylate), poly(hydroxyethyl methacrylate), poly(n-butyl acrylate), poly(lauryl acrylate-co-methacrylic acid), etc., many of which are available commercially as Elvacite® resins from Du Pont or Neocryl® resins from ICI; styrenic resins such as polystyrene and poly(alpha methyl)styrene; rubbers based on isoprene; poly(viny
  • acrylic polymers and self-oxidising polymers are most preferred.
  • resins which decompose according to so-called "chemical amplification” schemes described by Frechet et al (J. Imaging. Sci., 30(2), (1986), 59-64); Ito and Willson ("Polymers in Electronics", ACS Symposium Series, 242, T. Davidson, Ed., ACS, Washington, DC, (1984) p. 11); E. Reichmanis and L.F. Thompson (Microelectronic Engineering, 13, (1991), 3-10); and others.
  • acid-catalysed degradation of specific ester, ether, or carbonate moieties leads to generation of carbon dioxide and other gases, and regeneration of the catalyst acid, providing amplification.
  • poly(propylene carbonate) supplied as QPAC® by Air Products, Allentown, Pa.
  • poly(4-t-butoxycarbonyloxystyrene sulphone) poly(p-tert-butoxycarbonyloxy-alpha-methylstrene)
  • various polyurethanes which are described in PCT Application No. 90/12342.
  • Systems have also been described by Y. Jiang and J.M.J. Frechet (Macromolecules, 24 (12), 1991, 3528-32) and C.G. Wilson et al (Proc.
  • IUPAC Macromol, Symp., 28th, 1982, 448 in which a polymer with a ceiling temperature lower than the ambient is end-capped, conferring ambient stability. Removing the protecting group or otherwise initiating degradation drops the ceiling temperature and the polymer spontaneously decomposes.
  • Specific examples of such polymers are acetyl-capped poly(phthalaldehyde) and poly(vinyl-tert-butyl carbonate sulphone).
  • this may be any suitable substance which absorbs infra-red radiation such as an infra-red absorbing sensitizing dye or, preferably, carbon black.
  • an infra-red absorbing sensitizing dye or, preferably, carbon black.
  • Commercial predispersions of carbon black in suitable binders are especially preferred.
  • Suitable commercial materials are, for example, Dispercel® CBJ-A (Pigment Black 7 in nitrocellulose) and Magnacryl® (Pigment Black 7 in acrylic resin), both available from Tennant-KVK Ltd, London, England; Microlith® CWA (Pigment Black 7 in acrylic resin), Microlith® CK (Pigment Black 7 in vinyl chloride-vinyl acetate), and Microlith® CA (Pigment Black 7 in ethyl cellulose), available from Ciba-Geigy Pigments (Manchester, England).
  • Suitable sensitising dyes are cyanines, or variations of cyanines in which the central conjugation system contains squarylium, croconium, cyclopentenyl, or other structures capable of inducing appropriate bathochromic shifts, as described in, for example, Infrared Sensitizing Dyes , M. Matsuoka, Ed., Plenum Press, New York, NY (1990). Infra-red sensitising dyes are available from Sumitomo Chemical (Japan), Eastman Chemicals (Rochester, New York, USA), and other suppliers. For sensitisation to 830 nm diode output, certain squarane dyes are preferred as described in US Patent No. 5,019,549. For YAG laser exposure at 1064 nm, Cyasorb® IR 165 from American Cyanamid is preferred. Infra-red sensitising dyes can also be mixed with carbon black.
  • Optional additives to the ablatable layer include materials which thermally degrade to gaseous products (blowing agents), for example, azodicarbonamide, sulphonyl hydrazide, and dinitrosopentamethylene tetramine (Porofor® products available from Bayer, UK).
  • Blowing agents materials which thermally degrade to gaseous products
  • materials which thermally degrade to produce acid can be added to the layer.
  • materials include iodonium, sulphonium, and phosphonium salts, organic esters such as 2,6-dinitrobenzyl tosylate, oxime sulphonates, dicarboximide sulphonates, and triazines.
  • Additives which improve coating quality may be incorporated, and these include fluorinated surfactants (such as Zonyl® surfactants from Du Font and Fluorad® surfactants from 3M), silicone-based materials (Sil-Wet® products from Dow-Corning), and other well-known classes of surfactants.
  • fluorinated surfactants such as Zonyl® surfactants from Du Font and Fluorad® surfactants from 3M
  • silicone-based materials Silicon-Wet® products from Dow-Corning
  • Additives which improve adhesion to either the substrate or the overlying ink-repellant layer may be incorporated.
  • Such materials include chlorosiliane or methoxysilane bonding agents from Dow-Corning (Reading, England).
  • the ink-repellant properties of the coating are provided by a suitable ink-repellant material providing the required degree of toughness, impermeability to gases, adhesion to its underlayer and ink repellency.
  • a suitable ink-repellant material providing the required degree of toughness, impermeability to gases, adhesion to its underlayer and ink repellency.
  • Such materials include fluropolymers and silicone polymers, for example poly(dimethylsiloxane).
  • the preferred materials for producing ink-repellant coatings with the required characteristics are silicone oligomers which cure by an addition mechanism. Suitable silicone oligomers for this purpose are available, for example, from Dow Corning SA (Seneffe, Belgium) under the trade name Syl-off®, and from Thomas Goldschmidt AG (Essen, Germany) under the trade name TEGO® RC.
  • Dow-Corning Syl-Off® 7046 (30% reactive siloxane polymer, thought to be vinylsiloxane) may be combined with Dow-Corning Syl-Off® 7048 (>95% polymethylhydrogensiloxane, thought to contain a platinum catalyst) to produce a coatable mixture which can be heat cured to produce an ink-repellant film.
  • Additives are available from Dow-Corning which will improve the adhesion and toughness of the silicone film, such as Syl-Off® 297 (anchorage additive, a mixture of acetoxysilane and epoxy functional silane), and Syl-Off® 7210 (controlled release additive, 60% silicone resin solution in xylene). Fluropolymer oligomers are available, from example, from Du Pont (Wilmington, Delaware, USA) under the trade name Zonyl®.
  • the coating weight of ink repellant material may be from 0.1 to 5.0 g/m2 and the ablatable material and the ink-repellant material may be successively coated on the substrate by means of coating techniques such as spin coating, bar coating, dip coating, reverse roll coating, gravure coating, knife coating and vacuum or plasma deposition processes.
  • the layers may be cured by baking at 50-180°C for between 30 seconds and 10 minutes, or by exposure to ultra-violet radiation in the case where the layers are photocrosslinkable.
  • said single layer comprises (i) either (a) a suitable ablatable ink-repellant material, such as a fluropolymer or silicone polymer, for example a polysiloxane, or (b) a combination of an ablatable material and an ink-repellant material and, where necessary, (ii) a material capable of sensitising said ablatable material to infra-red radiation.
  • a suitable ablatable ink-repellant material such as a fluropolymer or silicone polymer, for example a polysiloxane
  • a material capable of sensitising said ablatable material to infra-red radiation may be any suitable substance which absorbs infra-red radiation, such as an infra-red absorbing sensitising dye or, preferably, carbon black.
  • the single layer may also contain a sensitivity enhancing agent such as a blowing agent or a non-absorbing, thermally degradable acid-release compound, in addition to additives which improve coating quality and adhesion.
  • a sensitivity enhancing agent such as a blowing agent or a non-absorbing, thermally degradable acid-release compound, in addition to additives which improve coating quality and adhesion.
  • the layer may be coated on the substrate by means of the coating techniques previously described, and cured.
  • the driographic plate precursor includes a transparent cover sheet overlaid on the surface of the coating.
  • the sheet is overlaid on the ink-repellant layer.
  • an adhesive layer may be present between the coating and the sheet.
  • Said cover sheet enables the loosely bound debris which is produced in the image areas on exposure to be trapped and, thus, be prevented from being released to the atmosphere. The debris may then be removed from the exposed precursor simply by removal of the sheet prior to inking.
  • the sheet may be comprised of, for example, polypropylene or poly(ethylene terephthalate), or other suitable film material which is transparent to infra-red radiation.
  • the cover sheet may be formed from a masking film having a structure and composition as described in EP-A-323880. The thickness of the sheet may be within the range of from 8 ⁇ m to 100 ⁇ m.
  • the driographic plate precursor may also contain an anti-reflective layer coated on the cover sheet.
  • Suitable anti-reflective coatings are described in US Patent Nos. 3,793,022 and 4,769,306 and have a refractive index of from 1.0 to 1.6, preferably about 1.3.
  • Suitable materials for inclusion in the anti-reflective layer include, for example, fluorinated polymers available from Du Pont under the trade name Zonyl®.
  • the driographic plate precursor is imaged by a beam of radiation from a laser operating in the infra-red region of the spectrum.
  • a laser operating in the infra-red region of the spectrum particularly preferred are YAG lasers and diode lasers, for example the Sanyo SDL-7032-101 100 mW diode laser, set to deliver energy of up to 3000 mJ/cm2 to the coating.
  • Exposure to the beam of radiation causes ablation of the coating, which in turn drives away the repellant material.
  • Loosely bound debris on the exposed precursor may then simply be peeled away together with the cover sheet to reveal the underlying ink-receptive surface. The remaining, unimaged, areas do not accept ink.
  • the images produced show a high degree of resolution.
  • This example demonstrates that the precursor of the present invention can be exposed with an infra-red diode laser to impart an image which accepts driographic printing ink.
  • An infra-red absorbing ablatable composition was prepared by mixing the following ingredients: Ciba-Geigy Microlith® CWA 30.0 g Ethanol, 95% in water 18.0 g Distilled water 50.0 g Ammonia 2.0 g to form a uniform mixture. (The binder of the Microlith CWA constituted the ablatable polymer). The viscosity of the mixture was reduced by adding 100.0 g of distilled water, and the mixture was coated onto Howcolon® polyester film with a wire-wound bar. The coating was dried in an oven for 90 seconds at 100°C. The coating weight after drying was 1.02 g/m2. Both the coating and the substrate accepted driographic ink.
  • a silicone coating composition was prepared by mixing the following ingredients: Dow-Corning Syl-Off® 7046 5.7 g Isopar® H 59.3 g Dow-Corning Syl-Off® 7048 0.1 g to form a uniform mixture (Isopar H is a proprietary hydrocarbon liquid).
  • the silicone mixture was spin-coated at 100 RPM onto the ablatable layer, forming a silicone overcoat with a coating weight of 0.78 g/m2.
  • the overcoat was cured at 140°C for 5 minutes. The overcoated film repelled driographic ink.
  • the resultant precursor was mounted on a motor-driven drum and imaged on the coated side with a scanning diode laser (Sharp LT015MDO, 40mW, 828 nm) configured to deliver 30 mW continuous wave to a 15 ⁇ m (micron)spot.
  • a scanning diode laser Sharp LT015MDO, 40mW, 828 nm
  • a plurality of precursors was imaged in this way using different energies. This was effected by changing the rotation speed of the drum which alters the exposure time per spot i.e. the so-called "dwell-time".
  • the dwell time was varied from 10 ⁇ sec (200 mJ/cm2) to 30 ⁇ sec (600 mJ/cm2).
  • the ablatable layer ablated from the substrate in the image areas thereby removing the overlying silicone layer in those areas to reveal the underlying ink-accepting material.
  • the surface of each exposed precursor was rubbed lightly with Isopar® H-dipped cotton cloth to removed loose debris and was then allowed to dry.
  • the dried precursors were then inked with DaiNippon Dricolor® QS magenta ink using a roller applicator.
  • This example demonstrates that the thickness of the ink-repellant overlayer can be varied by a factor of three without affecting sensitivity or resolution.
  • An infra-red absorbing ablatable composition was prepared and coated onto Howcolon® polyester substrate as described in Example 1.
  • the coating weight after drying was 3.1 g/m2. Both the coating and the substrate accepted driographic ink.
  • a silicone coating composition was prepared by mixing the following ingredients: Dow-Corning Syl-Off® 7046 20.0 g Isopar® H 119.8 g Dow-Corning Syl-Off® 7048 0.2 g to form a uniform mixture.
  • the silicone mixture was spin-coated at 100 RPM onto the ablatable coating to form a silicone overcoat with a coating weight of 2.1 g/m2.
  • the experiment was repeated with the silicone bath diluted 1:1 with an equal weight of Isopar® H to form a silicone overcoat with a coating weight of 0.73 g/m2. In each case, the overcoat was cured at 140°C for 5 minutes and repelled driographic ink.
  • a plurality of the resultant precursors were mounted on a motor-driven drum and imaged on the coated side with a scanning diode laser (Sanyo SDL-7032-101, 100 mW, 8302 nm) configured to deliver 55 mW continuous wave to a 25 ⁇ m (micron) spot.
  • the energies delivered to the precursors were varied by changing the rotation speed of the drum, which altered the dwell time.
  • the dwell times varied from 23 ⁇ sec (400 mJ/cm2) to 124 ⁇ sec (2300 mJ/cm2).
  • the infra-red absorbing layer ablated from the substrate, removing the overlying silicone layer and revealing ink-accepting material.
  • the total amount of silicone and ablatable polymer debris which remained in the exposed areas in each case was estimated by examining the coatings at 100 times magnification and is given in the table below.
  • the exposed precursors were rubbed lightly with Isopar® H-dipped cotton cloth and allowed to dry.
  • the resultant printing plates were then inked with DaiNippon Dricolor magenta ink using a roller applicator.
  • the imaged areas accepted ink with no discernible difference between the two layers of different coating weight.
  • Inked resolution was estimated by examining the plates at 100 times magnification. As the table shows, features imaged at the shortest dwell times had resolution narrower than 10 ⁇ m (microns) while at the longest dwell timer the feature size increased to about 20 ⁇ m (microns).
  • Percentage Remaining Debris 3.1 g/m2 Ablatable Layer Dwell Time ( ⁇ sec) Energy (mJ/cm2) Feature Size ( ⁇ m) 0.73 g/m2 Silicone 2.1 g/m2 Silicone 207 2320 20 10 10 127 1428 20 20 20 93 1040 15 20 20 72 803 15 30 50 63 702 15 30 60 53 596 12 30 50 46 519 10 40 50 42 465 10 40 50 40 449 9 50 50 38 422 8 50 50 50
  • This example demonstrates a composition which ablates from a conventional aluminium printing plate substrate when exposed with an infra-red diode laser.
  • Infra-red absorbing ablatable compositions were prepared by mixing the following ingredients: A. 10% Sensitiser Polymethylmethacylate (Medium Molecular weight, Aldrich) 10.8 g Ciba-Geigy Microlith® CA 1.2 g Methyl Ethyl Ketone (MEK) 178.0 g Dow-Corning 1248 wetting agent 3.0 ml B. 18% Sensitiser Polymethylmethacylate (Medium Molecular Weight, Aldrich) 10.8 g Ciba-Geigy Microlith® CA 2.4 g Methyl Ethyl Ketone (MEK) 178.0 g Dow-Corning 1248 wetting agent 3.0 ml to form uniform mixtures.
  • the mixtures were coated onto 30 gauge anodised aluminum sheets by whirling at 100 RPM, and the coatings were then dried at 60°C for 30 seconds. Each mixture was then diluted by adding MEK in an amount equal to the mass of the mixture and the experiment was repeated to obtain coated sheets of reduced coating weight. Each mixture was then diluted once more with an equal mass of MEK, and used to obtain further coated sheets of even further reduced coating weight.
  • the coated sheets were mounted on a motor-driven drum and imaged on the coated side with a scanning diode laser (Sharp LTO15MD, 40 mW, 828 nm) configured to deliver 30 mW continuous wave to a 15 ⁇ m (micron) spot.
  • the dwell times were varied from 10 ⁇ sec (200 mJ/cm2) to 30 ⁇ sec (600 mJ/cm2) by changing the rotation rate of the drum.
  • ablation was incomplete, and a roughened surface was observed when the coating was examined under magnification.
  • higher energy exposures or higher sensitivity levels, or a combination of both variants were employed, the coating ablated completely and ablated line widths could be determined.
  • This example demonstrates that metallised polyester coated sequentially with a primer layer, an ablatable layer, and an ink-repellant overlayer can be imaged by infra-red diode laser and inked with driographic ink to form a high resolution image.
  • a primer layer was prepared by mixing the following ingredients: Epikote® 1004 5g Methyl Ethyl Ketone 100 ml
  • the primer layer was coated onto Mylar® pre-coated with a 50 nm thick layer of smooth aluminum using a wire-wound bar and oven dried at 140°C for 30 seconds, reaching a dry coating weight of 2.69 g/m2.
  • An infra-red absorbing ablatable composition was prepared by mixing the following ingredients: Polymethylmethacylate (Low Molecular Weight, Aldrich) 20 g Microlith® Black CK 5 g Methyl Ethyl Ketone 100 ml This mixture was coated using a wire-wound bar onto the primer layer and oven dried at 140°C for 30 seconds, reaching a dry coating weight of 3.17 g/m2.
  • An ink-repellant layer was prepared by mixing the following ingredients: Dow-Corning Syl-Off® 7046 20.0 g Isopar® H 40.0 g Dow-Corning Syl-Off® 7048 0.5 g Dow-Corning Syl-Off® 297 0.2 g until a uniform mixture was achieved. The mixture was coated onto the primed ablatable layer with a wire-wound bar and then oven cured at 140°C for 2 minutes. The dry coating weight of the ink-repellant layer was 0.83 g/m2. The coating rejected driographic ink.
  • the resultant precursor was exposed with an infra-red laser according to Example 1.
  • the coating ablated.
  • the ablated areas could be seen as clearly defined lines, less than 10 ⁇ m wide.
  • the plate was wiped with an Isopar® H-dipped cloth and allowed to dry at room temperature.
  • driographic ink was applied according to Example 1, the image areas accepted ink, while the unexposed areas rejected it.
  • This example demonstrates the use of an ablatable layer with improved sensitivity, together with a driographic overlayer.
  • An infra-red absorbing ablatable composition comprising the following composition: Microlith® Black CK 5g Methyl Ethyl Ketone 100 ml
  • the mixture was coated using a wire wound bar onto aluminium coated Mylar® as used in Example 4.
  • the coated film was oven dried at 140°C for 30 seconds.
  • the coating weight was 0.17 g/m2.
  • the coated film was then overcoated with an ink-repellant layer according to Example 4, and the resultant precursor exposed to an infra-red laser according to Example 1.
  • the infra-red absorbing layer ablated, removing the ink-repellant overcoat.
  • the ablated areas could be seen as clearly defined lines, less than 10 ⁇ m wide.
  • An infra-red absorbing ablatable composition was prepared by blending the following ingredients: Dispercel® CBJ-A 2.0 g MEK 8.0 g to form a uniform mixture. The mixture was coated on Howcolon® polyester using a No. 5 gauge wire-wound bar and allowed to air dry for five minutes to form a coating with a dry weight of around 1.0 g/m2.
  • a silicone coating composition was prepared by mixing the following ingredients: Dow-Corning Syl-Off® 7046 20.0 g Dow-Corning Syl-Off® 7048 0.05 g Dow-Corning Syl-Off® 297 0.5 g Dow-Corning Syl-Off® 7210 5.0 g Isopar® G 40.5 g to form a uniform mixture (Isopar G is a proprietary liquid hydrocarbon).
  • the silicone mixture was coated onto the ablatable layer using a No. 8 gauge wire-wound bar and cured at 130°C for 3 minutes. The resultant precursor was cut into two pieces and mounted on the motor-driven drum of the write engine described in Example 3.
  • Example 3 Onto one of the precursors, there was applied a cover sheet in the form of a clear adhesive overlay film. Onto the other precursor there was taped an 8 ⁇ m Mylar® cover sheet bearing no adhesive. The precursors were then exposed as described in Example 3. When the adhesive cover sheet was removed, it bore the image written by the laser, consisting of ablated pigment, polymer residue, and silicone ablated from the film. The non-adhesive cover sheet bore a much fainter image. Without wiping away loose debris, the two exposed precursors were inked as described earlier, and the inked images were contact-transferred to smooth paper.
  • the precursor which had been provided with the adhesive cover sheet printed a clear image, whereas the precursors which had been provided with the non-adhesive cover sheet printed a faint, patchy image.
  • the adhesive cover sheet was an excellent means for not only trapping ablated material, but also for removing loose debris thus obviating the need for a cleaning step.
  • the adhesive cover sheet also carried a copy of the printed image, allowing verification of the exposure.
  • driographic plate precursors of the present invention can be imaged by continuous-wave infra-red diodes in a computer-driven write engine.
  • An infra-red absorbing ablatable composition was prepared by blending the following ingredients: Dispercel® CBJ-A 2.0 g MEK 8.0 g to form a uniform mixture. This mixture was coated on Howcolon® polyester using a No. 5 gauge wire-wound bar and allowed to air dry for five minutes to form a coating with a dry weight of around 1.0 g/m2.
  • a silicone coating composition was prepared by mixing the following ingredients: Syl-Off® 7046 20.0 g Syl-Off® 7048 0.5 g Syl-Off® 297 0.2 g Isopar® G 40.0 g to form a uniform mixture.
  • the silicone mixture was coated onto the ablatable layer using a No. 8 gauge wire-wound bar and cured at 130°C for 3 minutes. A Mylar cover sheet was then applied.
  • the resultant precursor was exposed through the cover sheet on a write engine supplied by CREO (Vancouver BC) using an array of 32 infra-red lasers emitting at 830 nm (Sanyo Semiconductor, SDL-7032-102, Allendale, NJ), to produce a 150 line screen text pattern, using 130 mJ/cm2 of incident laser energy.
  • the imaged precursor was removed from the drum and loose debris was wiped away with an Isopar® H-dampened cloth.
  • the resultant printing plate was inked as described previously, and the inked image was contact-transferred to smooth paper. A recognisable image was printed.
  • Example 6 was repeated using Automask® material as the adhesive overlay film.
  • Automask® is a laminated sheet product supplied by Autotype International Ltd for use as a masking film in the preparation of lithographic plates and screen printing stencils.
  • the red adhesive coated membrane was separated from the base film and applied to the surface of the ink repellant layer.
  • the precursor was exposed as described in Example 3 and the membrane was removed.
  • the resultant plate was found to be free of loose debris and did not require a cleaning step prior to printing.
  • the adhesive of the membrane was based on a natural rubber, with the addition of an alpha terpene resin to improve tack, and provided a peel resistance of 37-70 gm/30 mm sample width measured at an angle of 180° when the membrane and the base film were separated.
  • Example 6 was repeated using a cover sheet provided in situ .
  • An adhesive sublayer was produced by applying a solution of natural rubber (12g) and an alpha terpene resin (100 g) in hydrocarbon solvent (5000 ml) to the surface of the silicone layer of the ablatable precursor assembly described in Example 6.
  • a composition comprising a solution of an aliphatic polyurethane resin and cellulose nitrate as described in Example 1B of European Patent No.323,880 was coated over the adhesive layer to a thickness of 30 ⁇ m (microns).
  • Example 3 The precursor was exposed as described in Example 3. The cover sheet was removed to obtain a printing plate requiring no cleaning stage prior to printing.

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Printing Plates And Materials Therefor (AREA)
  • Photosensitive Polymer And Photoresist Processing (AREA)
  • Manufacture Or Reproduction Of Printing Formes (AREA)
  • Thermal Transfer Or Thermal Recording In General (AREA)
  • Materials For Photolithography (AREA)

Abstract

Un précurseur de plaque d'imprimerie driographique comprend un substrat de base, une couche répulsive d'encre effaçable par rayons infrarouges sur le substrat et une feuille de couverture transparente sur cette couche. Une image est formée sur la plaque de manière séquentielle en exposant les zones de la couche à un rayon laser pour effacer la couche dans ces zones. La feuille de couverture et les produits d'effacement sont alors enlevés.

Claims (10)

  1. Précurseur de plaque driographique, comprenant un support constituant la base, qui porte un revêtement repoussant l'encre, enlevable par les rayons infrarouges, le revêtement étant recouvert d'une feuille de recouvrement transparente.
  2. Précurseur de plaque selon la revendication 1, dans lequel le revêtement est sous la forme d'une couche unique comprenant une matière enlevable par les rayons infrarouges et une matière repoussant l'encre.
  3. Précurseur de plaque selon la revendication 1, dans lequel le revêtement comprend une couche renfermant une matière enlevable par les rayons infrarouges, et une couche externe renfermant une matière repoussant l'encre.
  4. Précurseur de plaque selon la revendication 2 ou 3, dans lequel la matière enlevable par les rayons infrarouges comprend un polymère enlevable et un agent absorbant les rayons infrarouges.
  5. Précurseur de plaque selon la revendication 4, dans lequel le polymère enlevable est un polymère acrylique ou un polymère à autooxydation.
  6. Précurseur de plaque selon la revendication 4 ou 5, dans lequel l'agent absorbant les rayons infrarouges est du noir de carbone ou un colorant sensibilisant aux infrarouges.
  7. Précurseur de plaque selon l'une quelconque des revendications 2 à 6, dans lequel la matière repoussant l'encre est un polymère silicone.
  8. Précurseur de plaque selon l'une quelconque des revendications précédentes, dans lequel la feuille de recouvrement adhère au revêtement.
  9. Procédé de formation d'image, qui comprend :
    (a) la fourniture d'un précurseur de plaque driographique, comprenant un support constituant la base, qui porte un revêtement repoussant l'encre, enlevable par les rayons infrarouges, ledit revêtement étant recouvert d'une feuille de recouvrement transparente,
    (b) l'exposition selon l'image du précurseur, que l'on réalise en dirigeant le faisceau provenant d'un laser à infrarouge sur des zones successives du revêtement, de sorte que le revêtement s'enlève et perd son aptitude à repousser l'encre dans ces zones, pour former une image,
    (c) l'élimination de la feuille de recouvrement et des produits provenant de l'ablation du revêtement, et
    (d) l'encrage de l'image.
  10. Procédé selon la revendication 9, dans lequel une couche antireflet est appliquée sur la feuille de recouvrement.
EP93914890A 1992-07-06 1993-07-06 Formation d'images Expired - Lifetime EP0649374B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB929214304A GB9214304D0 (en) 1992-07-06 1992-07-06 Improvements in or relating to image formation
GB9214304 1992-07-06
PCT/GB1993/001413 WO1994001280A1 (fr) 1992-07-06 1993-07-06 Formation d'images

Publications (2)

Publication Number Publication Date
EP0649374A1 EP0649374A1 (fr) 1995-04-26
EP0649374B1 true EP0649374B1 (fr) 1996-03-13

Family

ID=10718263

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93914890A Expired - Lifetime EP0649374B1 (fr) 1992-07-06 1993-07-06 Formation d'images

Country Status (7)

Country Link
EP (1) EP0649374B1 (fr)
JP (1) JP3289906B2 (fr)
CA (1) CA2139644A1 (fr)
DE (1) DE69301826T2 (fr)
ES (1) ES2084505T3 (fr)
GB (2) GB9214304D0 (fr)
WO (1) WO1994001280A1 (fr)

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US6066434A (en) * 1995-08-21 2000-05-23 E. I. Du Pont De Nemours And Company Waterless printing plates
JP3625089B2 (ja) * 1995-09-13 2005-03-02 富士写真フイルム株式会社 湿し水不要平版印刷版の形成方法
JPH09239943A (ja) * 1996-03-08 1997-09-16 Fuji Photo Film Co Ltd 湿し水不要平版原版
JPH09239942A (ja) * 1996-03-08 1997-09-16 Fuji Photo Film Co Ltd 湿し水不要平版印刷原版及びその製版方法
EP0816071B1 (fr) * 1996-07-04 2000-10-04 Agfa-Gevaert N.V. Elément d'enregistrement thermosensible et procédé pour la fabrication de plaques pour l'impression lithographiques utilisant cet élément
US6261739B1 (en) * 1996-09-11 2001-07-17 Fuji Photo Film Co., Ltd. Laser ablative recording material
US6358671B1 (en) * 1996-09-18 2002-03-19 Presstek, Inc. Methods and compositions for imaging and cleaning lithographic printing plates
US5924364A (en) * 1997-01-17 1999-07-20 Agfa-Gevaert N.V. Laser-imagable recording material and printing plate produced therefrom for waterless offset printing
JP2001508001A (ja) * 1997-01-17 2001-06-19 アグフア−ゲヴエルト・ナームローゼ・フエンノートシヤツプ レーザーで像形成可能な記録材料およびそれから製造される無水オフセット印刷用の印刷版
GB9702953D0 (en) * 1997-02-13 1997-04-02 Horsell Graphic Ind Ltd Planographic printing
DE19712323A1 (de) * 1997-03-24 1998-10-01 Agfa Gevaert Ag Strahlungsempfindliches Gemisch und damit hergestelltes Aufzeichnungsmaterial für Offsetdruckplatten
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EP1243433B1 (fr) 2001-03-22 2004-05-26 Agfa-Gevaert Méthode d'impression lithographique utilisant une encre comprenant un fluide unique
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Also Published As

Publication number Publication date
GB2283703B (en) 1996-06-26
DE69301826T2 (de) 1996-09-12
JP3289906B2 (ja) 2002-06-10
CA2139644A1 (fr) 1994-01-20
GB9214304D0 (en) 1992-08-19
ES2084505T3 (es) 1996-05-01
EP0649374A1 (fr) 1995-04-26
WO1994001280A1 (fr) 1994-01-20
JPH07508474A (ja) 1995-09-21
GB2283703A (en) 1995-05-17
GB9500281D0 (en) 1995-03-08
DE69301826D1 (de) 1996-04-18

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