EP0972637B1 - Précurseur de plaque d'impression lithographique thermique de longue conservation - Google Patents

Précurseur de plaque d'impression lithographique thermique de longue conservation Download PDF

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Publication number
EP0972637B1
EP0972637B1 EP99202011A EP99202011A EP0972637B1 EP 0972637 B1 EP0972637 B1 EP 0972637B1 EP 99202011 A EP99202011 A EP 99202011A EP 99202011 A EP99202011 A EP 99202011A EP 0972637 B1 EP0972637 B1 EP 0972637B1
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EP
European Patent Office
Prior art keywords
layer
infrared light
near infrared
light absorbing
absorbing compound
Prior art date
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EP99202011A
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German (de)
English (en)
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EP0972637A1 (fr
Inventor
Ludo Van Rompuy
August Meisters
Luc Leenders
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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
    • B41C1/1033—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
    • 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
    • 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
    • B41C1/00—Forme preparation
    • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
    • B41C1/1041—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by modification of the lithographic properties without removal or addition of material, e.g. by the mere generation of a lithographic pattern
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2201/00—Location, type or constituents of the non-imaging layers in lithographic printing formes
    • B41C2201/02—Cover layers; Protective layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C2201/00—Location, type or constituents of the non-imaging layers in lithographic printing formes
    • B41C2201/14—Location, type or constituents of the non-imaging layers in lithographic printing formes characterised by macromolecular organic compounds, e.g. binder, adhesives
    • 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
    • B41C2210/04—Negative working, i.e. the non-exposed (non-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
    • B41C2210/08—Developable by water or the fountain 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
    • B41C2210/22—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

Definitions

  • the present invention relates to a heat-mode lithographic printing plate precursor which is sensitive to near infrared light and to methods for making a lithographic printing master in computer-to-plate and computer-to-press procedures.
  • Rotary printing presses use a so-called master such as a printing plate which is mounted on a cylinder of the printing press.
  • the master carries an image which is defined by the ink accepting areas of the printing surface and a print is obtained by applying ink to said surface and then transferring the ink from the master onto a substrate, which is typically a paper substrate.
  • ink as well as an aqueous fountain solution are fed to the printing surface of the master, which is referred to herein as lithographic surface and 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.
  • Printing masters are generally obtained by the so-called computer-to-film method wherein various pre-press steps such as typeface selection, scanning, colour separation, screening, trapping, layout and imposition are accomplished digitally and each colour 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.
  • thermal materials disclosed in the prior art are suitable for exposure with either an internal drum image-setter (i.e. typically a high-power short-time exposure) or an external drum image-setter (i.e. relatively low-power long-time exposure).
  • an internal drum image-setter i.e. typically a high-power short-time exposure
  • an external drum image-setter i.e. relatively low-power long-time exposure
  • EP-A084444 describes a printing plate precursor comprising aluminium silicate as image forming material. Upon laser exposure, the aluminium silicate is converted to a more oleophilic form. However, the difference in oleophilicity between exposed and unexposed areas is rather low and it is necessary to apply a coating which comprises an organic, oleophilic phase that preferentially wets and deposits on the exposed areas and an aqueous phase that preferentially wets and deposits on the unexposed areas. This system does not fulfil the requirement of needing no processing.
  • DE-A-19814877 describes a printing member wherein a hydrophilic zirkonium oxide ceramic is converted upon exposure into an oleophilic phase.
  • This system is characterised by a low speed, requiring the use of a very powerful, Q-switched Nd:YAG laser and, accordingly, does not fulfil the requirement of being universally exposable.
  • Heat-mode materials have been described in the prior art wherein a light absorbing compound is used as a light-to-heat convertor and wherein the heat generated upon exposure triggers reactive compounds to undergo a (physico-)chemical reaction. Due to the presence of reactive compound(s), care must be taken with regard to storage conditions to guarantee a long shelf life of the material. In such materials the near infrared light absorbing compound is present in a typical amount relative to all the compounds in the material, excluding the support, of 1 to 10% by weight.
  • a printing master may be obtained by exposing a material comprising a metal support and provided thereon one layer or a stack of layers, characterised in that said layer or stack of layers comprises a near infrared light absorbing compound in an amount not less than 50% by weight, relative to all the compounds present in said layer or stack of layers, and that the amount of other reactive compounds in said layer or stack of layers is not more than 20% by weight, relative to all the compounds present in said layer or stack of layers.
  • the materials of the present invention require no processing or can be processed with plain water.
  • the latter property makes them very suitable for computer-to-press and on-press coating procedures.
  • Another major benefit of the materials of the present invention is the excellent stability : they can be stored during 2 minutes at 100°C without toning (ink acceptance in non-exposed areas), contrary to conventional thermal lithographic printing plate precursors which show significant toning when exposed to the above conditions.
  • Some materials according to the present invention, especially those comprising carbon as a near infrared light absorbing compound, can even be stored during 2 minutes at 150°C without noticeable toning.
  • the imaging mechanism of the materials according to the present invention is not known, but may rely on a thermal interaction between the near infrared light absorbing compound and the metal support. For instance, it was observed that the aluminium signal measured by secondary ion mass spectroscopy while sputtering away the upper 2 nm from the surface of a material, consisting of an anodised aluminium support and a layer consisting exclusively of near infrared light absorbing compound, drops upon image-wise exposure down to 50% or even 10% of the signal measured at unexposed areas, the specific value being highly dependent on the structure of the near infrared light absorbing compound used.
  • imaging material as used herein embraces a plate precursor consisting of a sheet-like metal support and one or more functional layers as well as a composition which may be applied directly on a cylinder of a printing press.
  • the cylinder is the metal support of the material according to the present invention.
  • image is used herein in the context of lithographic printing, i.e. "a pattern consisting of oleophilic and hydrophilic areas".
  • the material of the present invention is negative working, which means that the areas, which are exposed to light, are rendered oleophilic and thus ink accepting due to said exposure.
  • the feature "negative working” may be considered as an equivalent of the feature “non-ablative", since in ablative materials the functional layers are completely removed from the underlying (hydrophilic) metal support upon image-wise exposure so as to obtain a positive image (exposed areas are hydrophilic, ink repelling). Analysis of the exposed areas of the material according to the present invention indeed showed that the layer or stack of layers is not completely removed upon image-wise exposure but is converted into a hydrophobic surface on the metal support. The unexposed areas are hydrophilic or become hydrophilic after processing with plain water.
  • the feature "compound present in an amount not less than 50% by weight relative to said layer or stack of layers” may be referred to herein briefly as “main compound” (of said layer or stack of layers) and both terms shall be considered equivalent and are used hereinafter interchangeably.
  • the near infrared light absorbing compound is the main compound relative to all the compounds in all the layers of the material, excluding the metal support.
  • the amount of near infrared light absorbing compound is not less than 70% by weight and even more preferably not less than 90% by weight relative to the layer(s) of the material excluding the support.
  • the layer or stack of layers consists essentially of a near infrared light absorbing compound.
  • Mixtures of near infrared light absorbing compounds can also be used, and then, the total amount of all near infrared light absorbing compounds relative to all the compounds in all the layer(s) of the material excluding the support is not less than 50% by weight, preferably not less than 70% by weight and even more preferably not less than 90 % by weight.
  • the layer or stack of layers may comprise other compounds in addition to the near infrared light absorbing compound, the amount of other reactive compounds besides the near infrared light absorbing compound is less than 20% by weight relative to all the compounds in the layer or stack of layers that are provided on the metal support.
  • the feature "reactive compound” shall be understood as a compound which undergoes a (physico-)chemical reaction due to the heat generated during image-wise exposure. Examples of such reactive compounds are thermoplastic polymer latex, diazo resins, naphtoquinone diazide, photopolymers, resole and novolac resins, or modified poly(vinyl butyral) binders. More examples can be found in J. Prakt. Chem. Vol. 336 (1994), p. 377-389.
  • the amount of said other reactive compounds is less than 10% by weight and most preferably, the material is substantially free from reactive compounds other the near infrared light absorbing compound.
  • the words "substantially free” shall be understood as meaning that a small ineffective amount of such reactive compounds may be present in addition to the near infrared light absorbing compound. Said small ineffective amount is not essential for or does not significantly contribute to the imaging process of the material. This can be tested easily by preparing a material without said small amount of reactive compounds and establishing whether the material thus obtained can still be used to make a printing master.
  • the treshold value below which the amount of the other reactive compounds, besides the near infrared light absorbing compound, may be regarded as "ineffective” depends on the nature of the reactive compounds.
  • the material may further comprise non-reactive compounds, i.e. inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as e.g. a binder, surfactant, matting agent or filler.
  • inert components such as
  • hydrophilic binders e.g. carboxymethyl cellulose, homopolymers and copolymers of vinyl pyrrolidone, vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate or maleic anhydride/vinylmethylether copolymers.
  • the amount of hydrophilic binder in the layer or stack of layers is preferably less than 40% by weight and more preferably between 5 and 20% by weight.
  • the material of the present invention may comprise a stack of layers but a single layer is preferred.
  • the near infrared light absorbing compound may be present in all the layers of said stack or may be localised in just a single layer of said stack.
  • the layer comprising the near infrared light absorbing compound is preferably applied directly on the metal support.
  • the layer comprising the near infrared light absorbing compound is preferably very thin, i.e. having a dry layer thickness below 1 ⁇ m, preferably below 0.4 ⁇ m and even more preferably ranging from 0.1 to 0.25 ⁇ m. A layer thickness below 0.1 ⁇ m may still give satisfactory results.
  • anodised aluminium support provided with a 0.1 ⁇ m layer consisting of a near infrared light absorbing compound, which is cleaned by wiping thoroughly with a dry cloth and then image-wise exposed, still provides an excellent printing master.
  • the support used in the present invention is a metal support.
  • Preferred examples of said metal support are steel, especially polished stainless steel, and aluminium.
  • Phosphor bronze an alloy comprising >90 wt.% of copper, ⁇ 10 wt.% of tin and small amounts of phosphor
  • the aluminium support is preferably an electrochemically grained and anodised aluminium support. Most preferably said aluminium support is grained in nitric acid, yielding imaging elements with a higher sensitivity.
  • the anodised aluminium support may be treated to improve the hydrophilic properties of its surface.
  • the aluminium 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 aluminium oxide surface with a phosphate solution that may further contain an inorganic fluoride. Further, the aluminium 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 treatment may involve rinsing the aluminium oxide surface with a bicarbonate solution.
  • the aluminium oxide surface may be treated with poly(vinyl phosphonic acid), poly(vinyl methylphosphonic acid), phosphoric acid esters of poly(vinyl alcohol), poly(vinyl sulphonic acid), poly(vinyl benzenesulphonic acid), sulphuric acid esters of poly(vinyl alcohol), and acetals of poly(vinyl alcohols) formed by reaction with a sulphonated aliphatic aldehyde. It is evident that one or more of these post treatments may be carried out alone or in combination.
  • a highly preferred material according to the present invention comprises an anodised aluminium support and provided directly thereon a single recording layer which consists essentially of a near infrared light absorbing compound and is substantially free from other reactive compounds.
  • a top layer for protecting the recording layer against moisture, chemicals, oxygen, mechanical impact, etc.
  • the near infrared light absorbing compound used in the present invention is an organic or carbon-based compound which is capable of converting near infrared light into heat and which is selected from the group consisting of organic dyes, organic polymers such as a polypyrrole or polyaniline-based polymer dispersions, carbon and graphite, Dispersed carbon and the infrared dyes listed in Table 1 are highly preferred.
  • the near infrared light absorbing compound can be applied on the metal support by coating a solution or dispersion of said compound using the known coating techniques. Coating of an aqueous dispersion of carbon or a solution of an organic dye on a metal support are highly preferred embodiments of the method according to the present invention. Jet methods can be used as an alternative coating technique, whereby either a uniform layer of near infrared absorbing compound is jet-coated on the metal support and then image-wise exposed or whereby the near infrared light absorbing compound is image-wise applied to the metal support and then rendered hydrophobic by intense overall heating, e.g. by infrared laser exposure.
  • the material of the present invention can also be prepared by rubbing in a metal support with a dry powder of a near infrared light absorbing compound, e.g. carbon or an organic dye.
  • the material of the present invention can be used in computer-to-plate (off-press exposure) or computer-to-press (on-press exposure) procedures.
  • the material can also be prepared by on-press coating, i.e. by applying a composition, comprising a near infrared light absorbing compound as main component and not more than 20% by weight of other reactive compounds, directly on the metal surface of a cylinder of a rotary printing press.
  • Said on-press coating can also be performed indirectly by applying said composition on a metal support which is mounted on a cylinder of a rotary printing press.
  • said composition can be applied on a metal sleeve which, after image-wise exposure and optional processing, is then transferred to a cylinder of a rotary printing press.
  • the materials of the present invention may be exposed to near infrared light having a wavelength ranging from about 700 to about 1500 nm by a light source such as a light emitting diode or a laser, e.g. a semiconductor laser diode, a Nd:YAG or a Nd:YLF laser.
  • a light source such as a light emitting diode or a laser, e.g. a semiconductor laser diode, a Nd:YAG or a Nd:YLF laser.
  • the required laser power depends on 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 (i.e. the number of distinct pixels per unit of linear distance, often expressed in dots per inch or dpi; typical value : 1000-4000 dpi).
  • ITD image-setters are typically characterised by very high scan speeds up to 500 m/sec and may require a laser power of several Watts. Satisfactory results have also been obtained by using XTD image-setters having a typical laser power from 100 mW to 500 mW at a lower scan speed, e.g. from 0.1 to 10 m/sec.
  • the unexposed areas of the material according to the present invention can be removed easily by wiping the material after exposure with plain water. This step may be performed on-press, i.e. after mounting the exposed plate on the plate cylinder of a printing press.
  • the materials of the present invention can even be used as a printing master immediately after image-wise exposure without any additional processing because the unexposed areas are readily removed by the fountain solution or the ink applied during the first runs of the printing job.
  • a solution of 1 wt.% of cpd 1, defined above, in methylethyl ketone was prepared by stirring vigorously during 1 hour. This solution was coated at a wet thickness of 20 ⁇ m on an anodised aluminium support and then dried during 20 min. at 50 °C. Infrared reflection spectra showed that the plate absorbed light at 830 as well as 1060 nm.
  • Cpd 2 was dissolved in water by adding one equivalent of triethyl amine and stirring. This solution was coated at a coverage of 200 mg/m 2 of dye on an anodised aluminium support and then dried during 20 min. at 50 °C. This material was exposed using the same XTD image setter as described in Example 1 using a scan speed of 3.2 and 8.0 m/sec and a laser power of 228 and 305 mW (four different combinations, exposed on different areas of the plate). The material was then used as a master without any further processing on a GTO 46 press, supplied by Heidelberg, using Rubber Base Plus VS2329 Universal Black ink, trade name of Van Son, and Rota-Matic fountain solution, trade name of Rotaprint. A print job of 100 copies provided high quality prints over the whole area of the plate. Similar results were obtained with Cpd 3.
  • aqueous dispersion of 10 wt.% of carbon (Printex U, trade name, supplied by Degussa), which also contained 1.5 wt.% of Hyamine 1622, a cationic surfactant available from Merck, 2 wt.% of polyvinyl alcohol and a small amount of formaldehyde, was diluted with water and coated on an anodised aluminium support at a wet thickness of 40 ⁇ m. After drying during 20 minutes at 50°C a plate precursor was obtained having a dry layer coverage of 200 mg/m 2 . This material was exposed with a Nd:YAG XTD laser imager (1064 nm) at a power of 450 mW and a scan speed of 3 m/sec.
  • Nd:YAG XTD laser imager (1064 nm) at a power of 450 mW and a scan speed of 3 m/sec.
  • a solution of 0.75 wt.% of Cpd 4 in methylethyl ketone was prepared by stirring vigorously during 30 min. followed by ultrasonic treatment during 30 min. Two samples were prepared by coating this solution on an anodised aluminium support at a wet thickness of 20 ⁇ m and 40 ⁇ m respectively and then dried during 20 min. at 50 °C. Both these plate precursors could be used as a printing master after image-wise exposure at 830 nm with a power of 738 mW and a scan speed of 3.2 or 8.0 m/sec (two different exposures on different areas of each plate), and then processing the material by wiping with plain water (image-setter, press, ink and fountain as in Example 1).
  • aqueous dispersion of 10 wt.% of carbon (Printex U as in Example 3) was coated on an anodised aluminium support and allowed to dry during 20 min. at 50 °C. Two samples were prepared at a dry coverage of 100 and 200 mg/m 2 . Similar materials were prepared with an aqueous dispersion containing 10 wt.% of carbon and 2 wt.% of polyvinyl alcohol. These four plates were exposed with an XTD Nd:YLF laser at a power of 364 and 728 mW and a scan speed of 3.2 and 8.0 m/sec (four combinations on different areas of the same plate).
  • the plates were used as a master on a GTO 46 press (trade name of Heidelberg) using the same ink and fountain as in Example 1. It was observed that the plates containing polyvinyl alcohol had a higher speed and could be exposed using a laser power of 364 mW with satisfactory results.
  • Cpd 2 was dissolved in water by adding one equivalent of triethyl amine and stirring.
  • Three coating solutions were prepared by adding an aqueous solution of a non-reactive hydrophilic binder, i.e. polyvinyl pyrrolidone, polyvinyl alcohol and carboxymethyl cellulose respectively. These solutions were each coated on an anodised aluminium support and then dried during 20 min. at 50 °C so as to obtain different samples having a dry coverage of 200, 300 and 400 mg/m 2 .
  • the coverage of the above mentioned polymers polyvinyl pyrrolidone, polyvinyl alcohol and carboxymethyl cellulose was 10 wt.% relative to the total layer coverage.
  • Cpd 5, Cpd 6, Cpd 7 and Cpd 8 were each dissolved in methanol at a concentration of 1.0 wt.% and these solutions were then each coated on an anodised aluminium support and then allowed to dry during 20 min. at 50 °C so as to obtain four different samples at a dry coverage of 100 mg/m 2 .
  • the experiment was repeated at a dry coverage of 500 mg/m 2 .
  • aqueous dispersion containing 10 wt.% of carbon (Printex U as in Example 3) and 1.2 wt.% of Alkonol XC, a tenside available from DuPont, was diluted with water 20-fold and then coated on an anodised aluminium support. After drying during 20 min. at 50 °C, a layer having a dry coverage of 200 mg/m 2 was obtained.
  • a 0.125 wt.% aqueous solution of polyvinyl alcohol (Polyviol VX 48 20, trade name of Wacker-Chemie) was then coated on top of the first layer so as to obtain a protecting layer having a dry coverage of 12.5 mg/m 2 . The experiment was repeated with a protective layer of 50 mg/m 2 .
  • Three plate precursors were prepared by rubbing in the surface of an anodised aluminium plate with a dry powder consisting of Cpd 1, Cpd 4 or Cpd 9 respectively.
  • the samples were image-wise exposed with an XTD Nd:YLF laser (1060 nm) with a power of 150 mW at a scan speed of 2 m/sec.
  • the plates thus obtained were used as a master in a print job using the same press, ink and fountain as in Example 1.
  • No special measures were taken to ensure that the layer had a uniform thickness over the whole surface of the plate and it was observed that the plates were completely hydrophobic at the centre, where the coating thickness was the highest, regardless whether the plate had been exposed at that area or not.
  • a good printing quality was obtained with no toning in the non-exposed areas, indicating the a low layer thickness is preferred for these near infrared light absorbing compounds.
  • Lexmark Schwarz, type 4076 (trade name of Lexmark) was diluted 10-fold with water, coated on an anodised aluminium support at a wet thickness of 40 ⁇ m and then dried at 50 °C.
  • This material was exposed with a Nd:YLF XTD image-setter (1060 nm) at a laser power of 150 mW or 450 mW and a scan speed of 2 or 4 m/sec (four different combinations on different areas of the plate).
  • the plate was mounted on the plate cylinder, moistened with water and good prints were obtained in a print job of 100 copies (same press, ink and fountain as in Example 1).
  • aqueous dispersion containing 10 wt.% of carbon (Printex U as in Example 3) and 1.2 wt.% of Alkonol XC, a tenside available from DuPont, was mixed with a 20% dispersion of poly(vinyl pyrrolidone) (PVP) as a non-reactive hydrophilic binder so as to obtain a weight ratio of carbon vs. PVP of 1:9.
  • PVP poly(vinyl pyrrolidone)
  • Water was added up to a total concentration of 0.5% and then 0.05% of cetyltriethyl ammonium bromide was added as a spreading agent.
  • Samples 10-1 and 10-2 were obtained by coating this solution on an anodised aluminium support at a wet thickness of 20 and 40 ⁇ m respectively and then drying during 20 minutes at 50°C.
  • the total coverage of carbon and PVP of samples 10-1 and 10-2 was 100 and 200 mg/m 2 respectively.
  • Other samples having a different weight ratio of carbon vs. PVP as indicated in Table 2 were prepared according to the same procedure. These samples were exposed with the same image-setter as in Example 1 at a laser power of 305 mW and a print job was started using the same press, fountain and ink as in Example 1. None of the plates showed toning.
  • the visible contrast of the printed copies was established by visual inspection of the optical density of the printed areas corresponding to the hydrophobic areas of the plate.
  • Said visual contrast is expressed in Table 2 as a number on a scale from 0 (no visible density) to 10 (very high density). It may be concluded from Table 2 that the plates having more than 50% of carbon provide the best results. However the plates comprising no PVP show less contrast than the plates with a carbon vs. PVP ratio of 9:1, indicating that a small amount of hydrophilic binder is beneficial. sample no. carbon vs.
  • PVP total coverage (mg/m 2 ) visible contrast (0-10) 10-1 1:9 100 1 10-2 1:9 200 1 10-3 3:7 100 2 10-4 3:7 200 4 10-5 5:5 100 2 10-6 5:5 200 6 10-7 7:3 100 3 10-8 7:3 200 8 10-9 9:1 100 5 10-10 9:1 200 10 10-11 10:0 100 4 10-12 10:0 200 7
  • Table 3 shows the composition of ten plates of which some correspond to the invention and others are comparative examples comprising other reactive compounds, such as a novolac or thermoplastic polymer latex, besides the near infrared light absorbing compound which is carbon in all cases.
  • Samples no. 11-1, 11-2, 11-3 and 11-4 comprised no other reactive compound besides carbon.
  • the amount of other reactive compounds besides the near infrared light absorbing compound was less than 10% in samples no. 11-5 and 11-6 and more than 20% in 11-7, 11-8, 11-9 and 11-10.
  • the samples were prepared using the same coating methods as above. In addition to the composition given in Table 3 a small amount of surfactant was added to the coating solution as spreading agent. All these plates were subjected to a thermal treatment as indicated in Table 3 and were then used as a printing master without any exposure.
  • the plates according to the invention showed no toning (no ink acceptance due to the thermal treatment), which is indicated as "ok” in Table 3.
  • the plates comprising other reactive compounds besides carbon showed toning (some ink acceptance) or were even completely hydrophobic (very high ink acceptance over the whole plate), indicated as "X" in Table 3.
  • An aqueous carbon dispersion was prepared comprising 29 wt.% of Helioechtpapierschwartz A Regal 400R, available from Bayer AG (Germany) and 1 wt.% of Tamol NN9401, an anionic dispersing agent from BASF.
  • An electrochemically grained and anodised aluminium support (thickness 0.30 mm) was coated with a solution containing 3.5 vol.% of the above carbon dispersion and 2 vol.% of an aqueous solution comprising 5 wt.% of n-polyoxy-ethylene-ethyl-perfluoro-octanoicamide (degree of polymerisation of ethylene oxide is 17-20).
  • the temperature of the aluminium support during coating was 40 °C.
  • the coated layer was dried during 20 minutes at 50 °C.
  • Three samples were prepared with a dry thickness of the coated layer of 0.1, 0.2 and 0.4 ⁇ m respectively.
  • Sample layer thickness printed dot (%) obtained upon exposure of a dot of ( ⁇ m) 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 12-1 0.1 17 37 40 59 75 80 90 94 98 100 12-2 0.2 16 32 40 52 67 76 85 94 99 100 12-3 0.4 5 11 22 32 22 19 28 46 20 20

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  • 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)

Claims (15)

  1. Matériau de formation d'image non ablatif à traitement négatif qui est approprié pour fabriquer une matrice d'impression lithographique, ledit matériau comprenant un support métallique sur lequel est appliquée une couche ou une pile de couches, caractérisé en ce que ladite couche ou ladite pile de couches comprend un composé absorbant dans le domaine de l'infrarouge proche du spectre en une quantité qui n'est pas inférieure à 50 % en poids par rapport à tous les composés présents dans ladite couche ou dans ladite pile de couches, et en ce que la quantité des autres composés réactifs dans ladite couche ou dans ladite pile de couches n'est pas supérieure à 20 % en poids par rapport à tous les composés présents dans ladite couche ou dans ladite pile de couches, ledit composé absorbant dans le domaine de l'infrarouge proche du spectre étant choisi parmi le groupe constitué par des colorants organiques, des polymères organiques, du carbone et du graphite.
  2. Matériau selon la revendication 1, dans lequel la quantité desdits autres composés réactifs n'est pas supérieure à 10 % en poids.
  3. Matériau selon la revendication 1, dans lequel la couche ou la pile de couches est essentiellement exempte desdits autres composés réactifs.
  4. Matériau selon l'une quelconque des revendications précédentes, dans lequel la quantité du composé absorbant dans le domaine de l'infrarouge proche du spectre n'est pas inférieure à 70 % en poids.
  5. Matériau selon l'une quelconque des revendications précédentes, dans lequel la quantité du composé absorbant dans le domaine de l'infrarouge proche du spectre n'est pas inférieure à 90 % en poids.
  6. Matériau selon l'une quelconque des revendications précédentes, dans lequel la couche ou la pile de couches comprend en outre un liant hydrophile.
  7. Matériau selon l'une quelconque des revendications précédentes, dans lequel le composé absorbant dans le domaine de l'infrarouge proche du spectre représente le composant principal de la couche qui est la plus proche du support métallique.
  8. Matériau selon la revendication 7, dans lequel ladite couche la plus proche du support métallique est constituée essentiellement du composé absorbant dans le domaine de l'infrarouge proche du spectre.
  9. Matériau selon la revendication 7 ou 8, dans lequel l'épaisseur de la couche la plus proche du support n'est pas supérieure à 0,4 µm.
  10. Matériau selon l'une quelconque des revendications précédentes, dans lequel le support métallique est un cliché en aluminium anodisé.
  11. Procédé pour fabriquer une matrice d'impression lithographique comprenant les étapes consistant à :
    exposer en forme d'image un matériau selon l'une quelconque des revendications précédentes à de la lumière du domaine infrarouge proche ;
    le cas échéant, passer sur la composition avec de l'eau.
  12. Procédé pour fabriquer une matrice d'impression lithographique comprenant les étapes consistant à :
    appliquer sur un support métallique une couche d'une composition non ablative à traitement négatif contenant un composé absorbant dans le domaine de l'infrarouge proche ;
    exposer en forme d'image un matériau selon l'une quelconque des revendications précédentes à de la lumière du domaine infrarouge proche ;
    le cas échéant, passer sur la composition avec de l'eau ;
    caractérisé en ce que ladite composition comprend un composé absorbant dans le domaine de l'infrarouge proche du spectre en une quantité qui n'est pas inférieure à 50 % en poids par rapport à tous les composés présents dans ladite couche ou dans ladite composition, et en ce que la quantité des autres composés réactifs dans ladite composition n'est pas supérieure à 20 % en poids par rapport à tous les composés présents dans ladite composition, ledit composé absorbant dans le domaine de l'infrarouge proche du spectre étant choisi parmi le groupe constitué par des colorants organiques, des polymères organiques, du carbone et du graphite.
  13. Procédé selon la revendication 12, dans lequel le support métallique est un cliché en aluminium anodisé.
  14. Procédé selon la revendication 13, dans lequel le cliché en aluminium anodisé est monté sur le cylindre d'une presse d'impression rotative.
  15. Procédé selon la revendication 12, dans lequel le support métallique est un manchon ou un cylindre d'une presse d'impression rotative.
EP99202011A 1998-07-16 1999-06-23 Précurseur de plaque d'impression lithographique thermique de longue conservation Expired - Lifetime EP0972637B1 (fr)

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EP98202382 1998-07-16
EP98202382 1998-07-16
EP99202011A EP0972637B1 (fr) 1998-07-16 1999-06-23 Précurseur de plaque d'impression lithographique thermique de longue conservation

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US6593055B2 (en) * 2001-09-05 2003-07-15 Kodak Polychrome Graphics Llc Multi-layer thermally imageable element

Citations (1)

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Publication number Priority date Publication date Assignee Title
EP0974455A1 (fr) * 1998-07-16 2000-01-26 Agfa-Gevaert N.V. Procédé à sec de préparation d'un précurseur de plaque lithographique obtenue par voie thermique

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DE3369400D1 (en) * 1982-01-15 1987-02-26 Crosfield Electronics Ltd Products and processes for use in planographic printing
US5713287A (en) * 1995-05-11 1998-02-03 Creo Products Inc. Direct-to-Press imaging method using surface modification of a single layer coating

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0974455A1 (fr) * 1998-07-16 2000-01-26 Agfa-Gevaert N.V. Procédé à sec de préparation d'un précurseur de plaque lithographique obtenue par voie thermique

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