Classifications

• • 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
  • B41M5/36—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties
  • B41M5/366—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using a polymeric layer, which may be particulate and which is deformed or structurally changed with modification of its' properties, e.g. of its' optical hydrophobic-hydrophilic, solubility or permeability properties using materials comprising a polymeric matrix containing a polymeric particulate material, e.g. hydrophobic heat coalescing particles
• • 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
  • B41C1/1025—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 using materials comprising a polymeric matrix containing a polymeric particulate material, e.g. hydrophobic heat coalescing particles
• • 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
  • B41C2210/06—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
  • B41C2210/20—Preparation or type or constituents of the imaging layers, in relation to lithographic printing forme preparation characterised by inorganic additives, e.g. pigments, salts
• • 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
• • 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
  • B41C2210/264—Polyesters; Polycarbonates
• • 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
  • B41C2210/266—Polyurethanes; Polyureas

Definitions

• This invention relates to image formation and is concerned with the formation of images directly from electronically composed digital sources.
• Imaging systems are also available which involve a sandwich structure which, on exposure to a heat generating infra-red laser beam, undergoes selective (image-wise) delamination and subsequent transfer of materials.
• peel-apart systems are generally used as replacements for silver halide films.
• a radiation sensitive plate which comprises a substrate coated with (i) one or more layers each comprising core-shell particles each of which comprises a water-insoluble heat softenable core component (A) and a shell component (B) which is soluble or swellable in aqueous alkaline medium, and (ii) a substance capable of strongly absorbing radiation and transferring the energy thus obtained as heat to the core-shell particles so that at least partial coalescence of the particles occurs.
• the plate may contain one or more additional layers so as to increase adhesion to the substrate, improve resistance to abrasion, or to improve the performance of the system in other respects.
• the substrate material used depends upon the purpose for which the image is to be used and may be, for example, formed of metal or plastics material.
• the substrate is preferably electrochemically treated aluminium whereas the substrate may be a linear polyester in the case where a transparency is to be produced or copper in the case where the image is to be used in printed circuit board manufacture.
• the core-shell particles contain distinct domains of components (A) and (B).
• the domains are arranged so that component (A) (the core) is encapsulated by component (B) (the shell) with the core and shell being linked to each other by strong physical adsorption or, more preferably, by chemical bonding. Under ambient conditions, both components are preferably solid and immobile.
• core-shell particles are known and methods for preparing the same are described in US patent specification No.4868016 and in British patent specifications No.887356 and No.1107249 (Example 22).
• the component (A) is an oleophilic polymer, preferably having a minimum film forming temperature (MFT) above ambient temperature, and may be an addition polymer comprising residues derived from one or more of styrene, substituted styrenes, esters of (meth)acrylic acid, vinyl halides, (meth)acrylonitrile, vinyl esters or polyethers, or it may be a polyester, polyamide or polyurethane, or any thermally fusible oleophilic material or composition capable of forming a core-shell structure as defined above.
• Preferred materials are addition polymers containing 50% or more by weight of styrene or substituted styrenes.
• the component (B) is preferably polymeric and contains carboxylic acid, sulphonamido, or other groups capable of conferring solubility, or at least swellability, in aqueous alkaline solutions.
• Particularly suitable materials for component (B) are: i) copolymers derived from the copolymerisation of one or more ethylenically unsaturated carboxylic acids with one or more of styrene, substituted styrenes, (meth)acrylate esters, (meth)acrylonitrile or vinyl acetate; ii) dicarboxylic acid half-esters of hydroxyl group-containing polymers, such as phthalic, succinic or maleic acid half esters of a polyvinyl acetal and, in particular, of a polyvinyl butyral; and iii) alkyl or aralkyl half esters of styrene- or alkly vinyl ether-maleic anhydride copolymers
• the shell component of the core shell polymer is used as the film forming component in the imaging layer, but also fulfils a vital role in stabilising the polymer particles, both when in aqueous dispersion during coating of the substrate and when in the imaging layer on the substrate.
• the shell component may function as a protective colloid during the preparation of component (A) using an emulsion polymerisation process whereby little or no surfactant is necessary, or alternatively may colloidally stabilise polymer particles which have been preformed with insufficient surfactant to ensure stability.
• component (B) then subsequently acts as a film forming component in the imaging layer.
• the hydrophobic core particles can be stabilised by the shell when this is carboxyl functional either in the neutralised or unneutralised state. It is preferred that no carboxyl monomer is used in the core component as this can result in overdevelopment.
• the shell component will generally film form preferentially to the core component either by virtue of it having a lower MFT or by virtue of, for example, it having been solubilised by a volatile base such as ammonia.
• the shell component is non-water soluble.
• the shell component contains such groups as carboxyl and sulphonamido, which confer the required solubility or swellability in aqueous alkaline solution, it is not soluble in water per se and, when cast down as a component of the heat sensitive layer in accordance with the invention, it does not impart to that layer a sensitivity to water.
• a marked deterioration in the properties of these films occurs when water soluble materials, including surfactants, are present at levels over a low threshold value.
• Polymeric binders which are water soluble, such as poly(vinyl alcohol), poly(vinyl pyrrolidine), poly(ethylene oxide), gelatin, casein, etc., are thus unsuitable for use in this invention.
• colloidally stable polymer particles can be prepared which are virtually free of water soluble components and thus do not suffer from the disadvantages noted above.
• the coating of the radiation sensitive plate is generally water resistant and it is preferred that the plate is produced by applying the core-shell particles to the substrate from wholly or substantially aqueous media.
• non-aqueous vehicles and vehicles which are mixtures of aqueous and non-aqueous solvents may be used.
• volatile bases such as ammonia or amines are used to solubilise the shell components.
• the particle size of the core-shell particles is preferably less than 1 micron and more preferably less than 0.5 microns.
• the weight ratio of shell to core may be in the range of from 1:20 to 20:1 and preferably is in the range of from 1:9 to 1:1.
• the source of the high density radiation is a laser operating in the ultra violet, visible or infra-red region of the spectrum.
• Red and infra-red light emitting lasers are preferred, for example the semiconductor or diode lasers typical of which is the gallium aluminium arsenide laser which operates in the 750-870 nm region.
• the radiation-absorbing substance may be present in the same layer as the core-shell particles or it may be incorporated within the particles themselves or it may be present in a separate but adjacent layer.
• suitable laser radiation absorbing substances are carbon black and graphite and phthalocyanine, croconium and squarylium type dyestuffs.
• the radiation sensitive substance is present in an amount which is effective to cause some coalescence of the particles under the influence of the high intensity radiation.
• the radiation sensitive substance will constitute from 2.0 to 80%, by weight, of the coating.
• Typical developers for selectively removing the non-coalesced particles, in the non-image areas are aqueous alkalis such as solutions of ethanolamine, sodium metasilicate, an alkaline phosphate such as sodium phosphate, or an alkali metal hydroxide in water.
• the mixture was maintained at 65°C with vigorous stirring for a period of four hours to give a final product of solids content 25% w/w, with a particle size of less than 0.5 microns and a residual monomer content of 0.05% w/w.
• the final product was a core-shell dispersion composed of particles comprising a core of polystyrene and a shell of the carboxylated acrylic copolymer.
• Microlith Black C-WA a carbon black coated with an alkali soluble acrylic resin available from Ciba Geigy
• a mixture of 590 cm3 H2O and 250 cm3 of isopropyl alcohol with stirring.
• 10 cm3 of 25% aqueous ammonia were added and the mixture was stirred for 9 hours.
• the resultant fine particle size carbon dispersion was filtered through a Whatman GF-D filter paper to give a solids content of 15% w/w.
• the plate was exposed to the modulated radiation emanating from an array of 100 mW diode lasers outputting at 830 nm to selectively coalesce some of the core-shell particles to form an image. 200 mJ cm ⁇ 2 was applied to the plate which was then developed in an aqueous ethanolamine developer (Electrosol 85 of Du Pont-Howson Limited) to give a high resolution developed image. The plate was baked for two minutes at 200°C to give a durable printing plate which was capable of faithfully reproducing more than 90,000 copies.
• Example 1 The procedure of Example 1 was repeated except that a Nd YAG laser outputting at 1060 nm was used to expose the plate. A similar result was obtained.
• Example 2 The core shell dispersion from Example 1 was mixed with a squarylium dye (2% of total solids) and coated at 0.6gm ⁇ 2 onto an aluminium substrate. Max of the squarylium dye was 800nm in methylene chloride. The plate was exposed, developed and heated as in Example 1. Similar results were obtained.
• Carboset XL37 was diluted with 10 cm3 H2O and 0.5 cm3 of 25% aqueous ammonia was added to dissolve the polymer.
• 4.96g of Texicote 53.040 (a 50% w/w solids styrene homopolymer emulsion of MFT 105°C available from Scott Bader) were added, followed by 3.5g of the carbon dispersion of Example 1.
• the mixture was diluted with 30 ml of isopropyl alcohol and coated on a grained and anodised aluminium substrate to give a coat weight of 0.6 gm ⁇ 2.
• a plate of good appearance was obtained.
• the plate was imaged using a laser diode but more than 600 mJ cm ⁇ 2 was required in order to produce an image which was fully insoluble in the developer used in Example 1.
• Homopolymer styrene emulsions were formed by using of the following surfactants with 100g of styrene using a delayed addition process.
• the plates were stored in a humidity cabinet at 30°C and 97% RH for 1 week.
• the plates were very difficult to develop after this time. This is in contrast to the plate of Example 1 which, after imaging at 200 mJ and storing for four weeks in a humidity cabinet, could be readily developed with Electrosol 85.
• Example 2 Using an identical procedure to that described in Example 1, a styrene-butyl acrylate core-shell polyer was formed. 5 g of the styrene was replaced by 5 g of butyl acrylate. The results were similar to those obtained in Example 1.
• Example 2 In a 500 ml flask equipped as in Example 1, 43 ml of Carboset XL37 (35% w/w solids) were added to 240 ml of distilled water. The resin was dissolved by adding 6 ml of 25% aqueous ammonia and heating to 50°C. 0.75 g of ammonium persulphate was then added to the mixture, followed by 3.75 g of a mixture of 37.5 g of styrene and 37.5 g of acrylonitrile. After a further 10 minutes, the remainder of the monomer mixture was added over a period of two hours. The temperature was maintained at 60°C for a further four hours and the product was then filtered to give a 20.5% solids dispersion of very fine particle size. This performed in a similar fashion to the material described in Example 1.

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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)
• Thermal Transfer Or Thermal Recording In General (AREA)
• Tires In General (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (3)

Cited By (43)

Citations (4)

• 1991
  • 1991-05-14 GB GB9110417A patent/GB9110417D0/en active Pending
• 1992
  • 1992-05-13 CA CA 2068586 patent/CA2068586A1/en not_active Abandoned
  • 1992-05-13 EP EP92304296A patent/EP0514145A1/de not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (1)

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