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
  • B41C1/1066—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by spraying with powders, by using a nozzle, e.g. an ink jet system, by fusing a previously coated powder, e.g. with a laser

Definitions

• the present invention relates to a method for copying a printing plate for printing according to the wet offset technique.
• the wet offset printing process uses plates (made of steel or mainly aluminum electro-grended and anodized) which have a hydrophilic surface; Hydrophilic surface which, wet, does not take the ink. To improve its hydrophilicity, said hydrophilic surface has generally been treated.
• Said hydrophilic surface of said plates is covered with an ink-forming layer based on an ink-sensitive, ink-sensitive, ink-sensitive varnish.
• Said layer is generally from 1.4 to 2.7 ⁇ m thick.
• Said varnish is generally photosensitive to light rays, which have a wavelength between 320 and 450 nm.
• the varnish of such plates is conventionally insulated through silver films, which have opaque surfaces and transparent surfaces, representing (mainly) the patterns to be printed. Said insolated varnish is then developed with a developer. The parts of the plate where it remains will take the ink, the parts of the plate from which it has been removed discover the hydrophilic surface of said plate.
• the varnish in question is a negative varnish: in the parts having been insolated through the transparent surfaces of the negative film used, it is hardened, rendered insoluble in the developer. In the non-insolated parts, it is not hardened, it has remained soluble in the developer and is therefore removed, by development, by said developer.
• the varnish in question is a positive varnish: in the parts having been insolated through the transparent surfaces of the positive film used, it becomes soluble in the developer. It is removed, in development, by said developer. In non-insolated portions, it is not rendered soluble in said developer. He remains in development.
• the plaque after insolation and development (we have in fact insolated and developed the layer based on the encrophilic photosensitive varnish initially covering uniformly), is fixed on the printing machine. Rollers wet the hydrophilic surfaces (areas from which the inkjet lacquer has been removed) and other rollers deposit ink on the inkjet lacquer (in areas where it has remained). Said ink is then taken, from said inkjet areas of said plate, by the rubbery surface of a blanket, with a support in fabric or metal, which finally deposits it on the surface to be printed: paper, cardboard, metal ...
• the resins are generally loaded with coloring agents, wetting agents ...
• a solvent such as a ketone or Cellosolve ® type.
• These positive coatings advantageously have, on their surface, small particles intended to facilitate in the sunscreen frame the varnish-silver film contact.
• the present solubility inhibitor (s) is (are) neutralized.
• the insolated portions are rendered soluble in the developer while the non-insolated portions remain insoluble in said developer (at the usual operating temperatures of said developer).
• the positive varnish developers (aqueous alkaline solutions) have a pH generally between 10.5 and 13.5.
• These resins are generally also loaded with coloring agents, wetting agents etc. To be extended on the plate, they are also generally used with a solvent. They are also described in many patents.
• Some negative lacquers are protected from oxygen in the air by a transparent barrier layer based on polyvinyl alcohol.
• the insolubilization agents induce a polymerization and / or crosslinking of the resin, making it insoluble in the developer.
• the insolated parts made hard and resistant, are insoluble in the developer while the non-insolated parts remain soluble in said developer.
• Negative varnish developers also have a basic pH, generally between 7.5 and 10.
• a basic pH generally between 7.5 and 10.
• Pre-sensitized negative (wet) offset plates are used worldwide.
• the preparation of wet offset plates, to copy the pattern to be printed thus comprises a preliminary step of manufacturing a positive or negative film and a step of exposing the photosensitive inkjet lacquer of said plates through said film.
• Photosensitive inkjet enamels are directly insoluble with computer-controlled U.V. or I.R. lasers.
• the technology used is called "computer to plate”.
• This technology offers substantial advantages, particularly with regard to the quality of the work obtained, the speed of execution, but it is costly to implement (computer-based computers) and the technical assistance required. ).
• the technique known as inkjet, is used in some computer printers, especially to obtain proofs in black or in color, to produce posters, posters ...
• the machines "ink jet" are generally operational in four, six or eight colors.
• multi-color printing one usually has one color per head.
• single-color printing it is not excluded to involve the single color in several heads. We then gain in speed.
• the prints obtained are of good quality and in constant progression.
• This technique direct projection of the ink on the substrate to be printed, is experiencing a great development, particularly for small quantity printing.
• Printheads using "piezo" technology, are capable of projecting a jet at 1440 x 1440 dpi (dots per inch), that is to say generate small inked areas of less than 980 ⁇ m 2 . It is possible to adjust the dimensions of the projected droplets (from 1 to more than 60 picoliters), to have impact surfaces of different diameters (30, 40, 50, 65, 70, 85 ⁇ m, for example). .
• the surfaces of the varnish, which have not been rendered insoluble by the projected solution, are eliminated during development / rinsing.
• the thus-copied plate has encrophile lacquer surfaces for picking up the ink and hydrophilic surfaces (from which the lacquer has been removed) which, wet, will not pick up the ink.
• the patent application WO-A-0 178 984 describes a method of copying a printing plate, intended for printing according to the technique of dry offset (called “water-less”).
• a printing plate has, on a suitable support, an ink-accepting layer and a layer (based on silicones) repelling the ink, applied on the previous one.
• a developing liquid is sprayed onto said (upper) layer repelling the ink at the corresponding locations. the patterns to be printed, and then eliminating said charged developing liquid (thereby denuding the ink-accepting (lower) layer at said locations corresponding to said patterns to be printed).
• the development liquid remaining active during its elimination, this elimination, ineluctably, is not perfectly selective.
• the quality of the print is inexorably affected.
• Those skilled in the art are also aware that the printing domains of dry offset and wet offset are separate domains.
• the invention as indicated above and developed hereinafter, is in the context of wet offset.
• a solvent of the inkjet layer intervenes directly, to expose the base substrate of the plate, at locations not corresponding to the patterns to be printed and optionally, in addition, at small areas in locations corresponding to the patterns to be printed. Said solvent is removed, loaded, perfectly selective, insofar as it is inactive (no effect) during rinsing.
• the solvent is inactive.
• it is per se inactive.
• intervene hot (active) it is then cooled (inactive).
• it is placed in a new context where it is inactive.
• the change of context generally results from a change of state of the plate in question, for example, at the temperature of said plate (positive plate) or at the state of the photosensitive layer of said plate (plate negative).
• the conditions are adapted to involve the active solvent and to eliminate it, inactive.
• the process of the invention insofar as the action of the solvent remains very targeted, is suitable both for copying conventional plates and for copying lighter plates.
• an aqueous alkaline or acidic solution particularly preferably an aqueous alkaline solution.
• Such an alkaline aqueous solution may, quite logically, consist of a (or be of the type of) developer (s) used (s) to date with the pre-sensitized plates.
• the positive developers alkaline aqueous solutions whose pH is generally between 10.5 and 13.5
• negative aqueous solutions alkalis whose pH is generally between 7.5 and 10.
• Their formulation is in fact also advantageously modified, or even simplified, in view of their new use according to the invention.
• the solvents that can be used according to the invention advantageously contain additives, such as drying-delay agents (said solvents must be capable of being deposited, acting and being removed, charged, preferably before drying).
• the deposited solvent generally acts rapidly. It is evacuated, charged, inactive, as indicated above, by rinsing. Said rinsing is generally carried out with water, especially in the abovementioned contexts of intervention of an aqueous solvent. Said rinsing can involve a lot of water and be mechanically assisted. Brushes, as is common in copy shops, can be used to develop their action.
• the droplets of solvent deposited, during the implementation of the copying method of the invention generally have a volume (a capacity) of between 1 and 100 picoliters, advantageously between 4 and 30 picoliters.
• the said droplets do not necessarily all have the same volume.
• joint deposition of droplets of different volumes are provided in the context of the implementation of the method of the invention.
• Said droplets are generally deposited under conditions that involve impact surfaces, droplets / encrophile varnish, whose average diameter (s) is (are) between 10 and 150 microns, advantageously between 30 and 85 .mu.m.
• the droplets of solvent may be deposited, in particular projected, by any suitable technique and in particular by inkjet. It is indicated more specifically that, according to an advantageous variant, the deposition of the droplets is ensured by an ink jet printing head. Indeed, one does not deposit the ink but a solvent of encrophile varnish. To do this, it is therefore advantageous to use an inkjet printing head. We have spoken in the introduction of this text of this type of device, used, to date, to directly print a medium.
• Inkjet technology is evolving. It is particularly suitable for inks based on aqueous solutions.
• the method of the invention has been particularly tested with a machine of this type, a "High Fidelity Inkjet Printer” ROLAND Model FJ-500 / FJ-400, having “piezo inkjet heads” and using the latest technology double head with variable point diameter. It can be used to reach various resolutions and in particular that already indicated of 1440 x 1440 p.p.p. (point by inch).
• a trolley equipped with jet heads (spray nozzles) moves sideways with a regular back and forth. It allows regular deposits of solvent on a plate that scrolls, supported at the entrance and exit by trays. The solvent in question intervenes advantageously in several heads.
• the plate is stationary and the carriage, equipped with jet heads, moves laterally and progresses along the entire length of the plate.
• Inkjet printing is a printing technique familiar to those skilled in the art.
• the method of the invention offers an original outlet for this technique.
• intervene jets of solvent in place of the ink jets, intervene jets of solvent; the solvent discarded being then, once charged, removed.
• the method of the invention can be implemented on any type of plate, of the type specified above (comprising a substrate of base which has a hydrophilic surface covered with a photosensitive ink-based layer based on an enricophile varnish intrinsically soluble in a solvent); and in particular, the pre-sensitized plates used to date (positive plates and negative plates comprising a photosensitive ink-sensitive layer).
• the process of the invention consists essentially of the two operations specified above: the deposition of the solvent droplets and the rinsing to remove the loaded deposited solvent; it being understood that said rinsing is only carried out after the development of the action of said solvent and the cessation of any action of said solvent.
• the method of the invention implemented with the plates of the prior art - pre-sensitized plates (main plates existing to date) - comprise the operations recalled above, modified and / or supplemented to take into account the photosensitivity of the encrophile lacquer in question.
• the operation of the hot solvent and / or the solvent on a hot plate is particularly interesting in that it involves an action of said solvent, very targeted. Indeed, during the implementation of the rinsing, said hot solvent has cooled and / or said hot plate has cooled, so that said solvent is certainly inactive.
• the plate After the deposition (spraying) of the solvent droplets, the plate is treated so as to cause the encrophile layer to harden at the uncovered (unprotected) locations by said droplets.
• the treatment in question involves light rays. It consists of an insolation.
• the treated plate is then successively rinsed and then dried.
• the copying method of the invention advantageously implemented using a printing technology (inkjet printing) has proved, quite surprisingly, particularly effective.
• reproductions implemented with the plates copied according to the method of the invention are of a quality comparable to that of reproductions obtained in a conventional manner (with the same definition) with insolated photosensitive plates.
• the copying method of the invention is a faithful, economical, ecological process, easy to use. For its implementation, it does not require expensive equipment. It allows to copy plates at an advantageous cost price.
• the present invention has another particular outlet in the field of coated bimetallic surface plates.
• a photosensitive layer called reserve layer.
• the skilled person also knows this type of plate.
• the structure of these plates comprises a base substrate with a hydrophilic surface (generally matt surface aluminum or stainless steel) covered with a thin encrophilic metal layer (generally a copper layer having a thickness of about 2 ⁇ m), itself covered with a photosensitive layer (usually a varnish).
• a hydrophilic surface generally matt surface aluminum or stainless steel
• a thin encrophilic metal layer generally a copper layer having a thickness of about 2 ⁇ m
• a photosensitive layer usually a varnish
• the present invention transposed in this context selective removal of the photosensitive layer by solvent deposition and rinsing is advantageously substituted for the first steps (insolation + development) of the process of the prior art mentioned above.
• the droplets are deposited using a dropper or projected using the inkjet heads of a printer High Fidelity Inkjet Printer "ROLAND company (model FJ 500 / FJ 400). are fed from cartridges containing the solvent "B".
• Example 2 The procedure is as in Example 1 except that the plate is not heated and that the solvent "A” is at a temperature of 80 ° C. Said hot “A” solvent is left on the plate (unheated) for 60 seconds. He is cools and becomes inactive. After rinsing with water, it is observed that all the varnish is gone (in the places where the droplets intervened).
• solubility inhibitor present in the varnish of the plate is neutralized at this intervention temperature of the aqueous alkaline solvent.
• the said solvent "B” is allowed to act for 15 seconds and the entire surface of the negative lacquer is insoluble in order to render said surface not covered by said solvent "B” hard and insoluble.
• the plate is then rinsed with water. In places of droplets the varnish is gone. In other places, he remained, very resistant because of the insolation carried out.
• Example 4 is reproduced on an industrial scale using the ink jet heads of the printer identified above.
• the solvent droplets "B”, projected by said printer, have a volume of 24 picoliters. Their impact surface has a diameter of 55 microns.
• the digital recording represents Times New Roman texts (14).
• the negative plate used (LITHOPLATE) has the following dimensions: 510 x 400 x 0.30 (mm).
• the plate is then rinsed with water and then dried.
• the visual examination indicates a very good copy of the texts.
• the negative plates were, for the implementation of this example, manipulated in yellow ambient light.
• the solvent used is the developer of said photosensitive layer. It is projected in the form of droplets with a volume of about 40 picolites.
• the impact surface of said droplets has an average diameter of about 60 microns.
• the projection is done according to a digital recording which represents texts in Times New Roman (16).
• the plate is then insolated so that its photosensitive layer is rendered insoluble in the developer, the insolation obviously acting only on the surfaces of said photosensitive layer not covered by the solvent.
• the plate is then rinsed, dried and covered with a copper bite solution, supplied by P.D.I. This solution removes copper in places made accessible by removing the photosensitive layer and denudes the hydrophilic aluminum in these same places.
• the plate After rinsing and, if necessary, removing the photosensitive layer by the action of a suitable solvent, the plate has an encrophilic surface (Cu) and a hydrophilic surface (its treated surface) capable of being wetted and repelling the ink.
• Cu encrophilic surface
• hydrophilic surface its treated surface
• the plate is suitable for many millions of printing.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)
• Printing Plates And Materials Therefor (AREA)
• Ink Jet Recording Methods And Recording Media Thereof (AREA)
• Printing Methods (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (11)

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• 2002
  • 2002-08-13 FR FR0210250A patent/FR2843558B1/fr not_active Expired - Fee Related
• 2003
  • 2003-08-12 MX MXPA05001701A patent/MXPA05001701A/es active IP Right Grant
  • 2003-08-12 CA CA002495897A patent/CA2495897A1/en not_active Abandoned
  • 2003-08-12 WO PCT/FR2003/002511 patent/WO2004016428A2/fr not_active Application Discontinuation
  • 2003-08-12 ES ES03756541T patent/ES2329237T3/es not_active Expired - Lifetime
  • 2003-08-12 AT AT03756541T patent/ATE435747T1/de not_active IP Right Cessation
  • 2003-08-12 US US10/524,120 patent/US7089857B2/en not_active Expired - Fee Related
  • 2003-08-12 EP EP03756541A patent/EP1528980B1/fr not_active Expired - Lifetime
  • 2003-08-12 BR BR0313631-0A patent/BR0313631A/pt not_active IP Right Cessation
  • 2003-08-12 AU AU2003284988A patent/AU2003284988A1/en not_active Abandoned
  • 2003-08-12 DE DE60328290T patent/DE60328290D1/de not_active Expired - Lifetime

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