Classifications

• • 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
  • B41N1/04—Printing plates or foils; Materials therefor metallic
  • B41N1/06—Printing plates or foils; Materials therefor metallic for relief printing or intaglio printing

Definitions

• the invention relates to a method for producing a directly laser-engravable printing plate, in particular for flexographic printing.
• the invention is also directed to a directly laser-engravable printing plate, in particular for flexographic printing, which has a lower carrier film or plate and an elastomer layer made of silicone polymer, silicone fluoropolymer or silicone rubber applied thereon.
• flexographic printing also uses plate-shaped printing forms, which can be, for example, rubber clichés or photopolymer printing plates, which are often prepared for printing using high-quality flexographic printing using the "computer to plate” process.
• plate-shaped printing forms which can be, for example, rubber clichés or photopolymer printing plates, which are often prepared for printing using high-quality flexographic printing using the "computer to plate” process.
• these are mounted on cliché sleeves or format cylinders, on which they are either glued with the aid of adhesive tapes or foils - so-called “tapes” - or are held magnetically if the carrier foil or plate used is made of ferromagnetic material such as eg Tinplate exists and magnetic cylinders or sleeves are used, on which the tinplate foil lies tightly.
• vacuum cylinders it is also possible to hold the pressure plate on them by means of negative pressure.
• a method for producing a seamless printing form in which the elastomer layer is formed by a cold-curing silicone polymer or silicone fluoropolymer, which is applied to the cylindrical lateral surface of a carrier in a rotational molding process and, after curing, in a particularly advantageous manner directly can be engraved with a working laser.
• the elastomer layer consists of a heat-curing one-component or two-component silicone polymer, is known from DE 197 56 327.
• a plate printing form for the manufacture of which a layer of a curable elastomer is first applied to a carrier with a cylindrical outer surface in a rotary casting process as in the two aforementioned documents, the elastomer layer then cures and the resulting layer
• the printing plate blank is then ground and then cut along a cutting line which runs essentially parallel to the axial direction of the carrier, whereupon the printing plate thus produced can be removed from the lateral surface of the carrier.
• the length of the printing blankets which can be produced therewith is determined by the circumference of the cylindrical carrier used and is therefore not arbitrarily large and that the time required for the completion of the individual printing plates is comparatively large.
• the grinding or milling process that takes place after the elastomer material has hardened to achieve the required surface quality takes a relatively long time in the known method, since grinding generally requires several grinding passes in order to achieve surface accuracies in the 1/100 mm range and a high surface quality ,
• the object of the invention is to provide a method for producing a directly laser-engravable printing plate, in which the limitations associated with cylindrical production no longer exist.
• the new printing plate should achieve its required surface accuracy in a particularly simple and time-saving manner.
• an elastomer layer made of silicone polymer, silicone fluoropolymer or silicone rubber is applied to an initially approximately horizontally designed lower carrier film or plate and then post-treated to form a flat surface.
• the aftertreatment takes place in a particularly advantageous manner at least partially with a calibrating device with a calender nip through which the printing plate is transported in the not yet hardened state of its elastomer layer.
• the production of the directly laser-engravable printing plate therefore no longer takes place on a cylindrical outer surface, but rather the silicone polymer, silicone fluoropolymer or the silicone rubber used to form an elastomer layer is applied to the carrier film or plate lying flat.
• the application can take place in strips which are applied transversely to the longitudinal direction of the carrier film by an application head which moves relative to the carrier film from its one to the other longitudinal edge and back.
• an application head which extends over the width of the carrier film, for example, unwound from a large roll, through which the elastomer is applied over the entire width of the carrier film while the latter moves relative to the application head , for example, is pulled under it.
• This particularly advantageous procedure makes it possible to produce printing plates of practically any length, which is only limited by the length of the carrier film to which the elastomer layer is applied.
• the particularly advantageous post-treatment step in a calibration device with a calender gap ensures that the not yet hardened elastomer layer is deformed or rolled out in a particularly simple and rapid manner over the entire width of the printing plate to the desired thickness of the printing plate.
• the calibration device expediently consists essentially of a lower, precisely flat pressure bar and a likewise highly precise calender roller arranged parallel to it, which can be adjusted very precisely in terms of its distance from the pressure bar.
• the thickness of the printing plates produced according to the invention can be calibrated to the desired level with very high accuracy by calendering the not yet hardened elastomer layer Set dimension, the achievable accuracy only depends on the precision with which the calender roller and pressure bar are manufactured and with which the two main components of the calibration device can be adjusted in their distance from one another.
• the surface of the elastomer layer is provided with a cover film prior to its hardening, which is expediently applied to the elastomer layer before the calendering process and can be removed from the elastomer layer after it has hardened.
• the cover film effectively prevents the elastomer material used from adhering to the calender roll or to a calender squeegee used instead of it, which can otherwise lead to errors in the production of the printing plate.
• the cover film has a roughened and / or profiled surface on its underside facing the elastomer layer, which then presses into the still soft elastomer layer and, after the cover film has been pulled off, a correspondingly roughened and / or on the exposed side of the elastomer layer. or forms a profiled surface as desired or required for the color recording during later printing.
• the elastomer layer can be ground on its surface or subjected to high-speed milling if the surface quality is extremely high.
• grinding or milling can take place immediately after the elastomer has been applied to the carrier film or plate and has hardened. It is particularly advantageous, however, to calender the elastomer layer first by means of the calibration device and thereby thereby prior to grinding or milling. to obtain a very uniform thickness of the printing plate, the thickness deviations of which are only in the 1/10 mm range or even considerably less. It has been shown that the calendering process alone enables accuracies of less than 1/20 mm to be achieved. The accuracy of the printing plate can then be completed in just one grinding pass to the required high accuracy, for example in the 1/100 mm range.
• the carrier film or plate can be provided on its upper side facing the elastomer layer with a lamination made of a compressible intermediate layer.
• a compressible intermediate layer it is possible, in particular in the case of printing plates which are to be used for the direct printing of corrugated cardboard and other materials with an irregular surface, to set the compressibility of the entire printing plate desired for printing at a given printing height.
• the elastomer layer can be arranged directly on the lamination, ie without an intermediate layer or the like initially on it. to be arranged, so that the compressibility of the intermediate layer laminated onto the carrier film is completely available during later printing, that is, it is not reduced by an approximately interposed film.
• the correspondingly produced printing plate in which the elastomer layer is applied directly to the compressible intermediate layer laminated to the carrier film and then calendered to the desired thickness using the calibration device, is then no longer reworked, even if the surface of the elastomer layer has to meet high accuracy requirements must, but already after the pressure plate has passed through the calender gap and the cover film has been removed after the elastomer has hardened. Layer and cut the plate to the desired size, which can be immediately engraved with a laser.
• the compressible intermediate layer is able to reliably compensate for inaccuracies in the surface of the elastomer layer, which are in the 1/10 mm range, since their compressibility is not reduced by an additional intermediate layer of a film.
• the cover film used to cover the elastomer layer which has been removed from the elastomer layer after it has hardened, as a carrier film for a subsequently produced printing plate.
• the cover film is pretreated with a primer (solvent) before it is used as a carrier film.
• a directly laser-engravable printing plate is created, in particular for flexographic printing, with a lower carrier film or plate and an elastomer layer of silicone polymer, silicone fluoropolymer or silicone rubber applied thereon, the elastomer layer being processed by means of a calibrating device with a calender gap through which the printing plate is positioned in front of the Hardening of the elastomer layer is transported.
• the carrier film or plate can preferably be provided on its upper side facing the elastomer layer with a lamination made of a compressible intermediate layer on which the elastomer layer is arranged directly.
• Figure 1 shows a device for performing the method according to the invention for the production of a printing plate according to the invention in a schematic side view.
• FIG. 2 shows an enlarged detail II of the printing plate produced with the device according to FIG. 1 before it passes through the calibration device on average;
• FIG. 3 shows the subject of FIG. 2 after passing through the calibration device according to a detail III in FIG. 1;
• FIG. 4 shows a second embodiment of a printing plate according to the invention during its post-processing by means of a grinding tool in a longitudinal section.
• the device 10 shown schematically in FIG. 1 is used to produce a directly laser-engravable printing plate 11, which essentially consists of a lower carrier film 12 and an elastomer layer 13 arranged thereon made of a silicone polymer, silicone fluoropolymer or silicone rubber.
• the materials forming the elastomer layer can preferably be those as are known from the older patent specification DE 196 25 749 C2 or DE 197 56 327 AI, the disclosure content of which is hereby expressly made the subject of the present application.
• the carrier film 12 is provided on its upper side 14 with a liner 15 made of an elastic foam material, on which the elastomer layer 13 is arranged directly, ie without the interposition of a film or other intermediate layer.
• the elastomer layer 13 has a greater thickness and is applied directly to the upper side 14 of the carrier film 12 which has been pretreated with a primer.
• the printing plate according to the invention is produced continuously in the plane.
• the carrier film 12 is first unwound from a supply roll 16 and placed horizontally on a first conveyor belt 17.
• a guide roller 18 extending across the width of the carrier film and the conveyor belt ensures that the carrier film comes to lie on the conveyor belt 17 without creases.
• the silicone polymer, silicone fluoropolymer or silicone rubber forming the elastomer layer 13 is then applied directly to the liner of the carrier film 12 onto the carrier film 12 already provided with the liner 15 with the aid of a mixing and dosing head 19, working here with a small excess of material and the elastomer layer 13 immediately after its application still has a somewhat uneven surface 20.
• the not yet hardened elastomer layer is covered by the conveyor belt 17 with a cover film 21, which has a roughened surface on its underside 22 when the printing plate blank thus produced is transported onward.
• This sandwich-like structure consisting of lower carrier film 12, lamination 15, elastomer layer 13 and upper cover film 21 then runs from the first Conveyor belt 17 and on through a calender gap 23 of a calibration device 24, which essentially consists of a lower pressure bar 25 with a spherical, highly precise and preferably polished surface 26 and a calender roll 27, which is arranged exactly parallel to the pressure bar 25 above it and is just like this extends over the entire width of the carrier film 12.
• the height of the calender roll can be adjusted very precisely by means of a one-piece device 28 shown in a highly simplified manner, so that the thickness of the calender gap can be adjusted with an accuracy of up to 1/100 mm over the entire width of the carrier film.
• the previously uneven surface 20 of the not yet hardened elastomer layer is smoothed and excess material is pushed away to the side, so that the pressure plate has a largely uniform thickness with only very slight thickness deviations after it has passed through the calibration device are on the order of less than 1/10 mm.
• the pressure plate calibrated as described above passes from the calender gap 23 onto a second conveyor belt 29 on which the elastomer layer hardens, which, depending on the type of elastomer material used, is carried out by additional devices, for example radiant heaters or the like. can be favored, but which are not shown in Fig. 1.
• the cover film 21 is pulled off the top of the elastomer layer 13 and wound up on a roll 30.
• the roughened underside 22 of the cover film leaves a corresponding structure in the hardened elastomer layer, which holds the printing ink particularly well during later printing with the printing plate and a clean one Ensures transfer of the print image to the surface to be printed.
• the cover film wound on the roll 30 can either be used again to cover the not yet hardened elastomer layer before the printing plate passes through the calibration device or can also serve as a carrier film 12, for which purpose it is first pretreated on its upper side with a suitable primer and then if necessary. is provided with the liner 15 before it is wound onto a carrier film supply roll.
• the elastomer layer 13 is applied directly to the carrier film, i.e. a soft elastic lamination on the carrier film is not provided in this embodiment.
• the printing plate according to FIG. 4 is reground after passing through the calibration device according to FIG. 1 and curing the elastomer layer and peeling off the cover film, so that a highly precise surface with a thickness deviation in the 1/100 mm range is achieved.
• the surface of the printing plate is processed by means of a rapidly rotating grinding wheel 31, which allows the desired accuracy to be achieved in only one work step with a correspondingly low material removal.

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• Manufacture Or Reproduction Of Printing Formes (AREA)
• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (4)

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Family Cites Families (5)

• 2001
  • 2001-05-28 DE DE10126067A patent/DE10126067A1/de not_active Withdrawn
• 2002
  • 2002-05-22 EP EP02730270A patent/EP1390202B1/fr not_active Expired - Lifetime
  • 2002-05-22 WO PCT/EP2002/005611 patent/WO2002096648A1/fr not_active Ceased
  • 2002-05-22 DE DE50206313T patent/DE50206313D1/de not_active Expired - Lifetime
  • 2002-05-22 AT AT02730270T patent/ATE322381T1/de not_active IP Right Cessation

Non-Patent Citations (1)

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