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
  • B41N1/16—Curved printing plates, especially cylinders
  • B41N1/20—Curved printing plates, especially cylinders made of metal or similar inorganic compounds, e.g. plasma coated ceramics, carbides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C1/00—Forme preparation
  • B41C1/02—Engraving; Heads therefor
  • B41C1/04—Engraving; Heads therefor using heads controlled by an electric information signal
  • B41C1/05—Heat-generating engraving heads, e.g. laser beam, electron beam
• • 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
• • 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
  • B41N1/08—Printing plates or foils; Materials therefor metallic for lithographic printing
  • B41N1/10—Printing plates or foils; Materials therefor metallic for lithographic printing multiple

Definitions

• the invention relates to a method for producing a printing form for gravure printing, in particular rotogravure, being produced by means of a laser engraving cups in an engraving and wherein before the laser engraving a chromium layer is applied to the printing plate, and a printing form for gravure, especially rotogravure, with an engraving surface for laser engraving of wells.
• the invention relates to a use of a printing form for gravure printing, in particular rotogravure printing, wherein cells can be produced in a engraving surface by means of a laser engraving engraving.
• Printing forms for gravure printing also called impression cylinders or engraving cylinders, are mainly produced in engraving devices by means of a recording element in the form of an engraving element or by means of an electron beam or laser beam.
• a document to be reproduced is scanned point and line by line with a scanning device to obtain an image signal representing the tonal values of the scanned original.
• the image signal is corrected according to the requirements of the reproduction, for example according to a predetermined gradation curve, and superimposed on a raster signal for generating the printing raster.
• the recording signal formed by the superimposition of the image signal and the raster signal controls the recording member which moves along the printing cylinder in the axial direction and engraves a series of depressions or recesses, called cups, in the printing screen, engraved in the outer surface of the printing cylinder.
• the scanning of the original which follows the pre-recorded principle, is nowadays usually only with electronic scanning of the template.
• the image data supplied by the scan are transferred to a computer in which a program-based processing and processing takes place.
• the computer then provides the image signals, due to which the cells were formed either mechanically and / or by laser engraving in the lateral surface of the printing cylinder.
• the depths or volumes of the engraved wells determine the tonal values to be printed between "black” and “white”, also referred to in printing terminology as "depth” and "light”.
• the engraved printing cylinder is then clamped in a rotogravure machine.
• each well receives a volume of ink dependent on its volume, which corresponds to the tone value to be printed.
• the color transfer from the wells to the printing material takes place.
• a commonly used in practice gravure cylinder generally consists of a steel core, which may be additionally provided with a base copper layer. On the steel core or the base copper layer, a further copper layer is galvanized, in which the wells are engraved. Copper, due to its physical and chemical properties, has good engraving properties as well as good ink receptivity and ink delivery properties, which aid in the production of high quality prints.
• the thickness of the electroplated copper-engraving surface is approximately 100 ⁇ m.
• the copper layer to be engraved is polished, so that the surface is provided with a defined micro-roughness. Subsequently, the information to be printed from image and writing is introduced into the copper surface in the form of a fine cell grid by means of a diamond stylus in an electromechanical manner.
• the disadvantage of using copper as an engraving material is that it has a relatively low hardness. As a result, wear occurs in the printing process in the gravure rotary machine as a result of the mechanical stress of the copper layer by the doctor with increasing operating time, the Print quality is reduced and the service life of the printing cylinder and thus the print run is limited.
• the chromium layer and the underlying copper layer containing the engraving are removed from the printing plate chemically or mechanically.
• the impression cylinder is available for a new cycle for producing a further printing form.
• intaglio printing forms have been produced by etching, resulting in good results.
• the printing cylinder was covered with a mask layer, followed by a photographic exposure of the mask on film masters and the washing out of the mask and the etching of the copper surface with iron chloride.
• the disadvantages were the low process reliability and the insufficiently good representation of halftones for pictures.
• the etching process was further modified by exposing the mask layer to a laser beam. This modified method was not only expensive and expensive, but also had the disadvantages of the etching process, that the halftones could be displayed poorly for images.
• EP-A-0 473 973 it is known to apply the chromium layer before the laser engraving as abrasion and wear-resistant material on the engraving surface of zinc or a zinc alloy, but this also includes the aforementioned problems.
• DE-A-3035714 suggests first applying an etchant-resistant layer to an engraving layer prior to electronic engraving, in which, after the electronic engraving, the wells thus produced are still formed by means of an etching process to be increased. Thereafter, the resistant layer can be removed again.
• the object of the invention is achieved according to the method in that the chromium layer is applied as an engraving surface on the printing plate and the wells are formed in the chromium layer.
• the advantage of the solution according to the invention consists essentially in that instead of the previous engraving surface made of copper, an engraving surface made of chromium or a chromium alloy is used. It has surprisingly been found that in a laser beam engraving of a chromium layer, wells are produced with a higher efficiency than with a copper layer, although the thermodynamic data of chromium compared to copper did not suggest this at all.
• the formation of the wells is carried out by a molten ablation.
• the corresponding metal volume must be heated to the melting temperature by the laser beam and the amount of heat for phase transition must be applied to the melt in order subsequently to expel the melt from the resulting well in the engraving surface.
• the melting point of copper is approx.
• the melting point of chromium is 1890 ° C. From the thermodynamic data for copper and chromium it follows that for the melting of 1 cm 3 of metal with copper an energy of 5.515 kJ and with chromium an energy of 8.698 kJ is to be applied. The higher efficiency in chromium is due to the higher absorption by laser beams depending on the laser radiation used. Overall, the manufacturing process for gravure cylinders is significantly improved and simplified by the inventive solution, since the printing form according to the invention a long service life is achieved in the pressure due to the hard properties of chromium.
• a further reinforcement of the chromium layer, for example in the case of copper, is therefore unnecessary, so that further treatment processes of the engraving surface after the engraving of the wells are dispensed with.
• the printing form can thus be used immediately and directly in the printing press, specifically after a possibly preceding deburring operation.
• deburring can already take place during laser engraving.
• the total production time for the creation of a printing plate or a printing cylinder is significantly shortened.
• the chromium layer is applied galvanically.
• the electroplating is usually carried out on a cylindrical steel core, the lateral surface may be additionally provided with a base copper layer.
• Galvanization is applied to the steel core or to the base copper layer a layer of chromium or a chromium alloy with a predetermined thickness, for example of about 25 microns.
• One known chromium alloy is the chromium-vanadium alloy.
• the chromium layer is provided with a predetermined roughness, in particular micro-roughness. This surface treatment eliminates minor surface defects.
• the roughness is produced by polishing and / or grinding.
• the printing forme is placed in a printing press, in particular a rotary printing press, in order to print on printing material.
• a printing press in particular a rotary printing press
• the chromium layer is at least partially removed from the printing plate after printing so that the printing plate, in particular the printing cylinder, is available several times for a new production cycle of the printing plate.
• the removal of the chromium layer can be carried out in particular in a chemical or mechanical manner.
• the object is further achieved by a printing form for gravure printing, in particular rotogravure printing, with an engraving surface for laser engraving of wells, which is obtainable by carrying out at least one method step of the method described above.
• a printing form for gravure printing in particular rotogravure printing
• an engraving surface for laser engraving of wells which is obtainable by carrying out at least one method step of the method described above.
• the object is achieved by the use of a printing form for gravure printing, in particular rotogravure, wherein by means of a laser engraving cups in an engraving surface are generated, which is further developed in that a chromium layer is formed as Engierober Structure.
• the chromium layer is applied galvanically to the printing plate.
• the chromium layer is provided with a predetermined roughness, in particular micro-roughness.
• the roughness is generated by means of polishing and / or grinding.
• the printing plate in a printing machine in particular rotary printing machine, is inserted.
• the chromium layer is preferably at least partially removed from the printing form after printing.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Plasma & Fusion (AREA)
• Manufacturing & Machinery (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Inorganic Chemistry (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)
• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (4)

Publications (2)

Family

ID=32043973

Family Applications (2)

Family Applications After (1)

Country Status (6)

Cited By (1)

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• 2003
  • 2003-08-02 EP EP03017492A patent/EP1410923B1/de not_active Expired - Lifetime
  • 2003-08-02 DE DE50304555T patent/DE50304555D1/de not_active Expired - Fee Related
  • 2003-08-26 JP JP2003301643A patent/JP2004136660A/ja active Pending
  • 2003-09-02 CN CNA031557880A patent/CN1491794A/zh active Pending
  • 2003-09-10 EP EP03020399A patent/EP1410924A1/de not_active Withdrawn
  • 2003-09-22 US US10/667,822 patent/US20040129152A1/en not_active Abandoned
  • 2003-09-23 CA CA002442247A patent/CA2442247A1/en not_active Abandoned
  • 2003-10-07 US US10/680,514 patent/US6877423B2/en not_active Expired - Lifetime

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