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
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/08—Damping; Neutralising or similar differentiation treatments for lithographic printing formes; Gumming or finishing solutions, fountain solutions, correction or deletion fluids, or on-press development

Definitions

• the invention relates to an aqueous dampening solution for offset printing to prevent toning during the printing process and to largely reduce interference from foreign ions.
• Offset printing is a planographic printing process.
• this process is carried out by printing from a flat plate or cylinder with essentially no surface relief (hence the term "planographic"), with the dependence on various properties of the image and non-image areas of the surface on the printability .
• the image to be reproduced is applied to the plate by several methods in a known manner in such a way that the non-image areas are made hydrophilic while the image areas are hydrophobic.
• a commonly used technique uses a photosensitive coating for this purpose. After exposing the photosensitive coating, the latent image is developed with a portion of the coating removed from the plate. Thereafter, the plate is treated with a desensitizing solution to make the plate hydrophilic in the places from which the photosensitive coating has been removed.
• an aqueous dampening or printing solution is applied to the plate surface.
• the dampening solution keeps all parts of the surface that are not covered by the hydrophobic image moist.
• the dampening solution can be formulated so that it gradually etches the surface of the plate just enough, that the lines are kept sharp and that rapid wear is prevented.
• the dampening solution is applied to the plate by one or more rollers. At least one ink roller, which is covered with an oil-based ink, then contacts the entire surface of the plate, but only colors the lithographic image at the image areas, since the hydrophilic non-image areas repel the ink. For each impression that is made during a run, the lithographic plate is therefore first moistened or wetted with the aqueous dampening solution and then provided with a lithographic printing ink.
• the dampening solution and at least part of the oil-based ink can be applied to the plate simultaneously with a roller.
• the ink is evenly and finely distributed using a distributor roller system.
• the ink image is transferred to an offset printing blanket made of rubber or a synthetic material, which in turn transfers the ink to the printing medium.
• water can be used as the dampening solution.
• this is only a moderately suitable agent that easily causes color to transfer to areas not intended for printing.
• a disadvantage of the use of polymers is that drying on leads to sticking or soiling of the printing press, particularly in machines with a centrifugal dampening system.
• EP-OS 0 091 601 describes a wetting solution which contains water-miscible or water-soluble polymers instead of the isopropanol also used, cellulose ethers, polyacrylamides, polyvinyl alcohols or chemically modified rubber products being used in particular. Such solutions have the same defects as those already described for the polymers.
• an aqueous moistening solution the characteristic feature of which is that it contains aminomethylenephosphonic acid, preferably amino-tris (methylenephosphonic acid) and / or diethylenetriamine-penta- (methylenephosphonic acid) and / or derivatives of these acids.
• aminomethylenephosphonic acids such as amino-tris (methylenephosphonic acid) or diethylenetriaminepenta (methylenephosphone) acid
• the hydrophilization of the non-printing areas is renewed during the printing process, so that no toning occurs until the end of the print run.
• This effect is possible because the monomeric substances used are effective even in the cold and in low concentrations. It is therefore also possible to incorporate them into a concentrate that is diluted by the customer.
• this moistening solution also gives it the property of preventing faults caused by hard water or possibly copper ions carried in from lines.
• a certain degree of corrosion protection can also be achieved according to the invention.
• dampening solution as part of a buffer system and thus to further reduce the salt load in the washer fluid.
• the additives customary for moisturizing solutions such as glycols, alcohols, wetting agents, defoamers, buffer substances and, if appropriate, thickeners and corrosion inhibitors can be added, with which a synergistic effect can be achieved.
• the concentration of the compounds used according to the invention is generally 0.1 to 10% by weight; however, it is also possible in some cases, Konzen trations down to 0.001 wt .-%.
• the pH of the dampening solution is adjusted between 4.0 and 7.0, but preferably 4.0 to 5.5.
• Example 2 An electrolytically roughened and anodized aluminum plate was treated as in Example 1, but with a 0.5% solution of polyvinylphosphonic acid. The plate took on color.
• An electrolytically roughened and anodized aluminum niumplatte was immersed for 30 min in a moving 2% aqueous solution, which was prepared by dilution from a concentrate containing 5% glycerol, 0.4% diethylenetriamine-penta- (methylenephosphonic acid) and as much Na3PO4 as to achieve a pH - A value of 4.4 is required.
• the plate was then dried (as happens when the machine is at a standstill) and then treated with damp cotton wool and paint. The plate was perfectly hydrophilic and did not take on any color.
• the solution used contained 0.008% diethylenetriamine-penta- (methylenephosphonic acid).
• An electrolytically roughened and anodized aluminum plate was immersed in a moving 2% solution from a concentrate containing 5% glycerol and adjusted to pH 4.4 with H3PO4, taken out after 30 minutes and dried, then colored with moist cotton wool and paint . The plate took on color.
• the light-sensitive material obtained was exposed under a photographic, positive original, which included a 21-step wedge with density increments of 0.15.
• the exposure time was chosen so that level 9 was fully covered. It was developed with a 5% aqueous sodium metasilicate solution.
• the plate was clamped in a GTO printing machine.
• Two parts by weight of a dampening solution concentrate 0.25 part by weight of polyethylene oxide-polypropylene oxide block polymer with 20% ethylene oxide 1.0 part by weight of butyl diglycol 8.0 parts by weight of glycerin 5.0 parts by weight of amino-tris (methylenephosphonic acid) 6.1 parts by weight of trisodium citrate 0.7 part by weight of trisodium phosphate 78.95 parts by weight of water were diluted with 98 parts by weight of water and fed to the dampening unit of the printing press. 100,000 flawless prints were obtained with printing plates colored with 185 W Novatit black from Keuffel and Esser.

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• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

Country Status (7)

Cited By (2)

Families Citing this family (3)

Citations (5)

• 1985
  • 1985-10-31 DE DE19853538703 patent/DE3538703A1/de not_active Withdrawn
• 1986
  • 1986-10-21 EP EP86114580A patent/EP0220662A1/fr not_active Withdrawn
  • 1986-10-24 ZA ZA868102A patent/ZA868102B/xx unknown
  • 1986-10-29 FI FI864404A patent/FI864404A/fi not_active Application Discontinuation
  • 1986-10-30 JP JP61257078A patent/JPS62105692A/ja active Pending
  • 1986-10-30 BR BR8605348A patent/BR8605348A/pt unknown
  • 1986-10-31 AU AU64628/86A patent/AU6462886A/en not_active Abandoned

Patent Citations (5)

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