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
  • B41N3/03—Chemical or electrical pretreatment
  • B41N3/034—Chemical or electrical pretreatment characterised by the electrochemical treatment of the aluminum support, e.g. anodisation, electro-graining; Sealing of the anodised layer; Treatment of the anodic layer with inorganic compounds; Colouring of the anodic layer
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F3/00—Electrolytic etching or polishing
  • C25F3/02—Etching
  • C25F3/04—Etching of light metals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12993—Surface feature [e.g., rough, mirror]

Definitions

• the invention relates to a method for the electrochemical roughening of aluminum for printing plate supports, which is carried out with alternating current in an electrolyte containing nitrate and ammonium ions.
• Printing plates (this term means offset printing plates in the context of the present invention) generally consist of a support and at least one radiation (light) sensitive reproduction layer arranged thereon, this layer either by the consumer (in the case of non-precoated plates) or by the industrial manufacturer (with precoated boards) is applied to the substrate.
• Aluminum or one of its alloys has established itself as a layer support material in the printing plate field.
• These layer supports can in principle also be used without a modifying pretreatment, but they are generally modified in or on the surface, for example by mechanical, chemical and / or electrochemical roughening (sometimes referred to in the relevant literature as grain or etching), chemical or electrochemical oxidation and / or treatment with hydrophilizing agents.
• the roughening is carried out, for example, in aqueous acids such as aqueous HCl or HNO 3 solutions or in aqueous salt solutions such as aqueous NaCl or Al (NO 3 ) 3 solutions using alternating current.
• aqueous acids such as aqueous HCl or HNO 3 solutions
• aqueous salt solutions such as aqueous NaCl or Al (NO 3 ) 3 solutions using alternating current.
• the roughness depths that can be achieved in this way are in the range from about 1 to 15 ⁇ m, in particular in the range from 2 to 8 ⁇ m.
• the roughness depth is determined in accordance with DIN 4768 (as of October 1970).
• the roughness depth R z is then the arithmetic mean of the individual roughness depths of five adjacent individual measurement sections
• the roughening is a. therefore carried out in order to improve the adhesion of the reproduction layer on the layer support and the water flow of the printing plate resulting from the printing plate by irradiation (exposure) and development.
• irradiation and development or decoating in the case of reproduction layers working electrophatographically
• the image areas which carry color during later printing and the water-bearing non-image areas are produced on the printing plate, as a result of which the actual printing form is formed on the later topography of the roughened aluminum surface very different parameters have an impact.
• the following references provide information about this
• hydrochloric acid or nitric acid as an electrolyte for roughening aluminum substrates can therefore be assumed to be known.
• a uniform grain size can be obtained which is suitable for lithographic plates and is within a usable roughness range. It is difficult to achieve a flat and uniform surface topography in pure nitric acid electrolytes and it is necessary to adhere to the operating conditions within very narrow limits.
• JP application 91 334/78 describes AC roughening in a combination of hydrochloric acid and an alkali halide to produce a lithographic base material.
• DE-C 120 061 describes a treatment for producing a water-attracting layer by using electricity, which can also take place in hydrofluoric acid.
• the invention relates to a method for the electrochemical roughening of aluminum or its alloys for printing plate supports in an HNO 3 electrolyte under the action of alternating current.
• the process according to the invention is characterized in that an HNO, electrolyte is used, to which an ammonium ion-containing compound is added.
• an HNO 3 electrolyte is used, the nitric acid concentration between 1 and 80 g / l, particularly preferably between 5 and 50 g / l, and the concentration of the ammonium compound between 3.0 g / l and the saturation limit, is particularly preferably between 5.0 g / l and 300.0 g / l.
• the preferred compound containing ammonium ions is ammonium nitrate or ammonium chloride. Combinations of compounds containing ammonium ions are of course also within the scope of the invention.
• the method according to the invention can also be applied to other aluminum alloys.
• Direct current is preferably used for the anodic oxidation, however alternating current or a combination of these types of current (eg direct current with superimposed alternating current) can also be used.
• the layer weights of aluminum oxide range from 1 to 10 g / m 2 , corresponding to a layer thickness of approximately 0.3 to 3.0 ⁇ m.
• a modification causing surface abrasion from the roughened surface can also be used, as described, for example, in DE-A 30 09 103.
• Such a modifying intermediate treatment can include the build-up of abrasion-resistant oxide layers and enable a lower toning tendency when printing later.
• the stage of anodic oxidation of the aluminum printing plate support material can also be followed by one or more post-treatment stages.
• These post-treatment stages serve in particular to additionally increase the hydrophilicity of the aluminum oxide layer, which is already sufficient for many areas of application, the remaining known properties of this layer being at least retained.
• all layers are suitable as light-sensitive reproduction layers which, after exposure, possibly with subsequent development and / or fixation, provide an image-like area from which printing can take place and / or which represent a relief image of a template. They are either made by the manufacturer of presensitized printing plates or applied by so-called dry resists or directly by the consumer on one of the usual carrier materials
• the light-sensitive reproduction layers include such as z. B. in "Light-Sensitive Systems” by Jaromir Kosar, John Wiley & Sons Verlag, New York 1965, are described: The layers containing unsaturated compounds in which these compounds are isomerized, rearranged, cyclized or crosslinked during exposure (Kosar, chapter 4 ); the layers containing photopolymerizable compounds, in which monomers or prepolymers optionally polymerize during exposure by means of an initiator (Kosar, Chapter 5); and the layers containing o-diazo-quinones such as naphthoquinonediazides, p-diazo-quinones or diazonium salt condensates - (Kosar, Chapter 7).
• photo-semiconducting layers such as e.g. in DE-C 11 17 391, 15 22 497, 15 72 312, 23 22 046 and 23 22 047 are described, are applied to the support materials, whereby highly light-sensitive, electrophotographic layers are formed.
• the materials for printing plate supports roughened by the process according to the invention have a very uniform topography, which has a positive influence on the support stability and the water flow when printing printing forms made from these supports
• An aluminum sheet (DIN material no. 3.0255) is first pickled for 60 seconds in an aqueous solution of 20 g / l NaOH at room temperature. The roughening takes place in the specified electrolyte systems.
• aqueous solution 20 g / l NaOH at room temperature.
• the classification into the quality classes - is carried out by visual assessment under the microscope, whereby a homogeneously roughened and scar-free surface is assigned quality level "1" (best value).
• quality level "10" (worst value) is assigned to a surface with thick scars of a size of more than 30 ⁇ m and / or an extremely unevenly roughened or almost bare surface.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (2)

Publications (3)

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• 1985
  • 1985-02-06 DE DE19853503926 patent/DE3503926A1/de not_active Withdrawn
• 1986
  • 1986-01-25 DE DE8686101023T patent/DE3671255D1/de not_active Expired - Fee Related
  • 1986-01-25 EP EP86101023A patent/EP0194428B1/fr not_active Expired - Lifetime
  • 1986-02-04 US US06/825,930 patent/US4661219A/en not_active Expired - Lifetime
  • 1986-02-05 CA CA000501184A patent/CA1275068A/fr not_active Expired - Fee Related
  • 1986-02-06 JP JP61023076A patent/JPH0714674B2/ja not_active Expired - Lifetime

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