Classifications

• • 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
• • 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
• • 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 chloride and ammonium ions.
• Printing plates generally consist of a carrier and at least one radiation-sensitive reproduction layer arranged thereon, this layer either by the consumer (in the case of non-precoated plates) or by the industrial one Manufacturer (for pre-coated boards) is applied to the substrate.
• Aluminum or one of its alloys has established itself as the substrate material in the printing plate field. These substrates 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 electrophotographically
• the image areas which carry the color during subsequent printing and the water-bearing non-image areas are produced on the printing plate, which gives rise to the actual printing form on the subsequent topography of the aluminum surface to be roughened very different parameters have an impact.
• the following references provide information:
• the temperature variation between 16 ° C and 90 ° C shows a changing influence only from about 50 ° C, which is expressed, for example, by the sharp decline in the formation of layers on the surface.
• the roughening time change between 2 and 25 min also leads to an increasing metal dissolution with increasing exposure time.
• the variation of the current density between 2 and 8 A / dm 2 results in higher roughness values with increasing current density. If the acid concentration is in the range 0.17 to 3.3% of HCl then between 0.5 and 2% of HCI there are only insignificant changes in the hole structure, below 0.5% of HCI there is only a local attack on the surface and with the high values an irregular dissolution of aluminum instead of the addition of SO 4 2- ions or CI ions in salt form [e.g. B. by adding Al 2 (SO 4 ) 3 or NaCl] can also affect the topography of the roughened aluminum.
• the rectification of the alternating current shows that both types of half-wave are obviously required for a uniform roughening.
• hydrochloric acid as an electrolyte for roughening aluminum substrates can therefore be assumed to be known.
• a uniform grain can be obtained, which is suitable for lithographic plates and is within a usable roughness range.
• the setting of a flat and uniform surface topography is difficult in pure hydrochloric acid electrolytes, and the operating conditions must be maintained within very narrow limits.
• JP-Anmeidung 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.
• JP application 93 108/78 describes the production of a capacitor film; it is first roughened with alternating current in an electrolyte of 0.3 to 1.5% hydrochloric acid and 15 to 25% ammonium acetate and then further electrolyzed in HCl with pulsed current.
• these anticorrosive agents increase the roughness depth compared to pure hydrochloric acid electrolytes.
• the object of the present invention is therefore to propose a method for the electrochemical roughening of aluminum for printing plate supports with alternating current, which results in a uniform, scar-free and area-wide roughening structure and which can be dispensed with a large expenditure on equipment and / or particularly narrow parameter limits.
• the invention is based on a process for the electrochemical roughening of aluminum or its alloys for printing plate supports in an electrolyte containing chloride ions under the action of alternating current.
• the process according to the invention is characterized in that an electrolyte containing chloride ions is used, to which an ammonium ion-containing compound is added and the pH of which is adjusted to less than 4.5
• an HCI electrolyte is used, the hydrochloric acid concentration between 0.01 and 50.0 g / l, particularly preferably between 0.01 and 30.0 g / l, and the concentration of the ammonium compound between 40 g / l I and the saturation limit, particularly preferably between 70.0 g / 1 and the saturation limit
• Ammonium chloride is used as the preferred compound containing ammonium ions.
• Within the scope of the invention is also contemplated to employ combinations of ammonium salts, as long as the requirement is met that the pH ⁇ 4, 5, preferably ⁇ 3.0, is set.
• the process according to the invention is carried out either discontinuously or preferably continuously with strips made of aluminum or its alloys.
• the process parameters in continuous processes during roughening are in the following ranges: the temperature of the electrolyte between 20 and 60 ° C, the current density between 3 and 130 A / dm 2 , the residence time of a material point to be roughened in the electrolyte between 10 and 300 sec and the electrolyte flow rate on the surface of the material to be roughened between 5 and 100 cm / sec.
• the current densities required tend to be in the lower part and the residence times are in the upper part of the ranges specified; the flow of the electrolyte can also be dispensed with.
• the method according to the invention can also be applied to other aluminum alloys.
• an anodic oxidation of the aluminum can then follow in a further process step to be used, for example in order to improve the abrasion and adhesion properties of the surface of the carrier material.
• an alkaline but preferably an acidic, intermediate pickling can be carried out to remove any coating or to improve the water flow.
• 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 a subsequent development and / or fixation, provide an image-like area from which it is possible to print and / or which represent a relief image of a template. They are either from 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 photopolymerizable ver layers containing bonds, 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).
• Negative working layers according to DE-A 30 36 077 which contain a diazonium salt polycondensation product or an organic azido compound as the photosensitive compound and a high molecular weight polymer with pendant alkenylsulfonyl or cycloalkenylsulfonylurethane groups as the binder.
• photoconductive layers such as z. B. 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.
• Comparative examples 9 to 12 and 4 1 to 49 show in comparison with the other examples the effect of the addition of ammonium while maintaining a pH value ⁇ 4.5 as an aid for achieving flatter and nevertheless uniform surfaces. These surface properties can be realized without any great expenditure on equipment.
• An aluminum sheet (DIN material no. 3.0255) is first pickled for 60 seconds in an aqueous solution containing 20 g / 1 NaOH at room temperature. The roughening takes place in the specified electrolyte systems at 40 ° C.
• the classification into the quality classes - is carried out by visual assessment under the microscope, whereby a homogeneously roughened and grain-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.

Landscapes

• 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)
• Photosensitive Polymer And Photoresist Processing (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6261748

Family Applications (1)

Country Status (7)

Cited By (1)

Families Citing this family (9)

Family Cites Families (27)

• 1985
  • 1985-02-06 DE DE19853503927 patent/DE3503927A1/de not_active Withdrawn
• 1986
  • 1986-01-25 EP EP86101024A patent/EP0194429B1/fr not_active Expired
  • 1986-01-25 DE DE8686101024T patent/DE3667077D1/de not_active Expired
  • 1986-02-04 US US06/825,937 patent/US4666576A/en not_active Expired - Lifetime
  • 1986-02-05 CA CA000501182A patent/CA1280997C/fr not_active Expired - Fee Related
  • 1986-02-05 BR BR8600495A patent/BR8600495A/pt not_active IP Right Cessation
  • 1986-02-05 KR KR1019860000784A patent/KR930005014B1/ko not_active Expired - Fee Related
  • 1986-02-06 JP JP61023075A patent/JPH0667674B2/ja not_active Expired - Lifetime

Also Published As

Similar Documents

Legal Events