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

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 aqueous mixed electrolyte.
• Printing plates generally consist of a support and at least one radiation-sensitive reproduction layer arranged thereon, this layer either from the consumer (in the case of non-precoated plates) or from the industrial one Manufacturer (for pre-coated boards) is applied to the substrate.
• Aluminum or one of its alloys has established itself as a layer material in the printing plate field.
• these substrates can 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 also called grain or etching in literature), chemical or electrochemical oxidation and / or treatment with hydrophilizing agents.
• a combination of the above-mentioned Mo Types of dification applied, in particular a combination of electrochemical roughening and anodic oxidation, optionally with a subsequent hydrophilization step.
• the roughening is carried out, for example, in aqueous acids such as aqueous HCl or HN0 3 solutions or in 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 in the version from October 1970, the roughness depth R z is then the arithmetic mean of the individual roughness depths of five adjacent individual measuring sections.
• the roughening is carried out, inter alia, in order to improve the adhesion of the reproduction layer on the substrate 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 points which carry color during later printing and the water-bearing non-image points are produced on the printing plate, whereby the actual printing form is created.
• Various parameters have an influence on the later topography of the aluminum surface to be roughened, which may be exemplified by the following explanations of the prior art:
• aqueous HN0 3 solutions as an electrolyte solution for the electrochemical roughening of support materials made of aluminum is generally to be assumed to be known. It can be obtained - as many examples of commercial printing plates show - a relatively uniform grain, but often with a more or less pronounced scarring, which is suitable for the field of application of lithography and is within a roughness range that is generally useful in practice. For certain areas of application of printing plates (e.g.
• trolyt solution in the roughening of aluminum for printing plate supports aqueous solutions with a content of 0.3 to 2.0% by weight of HNO 3 and 0.1 to 8.0% by weight of oxalic acid, the solution also containing boric acid, Aluminum nitrate and / or H 2 O 2 can be present.
• the previously known complexing acting additives accelerate usually by "Wegrac” of released Al 3+ ions the dissolution of aluminum and thus lead to the reinforcement of the A ufrauhangriffs; However, this often leads to the fact that no additional hole nuclei are created, but that already formed nuclei and holes continue to grow, ie there is then increased scar formation.
• the previously known inhibitory additives generally have the effect that L is stopped ochwachstum individual holes relatively soon, and can add new hole nuclei are formed; However, they have the decisive disadvantage that this protective effect due to defects, alloy components and the like. ⁇ . can collapse; this then leads to deep holes in an otherwise flat and evenly roughened surface. Backing materials with such imperfections are unsuitable for lithographic purposes.
• the object of the present invention is therefore to propose a method for the electrochemical roughening of aluminum for printing plate supports, which enables To achieve a uniformly roughened surface topography with a wide range in the mean roughness values and to achieve long bath service lives and with the help of which aluminum alloys with less than 99.5% of Al can be roughened evenly.
• the invention is based on the known method for electrochemical roughening of aluminum or its alloys for printing plate supports in an aqueous mixed electrolyte solution containing HN0 3 and at least one other inorganic electrolyte under the action of alternating current.
• the process according to the invention is then characterized in that the further inorganic electrolyte is an inorganic fluorine compound which is present as an acid or alkali metal salt and whose anion contains fluorine and, if appropriate, at least one further E-element.
• the aqueous electrolyte solution contains 0.3 to 4% by weight, in particular 0.8 to 3% by weight, and preferably 1.0 to 2% by weight of HNO 3 and 0.05 to 5% by weight .-%, in particular 0.1 to 1.5 wt .-%, of the fluorine compound.
• the suitable inorganic fluorine compounds include in particular complex fluorine compounds or compounds comparable to them.
• Preferred examples of such fluorine compounds are acids or alkali salts (including the ammonium salts) with the anions: SiF 6 2- , TiF 6 2- , ZrF 6 2- , BF 4 - , PF 6 - , HfF 6 2- , SO 3 F - and PO 3 F 2- ; but it can also compounds with the following anions are used: NbF 6 - , TaF 6 - , FeF 6 3- , AsF 6 - and SbF 6 - .
• the compounds are preferably used individually, but can also be used as a mixture of several.
• Suitable base materials for the material to be roughened according to the invention include those made of aluminum or one of its alloys, which, for example, contain more than 98.0% by weight, in particular less than 99.5% by weight, of Al and proportions ar . Si, Fe, Ti, Cu, Zn, Mn and / or Mg.
• These aluminum carrier materials can also be roughened mechanically (for example by brushing and / or with abrasive treatments) before the electrochemical stage, if appropriate after pre-cleaning. All process steps can be carried out discontinuously with plates or foils, but they are preferably carried out continuously with tapes.
• the process parameters are in the following ranges: the temperature of the electrolyte between 20 and 60 ° C, the current density between 3 and 200 A / dm 2 , the residence time of a material point to be roughened in the electrolyte between 3 and 100 sec and the electrolyte flow rate at the surface of the material to be roughened between 5 and 100 cm / sec; in the batchwise process, the required current densities are in the lower part and the residence times are in upper part of the specified ranges, the flow of the electrolyte can also be dispensed with.
• alternating current of a frequency of 50 to 60 Hz is used as the type of current; however, modified types of current such as alternating current with different amplitudes of the current strength for the anode and cathode current, lower frequencies, current interruptions or superimposition of two currents of different frequency and waveform are also possible.
• the average roughness depth R z of the roughened surface is in the range from 1 to 15 ⁇ m, in particular from 1.5 to 8.0 ⁇ m.
• aluminum ions in the form of aluminum salts in particular 2% by weight to saturation and preferably 4 to 8% by weight of Al (NO 3 ) 3, can also be added to the aqueous electrolyte.
• Pre-cleaning includes, for example, treatment with aqueous NaOH solution with or without degreasing agent and / or complexing agents, trichlorethylene, acetone, methanol or other commercially available aluminum stains.
• non-electrochemical treatments are also known which essentially only have a rinsing and / or cleaning effect and, for example, for removing deposits formed during roughening ("Schmant") or simply for Serve removal of electrolyte residues; For example, dilute aqueous alkali hydroxide solutions or water are used for these purposes.
• an anodic oxidation of the aluminum can then preferably 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.
• the usual electrolytes such as H 2 SO 4 , H 3 PO 4 , H 2 C 2 O 4 , amidosulfonic acid, sulfosuccinic acid, sulfosalicylic acid or their mixtures are used; in particular, H 2 S0 4 and H 3 P0 4 are used alone, in a mixture and / or in a multi-stage anodizing process.
• the stage of anodic oxidation of the aluminum 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 often sufficient, while at least the other known properties of this layer are retained.
• the materials produced according to the invention are used as carriers for offset printing plates, ie a radiation-sensitive coating is applied to the carrier material on one or both sides either by the manufacturer of presensitized printing plates or directly by the consumer.
• a radiation-sensitive coating is applied to the carrier material on one or both sides either by the manufacturer of presensitized printing plates or directly by the consumer.
• all layers which are suitable for radiation (light) are suitable, if appropriate after irradiation (exposure) with a subsequent development and / or fixation provide a pictorial surface from which printing can take place.
• Suitable layers also include electrophotographic. phical layers, d. H. those containing an inorganic or organic photoconductor. In addition to the light-sensitive substances, these layers can of course also other components such. B. contain resins, dyes or plasticizers. In particular, the following light-sensitive compositions or compounds can be used in the coating of the carrier materials produced by the process according to the invention:
• o-quinonediazides in particular o-naphthoquinonediazides such as naphthoquinone- (1,2) -diazid- (2) -sulfonic acid esters or amides, which can be of low or higher molecular weight, as a photosensitive compound-containing reproduction layers, for example in the DE-C 854 890, 865 109, 879 203, 894 959, 938 233, 1 109 521, 1 144 705, 1 118 606, 1 120 273, 1 124 817 and 2 331 377 and EP-A 0 021 428 and 0 055 814 will;
• Negative-working reproduction layers with condensation products from aromatic diazonium salts and compounds with active carbonyl groups preferably condensation products from diphenylamine diazonium salts and formaldehyde, which are described, for example, in DE-C 596 731, 1 132 399, 1 138 399, 1 138 400, 1 138 401, 1 142 871, 1 154 123, U.S. 2,679,498 and 3,050,5C2 and GB 712,606;
• Reproductive layers containing negative-working, mixed condensation products of aromatic diazonium compounds for example according to DE-C 20 65 732, the products with at least one unit each of a) a condensable aromatic diazonium salt compound and b) a condensable compound such as a phenol ether or an aromatic thioether, connected by have a double bonded intermediate member derived from a condensable carbonyl compound such as a methylene group;
• positive-working layers according to DE-A 26 10 842, DE-C 27 18 254 or DE-A 29 28 636 which contain a compound which cleaves off under irradiation, a monomeric or polymeric compound which has at least one COC which can be cleaved off by acid Group (e.g. an orthocarboxylic acid ester group or a carboxylic acid amide acetal group) and optionally contain a binder;
• acid Group e.g. an orthocarboxylic acid ester group or a carboxylic acid amide acetal group
• optionally contain a binder e.g. an orthocarboxylic acid ester group or a carboxylic acid amide acetal group
• the monomers used here are, for example, acrylic and methacrylic acid esters or reaction products of diisocyanates with partial esters of polyhydric alcohols, as described, for example, in US Pat. Nos. 2,760,863 and 3,060,023 and DE-A 20 64 079 and 23 61 041;
• Negative-working layers according to DE-A 30 36 077, which contain a diazonium salt polycondensation product or an organic azido compound as a photosensitive compound and a high molecular weight polymer with pendant alkenylsulfonyl or cycloalkenylsulfonylurethane groups as a binder.
• 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 carrier materials produced according to the invention, thereby producing highly light-sensitive, electrophotographic printing plates.
• carrier materials coated Offsetcruckplatten be converted in a known manner by imagewise exposure or irradiation, and washing out the non-image areas with a developer, such as an aqueous alkaline developer solution in the g e-desired printing form.
• a developer such as an aqueous alkaline developer solution in the g e-desired printing form.
• % data always mean% by weight, unless stated otherwise. Parts by weight relate to parts by volume in the ratio of g to cm 3 .
• EXAMPLES 1 TO 38 AND COMPARATIVE EXAMPLES V1 TO V10 An aluminum sheet is first pickled for 60 seconds in an aqueous solution of 20 g NaOH per liter at room temperature and then freed of any alkali residues that may be present by briefly immersing it in a solution corresponding to the roughening electrolyte. The roughening takes place in the electrolyte systems shown in the following tables and under the conditions listed there. After roughening, an anodic oxidation is carried out in an aqueous electrolyte containing H 2 S0 4 and A1 3 + ions up to a layer weight of 3.0 g / m 2 .
• the classification into the quality classes is carried out by visual assessment under a microscope, with a homogeneously roughened and scarred free surface quality level "1" (best value) is assigned.
• Quality level "10" (worst value) is assigned to a surface with thick scars with a size of more than 100 ⁇ m or an extremely unevenly roughened or almost bare surface.
• Intermediate qualities are rated “2" to "9”. All examples and the comparative examples are carried out with symmetrical alternating current at a frequency of 50 Hz, one electrode being the aluminum sheet and the other a graphite plate.
• the layer is negatively charged to about 400 V in the dark by means of a corona.
• the charged plate is exposed imagewise in a repro camera and then with an electrophotographic suspension developer, which by dispersing 3.0 parts by weight of magnesium sulfate in a solution of 7.5 parts by weight of pentaerythritol resin ester in 1200 parts by volume of an isoparaffin mixture with a Boiling range of 185 to 210 ° C was obtained.
• the developer is fixed and the plate in a solution of 35 parts by weight of sodium metasilicate for 60 seconds.
• 9 H 2 0, 140 parts by weight of glycerol, 550 parts by weight of ethylene glycol and 140 parts by weight of ethanol immersed.
• the plate is then rinsed off with a powerful jet of water, removing the areas of the photoconductor layer not covered with toner.
• the printing form is then ready for printing.

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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)

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• 1984
  • 1984-01-05 DE DE19843400250 patent/DE3400250A1/de not_active Withdrawn
  • 1984-12-21 DE DE8484116022T patent/DE3463399D1/de not_active Expired
  • 1984-12-21 EP EP84116022A patent/EP0149833B1/fr not_active Expired
  • 1984-12-27 JP JP59274254A patent/JPS60159094A/ja active Granted
• 1985
  • 1985-01-04 US US06/689,003 patent/US4566960A/en not_active Expired - Fee Related
  • 1985-01-04 CA CA000471473A patent/CA1270791A/fr not_active Expired - Fee Related

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