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
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S204/00—Chemistry: electrical and wave energy
  • Y10S204/09—Wave forms

Definitions

• the invention relates to a process for the electrochemical roughening of aluminum or its alloys for printing plate supports, which in an acidic aqueous electrolyte which contains HCI or HN0 3 as the sole acid, optionally together with aluminum nitrate, under the action of an alternating current with a frequency of 0.3 up to 15 Hz.
• 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 types of modification is often used, 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 HCI 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 pm.
• 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 pulsed direct current according to US Pat. No. 3,085,950 has a frequency between 20 and 6000 Hz, in particular at approximately 100 Hz, and a pulse duration of 5 to 100 psec, in particular of approximately 20 psec; in the intervening times, the current intensity drops to 0.
• This treatment is intended to roughen the surface of aluminum foils which are used as electrolytic capacitors.
• GB-A 1 027 695 is concerned with a four-stage process for the treatment of aluminum or its alloys, in the second stage of the process an electrochemical etching using an electrolyte from nitric acid, a lignosulfonic acid-containing sulfite liquor and an organic compound, frequencies being used from 15 to 75 Hz.
• the products treated according to the four-step process can be used as printing plates.
• US-A4279714 and US-A 4,279,715 describe the roughening of aluminum for the field of electrolytic capacitors, in which alternating current of a frequency in the range from 20 to 60 Hz is used.
• a hydrochloric acid electrolyte in combination with at least one additive e.g. organic or inorganic acids or their salts can be used for etching.
• a frequency range from 5 to 120 Hz is mentioned.
• the object of the present invention is therefore to propose a method for the electrochemical roughening of aluminum, which is carried out with alternating current and leads to such a uniform roughening structure that the aluminum can be used as a printing plate carrier.
• the invention is based on the known method for the electrochemical roughening of aluminum or its alloys for printing plate supports in an aqueous electrolyte under the action of alternating current.
• the process according to the invention is then characterized in that the acidic aqueous electrolyte contains as the sole acid HCI or HN0 3 , optionally together with aluminum nitrate, and the roughening is carried out with an alternating current with a frequency of 0.3 to 15 Hz.
• the frequency range is between 0.8 and 15 Hz, in particular between 1.5 and 10 Hz.
• the shape of the alternating current - with a graphic representation of the course of the current density or voltage as a function of time - can for example be a rectangular, Trapezoidal or sinusoidal, the rectangular shape is preferred in the inventive method.
• 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 electrolyte (acid and / or salt) concentration between 1 and 250 g, in particular between 5 and 100 g / I, 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 at the surface of the material to be roughened between 5 and 100 cm / sec.
• For anodic oxidation is preferably equal current, but alternating current or a combination of these types of current (e.g. 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 can also be applied which causes surface abrasion from the roughened surface, as described, for example, in DE-OS 30 09 103.
• a modifying intermediate treatment can, among other things, enable the build-up of abrasion-resistant oxide layers and a lower tendency to tone in later prints.
• 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.
• Negative-working 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-PS 596 731, 1138399, 1138400, 1138401, 1142871, 1 154123, US-PS 2 679 498 and 3050502 GB-PS 712 606 are described.
• Negative mixed condensation products of aromatic diazonium compounds for example according to DE-OS 20 24 244, which each have at least one unit of the general types A (-D) n and B connected by a double-bonded intermediate member derived from a condensable carbonyl compound.
• A is the remainder of a compound containing at least two aromatic carbocyclic and / or heterocyclic nuclei, which is capable of condensing with an active carbonyl compound in an acidic medium at at least one position.
• D is a diazonium salt group attached to an aromatic carbon atom of A; n is an integer from 1 to 10; and B is the remainder of a compound free of diazonium groups and capable of condensing with an active carbonyl compound in an acidic medium at at least one position on the molecule.
• Positive-working layers according to DE-OS 26 10 842 which contain a compound which releases acid upon irradiation, a compound which has at least one C-O-C group which can be split off by acid (e.g. an orthocarboxylic acid ester group or a carboxylic acid amide acetal group) and optionally a binder.
• acid e.g. an orthocarboxylic acid ester group or a carboxylic acid amide acetal group
• optionally a binder optionally a binder.
• Negative working layers of photopolymerizable monomers, photoinitiators, binders and optionally other additives 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-OSes 20 64 079 and 23 61 041.
• Suitable photoinitiators include benzoin, benzoin ether, multinuclear quinones, acridine derivatives, phenazine derivatives, Quinoxaline derivatives, quinazoline derivatives or synergistic mixtures of different ketones.
• a large number of soluble organic polymers can be used as binders, for example polyamides, polyesters, alkyd resins, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, gelatin or cellulose ethers.
• Negative working layers according to DE-OS 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.
• photoconductive layers such as z. B. in DE-PS 11 17 391, 15 22 497, 1572312, 2322046 and 23 22 047 are described, are applied to the carrier materials, whereby highly light-sensitive, electrophotographic layers are formed.
• the materials for printing plate supports roughened by the method according to the invention have a uniform topography, which has a positive influence on the support stability and the water flow during printing of printing forms made from these supports.
• a uniform topography which has a positive influence on the support stability and the water flow during printing of printing forms made from these supports.
• scars prominent indentations compared to the roughening of the surroundings
• These surface properties can be achieved without great expenditure on equipment and without continuous qualitative and quantitative bath monitoring.
• the surface of aluminum roughened by the method according to the invention is also significantly lighter than that of aluminum roughened at higher frequencies, so that a clearer contrast is possible during exposure and after development.
• the positive influence on the topography may be due to an improved mass transfer at the phase boundary between aluminum and the electrolyte.
• 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 from any alkali residues that may be present by briefly immersing it in a solution corresponding to the roughening electrolyte.
• the roughening takes place either under galvanostatic or potentiostatic control in the specified electrolytes, the latter being saturated with the Ag / AgCI system as the reference electrode.
• Examples 1 to 33 and V1 to V33 are galvanostatically (Table I) and Examples 34 to 37 and V34 to V37 (Table 11) controlled potentiostatically.

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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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• 1982
  • 1982-05-10 DE DE19823217552 patent/DE3217552A1/de not_active Withdrawn
• 1983
  • 1983-04-28 EP EP83104144A patent/EP0093960B1/de not_active Expired
  • 1983-04-28 DE DE8383104144T patent/DE3372502D1/de not_active Expired
  • 1983-05-02 US US06/490,568 patent/US4482434A/en not_active Expired - Lifetime
  • 1983-05-03 ZA ZA833132A patent/ZA833132B/xx unknown
  • 1983-05-03 CA CA000427270A patent/CA1225065A/en not_active Expired
  • 1983-05-06 AU AU14299/83A patent/AU550991B2/en not_active Ceased
  • 1983-05-09 JP JP58079471A patent/JPS58207400A/ja active Granted
  • 1983-05-09 BR BR8302412A patent/BR8302412A/pt not_active IP Right Cessation

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