Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
• • 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
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
  • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
• • 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
  • Y10S205/00—Electrolysis: processes, compositions used therein, and methods of preparing the compositions
  • Y10S205/921—Electrolytic coating of printing member, other than selected area coating
• • 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
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/9335—Product by special process
  • Y10S428/934—Electrical process
• • 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
  • Y10T428/25—Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
  • Y10T428/256—Heavy metal or aluminum or compound thereof
  • Y10T428/257—Iron oxide or aluminum oxide
• • 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
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/269—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension including synthetic resin or polymer layer or component

Definitions

• the invention relates to an anodic oxidation process for aluminum, which is used in particular as a carrier material for offset printing plates, using an aqueous electrolyte based on phosphoric acid.
• Carrier materials for offset printing plates are provided either by the consumer directly or by the manufacturer of precoated printing plates on one or both sides with a radiation (light) sensitive layer (reproduction layer), with the help of which a printing image is generated photomechanically.
• the layer support carries the image areas which will guide the color during later printing and at the same time forms the hydrophilic image background for the lithographic printing process at the areas which are free of image (non-image areas) during later printing.
• Aluminum which is roughened on the surface by known methods by dry brushing, wet brushing, sandblasting, chemical and / or electrochemical treatment, is used particularly frequently as the base material for such layer supports.
• electrochemically roughened substrates in particular are subjected to an anodization step to build up a thin oxide layer.
• electrolytes such as H 2 SO 4 , H 3 PO 4 , H 2 C 2 O 4 , H 3 BO 3 , amidosulfonic acid, sulfosuccinic acid, sulfosalicylic acid or mixtures thereof.
• the oxide layers built up in these electrolytes or electrolyte mixtures differ in structure, layer thickness and resistance to about chemicals.
• aqueous H 2 SO 4 or H 3 PO 4 solution are used.
• Aluminum oxide layers produced in aqueous electrolytes containing H 2 S0 4 are amorphous and usually have a layer weight of about 0.5 to 10 g / m 2 in offset printing plates, corresponding to a layer thickness of about 0.15 to 3.0 ⁇ m.
• a disadvantage of the use of such anodically oxidized carrier material, in particular for offset printing plates is the relatively low resistance of the oxide layers produced in H 2 S0 4 electrolytes to alkaline solutions, such as are increasingly being used, for example, in the processing of presensitized offset printing plates, preferably in a contemporary manner Developer solutions for irradiated negative- or especially positive-working radiation-sensitive layers.
• these aluminum oxide layers often tend to more or less irreversible adsorption of substances from the applied reproduction layers, which can lead, for example, to a coloration of the oxide layers (“fogging”).
• oxide layers produced in H 3 P0 4 are often more resistant to alkaline media than oxide layers produced in an electrolyte based on H 2 S0 4 solution; they also have some other advantages, such as a lighter surface, better water flow or low adsorption of dyes ("fog" in the non-image areas), but they also have significant disadvantages.
• oxide layer weights In a modern belt plant for the production of printing plate supports, with practical tensions and dwell times, for example, only oxide layer weights of up to approximately 1.0 g / m 2 , and a maximum of approximately 1.5 g / m 2 can be produced. a layer thickness that naturally offers less protection against mechanical abrasion than a thicker oxide layer produced in an H 2 S0 4 electrolyte.
• the object of the present invention is therefore to propose a method for the anodic oxidation of roughened, flat aluminum, particularly suitable as a carrier material for offset printing plates, which can be carried out relatively quickly in a modern belt system and without great expenditure on apparatus and process technology and which supplies carrier materials, which are characterized by increased resistance to alkaline media and very good mechanical stability.
• the invention is based on a process for the anodic oxidation of plate, foil or tape-shaped materials made of mechanically, chemically and / or electrochemically roughened aluminum or one of its alloys in an aqueous electrolyte containing H 3 P0 4 and A1 3 + - Ions.
• the process according to the invention is then characterized in that the materials in a H 2 S0 4 -free aqueous electrolyte containing 25 to 500 g / 1 of H 3 P0 4 and at least 5 g / 1 of A1 3 + ions during a Period of 5 to 500 seconds, at an current density of 1 to 30 A / dm 2 and at a temperature of 35 to 95 ° C anodized.
• these values are: 50 to 15 U g / 1 of H 3 PO 4 , 10 to 20 g / l of Al 3+ ions, 10 to 300 sec, 2 to 20 A / dm 2 and 40 to 75 ° C.
• the concentration of the aqueous electrolyte is adjusted so that for 1 part by weight of A1 3 + ions there are 5 to 15 parts by weight of H 3 P0 4 .
• the aqueous electrolyte contains as Al3 + - ion source is preferably a salt of aluminum with a phosphoroxo anion, in particular an aluminum salt of orthophosphoric acid (H 3 P0 4).
• the upper limit of the concentration of A1 3 + ions is determined by the respective saturation of the aqueous electrolyte with aluminum salt.
• the concentration ranges of the electrolyte components are checked at regular intervals, since they are of crucial importance for an optimal process, and the electrolyte is then regenerated discontinuously or continuously.
• the process according to the invention itself can be carried out batchwise or in particular continuously. Good electrolyte circulation is preferred in the practice of the invention. This can be generated by stirring or pumping around the electrolyte.
• the electrolyte In the case of continuous operation, care must be taken that the electrolyte is guided as parallel as possible to the strip to be treated under turbulent flow at high speed while ensuring good material and heat exchange.
• the flow rate of the electrolyte relative to the strip is then expediently more than 0.3 m / sec.
• Direct current is used in particular as the type of current, but alternating current or a combination of these types of current (e.g. direct current with superimposed alternating current) can also be used selstrom) can be used.
• the voltages are generally between 20 and 100 V.
• oxide layer weight to be achieved by the process according to the invention increases with increasing aluminum salt concentration and with increasing voltage. While at concentrations of less than 5 g / l of Al 3+ ions, at voltages of up to 30 V and exposure times of up to 150 sec, oxide layer weights of up to about 0.8 g / m 2 can be achieved, at higher ones A13 + - ion concentrations surprisingly build up oxide layer weights of even over 3 g / m 2 , this can also be achieved if temperatures above 40 ° C are used.
• the highest oxide layer growth when using the aforementioned phosphoroxo anions is generally achieved with AlPO 4 ;
• the oxide layer weights and thicknesses to be achieved can then surprisingly be in the range of an oxide produced in an electrolyte containing H 2 SO 4 .
• the oxide layer's weight also increases the resistance of the oxide layer to mechanical abrasion.
• the correction contrast (due to corrections, the appearance of bright areas on a tinted background) and the "fog" are largely independent of the A1 3 + ion concentration. As the anodizing time increases with the same oxide layer weight, the mechanical abrasion values generally become more favorable.
• the oxide layers achieved in this way combine all the advantages known per se from supports anodized in phosphoric acid, such as, for. B. a light color, very good alkali resistance and low tendency to fog with the front part of a support anodized in sulfuric acid, which consists in its high oxide layer weight and the associated favorable values of mechanical abrasion.
• Suitable base materials for the material to be oxidized according to the invention include those made of aluminum or one of its alloys, which have, for example, a content of more than 98.5% by weight of Al and proportions of Si, Fe, Ti, Cu and Zn.
• These aluminum carrier materials are still, optionally after a preliminary cleaning, mechanically (e.g. by brushing and / or with abrasive treatments) and electrochemically (e.g. by AC treatment in aqueous HC1, HN0 3 - or in salt solutions) or only electrochemically roughened. All process steps can be carried out batchwise, but they are preferably carried out continuously.
• the process parameters are in the following ranges: the temperature of the electrolyte between 20 and 60 ° C., the active substance (acid, salt) concentration between 2 and 100 g / l (in the case of salts also higher), the current density between 15 and 250 A / dm 2 , the residence time between 3 and 100 sec and the electrolyte flow rate on the surface of the workpiece to be treated between 5 and 100 cm / sec;
• AC is usually used as the type of current, but modified types of current such as AC with different amplitudes of the current strength are also possible for the anode and cathode currents.
• the average roughness R z of the roughened surface is in the range from about 1 to 15 pm.
• the roughness depth is determined in accordance with DIN 4768 in the version from October 1970, the roughness depth R is then the arithmetic mean of the individual roughness depths of five adjacent individual measuring sections.
• 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.
• the roughening or, in the case of several roughening stages, also between the individual stages, an abrasive treatment can additionally be carried out, in particular a maximum of 2 g / m 2 being removed (up to 5 g / m 2 between the stages);
• aqueous solutions of alkali metal hydroxide or aqueous solutions of alkaline salts or aqueous acid solutions based on HN0 3 , H 2 SO 4 or H 3 PO 4 are used as abrasive solutions.
• the stage of anodic oxidation of the aluminum support material can also be one or more aftertreatments levels, which is often not necessary, especially in the present method.
• 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 preferably used as supports for offset printing plates, i.e. a radiation-sensitive coating is applied to one or both sides of the carrier material either by the manufacturer of presensitized printing plates or directly by the consumer.
• a radiation-sensitive coating is applied to one or both sides of the carrier material either by the manufacturer of presensitized printing plates or directly by the consumer.
• all layers are suitable as radiation (light) sensitive layers which, after irradiation (exposure), optionally with subsequent development and / or fixation, provide an imagewise surface from which printing can take place.
• 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.
• coated offset printing plates obtained from the carrier materials produced by the process according to the invention are imaged in a known manner moderate exposure or irradiation and washing out of the non-image areas with a developer, for example an aqueous alkaline developer solution, converted into the desired printing form.
• a developer for example an aqueous alkaline developer solution
• the aluminum oxide layer is formed by a solution of 37 ml H 3 P0 4 (density of 1.71 g / ml at 20 ° C corresponding to 85% H 3 PO 4 ), 20 g CrO 3 and 963 ml H 2 O dest. detached from base metal at 90 to 95 ° C for 5 min and the resulting weight loss determined by weighing the sample before and after detachment.
• the weight per unit area of the layer is calculated from the weight loss and the weight of the surface covered with the layer and is given in g / m 2 .
• a friction wheel is guided over the surface of an uncoated plate piece and the mass loss of the surface per unit area is determined (based on a standard treatment time).
• a bright rolled aluminum sheet with a thickness of 0.3 mm is degreased with an aqueous alkaline pickling solution at a temperature of 50 to 70 ° C.
• the electrochemical roughening of the aluminum surface takes place with alternating current in an electrolyte containing HCl.
• the subsequent anodic oxidation is carried out in an aqueous electrolyte containing 150 g / l of H 3 PO 4 .
• Table 1 contains the process parameters and the results of the measurements of the surface properties.
• the anodic oxidation is carried out with direct current at a voltage of approximately 35 to 45 V.
• the parameters of the surface properties, in particular the weight per unit area, are of the order of magnitude that those of the electrolyte without the addition of Al 3+ -Ions match.
• An aluminum substrate produced as described in Example 9 is provided with the following negative-working photosensitive layer:
• the printing plate produced in this way can be developed quickly and free of fog.
• the print run with a printing form produced in this way is 150,000.
• a carrier material produced in accordance with Comparative Example V9 and coated with the same formulation can only be developed under difficult conditions.
• a yellow haze may remain in the non-image areas after development, possibly caused by adhering particles of the diazonium compound.
• a carrier material according to comparative example V3 is used, a clear gloss is found in the non-image areas after printing after about 90,000 prints, which increases with increasing circulation. After 100,000 prints, the print quality has dropped to a level that is no longer accepted in practice.
• An aluminum substrate produced as described in Example 8 is coated with the following positive-working photosensitive solution:
• the coated tape is dried in the drying tunnel at temperatures up to 120 ° C.
• the printing plate thus produced is exposed under a positive template and developed with a developer of the following composition:
• the printing form obtained is perfect in terms of copying and printing technology and has a very good contrast after exposure, the print run is 150,000.
• a corresponding plate made from the carrier material of comparative example V10 shows a blue haze in the non-image areas. With prolonged exposure to the developer, there is a clear light-dark shade in the non-image areas, which indicates an attack by the developer solution of the oxide.
• An aluminum substrate manufactured according to the information in Example 9 is provided with the following negative-working photosensitive layer:
• the dry layer weight is 0.75 g / m 2 .
• the reproduction layer is exposed under a negative original for 35 seconds using a metal halide lamp with a power of 5 kW.
• the exposed layer is covered with a plush pad with a developer solution of the composition
• the print run of the plate in a printing press is 170,000.
• the copying layer adheres significantly less.
• a support anodically oxidized according to Example 7 is coated with the following solution to produce an electrophotographic offset printing 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 developed with an electrophotographic suspension developer which also contains a dispersion of 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 represents a boiling range of 185 to 210 ° C.
• the developer is fixed and the plate is poured out into a solution for 60 seconds submerged.
• the plate is then rinsed off with a powerful water jet, the areas of the photoconductor layer which are not covered with toner being removed, and the plate is then ready for printing.
• the non-image areas of the plate show good hydrophilicity and show no signs of attack even after exposure to alkaline solutions. Several thousand good prints can be achieved with the printing form.
• An aluminum sheet prepared according to the information in Example 2 is immersed in a further treatment step (additional hydrophilization) in a 0.2% aqueous solution of polyvinylphosphonic acid at 50 ° C. for 20 seconds. After drying, the substrate material additionally hydrophilized in this way is further processed as described in Example 10, it being possible to further improve the ink-repelling effect of the non-image areas.

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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)
• Inorganic Chemistry (AREA)
• Printing Plates And Materials Therefor (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)

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• 1984
  • 1984-04-13 DE DE19843413899 patent/DE3413899A1/de not_active Withdrawn
• 1985
  • 1985-04-03 DE DE8585104072T patent/DE3574743D1/de not_active Expired - Fee Related
  • 1985-04-03 EP EP85104072A patent/EP0161461B1/fr not_active Expired
  • 1985-04-09 CA CA000478562A patent/CA1236421A/fr not_active Expired
  • 1985-04-10 US US06/721,753 patent/US4608131A/en not_active Expired - Lifetime
  • 1985-04-11 ES ES542162A patent/ES8606539A1/es not_active Expired
  • 1985-04-12 ZA ZA852736A patent/ZA852736B/xx unknown
  • 1985-04-12 JP JP60076860A patent/JPS60236795A/ja active Granted
  • 1985-04-19 CN CN198585102958A patent/CN85102958A/zh active Pending

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