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
  • 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

Definitions

• the invention relates to a one-step anodic oxidation process for aluminum, which is used as a carrier material for offset printing plates.
• 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 S0 4 , H 3 P0 4 , H 2 C 2 0 4 , H3BO 3 , amidosulfonic acid, sulfosuccinic acid, sulfosalicylic acid or a mixture thereof.
• the oxide layers built up in these electrolytes or electrolyte mixtures differ in structure, layer thickness and resistance to 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 using such anodized substrate 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 modern developer solutions for irradiated, negative- or in particular positive-working, radiation-sensitive layers.
• the aluminum oxide layer produced in this way should have a weight of 10 to 200 mg / m 2 .
• the aluminum can also be mechanically or chemically roughened or etched beforehand.
• a water-soluble or water-dispersible coating substance contains 5 to 45% of silicates, 1 to 2.5% of permanganates or from 1% to saturation of borates, phosphates, chromates, molybdate or vanadates.
• a support material for printing plates which carries an oxide layer, the anodic oxidation of aluminum in an aqueous solution of H 3 P0 3 or a mixture H 2 S0 4 / H 3 P0 3 is generated; then this relatively porous oxide layer is overlaid with a second oxide film of the "barrier layer" type, which can be formed, for example, in aqueous solutions containing boric acid, tartaric acid or borates by anodic oxidation.
• Both the first stage (example 3, 5 min) as well as the second stage (example 3, 2 min) are carried out very slowly, furthermore the second at a relatively high temperature (80 °).
• An oxide layer produced in H 3 P0 4 is often more resistant to alkaline media than an oxide layer produced in an electrolyte based on H 2 S0 4 solution; it also has some other advantages, such as a lighter surface, better water flow or low adsorption of dyes ("fog" in the non-image areas), but it also has significant disadvantages.
• oxide layer weights of up to about 1.5 g / m 2 can be produced, a layer thickness that naturally offers less protection against mechanical abrasion than a thicker one in an H2S04 -Electrolyte-produced oxide layer.
• EP-A-0 050 216 it is known from EP-A-0 050 216, inter alia, to use a mixed electrolyte composed of an organic acid or a phosphoric acid mono- (dodecyloxy-polyoxyethylene) ester or a mixture with sulfuric acid and phosphoric acid or phosphoric acid. Even with these mixed electrolytes, however, only oxide layer weights below 0.5 g / m 2 are achieved.
• the object of the present invention is therefore to propose a method for the anodic oxidation of carrier materials for offset printing plates on the basis of roughened and anodically oxidized aluminum, which can be carried out relatively quickly in a modern belt system and without great outlay in terms of apparatus and process technology and which supplies carrier materials, which have an increased oxide layer weight and which are characterized by an increased resistance to alkaline media and by very good mechanical stability.
• the invention is based on a process for the production of plate, film or ribbon-shaped carrier materials for offset printing plates made of roughened aluminum or one of its alloys by a single-stage anodic oxidation in an aqueous electrolyte which contains inorganic compounds with phosphorus oxo anions.
• the process according to the invention is then characterized in that the aluminum is first roughened electrochemically or mechanically and electrochemically and then in an aqueous electrolyte composed of inorganic metaphosphoric acid, pyrophosphoric acid or polyphosphoric acids or an alkali metal, alkaline earth metal or ammonium salt of the acids mentioned, for a period of 1 up to 90 sec, anodized at a voltage between 20 and 100 V and at a temperature of 10 to 80 ° C up to an oxide layer thickness of at least 0.5 g / m 2 .
• stage a) is carried out for a period of 5 to 70 seconds, at a voltage between 20 and 80 V and at a temperature of 15 to 70 ° C., in particular from 10 to 60 seconds, at 30 up to 60 V and at 25 to 60 ° C.
• the corresponding ammonium and in particular potassium salts can be used in the same way.
• a preferred embodiment of the anodizing process according to the invention uses a solution of trisodium phosphate (Na 3 PO 4 ) or tripotassium phosphate (K 3 PO 4 ) in deionized water as the electrolyte.
• the oxide layer weight to be achieved by the method according to the invention increases with increasing electrolyte concentration and increasing voltage. While at electrolyte concentrations below 60 g / I, at voltages of up to 60 V and exposure times of up to 90 sec, oxide layer weights of up to about 1 g / m 2 can be achieved, surprisingly, at higher electrolyte concentrations oxide layer weights of even over 3 g / m 2 can be built.
• the highest oxide layer growth when using the aforementioned phosphoroxo anions is generally achieved with K 3 P0 4 or Na 3 P0 4 .
• the oxide layer thicknesses to be achieved in this electrolyte can surprisingly be in the range of an oxide produced in an electrolyte containing H 2 SO 4 .
• the aforementioned influence of the concentration of the electrolyte on the oxide layer weight to be achieved cannot be determined when using H 3 PO 4 in concentrations above 100 g / l, in contrast to the electrolytes used according to the invention.
• the current-time curves of the anodization in the various electrolytes used according to the invention show that a constant current flow is only maintained over time when Na 3 PO 4 or K 3 PO 4 is used. This means that when Na 3 P0 4 or K 3 PO 4 is used in the aqueous electrolyte for anodizing, the oxide layer growth depends on the anodizing time. However, in the case of long anodizing times, a redissolution of the oxide in the anodizing electrolyte must also be accepted.
• the alkali resistance (measured in the zincate test) of the oxide does not depend significantly on the concentration of the electrolyte from concentrations of more than 60 g / l. After reaching the maximum zincate test time at a concentration between 60 and 100 g / l of z. B. Na 3 P0 4 causes the further increase in the concentration of the electrolyte no increase in the zincate test time. At high voltage, there is a slight decrease. The anodizing time at a given concentration and voltage is also only of subordinate influence on the alkali resistance of the oxide.
• the main influence on the alkali resistance is exerted by the applied anodizing voltage.
• the increase in zincate test times coincides with an increase in voltage.
• 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 HCI, 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 depth R z of the roughened surface is in the range from about 1 to 15 ⁇ 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.
• 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 followed by one or more post-treatment stages, although this is often not necessary, particularly in the present process.
• 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 supports for offset printing plates, i. H. 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.
• 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, applied to the carrier materials produced according to the invention, whereby highly light-sensitive, electrophotographic printing plates are formed.
• coated offset printing plates obtained from the carrier materials produced by the process according to the invention are converted into the desired printing form in a known manner by imagewise exposure or irradiation and washing out of the non-image areas with a developer, for example an aqueous alkaline developer solution.
• a developer for example an aqueous alkaline developer solution.
• the sample of a defined size protected on the back by a layer of lacquer is moved in a bath which contains an aqueous solution of 6 g / l of NaOH.
• the weight loss experienced in this bath is determined gravimetrically. Times of 1, 2, 4 or 8 minutes are selected as the treatment time in the alkaline bath.
• 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 is carried out using alternating current in an electrolyte containing HN0 3 , a surface roughness having an R z value of about 6 ⁇ m being obtained.
• the subsequent anodic oxidation is carried out in accordance with the process described in EP-B-0 004 569 in an aqueous electrolyte containing H 2 S0 4 and A1 2 (S0 4 ) 3 , resulting in a layer weight of 2.8 g / m 2 leads.
• An aluminum strip roughened according to comparative example V1 is anodically oxidized in an aqueous electrolyte containing 100 g / l of H 3 PO 4 at a voltage of 40 V for 40 seconds.
• An oxide layer weight of 0.9 g / m 2 is obtained.
• An aluminum substrate produced in accordance with Example 8 is provided with the following negative-working photosensitive layer: developed.
• 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 170,000.
• a carrier material produced in accordance with Comparative Example VI and coated with the same formulation can only be developed under difficult conditions. After development, a yellow haze may remain in the non-image areas, which may be caused by adhering particles of the diazonium compound. If a carrier material according to Comparative Example V2 is used, then after printing about 90,000 prints, a clear gloss is found in the non-image areas, which increases with increasing circulation. After 120,000 prints, the print quality has dropped to a level that is no longer acceptable in practice.
• An aluminum substrate produced as described in Example 11 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 original and with a developer of the following Composition developed:
• 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 VI 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 14 is provided with the following negative-working photosensitive layer:
• the dry layer weight is 0.75 g / m 2 .
• the copy 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 made using a plush pad with a developer solution of the composition treated, the non-image areas are removed.
• the print run of the plate in a printing press is 170,000.
• the copying layer's adhesion is clearly reduced.
• Example 26 anodized support 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.
• Example 12 An aluminum strip prepared as described in Example 12 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 support material additionally hydrophilized in this way is further processed as described in Example 3, it being possible to improve the ink-repelling effect of the non-image areas.
• An even more favorable hydrophilization is achieved with the complex-type reaction products described in DE-A-31 26 636 from a) polymers such as polyvinylphosphonic acid and b) a salt of an at least divalent metal cation.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Printing Plates And Materials Therefor (AREA)
• Electrochemical Coating By Surface Reaction (AREA)

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• 1983
  • 1983-08-03 DE DE19833328049 patent/DE3328049A1/de not_active Withdrawn
• 1984
  • 1984-07-25 EP EP84108775A patent/EP0141056B1/de not_active Expired
  • 1984-07-25 DE DE8484108775T patent/DE3467191D1/de not_active Expired
  • 1984-07-26 US US06/634,588 patent/US4604341A/en not_active Expired - Fee Related
  • 1984-07-26 CA CA000459732A patent/CA1237693A/en not_active Expired
  • 1984-07-31 ZA ZA845905A patent/ZA845905B/xx unknown
  • 1984-08-02 BR BR8403870A patent/BR8403870A/pt not_active IP Right Cessation
  • 1984-08-02 AU AU31429/84A patent/AU565774B2/en not_active Ceased
  • 1984-08-03 JP JP59163018A patent/JPS6052596A/ja active Granted

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