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
  • C25D11/12—Anodising more than once, e.g. in different baths
• • 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 two-stage anodic oxidation process for aluminum for the production of 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 of a template is generated photomechanically.
• the 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.
• These anodic oxidation processes are usually carried out in aqueous electrolytes containing H 2 S0 4 .
• aqueous electrolytes or electrolyte mixtures differ in structure, layer thickness and resistance to chemicals. Such roughened and anodized materials also play a certain role in other technical fields, for example in electrolytic capacitors or in construction.
• aqueous H 2 S0 4 and / or H 3 P0 4 solutions are used.
• Aluminum oxide layers produced in this way are amorphous and usually have a layer weight of approximately 0.5 to 10 g / m 2 in offset printing plates, corresponding to a layer thickness of approximately 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.
• Electrolytes The anodic oxidation of aluminum in aqueous containing phosphoric acid Electrolytes are also known:
• An oxide layer produced in phosphoric acid 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 H 2 S0 4 electrolyte produced oxide layer. Due to the larger pore volume and diameter of an oxide layer built up in H 3 P0 4 , the mechanical stability of the oxide itself is also lower, which results in a further loss in terms of abrasion resistance.
• the actual oxide layer should have a weight per unit area of 1 to 6 g / m 2 , this weight decreasing significantly when immersed in the aqueous HgPO 4 solution, for example by about 2 to 3 g per minute immersion time in an aqueous H 3 PO 4 solution / m 2.
• An electrochemical treatment in the H 3 PO 4 solution should also be possible (Example 11) or the use of a mixed electrolyte composed of H 3 PO 4 / H 2 SO 4 (Example 12), an oxide layer also in these cases - Removal is done.
• US Pat. No. 3,940,321 also describes a two-stage anodic oxidation in an electrolyte based on H 2 SO 4 and then in an electrolyte based on H 3 P0 4 , a direct current with a voltage of 10 to 10 in both stages 15 V (1 to 15 A / dm 2 current density) is used. In the first stage, an aqueous electrolyte containing 5 to 50% and in the second stage 20 to 60% acid are used.
• support materials for printing plates made of aluminum are anodized so that they act as central conductors first through a bath with an aqueous 45% H 3 P0 4 solution and an anode and then into a bath run aqueous 15% H 2 S0 4 solution and a cathode.
• the two electrodes can also be connected to an AC voltage source (each about 16 to 21 V, 2 A / dm 2 ).
• the first bath is essentially used for contacting.
• the respective half-wave which results in the aluminum being switched as an anode, can also cause anodic oxidation in the first bath.
• a two-stage anodic oxidation process for printing plate support materials made of aluminum in which in the first stage an aqueous electrolyte containing 250 to 400 g of H 4 PO 4 per 1 for 15 to 240 seconds a voltage of 15 to 35 V and at a temperature of 15 to 46 ° C and in the second stage an aqueous electrolyte containing 20 to 150 g H 2 S0 4 and 250 to 380 g H 3 P0 4 per 1 under the previously specified conditions are used.
• the voltage in the second stage should be greater than or equal to the voltage in the first stage, the voltage used in the examples always goes back to a direct current source.
• the two-stage anodic oxidation or treatment method leads to the oxide layer built up in the H 2 S0 4 electrolyte being redissolved to an excessive extent in the H 3 P0 4 solution under the conditions known hitherto; this also applies to the known methods in which this step sequence is reversed, in particular when using alternating current and from the very high concentrations of H 3 P0 4 in the electrolyte.
• the bath monitoring problems also occur again.
• the method variant with a circuit for both stages can be disadvantageous since it is more difficult to control in terms of production technology.
• a two-stage anodization process using phosphoric acid in the first stage and sulfuric acid in the second stage is described, inter alia, using examples in GB-A 1 401 067.
• These strong, porous oxide layers are intended to accommodate coloring components in order to give the finished product, which is preferably used in the construction sector, a color effect.
• the object of the present invention is to propose a method for the anodic oxidation of carrier materials for offset printing plates of roughened flat aluminum, which can be carried out relatively quickly and without great effort in a modern belt system, in which the proportion of the oxide redissolution is low or a redissolution is not occurs, the oxide layers not having too high a layer thickness for a printing plate support in order to avoid dye adsorption and fog formation. Furthermore, the finished printing plate should have long print runs and good water flow.
• the invention relates to a process for the production of plate, film or tape-shaped printing plate support material made of chemically, mechanically and / or electrochemically roughened aluminum or one of its alloys by a two-stage anodic oxidation in a) an aqueous electrolyte containing phosphoric acid and subsequently in b) an aqueous electrolyte containing sulfuric acid.
• the process can be carried out batchwise or in particular continuously.
• the respective aqueous electrolytes should preferably not contain any other types of acids, since the composition of the baths and thus the product-true manufacture in modern high-speed systems would otherwise be difficult to set and control; Usually, however, both electrolytes still contain Al 3 + ions, which are used in salt form (as sulfate or phosphate) from the outset and / or are formed during the process.
• the components different from the respective acid - in addition to the water present as the basic solvent - should not exceed a maximum of 30 g / l in stage a) and a maximum of 50 g / l in stage b).
• 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 pre-cleaning, mechanical (e.g. by brushing and / or with abrasive treatments), chemical (e.g. by etching agents) and / or electrochemical (e.g. by AC treatment in aqueous HCl) -, HN0 3 - or in salt solutions) roughened.
• materials with electrochemical or a combination of mechanical and electrochemical roughening are used in the method according to the invention.
• the process parameters are in the roughening stage 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 / 1 (also in the case of salts 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 of about 1 to 15 I lm.
• 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.
• a first anodic oxidation [step a)] of the aluminum then follows in the further process steps. This is carried out in an electrolyte containing H 3 P0 4 , as described at the beginning when the prior art was assessed and as is also specified above in terms of parameters.
• a rinse stage can be switched on before stage b).
• Stage b) is carried out in an electrolyte containing H 2 S0 4 , as described at the outset in the assessment of the prior art and is defined in terms of parameters above.
• Direct current is preferably used for anodic oxidation in these stages, however alternating current or a combination of these types of current (e.g. direct current with superimposed alternating current) can also be used.
• the process time in both stages is preferably about 10 to 100 seconds.
• the layer weights of aluminum oxide range from 0.5 to 10 g / m 2 , corresponding to a layer thickness of about 0.15 to 3.0 ⁇ m; the aluminum oxide layers also contain Al 2 (S0 4 ) 3 and AIP0 4 .
• the steps of anodic oxidation of the aluminum support material can also be followed by one or more post-treatment steps.
• 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.
• the materials produced according to the invention are used in particular 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 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, preferably an aqueous developer solution.
• the materials produced according to the invention are distinguished by the fact that their alkali resistance is at least equivalent in quality to an oxide layer built up only in an H 3 P0 4 -containing electrolyte and is even quantitatively superior because of the greater layer thickness.
• the surface of the carrier material is lighter than when anodizing alone in H 2 SO 4 -containing electrolytes, which leads to an improved contrast between image and non-image areas of the printing form.
• the fog formation and adsorption of dyes that can often be observed after the anodization in electrolytes containing only H 2 SO 4 does not occur in the carrier surfaces produced according to the invention.
• the method according to the invention has the advantage that anodic oxidation can be carried out without problems even at high speeds of, for example, 40 to 50 m / min and more, without any appreciable negative influence on the oxide layer quality occurring.
• parts by weight relate to parts by volume, such as kg to dm 3
• percentages relate to the weight, unless stated otherwise.
• the layer weight is about 2 g / m 2 .
• To produce the printing form exposure is carried out in a known manner and developed with an aqueous alkaline solution. From such a printing form, around 200,000 prints of good quality can be produced with very good water flow.
• Example 1 In principle, the procedure of Example 1 is followed, but electrochemically in an aqueous solution of 0.7 parts by weight of HCl and 1.2 parts by weight of AlCl 3 .6H 2 O per 100 parts by volume of solution roughened.
• the anodic oxidation takes place in a 12% aqueous H 3 PO 4 solution and with a voltage of 50 V or in an aqueous H 2 SO 4 solution containing 15 parts by weight of H 2 SO 4 .
• the printing form produced from the photosensitive coated plate has an even lower water requirement during printing, and its print run is only slightly less than that achieved according to Example 1.
• Example 1 In principle, the procedure described in Example 1 is followed, but also roughened in several stages (see DE-A 33 05 067, filed on February 14, 1983).
• the first roughening stage by wire brushing is followed by an abrasive intermediate treatment in an aqueous NaOH solution and then an electrochemical roughening stage in an aqueous solution with a content of 1.5% of HNO 3 and 5% of Al (N0 3 ) 3 .
• the anodic oxidation is carried out in an 8% aqueous H 3 PO 4 solution at 60 ° C. or in an aqueous H 2 SO 4 solution containing 25 parts by weight of H 2 SO 4 at 40 °.
• the photosensitive coated plate shows a significantly lower tendency to under radiation than in Example 1 and, as a printing form, has the properties specified in Example 1.
• Example 2 In principle, the procedure of Example 2 is followed, but in an aqueous solution containing 10% of H 3 PO 4 at 55 ° C. for 40 seconds and with a voltage of 60 V in the first stage and in an aqueous solution a content of 15% of H 2 S0 4 at 45 ° C, anodized for 40 sec and with a voltage of 30 V in the second stage.
• the plate which is light-sensitive coated according to Example 1 has practically no dye adsorption and the abrasion of the oxide layer is 0.76 g / m 2 .
• the roughening step is carried out according to the information in Example 1, but the two-step anodic oxidation is carried out in accordance with the teaching of GB-A 2 088 901 cited and discussed at the beginning; namely in the first stage in an aqueous solution containing 30% of H 3 P0 4 at 55 ° C. for 240 seconds and with a voltage of 20 V, and in the second stage in an aqueous solution containing 27% at H 3 P0 4 and 15% at H 2 SO 4 at 45 ° C, for 240 sec and with a voltage of 35 V.
• the after Example 1 light-sensitive coated plate has - depending on the measurement method - about 3 to 22 times the color adsorption (compared to the values of Example 4) and the abrasion of the oxide layer is 1.18 g / m 2 .
• the roughening stage is carried out according to the instructions in Example 1, but the two-stage anodic oxidation is carried out according to the teaching of EP-B 0 007 234 cited and discussed at the beginning; namely in the first stage in an aqueous solution of 45% H 3 P0 4 and in the second of 15% H 2 S0 4 , with an alternating current having a current density of 2 A / dm 2 for 240 sec each is coming.
• the plate which is light-sensitive coated according to Example 1 has - depending on the measurement method - about 7 to 29 times the color adsorption (compared to the values of Example 4) and the abrasion of the oxide layer is 2.20 g / m 2 .

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Engineering & Computer Science (AREA)
• Printing Plates And Materials Therefor (AREA)
• Electrochemical Coating By Surface Reaction (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Cookers (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Bending Of Plates, Rods, And Pipes (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)
• Laminated Bodies (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6195673

Family Applications (1)

Country Status (11)

Cited By (2)

Families Citing this family (39)

Family Cites Families (11)

• 1983
  • 1983-04-07 DE DE19833312497 patent/DE3312497A1/de not_active Withdrawn
• 1984
  • 1984-03-27 ES ES531015A patent/ES531015A0/es active Granted
  • 1984-03-27 CA CA000450525A patent/CA1228049A/en not_active Expired
  • 1984-03-29 ZA ZA842333A patent/ZA842333B/xx unknown
  • 1984-03-30 EP EP84103540A patent/EP0121880B1/de not_active Expired
  • 1984-03-30 US US06/595,538 patent/US4566952A/en not_active Expired - Fee Related
  • 1984-03-30 AT AT84103540T patent/ATE30254T1/de not_active IP Right Cessation
  • 1984-03-30 DE DE8484103540T patent/DE3466784D1/de not_active Expired
  • 1984-04-03 AU AU26387/84A patent/AU559228B2/en not_active Ceased
  • 1984-04-05 JP JP59066835A patent/JPS59193298A/ja active Granted
  • 1984-04-05 FI FI841360A patent/FI76840C/fi not_active IP Right Cessation
  • 1984-04-06 BR BR8401621A patent/BR8401621A/pt not_active IP Right Cessation

Also Published As

Similar Documents

Legal Events