EP0268058A2 - Process for the electrochemical graining of aluminum or its alloys for supports for printing plates - Google Patents

Abstract

The invention relates to a method of multiple roughening of aluminum or its alloys for printing plate supports, a mechanical roughening being followed by a direct current roughening in an electrolyte containing nitrate. If necessary, anodization can be added after roughening.

Description

The invention relates to a method for the electrochemical roughening of aluminum for printing plate supports, which is carried out with direct current in an nitrate-containing electrolyte.

Printing plates (this term means offset printing plates in the context of the present invention) 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. In principle, 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 called grain or etching in the relevant literature), a chemical one or electrochemical oxidation and / or treatment with hydrophilizing agents.

In the modern, continuously operating high-speed systems of the manufacturers of printing plate supports and / or precoated printing plates, 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 HCl or HNO₃ solutions or in aqueous salt solutions such as aqueous NaCl or Al (NO₃) ₃ solutions using alternating current. The roughness depths that can be achieved in this way (given, for example, as the mean roughness depths R _z ) of the roughened surface are in the range from about 1 to 15 μm, in particular in the range from 2 to 8 μm. The roughness depth is determined in accordance with DIN 4768 (as of October 1970). The roughness depth R _z is then the arithmetic mean of the individual roughness depths of five adjacent individual measurement 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. By irradiation and development (or decoating in the case of reproductive layers working electrophotographically), the image points which carry color during later printing and the non-image points which carry water (generally the exposed carrier surface), which creates the actual printing form. Very different parameters have an influence on the later topography of the roughened aluminum surface. For example, the following references provide information:

In the article "The Alternating Current Etching of Aluminum Lithographic Sheet" by AJ Dowell in Transactions of the Institute of Metal Finishing, 1979, Vol. 57, pp. 138 to 144, basic explanations are given on the roughening of aluminum in aqueous hydrochloric acid solutions, the following process parameters varied and the corresponding effects were examined. The electrolyte composition is changed with repeated use of the electrolyte, for example with regard to the H⁺ (H₃O⁺) ion concentration (measurable via the pH) and the Al³⁺ ion concentration, with effects on the surface topography being observed. The temperature variation between 16 ° C and 90 ° C shows a changing influence only from about 50 ° C, which is expressed, for example, by the sharp decline in the formation of layers on the surface. The roughening time change between 2 and 25 min also leads to an increasing metal dissolution with increasing exposure time. The variation of the current density between 2 and 8 A / dm² results in higher roughness values with increasing current density. If the acid concentration is in the range 0.17 to 3.3% of HCl, then only insignificant changes in the hole structure occur between 0.5 and 2% of HCl, below 0.5% of HCl there is only a local attack on the Ober surface and with the high values an irregular dissolution of aluminum instead.

The use of hydrochloric acid or nitric acid as an electrolyte for roughening aluminum substrates can therefore be assumed to be known. A uniform grain size can be obtained which is suitable for lithographic plates and is within a useful roughness range. In pure nitric acid electrolytes, the setting of a flat and uniform surface topography is difficult, and it is necessary to maintain the operating conditions within very narrow limits.

The influence of the composition of the electrolyte on the roughening quality is also described, for example, in the following publications:

- DE-A 22 50 275 (= GB-A 1 400 918) names as electrolytes in the AC roughening of aluminum for printing plate supports aqueous solutions with a content of 1.0 to 1.5% by weight of HNO₃ or 0 , 4 to 0.6% by weight of HCl and optionally 0.4 to 0.6% by weight of H₃PO₄,

- DE-A 28 10 308 (= US-A 4 072 589) names as electrolytes in the AC roughening of aluminum aqueous solutions with a content of 0.2 to 1.0% by weight of HCl and O.8 to 6, O wt .-% of HNO₃.

Additions to the HCl electrolyte have the task of preventing an adverse local attack in the form of deep holes. So describes
DE-A 28 16 307 (= US Pat. No. 4,172,772) the addition of monocarboxy acids, such as acetic acid, to hydrochloric acid electrolytes,
US Pat. No. 3,963,594 to gluconic acid,
- EP-A 0 036 672 of citric and malonic acid and
- US-A 4 052 275 of tartaric acid.

All these organic electrolyte components have the disadvantage that they are electrochemically unstable and decompose at high current loads (voltage).

Inhibiting additives, as described in US Pat. No. 3,887,447 with phosphoric and chromic acid, in DE-A 25 35 142 (= US Pat. No. 3,980,539) with boric acid, have the disadvantage that the protective action frequently breaks down locally and there can be individual, particularly pronounced scars.

JP application 91 334/78 describes AC roughening in a combination of hydrochloric acid and an alkali halide to produce a lithographic base material.

DE-A 16 21 115 (= US-A 3 632 486 and US-A 3 766 043) describes direct current roughening in dilute hydrofluoric acid, the strip being switched as a cathode.

DE-C 120 061 describes a treatment for producing a water-attracting layer by using electricity, which can also take place in hydrofluoric acid.

Another known possibility of improving the uniformity of the electrochemical roughening is to modify the current form used, these include, for example
- The use of alternating current, in which the anode voltage and the anodic coulombic input are greater than the cathode voltage and the cathodic coulombic input, according to DE-A 26 50 762 (= US-A 4087341), the anodic half-period of the alternating current generally is set less than the cathodic half period; this method is also used, for example, in DE-A 29 12 060 (= US-A 4 301 229), DE-A 30 12 135 (= GB-A 2 047 274) or DE-A 30 30 815 (= US-A 4,272,342),
the use of alternating current, in which the anode voltage is significantly increased compared to the cathode voltage, according to DE-A 14 46 026 (= US-A 3 193 485),
- The interruption of the current flow for 10 to 120 sec and a current flow for 30 to 300 sec, with alternating current and an aqueous 0.75 to 2 N HCl solution with NaCl or MgCl₂ addition are used as electrolyte, according to GB-A 879 768. A similar process with an interruption of the current flow in the anode or cathode phase, the DE-A 30 20 420 (= USA-4 294 672).

Although the methods mentioned can lead to relatively uniformly roughened aluminum surfaces, they sometimes require a relatively large amount of equipment and can only be used within very narrow parameter limits.

Another method known from the patent literature is the combination of two roughening methods.

So describe US-A 3 929 591, GB-A 1 582 620, JP-A 1232 04/78, DE-A 30 31 764 (= GB-A 2 058 136), DE-A 30 36 174 (= GB -A 20 60 923), EP-A 0 131 926, DE-A 30 12 135 (= GB-A 20 47 274) and JP-B 16 918/82 in different versions the combination of a pre-structuring which takes place mechanically in the first step , which is followed by an electrochemical roughening with optionally modified alternating current in electrolytes containing hydrochloric acid or nitric acid, after a chemical cleaning (pickling), if appropriate, a further cleaning step then being able to take place.

All of the above-mentioned applications use the advantage of double roughening, which is in particular a power saving, but use alternating current in the second stage.

US Pat. No. 2,344,510 describes the use of a direct current roughening in an electrolyte containing hydrochloric acid, which follows a mechanical roughening as the second roughening.

The object of the present invention is therefore to propose a method for the electrochemical roughening of aluminum for printing plate supports with direct current, which results in a uniform, scar-free and area-covering roughening structure and which can be dispensed with a large outlay on equipment and / or particularly narrow parameter limits, and also Energy is saved. The finished printing plates should have a large print run and low wiping water consumption.

The invention is based on a process for the combined roughening of aluminum, wherein first mechanical roughening and then electrolytic roughening are carried out in an nitrate-containing electrolyte.

Surprisingly, however, the use of direct current in a known electrolyte containing nitrate after mechanical pre-roughening with or without a post-cleaning step results in a surface which is outstandingly suitable for lithographic applications and which, besides the energy saving due to the special shape and arrangement of the micropores, has the advantages a reduction in water consumption and increased circulation stability. These advantages cannot be achieved by using alternating current in systems containing hydrochloric or nitric acid, nor by using direct current in hydrochloric acid as described in US Pat. No. 2,344,510 (see comparative examples V1-V5).

Alternating current in nitric acid electrolytes leads to largely deposit-free surfaces, while the process according to the invention with direct current in the weakly corrosive, nitrate-containing electrolyte during the electrochemical step creates a protective whitish deposit in the pores, which can favorably influence the roughening process. Obviously, the action of more corrosive chloride ions when using DC leads to other carrier structures that are not so suitable for modern lithographic printing plates.

The step that characterizes the invention is that electrolytic roughening is carried out with direct current.

The mechanical roughening is preferably carried out with a moist abrasive (wet brushing), but other mechanical pre-structuring, such as dry brushing, sandblasting, spherical grain, embossing and similar processes, can also be used.

After the roughening steps, the sheet is preferably cleaned by an etching step with metal removal. This etching step (pickling) can be carried out either with acids or alkalis or by means of aggressive agents generated electrochemically in the bath, for example by generating cathodic hydroxyl ions.

In a preferred embodiment, a nitrate electrolyte is used, the concentration of the nitrate compound being between 1.0 g / l and the saturation limit, particularly preferably between 5.0 g / l and 100.0 g / l. Aluminum nitrate and / or nitric acid and / or sodium nitrate is used as the preferred compound containing nitrate ions. Combinations of other compounds containing nitrate ions are of course also within the scope of the invention.

It has proven to be particularly advantageous if aluminum salts are added to the electrolyte, preferably in an amount of 20 to 150 g / l.

As a direct current, a current density of 1 to 300 A / dm², preferably 10 to 100 A / dm², is used for the plate, which is preferably connected as an anode, so that a charge of 1 to 400 C / dm², preferably 10 to 200 C / dm², flows.

The current density used is less critical than the total amount of charge.

The result of a surface produced by the method according to the invention is a very uniform support surface with excellent lithographic properties that can be varied over a wide roughness depth range (R _z = 2 to 7 μm).

The process according to the invention is carried out either discontinuously or preferably continuously with strips made of aluminum or its alloys. In general, the process parameters in continuous processes during electrochemical roughening are in the following ranges: the temperature of the electrolyte between 20 and 80 ° C, the current density between 1 and 300 A / dm², the residence time of a material point to be roughened in the electrolyte between 1 and 300 s, preferably between 2 and 60 s, and the electrolyte flow rate at the surface of the material to be roughened between 5 and 1000 cm / s. In discontinuous processes, the required current densities tend to be in the lower part and the dwell times are in the upper part of the ranges specified, and the flow of the electrolyte can also be dispensed with.

In addition to pure direct current, pulsed, corrugated and differently shaped direct currents can also be used as long as the plate does not change polarity during the entire roughening process.

In the process according to the invention, the following can be used as materials to be roughened, for example, which are either in the form of a plate, film or tape:
- "Pure aluminum" (DIN material no. 3.0255), ie consisting of more than 99.5% Al and the following admissible admixtures of (maximum sum of 0.5%) 0.3% Si, 0.4% Fe, 0.03% Ti, 0.02% Cu, 0.07% Zn and 0.03% others, or
- "Al alloy 3003" (comparable to DIN material no. 3.0515), ie consisting of more than 98.5% Al, the alloy components 0 to 0.3% Mg and 0.8 to 1.5% Mn and the following admissible admixtures of 0.5% Si, 0.5% Fe, 0.2% Ti, 0.2% Zn, 0.1% Cu and 0.15% other.

However, the method according to the invention can also be applied to other aluminum alloys.

According to the electrochemical roughening step which characterizes the invention, after a possible further cleaning step with metal removal, as described previously, an anodic oxidation of the aluminum can 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. For anodic oxidation, the usual electrolytes, such as H₂SO₄, H₃PO₄, H₂C₂O₄, amidosulfonic acid, sulfosuccinic acid, sulfosalicylic acid or mixtures thereof be set. Reference is made, for example, to the following standard methods for the use of aqueous electrolytes containing H₂SO₄ for the anodic oxidation of aluminum (see, for example, BM Schenk, material aluminum and its anodic oxidation, Francke Verlag, Bern 1948, page 760; Praktische Galvanotechnik, Eugen G Leuze Verlag, Saulgau 1970, pages 395 ff. And pages 518/519; W. Hübner and CT Speiser, The Practice of Anodic Oxidation of Aluminum, Aluminum Verlag, Düsseldorf 1977, 3rd edition, pages 137 ff.):

- The direct current sulfuric acid process in which in an aqueous electrolyte from usually about 230 g of H₂SO₄ per 1 liter of solution at 10 to 22 ° C and a current density of 0.5 to 2.5 A / dm² for 10 to 60 min is anodized. The sulfuric acid concentration in the aqueous electrolyte solution can also be reduced to 8 to 10% by weight of H₂SO₄ (approx. 100 g / l H₂SO₄) or increased to 30% by weight (365 g / l H₂SO₄) and more.
- The "hard anodization" with an aqueous H₂SO₄ containing electrolyte at a concentration of 166 g / l H₂SO₄ (or about 230 g / l H₂SO₄) at an operating temperature of 0 to 5 ° C, at a current density of 2 to 3 A / dm² , a rising voltage of about 25 to 30 V at the beginning and about 40 to 100 V towards the end of the treatment and for 30 to 200 minutes.

In addition to the processes for anodic oxidation of printing plate support materials already mentioned in the previous paragraph, the following processes can also be used, for example: B. can the anodic oxidation of aluminum in an aqueous H₂SO₄ containing electrolyte, the Al³⁺ ion content is set to values of more than 12 g / l (according to DE-A 28 11 396 = US-A 4 211 619) in an aqueous electrolyte containing H₂SO₄ and H₃PO₄ (according to DE-A 27 07 810 = US-A 40 49 504) or in an aqueous electrolyte containing H₂SO₄, H₃PO₄ and Al³⁺ ions (according to DE-A 28 36 803 = US-A 4,229,226).

Direct current is preferably used for the anodic oxidation, but alternating current or a combination of these types of current (eg direct current with superimposed alternating current) can also be used. The layer weights of aluminum oxide range from 1 to 10 g / m², corresponding to a layer thickness of approximately 0.3 to 3.0 µm. After the stage of electrochemical roughening and before an anodic oxidation, a modification can also be applied, causing a surface removal from the roughened surface, as described, for example, in DE-A 30 09 103. Such a modifying intermediate treatment can u. a. allow the build-up of abrasion-resistant oxide layers and a lower tendency to tone when printing later.

The stage of anodic oxidation of the aluminum printing plate support material can also be one or multiple post-treatment levels can be recreated. Aftertreatment is understood to mean in particular a hydrophilizing chemical or electrochemical treatment of the aluminum oxide layer, for example an immersion treatment of the material in an aqueous polyvinylphosphonic acid solution according to DE-C 16 21 478 (= GB-A 12 30 447), an immersion treatment in an aqueous alkali silicate Solution according to DE-B 14 71 707 (= US-A 31 81 461) or an electrochemical treatment (anodization) in an aqueous alkali silicate solution according to DE-A 25 32 769 (= US-A 39 02 976). 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.

In principle, all layers are suitable as light-sensitive reproduction layers which, after exposure, optionally with subsequent development and / or fixation, provide an image-like area from which printing can take place and / or which represent a relief image of an original. They are applied either by the manufacturer of presensitized printing plates or by so-called dry resists or directly by the consumer to one of the usual carrier materials.

The light-sensitive reproduction layers include such as z. B. in "Light-Sensitive Systems" by Jaromir Kosar, John Wiley & Sons Verlag, New York 1965, are described: The layers containing unsaturated compounds, in which these compounds are isomerized, rearranged, cyclized or crosslinked during exposure (Kosar, Chapter 4); the layers containing photopolymerizable compounds, in which monomers or prepolymers optionally polymerize during exposure by means of an initiator (Kosar, Chapter 5); and the layers containing o-diazo-quinones such as naphthoquinonediazides, p-diazo-quinones or diazonium salt condensates (Kosar, Chapter 7).

The suitable layers also include the electrophotographic layers, ie those which contain an inorganic or organic photoconductor. In addition to the light-sensitive substances, these layers can of course also contain other constituents, such as, for example, resins, dyes, pigments, wetting agents, sensitizers, adhesion promoters, indicators, plasticizers or other customary auxiliaries. In particular, the following light-sensitive compositions or compounds can be used in the coating of the carrier materials:
positive-working, o-quinonediazide, preferably o-naphthoquinonediazide compounds, which are described, for example, in DE-C 854 890, 865 109, 879 203, 894 959, 938 233, 1 109 521, 1 144 705, 1 118 606, 1 120 273 and 1 124 817;
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-C 596 731, 1 138 399, 1 138 400, 1 138 401, 1 142 871, 1 154 123, US Pat. Nos. 2,679,498 and 3,050,502 and GB-A 712 606;
Negative working, mixed condensation products of aromatic diazonium compounds, for example according to DE-A 2024244, 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. These symbols are defined as follows: 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 residue of a diazonium group-free compound capable of condensing with an active carbonyl compound in at least one position of the molecule in an acid medium;
positive-working layers according to DE-A 26 10 842, which contain a compound which cleaves off on irradiation, a compound which has at least one COC group which can be cleaved by acid (for example an orthocarboxylic acid ester group or a carboxylic acid amide acetal group) and optionally a binder;
Negative working layers of photopolymerizable monomers, photoinitiators, binders and optionally other additives. 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 2,361,041. Suitable photoinitiators include benzoin, benzoin ethers, multinuclear quinones, acridine derivatives, phenazine derivatives, quinoxaline derivatives, quinazoline derivatives or synergistic mixtures of various ketones. A variety of soluble organic polymers can be used as binders, e.g. B. polyamides, polyesters, alkyd resins, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, gelatin or cellulose ether;
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.

It is also possible to apply photo-semiconducting layers, such as are described, for example, in DE-C 11 17 391, 15 22 497, 15 72 312, 23 22 046 and 23 22 047, to the support materials, thereby producing highly light-sensitive, electrophotographic layers.

The materials for printing plate supports roughened by the process according to the invention have a very uniform topography, which has a positive influence on the support stability and the water flow during printing of printing forms made from these supports. Compared to the use of other processes, "scars" (compared to the roughening of the surroundings: distinctive depressions) occur less frequently, and these can even be completely suppressed; the method according to the invention is particularly successful in producing flat, scar-free supports. Comparative examples V1 to V5 show in direct comparison with examples 1 to 4 the effect of direct current in electrolytes containing nitrate ions as a means of achieving uniform surfaces which have significant advantages in printing in terms of reducing the wiping water requirement and increasing the circulation . These surface properties can be realized without any great expenditure on equipment.

example 1

An aluminum sheet is pre-structured wet with cutting abrasives using rotating brushes to a roughness depth R _z of 4.3 µm, then pickled in a 3% sodium hydroxide solution for 30 s, in the next step with a direct current of 20 A / dm² for 10 s anodically roughened at 40 ° C in an electrolyte of 20 g / l HNO₃ and 50 g / l Al (NO₃) ₃ · 9 H₂O and then cleaned for 1 min in a bath of 2.5% NaOH at 60 ° C. After anodizing to 3 g / m² oxide and coating with a solution
6.6 parts by weight of cresol-formaldehyde novolak (with a softening range of 105 ° - 120 ° C according to DIN 53 181),
1.1 parts by weight of the 4- (2-phenyl-prop-2-yl) phenyl ester of naphthoquinone (1,2) diazide (2) sulfonic acid (4),
0.6 part by weight of 2,2ʹ-bis-naphthoquinone- (1,2) -diazide- (2) -sulfonyloxy- (5) -dinaphthyl- (1,1ʹ) -methane,
0.24 part by weight of naphthoquinone- (1,2) -diazide- (2) -sulfochloride- (4),
0.08 part by weight of crystal violet,
91.36 parts by weight of a mixture of 4 parts by volume of ethylene glycol monomethyl ether, 5 parts by volume of tetrahydrofuran and 1 part by volume of butyl acetate
prints a print form thus obtained with a wash water consumption of 23 scale parts and a print run of 175,000.

Example 2

A plate produced and coated as in Example 1, but anodically roughened in the electrochemical step with 60 A / dm 2 for 3 s in the same electrolyte prints 165,000 copies with the same coating. The water consumption is 25 divisions.

Example 3

A prepared and coated as in Example 1, but in 10% aluminum nitrate solution at 20 A / dm² for 5 s anodically roughened plate, which was cleaned in 2.5% NaOH at 60 ° C for 60 s, prints 150,000 copies under the same conditions with a water consumption of 30 scale divisions.

Example 4

A plate produced and coated as in Example 1, but anodically roughened in 7% sodium nitrate solution at 30 A / dm² for 5 s, prints 155,000 copies under the same conditions with a water consumption of 32 scale parts.

Comparative Example V1

A plate produced and coated as in Example 1, but anodically roughened with an alternating current of 20 A / dm 2 for 10 s, has a print run of 110,000 prints and a water consumption of 45 scale divisions.

Comparative example V2

A plate produced and coated analogously to Example 1, but anodically roughened with an alternating current of 20 A / dm 2 for 20 s has a circulation of 120,000 and a water consumption of 40 scale parts.

Comparative Example V3

A plate produced and coated as in Example 1, but anodically roughened with direct current of 20 A / dm 2 for 10 s in 20 g / l HCl, prints 110,000 copies and has a water consumption of 42 divisions.

Comparative Example V4

A plate produced and coated in the same way as in Example 1, with DC current of 20 A / dm 2 for 10 s but anodically roughened in 10 g / l HCl, prints 115,000 and has a wiping water consumption of 41 scale parts.

Comparative Example V5

A plate manufactured and coated as in Comparative Example V4, but anodically roughened in 12 g / l HCl and 50 g AlCl₃ · 6 H₂O has a circulation of 115,000 and a water consumption of 39 scale parts.

In all examples, the printing was carried out under the same conditions using the same printing press (Roland Favorit). The application quantity of the wiping water is determined by a display device in a dampening unit from Dahlgren. These are relative comparative measurements. The lower the scale divisions, the lower the water consumption.

Claims (18)

1. A process for the production of plate, foil or tape-shaped aluminum or its alloys for use in printing plates, wherein one a) first a mechanical roughening and then b) undergoes electrochemical roughening in a nitrate-containing electrolyte, characterized in that the electrochemical roughening is carried out with direct current. 2. The method according to claim 1, characterized in that adjusting the concentration of the nitrate compound to 1.0 g / l up to the saturation limit. 3. The method according to claim 2, characterized in that the nitrate compound is adjusted to 5.0 g / l to 100 g / l. 4. The method according to any one of claims 1 to 3, characterized in that nitric acid is used as the nitrate-containing electrolyte. 5. The method according to any one of claims 1 to 3, characterized in that solutions of alkali metal, alkaline earth metal, ammonium or aluminum nitrate and / or mixtures thereof and / or mixtures with nitric acid are used as the nitrate-containing electrolyte. 6. The method according to any one of claims 1 to 5, characterized in that roughening with a direct current of 1 to 300 A / dm² with a charge of 1 to 400 C / dm². 7. The method according to claim 6, characterized in that roughening with a direct current of 10 to 100 A / dm² with a charge of 10 to 200 C / dm². 8. The method according to any one of claims 1 to 7, characterized in that it is roughened electrochemically for a time of 1 to 300 s. 9. The method according to claim 8, characterized in that it is roughened electrochemically for a time of 2 to 60 s. 10. The method according to any one of claims 1 to 9, characterized in that one carries out a cleaning step after the mechanical and / or electrochemical roughening. 11. The method according to claim 10, characterized in that one carries out an alkaline cleaning. 12. The method according to claim 11, characterized in that one carries out the cleaning with alkali metal hydroxide. 13. The method according to any one of claims 1 to 12, characterized in that an anodizing is carried out after the roughening. 14. The method according to claim 13, characterized in that one carries out the anodization up to an oxide layer weight of 5 g / m². 15. The method according to any one of claims 1 to 14, characterized in that it is roughened electrochemically at a temperature of 20 to 80 ° C. 16. The method according to any one of claims 1 to 15, characterized in that one carries out the mechanical roughening as a wet brushing. 17. The method according to any one of claims 1 to 15, characterized in that one carries out the electrochemical roughening in a moving electrolyte with a flow rate between 5 and 1000 cm / s.