EP0004569A1 - Process for the anodic oxydation of aluminium and its use as printing plate carrier material - Google Patents

Abstract

The invention relates to a process for the anodic oxidation of strip, foil or plate-shaped material made of aluminum or its alloys in an aqueous electrolyte which contains sulfuric acid and aluminum ions; the material can also be mechanically, chemically or electrochemically roughened before carrying out the anodic oxidation. The anodic oxidation of the material takes place in an electrolyte with a concentration of sulfuric acid of 25 to 100 g / l and aluminum ions of 10 to 25 g / l, at a current density of 4 to 25 A / dm² and at a temperature of 25 ° to 65 ° C. The method is used in particular in the production of a strip, film or plate-shaped printing plate carrier material, after which these carrier materials can be coated with a photosensitive composition by the manufacturer of presensitized printing plates or by the consumer himself. These light-sensitive layers are optionally colored and preferably contain diazo compounds, diazoquinones, diazo mixed condensates or photopolymerizable compounds.

Description

The invention relates to a method for the anodic oxidation of aluminum, the use of the material produced thereafter as a printing plate carrier material and a method for producing a printing plate carrier material.

In the processing of aluminum or its alloys, for example in the form of strips, foils or plates, there has been a trend in recent decades towards the continuous improvement of the aluminum surface in order to prepare it for a wide variety of applications. The most diverse properties that are to be achieved in relation to the surface include, for example: corrosion resistance, appearance, density, hardness, wear resistance, absorption capacity and adhesion for lacquer or synthetic resin coatings, dyeability, gloss, etc. The development of bright rolled Aluminum based on chemical, mechanical and electrochemical surface treatment processes, whereby combinations of the different processes are also used in practice.

In particular when processing such strip, foil or plate-shaped material made of aluminum or its alloys, which is to be used as a carrier material for (planographic) printing plates, the combination of a mostly mechanical or electrochemical roughening stage has become the preliminary conclusion of technical development a subsequent treatment step by anodic oxidation of the roughened aluminum surface. However, depending on the desired print run of the treated printing plate, anodic oxidation can also occur on such aluminum materials are carried out that have not been subjected to a separate roughening treatment, they then only have to have a surface to which an adhesive aluminum oxide layer can be applied by the anodic oxidation.

Anodic layers on (planographic) printing plates are particularly suitable for better guidance of the fountain solution (= increased hydrophilicity) and for increasing the resistance to abrasion and thus, for example, to prevent the loss of printing parts on the surface during the printing process and also have, for example, a increased adhesive strength compared to the photosensitive layer.

Due to their natural porosity, conventional anodic layers also have disadvantages. Depending on the anodizing conditions, these are an increased susceptibility to alkali, which is found, for example, in the customary media; which serve for the development of the light-sensitive layers, or can be in the fountain solution, as well as a more or less strong irreversible absorption of substances from the applied coating. This absorption can then lead to what is known as "fogging", ie discoloration of the oxide layer which becomes visible in the then image-free parts of the printing plate after the development of the exposed photosensitive layer. This "fog" is particularly evident in the frequently required chemical correction, e.g. B. to remove film edges of the printed image, the causing the fog Substances can also be detached from the depth of the oxide layer. The corrected areas appear as bright areas on a tinted background. In the worst case, the sensitivity to alkali and the correction spots mentioned lead to difficulties in printing, which can be caused by the tendency of the printing plates to toning in their non-image areas and by a reduced circulation of the printing plates.

• 1 Das Gleichstrom-Schwefelsäure-Verfahren, bei dem in einem wäßrigen Elektrolyten aus üblicherweise 231 g H₂SO₄ pro 1 ltr. Lösung bei 10° bis 22° C und einer Stromdichte von 0,5 bis 2,5 A/dm² während 10 bis 60 min anodisch oxidiert wird. Die Schwefelsäurekonzentration in der wäßrigen Elektrolytlösung kann dabei auch bis auf 8 bis 10 Gew.-% H₂SO₄ (ca. 100 ^g H₂SO₄/ltr.) verringert oder auch auf 30 Gew.-% (365 g H₂SO4/ltr.) und mehr erhöht worden. Durch die bei der anodischen Oxidation aus Al-Atomen entstehenden Al³⁺-Ionen befindet sich im wäßrigen, H₂S0₄ enthaltenden Elektrolyten auch immer ein bestimmter Anteil an Al³⁺-Ionen, der jedoch möglichst konstant gehalten wird, um reproduzierbare Ergebnisse hinsichtlich der Schichteigenschaften zu erzielen. Diese Konstanthaltung der AK³⁺-Ionenkonzentration wird durch eine kontinuierliche Elektrolytregeneration erreicht, wobei der Al³⁺-Ionen- gehalt im Bereich von etwa 8 bis 12 g A¹³⁺/ltr. gehalten wird. Die Erschöpfung eines für das genannte Verfahren geeigneten wäßrigen, H₂SO₄ enthaltenden Elektrolyten tritt spätestens bei etwa 15 bis 18 g Ak³⁺/ltr. ein, wobei Werte von mehr als 12 g Al³⁺/ltr. bereits in der Praxis möglichst vermieden werden.
• 2 Die "Hartanodisierung" wird mit einem wäßrigen, H₂SO₄ enthaltenden Elektrolyten einer Konzentration von 166 ^g H₂S0₄ (oder 231 g H₂S0₄) / ltr. bei einer Betriebstemperatur von 0° bis 5° C, bei einer Stromdichte von 2 bis 3 A/dm², einer steigenden Spannung von etwa 25 bis 30 V zu Beginn und etwa 40 bis 100 V gegen Ende der Behandlung und während 30 bis 200 min durchgeführt.

The following two standard methods for the anodic oxidation of aluminum in aqueous electrolytes containing H ₂ SO ₄ are known from the prior art (see, for example, BM Schenk, material aluminum and its anodic oxidation, Francke Verlag - Bern, 1948, page 760; practical ones Galvanotechnik, Eugen G. Leuze Verlag - Saulgau, 1970, page 395 ff. And pages 518/519; W. Hübner and CT Speiser, The Practice of Anodic Oxidation of Aluminum, Aluminum Verlag - Düsseldorf, 1977, 3rd edition, page 137 ff.), whereby H ₂ SO _{4 has} proven to be the most useful electrolyte acid for most applications:

• 1 The direct current sulfuric acid process, in which in an aqueous electrolyte usually 231 g H ₂ SO ₄ per 1 liter. Solution is anodized at 10 ° to 22 ° C and a current density of 0.5 to 2.5 A / dm ² for 10 to 60 min. The sulfuric acid concentration in the aqueous electrolyte solution can also be reduced to 8 to 10% by weight H ₂ SO ₄ (approx. 100 ^g H ₂ SO ₄ / liter) or to 30% by weight (365 g H ₂ SO4 / ltr.) and more. By the at the anodic Oxidation of Al ³⁺ ions formed from Al atoms is always a certain proportion of Al ³⁺ ions in the aqueous electrolyte containing H ₂ S0 ₄ , but this is kept as constant as possible in order to achieve reproducible results with regard to the layer properties. This constant maintenance of the AK ³⁺ ion concentration is achieved by continuous electrolyte regeneration, the Al ³⁺ ion content being in the range of approximately 8 to 12 g A ¹³⁺ / ltr. is held. The exhaustion of an aqueous electrolyte containing H ₂ SO ₄ suitable for the process mentioned occurs at the latest at about 15 to 18 g Ak ³⁺ / ltr. a, where values of more than 12 g Al ³⁺ / ltr. should be avoided as far as possible in practice.
• 2 The "hard anodizing" is carried out with an aqueous electrolyte containing H ₂ SO _{4 at} a concentration of 166 ^g H ₂ S0 ₄ (or 231 g H ₂ S0 ₄ ) / liter. at an operating temperature of 0 ° to 5 ° C, at a current density of 2 to 3 A / dm ² , 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 min carried out.

Although both processes provide oxide layers on aluminum which can be used for many areas of application, they have some disadvantages, for example, when used for the production of support materials for printing plates. These include, on the one hand, the increased susceptibility of the layers produced thereafter to alkali and the "formation of fog", and, on the other hand, that particularly with "hard anodizing" Energy to be used to achieve and keep the low electrolyte temperatures constant and the relatively long residence times of the aluminum in the electrolyte for the economically advantageous continuous anodization of aluminum.

• In der DE-OS 14 96 711 wird ein Verfahren zur anodischen Oxidation von u.a. Aluminium beschrieben, bei dem in einem wäßrigen H₂S0₄ enthaltenden Elektrolyten einer Temperatur von nicht über 20° C unter Anwendung einer Stromdichte von mehr als 20 A/dm², zweckmäßig jedoch von mehr als 80 A/dm², die Werkstücke unter gleichzeitiger Unterkühlung anodisiert werden.

Furthermore, some modified anodizing processes are known from the prior art, in which either specific changes are made in the anodizing conditions or in the bath compositions. Examples include the following fonts:

• DE-OS 14 96 711 describes a process for the anodic oxidation of, inter alia, aluminum, in which in an aqueous electrolyte containing H ₂ S0 ₄ a temperature of not more than 20 ° C. using a current density of more than 20 A / dm ² , but expediently more than 80 A / dm ² , the workpieces are anodized with simultaneous hypothermia.

The process for the anodic oxidation of printing plate support materials made of aluminum according to DE-OS 23 28 606 is with an aqueous electrolyte of about 15 wt .-% H ₂ S0 ₄ (about 165 g H ₂ S0 ₄ / ltr.) At more than 70 ° C, a current density of 16.1 A / dm ² to 108 A / dm ² for 10 sec to 60 sec. The anodic oxidation can be preceded by an electrochemical roughening or a further chemical treatment step can be added.

Based on the recognized problem of "fogging" in conventional anodic oxidation processes (see DC current Sulfuric acid process, above) in DE-OS 22 48 743 an aqueous H ₂ S0 ₄ containing electrolyte for the production of printing plate support materials of about 10 to 35 wt .-% H ₂ SO ₄ (about 106 to 435 g H ₂ S0 ₄ / ltr.), which is used at 20 to 40 ° C, a current density of 4 to 15 A / dm ² and a relative linear velocity against the aluminum strip of at least 2 m / min.

From CH-PS 171 733 a process for the anodic oxidation of aluminum is known, in which an aqueous electrolyte with a content of 35 to 60% by weight H ₂ SO ₄ (ie more than 435 g N ₂ SO ₄ / ltr.) at a current density of 0.32 to 1.08 A / dm ² , at a temperature of 18 to 30 ° C and with the addition of 2 to 3% aluminum sulfate (approx. 1.6 to 2.4 g Al ³⁺ / ltr.) is used.

CH-PS 161 851 describes a process for the anodic oxidation of aluminum, in which, in an aqueous electrolyte made of, for example, 900 g of aluminum sulfate (approx. 3.95 g of A7 ³⁺ / liter), 13.5 liters. H ₂ 0 and 4.5 ltr. N ₂ SO ₄ (approx. 450 g H ₂ S0 ₄ / ltr.); at a current density of 0.1 to 0.35 A / dm ² , at a temperature of 15 to 32 ° C and for 15 to 50 min.

The process for producing a corrosion-resistant layer of high wear resistance on aluminum alloys with about 6% Cu content according to DE-AS 12 57 523 is carried out in an aqueous electrolyte from 240 to 300 g H ₂ SO ₄ / ltr., A content of at least 50 g A1 ₂ 0 ₃ / ltr. (approx. 27 g Al ³⁺ / ltr.) and a current density of up to 12 A / dm ² for about 30 minutes.

Hard layers with a thickness of 100 to 180 µm are according to DE-OS 12 33 472 at a temperature of about 15 ° C to 20 ° C in a bath of 250 to 300 g aluminum sulfate / liter, 30 to 40 g oxalic acid / ltr. and 7 to 20 g glycerol / liter. on aluminum with a current density of 2.5 to 3 A / dm ² for 1 to 2.5 hours.

From DE-OS 22 51 710 (= GB-PS 1 410 768) a method for producing printing plate support materials is known, in which, for. B. a flat aluminum plate after mechanical roughening in an aqueous electrolyte from 30% H ₂ S0 ₄ (about 365 g H ₂ SO ₄ / ltr.) And 20 g aluminum sulfate / ltr. _(Approx. 1, ₆ g of Al ³⁺ / ltr.) For 6 min at a current density of 4 A / dm ² is oxidized anodically.

However, all known methods are either only suitable for the production of thick aluminum oxide layers or only provide layers which, in particular, cannot meet the requirements placed on a (planographic) printing plate support.

The object of the invention is therefore to propose a process for the production of anodically oxidized aluminum, with which abrasion-resistant, alkali-resistant, less porous aluminum oxide layers can be produced in sufficient strength at economically justifiable energy costs on aluminum strips, foils or plates.

The invention is based on the known process for the anodic oxidation of strip, sheet or plate-shaped material made of aluminum or its alloys in an aqueous electrolyte containing sulfuric acid and aluminum ions, if appropriate after prior mechanical, chemical or electrochemical roughening. The process according to the invention is characterized in that the material in an electrolyte has a concentration of sulfuric acid of 25 to 100 g / ltr. and anodized on aluminum ions of 10 to 25 g / l, at a current density of 4 to 25 A / dm ² and at a temperature of 25 ° to 65 ° C. In a preferred embodiment, this method, with the features specified, is used to produce a strip, film or plate-shaped printing plate carrier material. In the further explanations, the term printing plate is generally to be understood as a printing plate for planographic printing, which mainly consists of a flat support made of one or more materials and one or more likewise light-sensitive sheets attached to it. layers.

Both methods are used in particular in an electrolyte with a concentration of sulfuric acid of 30 to 75 g / ltr. and on aluminum ions of 15 to 20 g / liter, at a current density of 6 to 15 A / dm ² and at a temperature of 40 ° to 55 ° C.

• - "Reinaluminium" (DIN-Werkstoff Nr. 3.0255), d. h. bestehend aus > 99,5 % Al und den folgenden zulässigen Beimengungen von (maximale Summe von 0,5 %) 0,3 % Si, 0,4 % Fe, 0,03 % Ti, 0,02 % Cu, 0,07 % Zn und 0,03 % sonstigem, oder
• - "Al-Legierung 3003" (vergleichbar mit DIN-Werkstoff Nr. 3.0515), d. h. bestehend aus > 98,5 % Al, den Legierungsbestandteilen 0 bis 0,3 % Mg und 0,8 bis 1,5 % Mn und den folgenden zulässigen Beimengungen von 0,5 % Si, 0,5 % Fe, 0,2 % Ti, 0,2 % Zn, 0,1 % Cu und 0,15 % sonstigem

Aluminum or one of its alloys is used as the metal base for the strip, foil or plate-shaped material. Among them are preferred (also used in the following examples):

• - "Pure aluminum" (DIN material no. 3.0255), ie consisting of> 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% other, or
• - "Al alloy 3003" (comparable to DIN material no. 3.0515), ie consisting of> 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

to understand.

The electrolyte is made of conc. H ₂ S0 ₄ , water and an added aluminum salt, especially aluminum sulfate, prepared so that it to 1 liter. Electrolyte based 25 to 100 g H ₂ SO ₄ , preferably 30 to 75 g H ₂ SO ₄ , and 10 to 25 g Al ³⁺ ions in solution, preferably 15 to 20 g Al ³⁺ ions, contains. The concentration ranges of the electrolyte components are checked at regular intervals, since they are of crucial importance for an optimal course of the process, and the electrolyte is then regenerated discontinuously or preferably continuously. Detailed information on the production, monitoring and regeneration of electrolytes in the anodic oxidation of aluminum can be found in W. Hübner, CT Speiser, The Practice of Anodic Oxidation of Aluminum, Aluminum Verlag - Düsseldnrf, 1977, 3rd edition, Pages 141 to 148 and Pages 154 to 157 can be found there, there are also basic information on the procedure for the anodic oxidation of aluminum (Page 149 and Page 150).

The process according to the invention can be carried out batchwise or in particular continuously. A device such as that described in DE-AS 22 34 424 (= US Pat. No. 3,871,982) is suitable for carrying out the continuous procedure. This device has a treatment tub filled with the electrolyte, an inlet and an outlet for the band to be treated in each of the two end walls of the tub below the liquid level of the electrolyte, at least one electrode arranged above the metal band and devices for generating a rapid electrolyte flow between the transport path of the tape and the electrode surface. The electrolyte flow is generated by a bell-like chamber arranged along each end wall of the trough, which overflows for the electrolyte with a liquid drain into a reserve container located below the trough, a gas space above the liquid level that is sealed off from the outside air, and a gas chamber that begins in this gas space. contains gas line connected to a suction pump. In addition, this device also has a pump for conveying the electrolyte from the reserve container into the tub.

The process according to the invention is expediently carried out in such a way that the treatment time of the anodic oxidation - ie the stay of a surface point in the area of influence of the electrode (s) - ranges from 5 to 60 sec, preferably from 10 to 35 sec. Layer weights of aluminum oxide in the range of 1 to 10 g / m ² (corresponding to a layer thickness of approximately 0.3 to 3.0 μm), preferably of approximately 2 to 4 g / m ² , can then be obtained.

Good electrolyte circulation is required in the practice of the invention. This can be generated either by stirring or by pumping around the electrolyte. In the case of continuous operation (see, for example, DE-AS 22 34 424), care must be taken to ensure that the electrolyte is guided as parallel as possible to the strip to be treated under high-speed turbulent flow 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 preferably used for the anodic oxidation, but alternating current or a combination of these types of current (eg direct current with superimposed alternating current or the like) can also be used.

The process according to the invention for the anodic oxidation of aluminum can also be preceded by one or more pretreatment stages, in particular a roughening stage, in particular in the embodiment of the method according to the invention for producing a printing plate carrier material. Pretreatment is either a mechanical surface treatment by grinding, polishing, brushing or blasting, a chemical surface treatment understood for degreasing, pickling or matting or an electrochemical surface treatment by the action of electrical current (mostly from alternating current) in an acid such as HCl or HN0 ₃ . Under these pretreatment stages, the mechanical and electrochemical treatment of the surfaces of the aluminum in particular lead to roughened surfaces. The average roughness depth R _z is in the range from about 1 to 15 μm, in particular in the range from 4 to 8 pm.

The roughness depth is determined in accordance with DIN 4768 in the version from October 1970, the roughness depth R _z is then the arithmetic mean of the individual roughness depths of five adjacent individual measuring sections. The individual roughness depth is defined as the distance between two parallels to the middle line, which touch the roughness profile at the highest or lowest point within the individual measuring section. The individual measuring section is the fifth part of the length of the part of the roughness profile which is used directly for evaluation and is projected perpendicularly onto the middle line. The middle line is the line parallel to the general direction of the roughness profile from the shape of the geometrically ideal profile, which divides the roughness profile so that the sums of the material-filled areas above it and the material-free areas below it are equal.

The method according to the invention for the anodic oxidation of aluminum can also - or likewise in particular in the embodiment of the method according to the invention for producing a printing plate support material - have one or multiple post-treatment levels can be recreated. Aftertreatment means in particular a 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-PS 16 21 478, an immersion treatment in an aqueous alkali silicate solution according to DE-AS 14 71 707 (= US Pat. No. 3,181,461) or an electrochemical treatment (anodization) in an aqueous alkali silicate solution according to DE-OS 25 32 769 (= US Pat. No. 3,902,976). 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.

• Als lichtempfindliche Schichten sind grundsätzlich alle Schichten geeignet, die nach dem Belichten, gegebenenfalls mit einer nachfolgenden Entwicklung und/oder Fixierung eine bildmäßige Fläche liefern, von der gedruckt werden kann.

A field of application for a material anodically oxidized by the process according to the invention and optionally also pretreated and / or post-treated is in particular its use as a carrier material in the production of printing plates bearing a photosensitive layer. Here, either at the manufacturer of presensitized printing plates or when coating a carrier material at the consumer, the carrier material is coated with one of the following light-sensitive materials:

• In principle, all layers are suitable as light-sensitive layers which, after exposure, optionally with subsequent development and / or fixation, provide an imagewise surface from which printing can take place.

In addition to the layers containing Siiberhalogenide used in many fields, various others are known, such as z. As described in "Light-Sensitive Systems by Jaromir Kosar, John Wiley & Sons Verlag, New York 1965": the coiloid layers containing chromates and dichromates (Kosar, Chapter 2); 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). Suitable layers also include the electrophotographic layers, i.e. H. those containing an inorganic or organic photoconductor. In addition to the light-sensitive substances, these layers can of course also other components such. B. contain resins, dyes or plasticizers.

• Positiv arbeitende o-Chinondiazid-, bevorzugt o-Naphthochinondiazid-Verbindungen, die beispielsweise in den DE-PSen 854 890, 865 109, 879 203, 894 959 938 233, 1 109 521, 1 114 705, 1 118 606, 1 120 273 und 1 124 817 beschrieben werden.

In particular, the following light-sensitive compositions or compounds can be used in the coating of the carrier materials produced by the process according to the invention:

• Positive-working o-quinonediazide, preferably o-naphthoquinonediazide compounds, which are described, for example, in DE-PS 854 890, 865 109, 879 203, 894 959 938 233, 1 109 521, 1 114 705, 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 diazomium salts and formaldehyde, which are described, for example, in DE-PS 596 731, 1 138 399, 1 138 400, 1 138 401, 1 142 871, 1 154 123 , U.S. Patents 2,679,498 and 3,050,502 and British Patent 712,606.

Negative mixed condensation products of aromatic diazonium compounds, for example according to DE-OS 20 24 244, which each have at least one unit of the general types A (-D) 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 condensation with an active carbonyl compound in at least one position in an acid medium. D is a diazonium salt group attached to an aromatic carbon atom of A; n is an integer from 1 to 10; and B is the remainder of a compound free of diazonium groups and capable of condensing with an active carbonyl compound in an acidic medium at at least one position on the molecule.

Positive-working layers according to DE-OS 26 10 842, which contain a compound which cleaves off on irradiation, a compound which has at least one C-O-C 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-OSes 20 64 079 and 23 61 041. As photoinitiators are u. a. Benzoin, benzoin ethers, multinuclear quinones, acridine derivatives, phenazine derivatives, quinoxaline derivatives, quinazoline derivatives or synergistic mixtures of different 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.

In summary, an anodically oxidized strip, foil or plate-shaped material made of aluminum or. his alloys are produced, which has an abrasion-resistant, alkali-resistant and less porous surface in sufficient strength for many areas of application. In particular, a printing plate carrier material produced by this method and provided with a light-sensitive layer shows no or at least reduced "fog". This goal could be achieved in the process according to the invention by the combination of process features which were judged to be rather detrimental to the achievement of this goal, namely the use of a low H ₂ SO ₄ concentration and a high Al ³⁺ ion concentration tration, a relatively high electrolyte temperature, a high current density and a high flow rate of the electrolyte. It is possible that some of the features of the method have already become known in certain sub-areas, but this does not apply to the combination of all features. Despite the relatively high electrolyte temperature, the back-dissolving capacity of the electrolyte is of the order of magnitude that can be observed at lower electrolyte temperatures. Likewise, the "burns" of the aluminum oxide that are often feared due to the higher current density surprisingly fail to materialize.

• - Bestimmung des Flächengewichts von Aluminiumtixidschichten durch chemisches Ablösen (nach DIN 50 944 in der Ausgabe vom März 1969): Die Aluminiumoxidschicht wird durch eine Lösung aus 37 ml H₃PO₄ (Dichte von 1,71 g/ml bei 20° C entsprechend _{85 %} H₃PO₄), ₂₀ g CrO₃ und 963 ml H20 dest. bei 90 bis 95° C während 5 min vom Grundmetall abgelöst und der dabei entstehende Gewichtsverlust durch Wiegen der Probe vor und nach dem Ablösen bestimmt. Aus dem Gewichtsverlust und dem Gewicht der mit der Schicht bedeckten Oberfläche wird das Flächengewicht der Schicht berechnet und in g/m² angegeben.
• Prüfung der Güte der Verdichtung anodisch erzeugter Oxidschichten im Anfärbeversuch (angelehnt an DIN 50 946 in der Ausgabe vom Juni 1968): Diese qualitative Meßmethode läßt insbesondere in Kombination mit einer nachfolgenden quantitativen Farbortbestimmung Aussagen darüber zu, ob und in welchem Ausmaß die anodisch oxidierte Oberfläche eines Aluminiummaterials zur "Schleierbildung" neigt. Zur Messung wird ein flächiger Materialabschnitt von 5 cm 12 cm hälftig während 20 min in eine Lösung von 0,5 g/ltr. an Aluminium-Blau ( ^R Solway Blue BN 150 der ICI) in H₂0 dest. bei 40° bis 45° C eingetaucht, mit H₂0 dest. abgespült und getrocknet. Der Grad der Anfärbung ist ein Maß für die Güte der Verdichtung. Je weniger Farbstoff aufgenommen worden ist, desto besser ist die Verdichtung, d. h. je weniger neigt die untersuchte Oberfläche zur "Schleierbildung".
• Farbortbestimmung (nach DIN 5033 Blatt 1 vom Juli 1962, Blatt 3 vom April 1954, Blatt 6 vom September 1964 und Blatt 7 vom Oktober 1966): Dabei werden die Farbmaßzahlen für den ungefärbten und den angefärbten Teil der Probe (angefärbt mit Aluminium-Blau) bestimmt. Als Normlichtart wird die Normlichtart C (spektrale Strahlungsverteilung einer gasgefüllten Wolfram-Glühlampe der Verteilungstemperatur von 2854 K) verwendet und die drei Farbwerte der zu messenden Farbvalenz bestimmt. Als Ergebnis können die trichromatischen Farbmaßzahlen des Norntval enz-Systews angegeben werden, in der Praxis genügt (zumindest im vorliegenden Falle) häufig bereits die Angabe eines Normfarbwertes oder Normfarbarertanteils. Bei der Farbortbestimmung der Probe ist dann die Differenz zwischen den Normfarbwertanteilen x₁ des ungefärbten Teils der Probe und x_II des angefärbten Teils der Probe ein Maß für die Verdichtung der Oberfläche, d. h. je größer der Differenzwert desto weniger dicht ist die Oberfläche und desto eher tritt die "Schleierbildung" auf.
• - Prüfung der Alkaliresistenz der Oberfläche (nach US-PS 3 940 321, Spalten 3 und 4, Zeilen 29 bis 68 und Zeilen 1 bis 8): Als Maß für die Alkaliresistenz einer Aluminiumoxidschicht gilt die Auflösegeschwindigkeit der Schicht in sec in einer alkalischen Zinkatlösung. Die Schicht ist umso alkalibeständiger je länger sie zur Auflösung braucht. Die Schichtdicken sollten in etwa vergleichbar sein, da sie natürlich auch einen Parameter für die Auflösegeschtrindigkeit darstellen. Man bring_-t einen Tropfen einer Lösung aus 500 ml H20 dest., 480 g KOH und 80 g Zinkoxid auf die zu untersuchende Oberfläche und bestimmt die Zeitspanne bis zum Auftreten von metallischem Zink, was an einer Schwarzfärbung der Untersuchungsstelle zu erkennen ist.

Percentages in the following examples are based on weight, parts by weight to parts by volume are in the same ratio as kg to ltr. The following standard methods are used to assess the aluminum materials anodized by the method according to the invention:

• - Determination of the weight per unit area of aluminum oxide layers by chemical detachment (according to DIN 50 944 in the March 1969 edition): The aluminum oxide layer is replaced by a solution of 37 ml H ₃ PO ₄ (density of 1.71 g / ml at 20 ° C corresponding to _{85 %} H ₃ PO ₄ ), ₂₀ g CrO ₃ and 963 ml H20 dist. 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 .
• Testing the quality of the compaction of anodically produced oxide layers in a coloring test (based on DIN 50 946 in the June 1968 edition): This qualitative measuring method, particularly in combination with a subsequent quantitative determination of the color location, allows statements to be made as to whether and to what extent the anodized surface of a Aluminum material tends to "fog". For the measurement, a flat material section of 5 cm is divided by 12 cm in half into a solution of 0.5 g / ltr for 20 min. on aluminum blue ( ^R Solway Blue BN 150 from ICI) in H ₂ 0 dest. immersed at 40 ° to 45 ° C, with H ₂ 0 dist. rinsed and dried. The degree of staining is a measure of the quality of the compression. The less dye is absorbed, the better the compression, ie the less the surface examined tends to "fog".
• Color locating (according to DIN 5033 sheet 1 from July 1962, sheet 3 from April 1954, sheet 6 from September 1964 and sheet 7 from October 1966): The color measures for the undyed and the stained part of the sample (stained with aluminum blue) certainly. The standard illuminant C is used (spectral radiation distribution of a gas-filled tungsten light bulb with a distribution temperature of 2854 K) and the three color values of the color valence to be measured are determined. As a result, the trichromatic color measures of the Norntval enz-Systews can be specified, in practice it is often sufficient (at least in the present case) to specify a standard color value or standard color percentage. At the color locus The determination of the sample is then the difference between the standard color value components x _{1 of} the undyed part of the sample and x _{II of} the colored part of the sample a measure of the compaction of the surface, ie the larger the difference value, the less dense the surface and the sooner the " Fog ".
• - Testing the alkali resistance of the surface (according to US Pat. No. 3,940,321, columns 3 and 4, lines 29 to 68 and lines 1 to 8): The measure of the alkali resistance of an aluminum oxide layer is the dissolution rate of the layer in seconds in an alkaline zincate solution. The layer is more alkali-resistant the longer it takes to dissolve it. The layer thicknesses should be roughly comparable, since they naturally also represent a parameter for the dissolution rate. One bring _- t a drop of a solution of 500 ml H20 least 480 g KOH and 80 g of zinc oxide on the examined surface and determines the time to onset of metallic zinc, which can be seen on a black coloration of the examination site..

example 1

Blank aluminum strip with a thickness of 0.3 mm is degreased with an alkaline pickling solution (an aqueous solution of 20 g NaOH per liter of solution) at an elevated temperature of about 50 to 70 ° C. The electrochemical roughening of the aluminum surface takes place in an apparatus created according to the teaching of DE-AS 22 34 424 with alternating current and in one HNO ₃ containing electrolytes. A similar device is used for the subsequent anodic oxidation with direct current, but the current is supplied via a contact roller.

The anodizing electrolyte contains 50 g H ₂ SO ₄ / ltr. and 20 g Al ³⁺ / ltr. Aluminum ion, wherein the Al ³⁺ ion concentration by dissolving 247 g Al ₂ (SO ₄₎ of ₃ - 18 H ₂ 0 per liter. is produced. At a bath temperature of 40 ° C and a current density of 10 A / dm ² (direct current), about 2.9 g / m ^{2 of} aluminum oxide can be obtained in about 25 seconds of anodizing. The flow in the above-mentioned apparatus is turbulent for achieving a good mass and heat exchange, the flow rate of the electrolyte is more than 0.3 m / sec.

• 0,58 Gew.-Teile des Veresterungsproduktes aus 1 Mol 2,2'-Dihydroxi-dinaphthyl-(1,1')-methan und 2 Molen Naphthochinon-(1,2)-diazid-(2)-5-sulfonsäurechlorid
• 1,16 Gew.-Teile des p-Cumylphenolesters der Naphthochinon-(1,2)-diazid-(2)-4-sulfonsäure
• 6,92 Gew.-Teile Novolakharz (Erweichungspunkt 112 bis 118° C, Gehalt an phenolischen OH-Gruppen 14 Gew.-%)
• 0,08 Gew.-Teile Kristallviolettbase
• 0,26 Gew.-Teile Naphthochinon-(1,2)-diazid-(2)-4-sulfonsäurechlorid
• 36,00 Gew.-Teile Ethylenglykol-mono-ethylether
• 47,00 Gew.-Teile Tetrahydrofuran
• 8,00 Gew.-Teile Butylacetat

A solution with the following components is used to produce a presensitized printing plate from this material:

• 0.58 parts by weight of the esterification product from 1 mole of 2,2'-dihydroxy-dinaphthyl- (1,1 ') - methane and 2 moles of naphthoquinone- (1,2) -diazide- (2) -5-sulfonic acid chloride
• 1.16 parts by weight of the p-cumylphenol ester of naphthoquinone- (1,2) -diazid- (2) -4-sulfonic acid
• 6.92 parts by weight of novolak resin (softening point 112 to 118 ° C., content of phenolic OH groups 14% by weight)
• 0.08 part by weight of crystal violet base
• 0.26 part by weight of naphthoquinone- (1,2) -diazide- (2) -4-sulfonic acid chloride
• 36.00 parts by weight of ethylene glycol monoethyl ether
• 47.00 parts by weight of tetrahydrofuran
• 8.00 parts by weight of butyl acetate

The weight of the photosensitive layer applied to the anodized support is approximately 3 g / m ² .

To produce a printing form, exposure is carried out in a known manner and developed with an aqueous alkaline solution. With a printing form prepared in this way, between 150,000 and 180,000 prints can be produced in good quality using the offset process.

In order to measure the "fog" sensitivity of the printing plate, it is stained before the photosensitive layer is applied.

When determining the color, the difference for the color acceptance of the surface is 3 x _I - x _II of 6.4 x 10 ³ .

The zincate test gives a measuring time of about 35 seconds. The "fog" of the printing plate support is low and the alkali resistance is good.

Example 2

Rolled aluminum strip with a thickness of 0.3 mm is alkali-pickled and roughened according to the instructions in Example 1. The subsequent anodic oxidation takes place in an apparatus produced according to the teaching of DE-AS 22 34 424 with an electrolyte containing 100 g H ₂ SO _{4 /} ltr. and 20 g Al ³⁺ / ltr. contains. At a bath temperature of 35 ° C and a current density of 10 A / dm ² , 3 g / m ^{2 of} aluminum oxide can be built up in 25 seconds.

The coloring test gives a difference in the color value fraction x _I - x _II of 18. 10 ³ , the zincate test a measuring time of 24 sec.

After applying a light-sensitive layer as described in Example 1, between 150,000 and 180,000 prints of good quality can be obtained in the offset process.

The "fogging" of the printing plate support is low and the alkali resistance is good.

Example 3

Rolled aluminum strip with a thickness of 0.3 mm is alkali pickled and electrochemically roughened as described in Example 1. The anodic oxidation takes place in a device created according to the teaching of DE-AS 22 34 424. The electrolyte contains 30 g H ₂ S0 _{4 /} ltr. and 15 g Al ³⁺ / ltr .. At 35 ° C bath temperature and a current density of 5 A / dm ² , an aluminum oxide layer of about 2.3 g / m ^{2 can be obtained} in 30 seconds build up. The dye test gives a difference in color value x _I - x _II of 5 10 ³ , the zincate test a measuring time of 55 sec.

After coating with a light-sensitive solution according to Example 1, over 100,000 prints can be made in good quality using the offset method. The "fogging" of the printing plate support is very low and the alkali resistance is good.

If the bath temperature is increased to 55 ° C and the current density to 9 A / dm ² , about 3 g / m ^{2 of} aluminum oxide can be built up. The color value portion difference in staining test increases only mild fo ^g i ^g x _I - _II of x = 8 10. ³ The zincate test time increases to about 77 seconds. This unpredictable improvement in alkali resistance at higher bath temperatures clearly demonstrates the practical utility of the invention.

After coating with the solution described in Example 1, about 170,000 prints of good quality can be produced in the offset process. The copied printing plate shows very little "fog".

Example 4

Rolled aluminum strip is pretreated and anodized according to the instructions in Example 1. The anodic oxidation takes place in an electrolyte of 75 g H ₂ S0 ₄ / ltr. and 20 g A1 ³⁺ / ltr. contains.

At 40 ° C bath temperature and a current density of 9 A / dm ² , approximately 2.5 g / m ^{2 of} aluminum oxide can be applied. The dyeing test gives a difference in color values x _I - x _II of 16. 10 ³ , in the zincate test 32 seconds are reached.

After coating with the solution described in Example 1, about 150,000 prints of good quality can be produced after copying and development.

The "fogging" of the printing plate support is low and the alkali resistance is good.

Example 5 (comparative example)

Aluminum strip sections are alkali pickled and electrochemically roughened with HN0 ₃ in the tank process, similar to that described in DE-AS 12 38 049. The anodic oxidation takes place in a tank with aluminum or graphite as the cathode material. A pump is pumped through a heating and cooling system for circulation and temperature control. At a concentration of 125 g H ₂ SO ₄ / ltr. and a maximum concentration of 7 g Al ³⁺ / ltr. are generated with a current density of 2.5 A / dm ² in 180 sec at 40 ° C about 2.5 to 3 g / m ^{2 of} aluminum oxide.

The dyeing test gives a difference in color values x _I - X _II of 36 - 10 ³ .

The aluminum oxide produced in this way only withstands the attack of the alkaline solution for 20 seconds in the zincate test.

After coating with a solution according to Example 1, the copied printing plate shows a strong formation of fog on the printing plate carrier. I.e. with a higher H ₂ S0 ₄ concentration and a lower A1 ^{3 +} ion concentration than in the process according to the invention, no comparable good aluminum oxide layers can be produced.

Example 6 (comparative example)

Aluminum strip with a thickness of 0.3 mm is alkali pickled, electrochemically roughened and anodized according to the information in Example 1. The anodic oxidation is carried out with an electrolyte of 150 g H ₂ SO _{4 /} ltr. and 5 g Al ³⁺ / ltr. carried out.

At 40 ° C bath temperature and a current density of 12 A / dm ² , about 2.8 g / m ^{2 of} aluminum oxide can be applied in about 30 seconds.

The coloring test gives a difference in the color value fraction x _I - x _II of 27. 10 ³ . In the zincate test, the oxide layer is already penetrated after 22 seconds.

After coating with a solution corresponding to Example 1, a printing plate is obtained which, after being copied, shows a strong fog. Around 140,000 good prints can be produced using the offset process.

If you increase the temperature to 55 ° C and the current density to 16 A / dm ² during anodic oxidation, you can: generate about 3.4 g / m ^{2 of} oxide. The dyeing test experienced an increase in the difference in color values x _I - x _II to 42 10 ³ , while the resistance in the zincate test decreased to 16 seconds. Example 3 shows the progress which can be achieved according to the invention in the dyeing test (ie reduced fog formation) and alkali resistance at an likewise increased temperature and current density.

After the copy, the undercoat which is light-sensitive coated according to Example 1 shows a very strong fog. The print run using the offset process only reaches about 95,000 prints in good quality.

Example 7

Roll-bright aluminum strip with a thickness of 0.3 mm is degreased with an alkaline solution, electrochemically roughened and anodically oxidized, as described in Example 1. The electrolyte in the anodic oxidation contains 50 g H ₂ SO ₄ / ltr. and 20 g Al ³⁺ / ltr. At 40 ° C bath temperature and 10 A / dm ² current density, approx. 3 g / m ² oxide can be built up in 25 seconds.

The surface is prepared for the subsequent sensitization by immersing the aluminum support in a 0.1% aqueous solution of polyvinylphosphonic acid (molecular weight about 100,000) at 60 ° C. for 4 minutes.

The photosensitive coating is carried out using 1.4 parts by weight of mixed condensate from 1 mol of 3-methoxydiphenylamine-4-diazonium sulfate and 1 mole of 4,4'-bis-methoximethyldiphenyiether, prepared in 85% aqueous phosphoric acid and precipitated as mesitylene sulfonate, 0.2 parts by weight of p-toluenesulfonic acid mono-. hydrate, 3 parts by weight of polyvinyl butyral, (containing 69 to 71% polyvinyl butyral, 1% polyvinyl acetate and 24 to 27% polyvinyl alcohol units, the viscosity of a 5% solution in butanol at 20 ° C is 20-30 mPas ), 80 parts by volume of ethylene glycol monomethyl ether and 20 parts by volume of butyl acetate. The diazo mixed condensate layer exposed under a negative is mixed with a mixture of 50 parts by weight of water, 15 parts by weight of isopropanol, 20 parts by weight of n-propanol, 12.5 parts by weight of n-propyl acetate, 1.5 Parts by weight of polyacrylic acid and 1.5 parts by weight of acetic acid developed.

From the printing form thus obtained. produce very good prints. The non-image areas are free of fog. Oxide layers produced according to the invention thus allow the use of methods and chemicals which are usually used to improve the operation of negative layers without restriction.

Example 8

A roughened aluminum strip prepared according to the instructions in Example 1 is made in an electrolyte from 30 g H ₂ SO ₄ / ltr. and 15 g Al ³⁺ / ltr. anodized. At a bath temperature of 55 ° C and a current density of 8 A / dm ² , 2.7 to 3 g / m ^{2 of} aluminum oxide can be built up in 30 seconds. In the dyeing test, there is a difference in color values x _I - x _II of 12. 10 ³ and a zincate test time of about 69 sec.

In addition to a positive working solution, as described in Example 1, a negative working photopolymer solution of the following proportions can also be used for the light-sensitive coating:

The aluminum support provided with this photopolymer layer in an amount of 5 g / m ^{2 also} receives a cover layer of approx. 1 g / m ² , which is produced from the following solution:

After exposure and development, according to that in the. DE-PS 1 193 366 specified way, one obtains a veil-free printing form with high printing performance at the image-free locations.

Example 9

An aluminum strip is pretreated and roughened according to the instructions in Example 1. Anodization is carried out in an electrolyte made from ₁₀₀ g H ₂ SO ₄ / ltr. and 2 ₀ g Al ³ + / ltr. At a bath temperature of 40 ° C. and an anodic current density of 10 A / dm ² , approximately 3 g / m ^{2 of} aluminum oxide can be generated in approximately 30 seconds. This oxide has a difference in color value in the coloring test

A light-sensitive coating is applied with a negative working solution of the following composition:

100 g of finely powdered novolak are slowly sprinkled into a solution of 36 g of NaOH in 500 ml of water at 50 ° C. After the novolak has dissolved, the solution is heated to the boil and 125 g of powdered Na monochloroacetate are added in the course of about 20 minutes, after which boiling is continued for about 1.5 hours. Any turbidity that may occur is brought back into solution by adding as little NaOH as possible. The reaction mixture is then diluted with twice the amount of water at 40 ° C. and then made weakly acidic with hydrochloric acid (1: 2). The deposited resin is filtered, extracted thoroughly with water and dried at 110 ° C. About 100 g of a resin with 10 to 11% carboxyl groups are obtained, corresponding to a degree of esterification of 30 to 34%.

The coated aluminum support is dried and then exposed under a negative film template. A solution of 2 parts by weight of trisodium phosphate and 4 parts by weight of disodium phosphate in 100 parts by volume of water is used for developing the image. After development, the plate is rinsed with water and then wiped with a 1% aqueous phosphoric acid on its image side, then colored with a bold color. The print form obtained is good in its non-image parts, ie free of clay, decoatable and free of fog. It can produce around 55,000 prints in good quality using the offset process.

A carrier prepared according to Example 6, on the other hand, cannot be developed free of clay after a similar coating with this photosensitive composition and exposure, as explained above, i. H. In the non-image areas, the uncured light-sensitive layer with developer can only be imperfectly removed from the support.

Claims (6)

1. A process for the anodic oxidation of strip, sheet or plate-shaped material made of aluminum or its alloys in an aqueous electrolyte containing sulfuric acid and aluminum ions, optionally after previous mechanical, chemical or electrochemical roughening, characterized in that the material in an electrolyte Concentration of sulfuric acid from 25 to 100 g / 1 and of aluminum ions from 10 to 25 g / 1, at a current density of 4 to 25 A / dm ² and at a temperature of 25 ° to 65 ° C is anodized. 2. The method according to claim 1, characterized in that the material in an electrolyte with a concentration of sulfuric acid from 30 to 75 g / 1 and aluminum ions from 15 to 20 g / l, at a current density of 6 to 15 A / dm ² and is anodized at a temperature of 40 ° to 55 ° C. 3. A process for the production of a tape, film or plate-shaped printing plate carrier material by anodic oxidation of aluminum or its alloys in an aqueous electrolyte containing sulfuric acid and aluminum ions, optionally after previous mechanical, chemical or electrochemical roughening, characterized in that the carrier material is anodized in an electrolyte with a concentration of sulfuric acid of 25 to 100 g / 1 and aluminum ions of 10 to 25 g / 1, at a current density of 4 to 25 A / dm ² and at a temperature of 25 ° to 65 ° C . 4. The method according to claim 3, characterized in that the carrier material in an electrolyte of a concentration of sulfuric acid from 30 to 75 g / 1 and aluminum ions from 15 to 20 g / 1, at a current density of 6 to 15 A / dm ² and is anodized at a temperature of 40 ° to 55 ° C. 5. Use of the anodically oxidized material according to the method of claim 1 or 2 as a carrier material in the production of printing plates bearing a photosensitive layer. 6. Use according to claim 5, characterized in that the optionally colored light-sensitive layers contain diazo compounds, diazoquinones, diazo mixed condensates or photopolymerizable compounds.