EP0162283B1 - Process for the electrochemical roughening of aluminium printing plate supports in an aqueous mixed electrolyte - Google Patents

Description

The invention relates to a method for producing printing plate supports made of aluminum or its alloys by electrochemical roughening, which is carried out with alternating current in an aqueous mixed 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 (in the case of precoated 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 also called grain or etching in literature), chemical 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 HCI or HN0 ₃ solutions, in aqueous salt solutions such as aqueous NaCl or Al (NO ₃ ) ₃ solutions or in combinations of these components using alternating current. The roughness depths that can be achieved in this way (given, for example, as mean roughness depths R _z ) of the roughened surface are in the range from about 1 to 15 μm. 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 roughening is therefore carried out in order to improve the adhesion of the reproduction layer on the layer support and the water flow of the printing plate resulting from the printing plate by irradiation (exposure) and development. By irradiation and development (or de-coating in the case of reproduction layers working electrophotographically), the image points which carry color during later printing and the water-bearing non-image points (generally the exposed carrier surface) are produced on the printing plate, as a result of which the actual printing form is created. Various parameters have an influence on the later topography of the aluminum surface to be roughened, which may be exemplified by the following explanations of the prior art:

The essay "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 contains basic explanations made for roughening aluminum in aqueous hydrochloric acid solutions, the following process parameters being varied and the corresponding effects being investigated. The electrolyte composition is changed with repeated use of the electrolyte, for example with regard to the H ⁺ (H ₃ O ⁺ ) ion concentration (measurable via the pH value) and the AI ³⁺ ion concentration, effects on the surface topography being observed. The temperature variation between 16 ° C and 90 ° C shows a changing influence only from around 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 Aldm ² results in higher roughness values with increasing current density. If the acid concentration is in the range 0.17 to 3.3% of HCI, then between 0.5 and 2% of HCI only minor changes occur in the hole structure, below 0.5% of HCI there is only a local attack on the Surface and at the high values an irregular dissolution of AI instead. The addition of S0 ₄ ² ions or CI ions in salt form [e.g. B. by adding Al ₂ (SO ₄ ) ₃ or NaO] can also affect the topography of the roughened aluminum. The rectification of the alternating current shows that both types of half-wave are obviously required for a uniform roughening.

The use of aqueous HCI solutions as an electrolyte solution for the electrochemical roughening of carrier materials made of aluminum must therefore be assumed to be known. As can also be seen in many examples of commercial printing plates, it can thus be used to obtain a uniform grain size which is particularly suitable for the field of application of lithography and is within a roughness range which is generally usable in practice. For certain areas of application of printing plates (e.g. with certain negative working reproduction layers), a uniform and relatively «flat» roughened surface topography is required, which, however, can be found in the previously known electrolyte solutions based on aqueous HCI solutions in modern, high-speed, high-performance systems can only be achieved under difficult conditions; For example - what is always difficult to control in terms of process - the process parameters must be kept within very narrow limits.

• - Die DE-A-2250275 (= GB-A-1400918) nennt als Elektrolytlösung bei der Wechselstrom-Aufrauhung von Aluminium für Druckplattenträger wässrige Lösungen eines Gehalts von 1,0 bis 1,5% an HN0₃ oder von 0,4 bis 0,6% an HCI und gegebenenfalls 0,4 bis 0,6% an H₃P0₄,
• - die DE-B-2327764 (= US-A-3887447) nennt als Elektrolytlösung bei der Wechselstromaufrauhung von Aluminium wässrige Lösungen eines Gehalts von 0,2 bis 2% an HCI und 0,15 bis 1,5% an H₃P0₄,
• - die DE-A-2708669 (= US-A-4052275) nennt als Elektrolytlösung bei der Aufrauhung von Aluminium wässrige Lösungen eines Gehalts von 0,75 bis 3,5% an HCI und 0,2 bis 1% an Weinsäure [2,3-Dihydroxybutandisäure (1,4)],
• - die DE-A-2816307 (= US-A-4172772) nennt als Elektrolytlösung bei der Wechselstromaufrauhung von Aluminium wässrige Lösungen eines Gehalts von 0,2 bis 1,7% an HCI und 0,5 bis 4% an einer Alkansäure von C, bis C₄ (insbesondere Essigsäure - Ethansäure),
• - die DE-A-3127329 (= US-A-4367124) nennt als Elektrolytlösung bei der Aufrauhung von Aluminiumträgermaterialien für Druckplatten wässrige Lösungen eines Gehalts von 0,35 bis 3,5% an HCI und 0,001 bis 2% an einer β-Dicarbonylverbindung wie Acetylaceton oder Acetessigsäureethylester, und
• -die EP-B-0036672 (= US-A-4339315) nennt als Elektrolytlösung bei der Aufrauhung von Aluminiumträgermaterialien für Druckplatten wässrige Lösungen eines Gehalts von 0,1 bis 1,0 Mol/1 an HCI und 0,01 bis 1 Mol/1 an Citronen- oder Äpfelsäure [3-Hydroxy-pentantrisäure (1,3,5) und 2-Hydroxy-butandisäure (1,4)],
• - die DE-B-2218471 (= US-A-3755116) nennt den Zusatz antikorrosiver Mittel -wozu Monoamine, Diamine, aliphatische Aldehyde, Carbonsäureamide wie Acetamid, Harnstoff, Chromsäure und nichtionische Tenside wie Polyethylenglykolether oder -ester gezählt werden - zu einem wässrigen Salzsäureelektrolyten für die Aufrauhung von Aluminium für Druckplattenträger.

The influence of the composition of the electrolyte on the roughening quality is, for example also described in the following publications, in which aqueous mixed electrolytes are used:

• - DE-A-2250275 (= GB-A-1400918) names as an electrolytic solution in the AC roughening of aluminum for printing plate supports aqueous solutions with a content of 1.0 to 1.5% of HN0 ₃ or from 0.4 to 0 , 6% in HCl and optionally 0.4 to 0.6% in H ₃ P0 ₄ ,
• - DE-B-2327764 (= US-A-3887447) mentions aqueous solutions with a content of 0.2 to 2% of HCl and 0.15 to 1.5% of H ₃ P0 ₄ as the electrolyte solution in the AC roughening of aluminum ,
• - DE-A-2708669 (= US-A-4052275) mentions aqueous solutions with a content of 0.75 to 3.5% in HCl and 0.2 to 1% in tartaric acid as electrolyte solution when aluminum is roughened [2, 3-dihydroxybutanedioic acid (1,4)],
• - DE-A-2816307 (= US-A-4172772) mentions aqueous solutions with a content of 0.2 to 1.7% of HCl and 0.5 to 4% of an alkanoic acid of C as electrolyte solution in the AC roughening of aluminum to C ₄ (especially acetic acid - ethanoic acid),
• - DE-A-3127329 (= US-A-4367124) names as an electrolyte solution for the roughening of aluminum support materials for printing plates, aqueous solutions with a content of 0.35 to 3.5% in HCl and 0.001 to 2% in a β-dicarbonyl compound such as acetylacetone or ethyl acetoacetate, and
• EP-B-0036672 (= US-A-4339315) mentions aqueous solutions with a content of 0.1 to 1.0 mol / l of HCl and 0.01 to 1 mol / l as the electrolyte solution for the roughening of aluminum support materials for printing plates. 1 on citric or malic acid [3-hydroxy-pentanetrioic acid (1,3,5) and 2-hydroxy-butanedioic acid (1,4)],
• - DE-B-2218471 (= US-A-3755116) calls the addition of anti-corrosive agents -which includes monoamines, diamines, aliphatic aldehydes, carboxamides such as acetamide, urea, chromic acid and nonionic surfactants such as polyethylene glycol ether or ester - to an aqueous Hydrochloric acid electrolytes for roughening aluminum for printing plate supports.

The previously known organic additives to aqueous acid electrolytes such as HCI or HN0 ₃ solutions have the disadvantage that they become electrochemically unstable and at least partially decompose in modern, continuously operating conveyor systems when there is a high current load (voltage). The known inorganic additives such as phosphoric, chromic or boric acid have the disadvantage that the intended protective effect often breaks down locally and individual, particularly pronounced scars then develop there. For example, the addition of H ₃ P0 ₄ can lead to flat roughened surfaces, which, however, have the disadvantage of many deep individual holes.

The previously known complexing additives generally accelerate the “trapping” of released A13, ions to dissolve the aluminum and thereby increase the roughening attack; however, this often leads to the fact that no additional hole nuclei are created, but that already formed nuclei and holes continue to grow, i.e. then there is increased scarring. The previously known inhibitory additives generally have the effect that the hole growth of individual holes is stopped relatively soon and new hole nuclei can arise; However, they have the decisive disadvantage that this protective effect is caused by imperfections, alloy components and the like. can collapse; this then leads to deep holes in an otherwise flat and evenly roughened surface. Carrier materials with such defects are unsuitable for lithographic purposes.

On the other hand, in the production of capacitors from aluminum or its alloys - in contrast to the production of printing plate supports - deep holes are desired. JP-A-8011364 describes the electrochemical roughening of capacitor foils, in which a mixed electrolyte of hydrochloric acid and tripolyphosphate is used. As the examples show, a specially pretreated aluminum is treated in an electrolyte solution which, in addition to the component mentioned, also contains other constituents, such as phosphoric acid, nitric acid, sulfuric acid and oxalic acid, which achieves the properties desired for a capacitor.

The object of the present invention is therefore to propose a method for the electrochemical roughening of aluminum for printing plate supports, which makes it possible to achieve a uniformly roughened surface topography with a wide range in the mean roughness depth values and to achieve long bath service lives.

The invention is based on the known method for producing printing plate supports from aluminum or its alloys by electrochemical roughening in an aqueous mixed electrolyte solution containing HCl and at least one other inorganic electrolyte under the action of alternating current. The process according to the invention is then characterized in that the mixed electrolyte consists only of HCl and a compound from the group of condensed phosphoric acids and amidosulfonic acid and their water-soluble alkali metal or ammonium salts as further electrolytes. In a preferred embodiment, the aqueous electrolyte solution consists of 0.5 to 10.0%, in particular 0.8 to 5.0%, of HCl and 0.05 to 5.0%, in particular 0.1 to 2.0% the further electrolyte.

The condensed phosphoric acids include in particular diphosphoric acid (H ₄ P ₂ O ₁ ) and various polyphosphoric acids (H, ₊₂ Pn0 _{3n + i} with, for example, n = 3 or 6 or H _n P _n 0 _3n with, for example, n = 6) and the Salts sodium salts of these acids such as sodium pyrophosphate (Na ₄ P ₂ 0 ₇ ), sodium tripolyphosphate (Na ₅ P ₃ 0 ₁₀ ), Sodium hexametaphosphate (Na ₆ P ₆ 0 ₁₈ ) and sodium hexapolyphosphate (Na8Pr, 019).

Suitable base materials for the material to be roughened 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 can also be roughened mechanically (e.g. by brushing and / or with abrasive treatments) before the electrochemical stage, if necessary after pre-cleaning. All process steps can be carried out discontinuously with plates or foils, but they are preferably carried out continuously with tapes.

In general, the process parameters, particularly in the case of continuous process control, in the electrochemical roughening stage lie in the following ranges: the temperature of the electrolyte between 20 and 60 ° C., the current density between 3 and 200 A / dm ² , the residence time of a material point to be roughened in the electrolyte between 1 and 300 sec and the electrolyte flow rate on the surface of the material to be roughened between 5 and 100 cm / sec; in the batchwise process, 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. Normally, alternating current with a frequency of 50 to 60 Hz is used as the type of current, but modified types of current such as alternating current with different amplitudes of the current strength for the anode and cathode current, lower frequencies, current interruptions or superimposition of two currents of different frequency and waveform are also possible. The average roughness depth R _{z of} the roughened surface is in the range from 1 to 15 _l , in particular from 1.5 to 8.0 μm. In addition to HCI and at least one of the other inorganic electrolytes, aluminum ions in the form of aluminum salts, in particular 0.5 to 5.0% of AICI _3, can also be added to the aqueous electrolyte.

Pre-cleaning includes, for example, treatment with aqueous NaOH solution with or without degreasing agents 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); In general, 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. In addition to an abrasive treatment stage between the roughening stage and a subsequent anodizing stage, such non-electrochemical treatments are also known which essentially have only a rinsing and / or cleaning effect and, for example, for removing deposits formed during roughening ("Schmant") or simply for Serve removal of electrolyte residues; For example, dilute aqueous alkali hydroxide solutions or water are used for these purposes.

According to the electromechanical roughening process according to the invention, an anodic oxidation of the aluminum can then preferably 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. The usual electrolytes such as H ₂ S0 ₄ , H ₃ P0 ₄ , H ₂ C ₂ 0 ₄ , amidosulfonic acid, sulfosuccinic acid, sulfosalicylic acid or mixtures thereof can be used for anodic oxidation; in particular, H ₂ S0 ₄ and H ₃ P0 _{4 are used} alone, in a mixture and / or in a multi-stage anodizing process.

The stage of anodic oxidation of the aluminum support material can also be followed by one or more post-treatment stages. Aftertreatment means 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-1621478 (= GB-A-1230447), an immersion treatment in an aqueous alkali silicate solution according to DE-B-1471707 (= US-A-3181461) or an electrochemical treatment (anodization) in an aqueous alkali silicate solution according to DE-A-2532769 (= US-A-3902976). These post-treatment stages serve in particular to additionally increase the hydrophilicity of the aluminum oxide layer, which is often sufficient, while at least the other known properties of this layer are retained.

The materials produced according to the invention are used as supports for offset printing plates, i.e. a radiation-sensitive coating is applied to one or both sides of the carrier material either by the manufacturer of presensitized printing plates or directly by the consumer. In principle, all layers are suitable as radiation (light) sensitive layers which, after irradiation (exposure), possibly with subsequent development and / or fixation, provide an imagewise surface from which printing can take place.

In addition to the layers containing silver halides used in many fields, various others are also known, such as e.g. B. in “Light-Sensitive Systems” by Jaromir Kosar, John Wiley & Sons Verlag, New York 1965: The colloid layers containing chromates and dichromates (Kosar, Chapter 2); the layers containing unsaturated compounds in which these compounds are isomerized, rearranged, cyclized or when exposed be networked (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-diazoquinones such as naphthoquinone diazides, p-diazoquinones or diazonium salt condensates (Kosar, Chapter 7). The suitable layers also include the electrophotographic layers, ie those containing one anor ^g ani- or organic photoconductor. In addition to the light-sensitive substances, these layers can of course also other components, such as. B. resins, dyes or plasticizers.

• Positiv-arbeitende, o-Chinondiazide, insbesondere o-Naphthochinondiazide wie Naphthochinon-(1,2-diazid-(2)-sulfonsäureester oder -amide, die nieder- oder höhermolekular sein können, als lichtempfindliche Verbindung enthaltende Reproduktionsschichten, die beispielsweise in den DE-C-854890, 865109, 879203, 894959, 938233, 1109521, 1144705, 1118606, 1120273, 1124817 und 2331377 und den EP-A-0021428 und 0055814 beschrieben werden;
• negativ-arbeitende Reproduktionsschichten mit Kondensationsprodukten aus aromatischen Diazoniumsalzen und Verbindungen mit aktiven Carbonylgruppen, bevorzugt Kondensationsprodukte aus Diphenylamindiazoniumsalzen und Formaldehyd, die beispielsweise in den DE-C-596731, 1138399, 1138400, 1138401, 1142871, 1154123, den US-A-2679498 und 3050502 und der GB-A-712606 beschrieben werden;
• negativ-arbeitende, Mischkondensationsprodukte aromatischer Diazoniumverbindungen enthaltende Reproduktionsschichten, beispielsweise nach der DE-C-2065732, die Produkte mit mindestens je einer Einheit aus a) einer kondensationsfähigen aromatischen Diazoniumsalzverbindung und b) einer kondensationsfähigen Verbindung wie einem Phenolether oder einem aromatischen Thioether, verbunden durch ein zweibindiges, von einer kondensationsfähigen Carbonylverbindung abgeleitetes Zwischenglied wie einer Methylengruppe aufweisen;
• positiv-arbeitende Schichten nach der DE-A-2610842, der DE-C-2718254 oder der DE-A-2928636, die eine bei Bestrahlung Säure abspaltende Verbindung, eine monomere oder polymere Verbindung, die mindestens eine durch Säure abspaltbare C-O-C-Gruppe aufweist (z. B. eine Orthocarbonsäureestergruppe oder eine Carbonsäureamidacetalgruppe) und gegebenenfalls ein Bindemittel enthalten;
• negativ-arbeitende Schichten aus photopolymerisierbaren Monomeren, Photoinitiatoren, Bindemitteln und gegebenenfalls weiteren Zusätzen; als Monomere werden dabei beispielsweise Acryl-und Methacrylsäureester oder Umsetzungsprodukte von Diisocyanaten mit Partiaiestern mehrwertiger Alkohole eingesetzt, wie es beispielsweise in den US-A-2760863 und 3060023 und den DE-A-2064079 und 2361041 beschrieben wird;
• negativ-arbeitende Schichten gemäss der DE-A-3036077, die als lichtempfindliche Verbindung ein Diazoniumsalz-Polykondensationsprodukt oder eine organische Azidoverbindung und als Bindemittel ein hochmolekulares Polymeres mit seitenständigen Alkenylsulfonyl- oder Cycloalkenylsulfonylurethan-Gruppen enthalten.

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-quinonediazides, in particular o-naphthoquinonediazides such as naphthoquinone- (1,2-diazide- (2) -sulfonic acid esters or amides, which can be of low or higher molecular weight, as reproduction photosensitive compound-containing, for example in DE -C-854890, 865109, 879203, 894959, 938233, 1109521, 1144705, 1118606, 1120273, 1124817 and 2331377 and EP-A-0021428 and 0055814;
• negative working reproduction layers with 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-596731, 1138399, 1138400, 1138401, 1142871, 1154123, US-A-265024949 and 3050 and GB-A-712606;
• Reproduction layers containing negative-working, mixed condensation products of aromatic diazonium compounds, for example according to DE-C-2065732, the products with at least one unit each of a) a condensable aromatic diazonium salt compound and b) a condensable compound such as a phenol ether or an aromatic thioether, connected by a have divalent linkage derived from a condensable carbonyl compound such as a methylene group;
• positive-working layers according to DE-A-2610842, DE-C-2718254 or DE-A-2928636, which contain a compound which cleaves off on irradiation, a monomeric or polymeric compound which has at least one COC group which can be cleaved off by acid (e.g. an orthocarboxylic acid ester group or a carboxylic acid amide acetal group) and optionally contain a binder;
• negatively working layers made of photopolymerizable monomers, photoinitiators, binders and optionally other additives; the monomers used are, for example, acrylic and methacrylic acid esters or reaction products of diisocyanates with part esters of polyhydric alcohols, as described, for example, in US Pat. Nos. 2760863 and 3060023 and DE-A-2064079 and 2361041;
• Negative-working layers according to DE-A-3036077, which contain a diazonium salt polycondensation product or an organic azido compound as the photosensitive compound and a high molecular weight polymer with pendant alkenylsulfonyl or cycloalkenylsulfonylurethane groups as the binder.

It is also possible to use photo-semiconducting layers such as e.g. in DE-C-1117391, 1522497, 1572312, 2322046 and 2322047 are described, are applied to the carrier materials produced according to the invention, thereby producing highly light-sensitive, electrophotographic printing plates.

The coated offset printing plates obtained from the carrier materials produced by the process according to the invention are converted into the desired printing form in a known manner by imagewise exposure or irradiation and washing out of the non-image areas with a developer, for example an aqueous alkaline developer solution.

• - Die Verfahrensprodukte weisen eine gleichmässige Oberflächentopographie auf, eine Eigenschaft, die sowohl die Stabilität der Druckauflage von aus diesen Trägermaterialien hergestellten Druckformen als auch die Wasserführung beim Drucken positiv beeinflusst.
• - Es treten - verglichen mit reinen Salzsäureelektrolyten -weniger häufig «Narben» (= mit der Umgebungsaufrauhung verglichen markante Vertiefungen) auf, diese können sogar vollständig unterdrückt sein. _ _ _
• - Gegenüber dem Einsatz von H₃P0₄ (siehe auch Vergleichsversuche weiter unten) werden gleichmässigere und flach aufgerauhte Oberflächenstrukturen erhalten, die weitgehend oder vollständig frei von einzelnen Narben (Löchern) sind.
• - Zur Erzielung der genannten Oberflächeneigenschaften ist kein grosser apparativer Aufwand erforderlich, und diese Eigenschaften sind über einen grossen Bereich der Rauhstufe zu realisieren.
• - Das Verfahren ermöglicht auch die Bildung von besonders flach und gleichmässig aufgerauhten Oberflächen, eine Eigenschaftskombination, die mit den bekannten Elektrolyten nicht in diesem Umfang zu erzielen ist.
• - Der Mischelektrolyt im erfindungsgemässen Verfahren ist elektrochemisch stabil, d. h. es findet auch bei höherer Strombelastung (Spannung) praktisch keine Zersetzung statt.

The method according to the invention combines the following advantages:

• - The process products have a uniform surface topography, a property that positively influences both the stability of the print run of printing forms made from these carrier materials and the water flow during printing.
• - Compared to pure hydrochloric acid electrolytes, there are fewer “scars” (= noticeable depressions compared to the roughening of the surroundings), and these can even be completely suppressed. _ _ _
• - Compared to the use of H ₃ P0 ₄ (see also comparison tests below), more uniform and shallow roughened surface structures are obtained that are largely or completely free of individual scars (holes).
• - To achieve the surface properties mentioned, no great expenditure on equipment is required, and these properties can be achieved over a large range of the roughness level.
• - The process also enables the formation of particularly flat and uniformly roughened surfaces, a combination of properties that cannot be achieved to this extent with the known electrolytes.
• - The mixed electrolyte in the process according to the invention is electrochemically stable, ie there is practically no decomposition even with a higher current load (voltage).

In the above description and the examples below,% data always mean% by weight, unless stated otherwise, parts by weight are in relation to parts by volume in the ratio of g to _cm ³ . Examples 1 to 25 and comparative examples V1 to V16

An aluminum sheet is first pickled for 60 seconds in an aqueous solution of 20 g NaOH per at room temperature and then freed from any alkali residues by briefly immersing it in a solution corresponding to the roughening electrolyte. The roughening takes place in the electrolyte systems shown in the following tables and under the conditions listed there. After roughening, an anodic oxidation is carried out in an aqueous electrolyte containing H ₂ S0 ₄ and Al ³⁺ ions up to a layer weight of 3.0 g / m ² .

The classification into the quality classes (surface topography) takes place by visual assessment under the microscope, whereby the quality level "1" (best value) is assigned to a homogeneously roughened and scar-free surface. Quality level "10" (worst value) is assigned to a surface with thick scars of a size of more than 100 µm or an extremely unevenly roughened or almost rolled surface. Intermediate qualities are rated "2" to "9". All examples and the comparative examples are carried out with symmetrical alternating current at a frequency of 50 Hz, one electrode being the aluminum sheet and the other a graphite plate.

Example 26

• 0,70 Gew.-Teile des Polykondensationsproduktes aus 1 Mol 3-Methoxy-diphenylamin-4-diazo- niumsulfat und 1 Mol 4,4'-Bis-methoxymethyl-diphenylether, ausgefällt als Mesitylensulfonat,
• 3,40 Gew.-Teile 85%ige wässrige H₃P0₄,
• 3,00 Gew.-Teile eines modifizierten Epoxidharzes, erhalten durch Umsetzen von 50 Gew.-Teilen eines Epoxidharzes mit einem Molgewicht unterhalb 1000 und 12,8 Gew.-Teilen Benzoesäure in Ethylenglykolmonomethylether in Gegenwart von Benzyltrimethylammoniumhydroxid,
• 0,44 Gew.-Teile feingemahlenes Heliogenblau G (C.I. 74100),
  • 62,00 Vol.-Teile Ethylenglykolmonomethylether,
  • 30,60 Vol.-Teile Tetrahydrofuran, und
  • 8,00 Vol.-Teile Essigsäurebutylester.

An aluminum sheet prepared according to Example 2 is immersed at 40 ° C. for 30 seconds in an aqueous solution containing 5 g / l of polyvinylphosphonic acid and then rinsed with deionized water and dried. To produce a lithographic printing plate, the sheet is coated with the following negative working light-sensitive solution:

• 0.70 parts by weight of the polycondensation product from 1 mol of 3-methoxy-diphenylamine-4-diazo-niumsulfate and 1 mol of 4,4'-bis-methoxymethyl-diphenyl ether, precipitated as mesitylene sulfonate,
• 3.40 parts by weight of 85% aqueous H ₃ P0 ₄ ,
• 3.00 parts by weight of a modified epoxy resin obtained by reacting 50 parts by weight of an epoxy resin with a molecular weight below 1000 and 12.8 parts by weight of benzoic acid in ethylene glycol monomethyl ether in the presence of benzyltrimethylammonium hydroxide,
• 0.44 part by weight of finely ground heliogen blue G (CI 74100),
  • 62.00 parts by volume of ethylene glycol monomethyl ether,
  • 30.60 parts by volume of tetrahydrofuran, and
  • 8.00 parts by volume of butyl acetate.

After image-wise exposure and rapid and fog-free development with an aqueous solution containing Na ₂ S0 ₄ , MgS0 ₄ , H ₃ P0 ₄ , a nonionic surfactant, benzyl alcohol and n-propanol, a very good color is obtained when printing with the printing form. Water balance and excellent layer adhesion found. The circulation is 200,000.

Example 27

• 6,60 Gew.-Teile Kresol-Formaldehyd-Novolak (mit dem Erweichungsbereich 105 bis 120 °C nach DIN 53181)
• 1,10 Gew.-Teile des 4-(2-Phenyl-prop-2-yl)-phe- nylesters der Naphthochinon-(1,2)-diazid-(2)-sulfonsäure-(4),
• 0,60 Gew.-Teile 2,2'-Bis-[naphthochinon-(1,2)-diazid-(2)sulfonyloxy-(5)]-dinaphthyl-(1,1')-methan,
• 0,24 Gew.-Teile Naphthochinon-(1,2)-diazid-(2)-sulfonsäurechlorid-(4),
• 0,08 Gew.-Teile Kristallviolett,
• 91,36 Gew.-Teile Gemisch aus 4 Vol.-Teilen Ethylenglykolmonomethylether, 5 Vol.-Teilen Tetrahydrofuran und 1 Vol.-Teil Essigsäurebutylester.

The following positive-working light-sensitive solution is applied to an aluminum foil produced according to Example 15 and after-treated according to Example 26:

• 6.60 parts by weight of cresol-formaldehyde novolak (with a softening range of 105 to 120 ° C according to DIN 53181)
• 1.10 parts by weight of the 4- (2-phenyl-prop-2-yl) phenyl ester of naphthoquinone (1,2) diazide (2) sulfonic acid (4),
• 0.60 parts by weight of 2,2'-bis- [naphthoquinone- (1,2) -diazide- (2) sulfonyloxy- (5)] -dinaphthyl- (1,1 ') - methane,
• 0.24 part by weight of naphthoquinone- (1,2) -diazide- (2) -sulfonic acid chloride- (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.

After the imagewise exposure and development in an aqueous solution containing Na ₂ Si0 ₃ , Na ₃ P0 ₄ and NaH ₂ P0 ₄ , a printing form produced from this plate prints an edition of 160,000.

Example 28

• 10,00 Gew.-Teile 2-Vinyl-5-(4'-diethylaminophenyl)-4-(2'-chlorphenyl)-oxazol
• 10,00 Gew.-Teile eines Mischpolymerisats aus Styrol und Maleinsäureanhydrid mit einem Erweichungspunkt von 210 °C
• 0,02 Gew.-Teile ^@Rhodamin FB
• 300,00 Gew.-Teile Ethylenglycolmonomethylether

A carrier material produced according to Example 23 is coated with the following solution in order to produce an electrophotographic offset printing plate:

• 10.00 parts by weight of 2-vinyl-5- (4'-diethylaminophenyl) -4- (2'-chlorophenyl) oxazole
• 10.00 parts by weight of a copolymer of styrene and maleic anhydride with a softening point of 210 ° C.
• 0.02 part by weight ^@ Rhodamine FB
• 300.00 parts by weight of ethylene glycol monomethyl ether

The layer is negatively charged to about 400 V in the dark by means of a corona. The charged plate is exposed imagewise in a repro camera and then with an electrophotographic suspension developer, which by dispersing 3.0 parts by weight of magnesium sulfate in a solution of 7.5 parts by weight of pentaerythritol resin in 1200 parts by volume of an isoparaffin mixture with a Boiling range of 185 to 210 ° C was obtained. After removing the excess developer liquid, the developer is fixed and the plate in a solution of 35 parts by weight of sodium metasilicate for 60 seconds. 9 H ₂ 0, 140 parts by weight of glycerol, 550 parts by weight of ethylene glycol and 140 parts by weight of ethanol immersed. The plate is then rinsed off with a powerful jet of water, removing the areas of the photoconductor layer not covered with toner. The printing form is then ready for printing.

Claims (5)

1. Process for the production of printing plate supports from aluminium or-itsattoys, by means of electrochemical roughening in an aqueous mixed electrolyte solution containing HCI and at least one additional inorganic electrolyte, under the action of alternating current, wherein the mixed electrolyte only comprises HCI and a compound selected from the group including condensed phosphoric acids, amidosulfonic acid, and the water-soluble alkali metal salts or ammonium salts thereof, as the additional electrolyte.

2. A process as claimed in claim 1, wherein the mixed electrolyte contains from 0.5 to 10% by weight of HCI and from 0.05 to 5.0% by weight of the additional electrolyte.

3. A process as claimed in claim 1 or claim 2, wherein the mixed electrolyte contains from 0.8 to 5.0% by weight of HCI and from 0.1 to 2.0% by weight of the additional electrolyte.

4. A process as claimed in any of claims 1 to 3, wherein the condensed phosphoric acid comprises diphosphoric acid or a polyphosphoric acid.

5. Use of the process as claimed in any of claims 1 to 4 in the production of an offset-printing plate carrying a radiation-sensitive layer.