EP0318820A2 - Process for anodising surfaces of aluminium or aluminium alloys - Google Patents

Abstract

Process for anodising the surface of plates, foils or strips made of aluminium or aluminium alloys in an aqueous electrolyte which contains one or more acids and also, optionally, one or more additives and which contains, as additive or as one of the additives or as acid or as one of the acids, a silane or a plurality of silanes of the general formula I <IMAGE> where the indices and the variables have the following meaning: y is an integer from 1 to 4; n is 0, 1 and 2 independently of y; R<1> and R<2> are C1-C9-alkyl and C6-C12-aryl, R<1> and R<2> being identical to, or different from, each other; and X is the radicals X<1> to X<1><1>, <IMAGE> where the variables have the following meaning: R<3> is a hydrogen atom, C1-C9-alkyl, an alkane-carboxylic anhydride ring formed from the alkanecarboxylic acid radical containing 1 to 9 carbons atoms and a carboxylic acid group linked to R3 <IMAGE> R<4> and R<5> are the radical R<1>; R<6> is a hydrogen atom and the radical R<1>; Z is a hydrogen atom and an alkali metal cation; Ar is C6-C12-arylene; and Hal is a chlorine and bromime atom; the silanes of the general formula I (= silanes I) being dissolved in the electrolyte solution in hydrolysed and/or condensed form. Also the use of the plates, foils or strips made of aluminium or aluminium alloy anodised by this process for producing bases for photosensitive lithographic printing plates or offset printing plates.

Description

The invention relates to a new process for the anodic oxidation of the surface of plates, foils or strips made of aluminum or aluminum alloys in an aqueous electrolyte containing one or more acids and one or more additives. The invention also relates to the use of the process products obtained with the aid of the new process for the production of photosensitive lithographic printing plates or offset printing plates.

Parts made of aluminum or aluminum alloys are used in various forms in a wide variety of technical fields due to their advantageous property profile. For example, they are used for architectural purposes, are used for the construction of light engines or serve in the form of plates, foils or tapes as supports for printing plates, in particular lithographic printing plates, which are also generally referred to as offset printing plates.

Prerequisite for that parts made of aluminum or aluminum alloys despite the strongly negative normal potential e₀ of the Al ^3⊕ cation of -1.66 V (see KH Näser, Physico-chemical calculation tasks, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1970, 4th Edition, page 370) can be used for all of these applications and can develop their advantages there, is the permanent so-called passivation of their surface by a surface layer essentially made of aluminum oxides.

This surface layer mainly defines the application properties and thus the usability of the molded parts made of aluminum or aluminum alloys. The most important properties that this surface layer must have include, for example, high corrosion resistance, good appearance, precisely adjustable density, high hardness, good wear resistance, high absorption capacity and adhesion for paints, synthetic resins and light-sensitive mixtures, good colorability , high gloss or good hydrophilicity. In the case of plates, foils or strips made of aluminum or aluminum alloys, which are used as supports for photosensitive lithographic printing plates or offset printing plates, particularly high demands are placed on density, hardness, and wear strength, absorption capacity and adhesion for light-sensitive mixtures of all kinds, the hydrophilicity and, moreover, the toughness and breaking strength, the layer structure, the chemical and physical stability and the color management properties.

As is known, these surface layers essentially composed of aluminum oxides are produced by the anodic oxidation of molded parts made of aluminum or aluminum alloys in an aqueous electrolyte containing sulfuric acid or phosphoric acid. The quality of the surface layers produced in this way depends above all on the preselection of the process parameters such as the duration of the electrolysis, electrolysis voltage, current density, electrolyte temperature and acid concentration. With a skilful choice of parameters, usable surface layers can be produced. However, these do not fully meet the high demands that are placed in practice on the surface layers of the plates, foils or tapes used for printing purposes.

It has therefore been a long time since the aqueous electrolytes other than sulfuric and / or phosphoric acid and other acids from the group of inorganic mineral acids, the low molecular weight, mono- and polyfunctional organic carboxylic, sulfonic and phosphonic acids as well as the oligomeric and high molecular weight, add polyfunctional carboxylic, sulfonic and phosphonic acids. In addition, numerous additives from the group of inorganic and organic salts and of low molecular weight, oligomeric and high molecular weight, non-acidic organic compounds have been admixed with the aqueous electrolytes in molecularly dispersed or colloidal solution. Instead of a longer list, reference is made here to EP-B-0 048 909 and EP-B-0 050 216 in which the relevant prior art is dealt with extensively.

All these material variations of the electrolyte composition ultimately aimed to gain additional degrees of freedom in the choice of the process parameters of the anodic oxidation and to change the chemical composition, the structure and the physical properties of the surface layers essentially consisting of aluminum oxides so that they differ from the one in question Required property profile.

However, this goal has not yet been achieved to the full satisfaction of practice in the case of plates, foils or tapes which are used as supports for photosensitive lithographic printing plates or offset printing plates, as can be seen from the large number of ver drive to rework the surface layers produced with the aid of known methods of anodic oxidation, which essentially consist of aluminum oxides. Here too, reference is made to EP-P-0 048 909 and EP-B-0 050 216, in which such methods are dealt with for improvement.

There is therefore still a great need for a process for the anodic oxidation of plates, foils or strips made of aluminum or aluminum alloys, which is simple to carry out, does not require any changes in existing systems and apparatus and therefore does not require new investments, and which support for photosensitive lithographic printing plates or offset printing plates that also meet the highest requirements in practice.

This goal has been partly achieved with the aid of the anodic oxidation process described in EP-B-048 909, but it has not been entirely achieved. In the process described there, oligomeric or high molecular weight, polyfunctional acids are added to the aqueous electrolyte, of which polyvinylphosphonic acid has become particularly important. This known method can be used to produce anodized plates, foils or tapes from aluminum or aluminum alloys which, when used as supports for photosensitive lithographic printing plates or offset printing plates, have certain advantages with regard to the adhesiveness of the photosensitive recording layers to the support, the corrosion resistance and the shelf life . The lithographic printing plates or offset printing plates produced from these photosensitive lithographic printing plates or offset printing plates, imagewise exposed to actinic light and washed out with developer solvents also offer certain advantages with regard to the hydrophilicity of their carrier surface and with regard to the high number of good printed products.

Nevertheless, the known method still has disadvantages. Thus, the polyvinylphosphonic acid which is particularly preferably used in the context of this process frequently leads to the deposition of poorly soluble polyvinylphosphonic acid-aluminum complexes on the surfaces to be anodized in the course of the electrolysis, which leads to disturbances in the layer structure. Ultimately, this results in sensitive wetting disturbances in the lithographic printing plates or offset printing plates which have been imagewise exposed to actinic light and washed out with developer solvents, which leads to poor color guidance or even breakouts in the printing areas of the printing plates during printing, as a result of which both the quality of the printed products and whose circulation will be reduced. Furthermore show the plates, foils or strips made of aluminum or aluminum alloys anodically oxidized by the known process during storage in their surface layers essentially made of aluminum oxides, which lead to reduced hydrophilicity. This reduced hydrophilicity then manifests itself in particular in the significantly poorer washability of the lithographic printing plates or offset printing plates exposed imagewise with actinic light and ultimately again in their moderate printing behavior and in the quality and circulation of the printed products.

The pressure to further develop the already known methods for the anodic oxidation of plates, foils or strips made of aluminum or aluminum alloys has in no way decreased. On the contrary, it has increased due to the higher demands in practice.

The object of the present invention is to propose a new process for the anodic oxidation of plates, foils or strips made of aluminum or aluminum alloys, which no longer has the disadvantages of the prior art both with regard to its implementation and with regard to its process products and their secondary products.

worin die Indices und die Variablen die folgende Bedeutung haben:

R³      Wasserstoffatom, C₁- bis C₉-Alkyl, Alkancarbonsäurerest mit 1 bis 9 Kohlenstoffatomen und Carbonsäureanhydridring, gebildet aus dem Alkancarbonsäurerest mit 1 bis 9 Kohlenstoffatomen und der mit R³ verknüpften Methylencarbonsäuregruppe

R⁴ u. R⁵      Rest R¹;
R⁶      Wasserstoffatom und Rest R¹;
Z      Wasserstoffatom und Alkalimetallkation;
Ar      C₆- bis C₁₂-Arylen; und
Hal      Chlor- und Bromatom;

wobei die Silane der allgemeinen Formel I (= Silane I) in der Elektrolyt­lösung in hydrolysierter und/oder kondensierter Form gelöst vorliegen.Accordingly, a process for the anodic oxidation of plates, foils or strips made of aluminum or aluminum alloys has been found, in which the anodic oxidation is carried out in an aqueous electrolyte containing one or more acids and optionally one or more additives, and which is characterized in that one uses one or more silanes of the general formula I as an additive or as one of the additives or as an acid or as one of the acids,

X- (CH₂) _y -Si (R¹) _n (OR²) _3-n I,

where the indices and the variables have the following meaning:

y is an integer from 1 to 4;
n independently of y 0, 1 and 2;
R¹ u. R² is C₁ to C₉ alkyl and C₆ to C₁₂ aryl, where R¹ and R² are the same or different; and
X residues X¹ to X¹¹

where the indices and the variables have the following meaning:

R³ is hydrogen atom, C₁ to C₉ alkyl, alkane carboxylic acid residue having 1 to 9 carbon atoms and carboxylic acid anhydride ring formed from the alkane carboxylic acid residue having 1 to 9 carbon atoms and the methylene carboxylic acid group linked to R³

R⁴ u. R⁵ radical R¹;
R⁶ is hydrogen and R¹;
Z hydrogen atom and alkali metal cation;
Ar C₆ to C₁₂ arylene; and
Hal chlorine and bromine;

wherein the silanes of the general formula I (= silanes I) are present in the electrolyte solution in hydrolyzed and / or condensed form.

The process according to the invention for the anodic oxidation of plates, foils or strips made of aluminum or aluminum alloys is referred to below as the "process according to the invention".

What is essential for the process according to the invention is the new aqueous electrolyte to be used, which contains the silanes of the general formula I (= silanes I).

Examples of suitable radicals R 1 and R 2 in the silanes I to be used according to the invention are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl, Heptyl, octyl, iso-octyl, nonyl, phenyl, benzyl, o-, m- and p-tolyl, 2,4-dimethylphen-1-yl, 3,5-dimethylphen-1-yl, naphth-1-yl and Naphth-2-yl. Here, the radicals R¹ and R² in the silanes I used in each case are the same or different from one another.

Suitable radicals X in the silanes I to be used according to the invention are the radicals X 1 to X 11.

gebildet wird, wie etwa 2,4-Dioxo-oxetan-3-yl, 2,5-Dioxo-oxalan-3-yl oder 2,6-Dioxo-oxan-3-yl.Examples of suitable radicals X 1 are those in which Z represents a hydrogen atom or a lithium, sodium or potassium cation and R 3 is one of the alkyl radicals R 1 mentioned above, a carboxyl group, a methane carboxylic acid, ethan-1-yl-2-carboxylic acid, Propan-1-yl-3-carboxylic acid, n-butan-1-yl-2-, -3- or -4-carboxylic acid, n-pentan-1-yl-2-, -3-, -4- or - 5-carboxylic acid, n-hexan-1-yl-6-carboxylic acid, n-heptan-1-yl-7-carboxylic acid, n-octan-1-yl-8-carboxylic acid or an n-nonan-1 -yl-9-carboxylic acid residue or a carboxylic acid anhydride ring, which consists of one of the abovementioned alkane carboxylic acid residues with 1 to 9 carbon atoms and the methylene carboxylic acid group associated therewith

is formed, such as 2,4-dioxo-oxetan-3-yl, 2,5-dioxo-oxalan-3-yl or 2,6-dioxo-oxan-3-yl.

Examples of suitable radicals X² are those in which R⁴ represents one of the radicals R¹ mentioned above.

Examples of suitable radicals X³ are those in which Z has the meaning given above and R⁵ represents one of the radicals R¹ mentioned above.

Another suitable radical X is the maleic anhydride radical X⁵.

Examples of suitable radicals X⁶ are those in which R⁶ represents a hydrogen atom or one of the radicals R¹ mentioned above.

The suitable radicals X⁷ are the dichloro, dibromo and chlorobromophosphonyl groups.

The suitable radicals X⁸ are the sulfonic acid group and the lithium, sodium and potassium sulfonate groups.

The suitable radicals X⁹ are the sulfochloride and sulfobromide groups.

Examples of suitable radicals X¹⁰ are phen-1-yl-2-, -3- and -4-sulfonic acid, 2-methyl-phen-1-yl-3-, -4-, -5- and -6-sulfonic acid, 4 -Methyl-phen-1-yl-2- and -3-sulfonic acid, benzyl-2-, -3- and -4-sulfonic acid, naphth-1-yl-2-, -3-, -4-, -5 -, -6-, -7- and -8-sulfonic acid, naphth-2-yl-1-, -3-, -4-, -5-, -6-, -7- and -8-sulfonic acid and the Lithium, sodium and potassium salts of these sulfonic acids.

Examples of suitable radicals X¹¹ are the chlorides and bromides of the aforementioned sulfonic acids X¹⁰.

In the silanes I to be used according to the invention, y stands for an integer from 1 to 4, and n stands independently of y for 0, 1 or 2.

Examples of silanes I which are used with particular advantage in the process according to the invention are (2-tripropoxisilylethyl) carboxylic acid, (3-trimethoxisilylpropyl) carboxylic acid, (4-trimethoxisilylbutyl) carboxylic acid and its methyl, ethyl, propyl and butyl ester, (3-triethoxisilylpropyl) succinic anhydride, (3-triethoxisilylpropyl) maleic anhydride, (2-trimethoxisilylethyl) phosphonic acid, (2-trimethoxisilylethyl) phosphonic acid dimethyl diethyl (3) diethyl phosphonic acid, (2-trimethoxisilylmethyl) phosphonic acid dichloride, (3-trimethoxisilylpropyl) phosphonic acid dichloride, (3-trimethoxisilylpropyl) phosphonic acid, 2- (4-chlorosulfonylphenyl) ethyltrimethoxisilane, 2- (4-sulfonylethoxyl) siloxyloxyloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxyliloxylsiloxylsiloxylsiloxylsiloxylsiloxylsiloxyl -Trimethoxisilylpropyl) sulfonic acid.

The silanes I are well-known compounds which are synthesized in a simple manner from commercially available compounds using the customary and known methods of silicon chemistry. For this purpose, silicon halides and the corresponding organic compounds are used, for example, which contain the desired radicals - (CH₂) _y -X, R¹ and R² of the silanes I or the precursors of these radicals.

The hydrolysis of the silanes I takes place when the silanes I are dissolved in the aqueous electrolyte. As is known, this sets in motion the condensation of the silanes I, which takes place with the elimination of alcohol. Depending on the silane I used, the condensation reaction proceeds more or less completely and therefore leads to mixtures of hydrolyzed, condensed silanes I of different molecular weights, i.e. different degrees of condensation. In the hydrolysis of silanes I, the corresponding free acid groups are of course formed from the ester, anhydride or acid halide groups. The degree of reaction, i.e. the degree of hydrolysis, depending on the particular silane I used. Accordingly, with a given silane I, the degree of hydrolysis can be low, but the degree of condensation can be high. The reverse can also occur, i.e. the degree of hydrolysis is high, whereas the degree of condensation is low. Or both reactions, both hydrolysis and condensation, are to a high degree, i.e. almost complete or almost complete, expired.

In addition, the hydrolysis and condensation of the silanes I takes place by dissolving the silanes I in water or aqueous alcoholic solutions before adding these solutions to the electrolyte.

Since these modes of reaction of the silanes I are common, known and characteristic of the compounds and they necessarily take place when the silanes I are used according to the invention, they are no longer expressly mentioned below.

Regardless of which procedure is chosen for the addition of silanes I to the aqueous electrolyte, the advantages of the process according to the invention are always reliable. If the silanes I are hydrolyzed and / or condensed separately before addition to the aqueous electrolyte, of course only so much solvent is used for this that the desired silane I concentration is established after the addition of the silane I solution to the aqueous electrolyte.

The silanes I to be used according to the invention fulfill the function of additives in the aqueous electrolyte, which additives are added to the aqueous electrolyte in addition to one or more acids. However, the silanes I are also used together with other additives which generally serve to modify or color the surface layer which is formed, which is mainly composed of aluminum oxides, during the anodic oxidation, or to coat another layer on this surface layer to deposit from, for example, organic material.

If the silanes I have acid groups or form acid groups during their hydrolysis and condensation, they simultaneously fulfill the function of the single acid or the function of one of several acids in the aqueous electrolyte. Usually, the acids in the aqueous electrolyte serve to increase its conductivity, and they are known to have a considerable influence on the physico-chemical and application properties of the surface layers, which are mainly composed of aluminum oxides and which form during the anodic oxidation.

Whether the effect of the silanes I should rather be regarded as additives or as acids cannot be determined precisely because the silanes I perform both functions in an advantageous manner in the process according to the invention, i.e. the silanes I have an application-related property profile, which otherwise can only be achieved at best by combining several different substances at best.

The aqueous electrolyte advantageously contains the silanes I in an amount of 0.001 to 50% by weight, based on the electrolyte. If the aqueous electrolyte contains less than 0.001% by weight of the silanes I, their advantageous technical effect cannot be reliably reproduced in all cases. On the other hand, it is not necessary because of the advantageous technical effect of the silanes I to increase their content in the aqueous electrolyte to over 50% by weight, because the additional advantages which can still be achieved thereby do not increase the higher consumption of silanes I. absolutely justify. Thus, the content of 0.001 to 50% by weight of silanes I in the aqueous electrolyte is an optimal range, both from an application point of view and for economic reasons, within which the silane I concentration varies widely and both the technical problems to be solved and the apparatus conditions is adapted in a simple and advantageous manner.

If, for example, only the silanes I are added to the aqueous electrolyte, a silane I content of 0.05 to 30, preferably 0.1 to 25 and in particular 1 to 10% by weight, based on the electrolyte, proves to be special advantageous.

If the silanes I are used together with an acid or with several acids in the aqueous electrolyte, a silane I content of 0.005 to 25, preferably 0.05 to 20 and in particular 0.08 to 10% by weight, based on the electrolyte, is of particular advantage. It is of additional advantage here if the content of the aqueous electrolyte in the acid (s) used is 0.5 to 50, preferably 1 to 35 and in particular 3 to 30% by weight. The acids used are selected from the group of inorganic mineral acids, low molecular weight, mono- and polyfunctional organic carboxylic, sulfonic and phosphonic acids as well as oligomeric and high molecular weight, polyfunctional carbon, sulfonic and phosphonic acids. Suitable acids are known from EP-A-0 048 909 and EP-A-0 050 216 as well as from the prior art dealt with extensively in these patents.

If, in addition, customary and known additives are added to the aqueous electrolyte in a molecularly dispersed or colloidal solution, their amount depends primarily on their solubility in the aqueous electrolyte and on the extent to which they influence the solubility of the silanes I. Accordingly, the customary and known additives can be added in the amounts which are necessary for achieving the respective technical effect usually caused by them, as long as they do not cause the aqueous electrolyte to be de-homogenized, for example by forming separate liquid phases or insoluble precipitates. The usual and known additives are generally selected from the group of inorganic and organic salts and of low molecular weight, oligomeric and high molecular weight non-acidic organic compounds. Examples of suitable additives are also known from EP-A-0 048 909 and EP-A-0 050 216 as well as from the prior art dealt with extensively therein.

According to the invention, it is very particularly advantageous to use an aqueous electrolyte in the process according to the invention which, in addition to the silanes I, contains sulfuric acid and / or phosphoric acid.

In addition, it is particularly advantageous according to the invention to carry out the process according to the invention in two stages, ie that the surface of the plates, foils and strips made of aluminum or aluminum alloys is firstly used in a known aqueous electrolyte and then in the second stage in the one to be used according to the invention , anodically oxidizing the aqueous electrolytes containing silanes I.

The process according to the invention is carried out in apparatus or plants as are customary and known for the anodic oxidation of aluminum. The method according to the invention therefore does not require any new investments in equipment and systems to be specially developed for this purpose, on the contrary, it does not even require major modifications to existing equipment and systems.

The apparatuses and plants in which the process according to the invention is carried out essentially comprise electrolysis troughs, controllable current and voltage sources, holders for the plates, foils or tapes and the customary and known regulating and measuring devices. In addition, the electrolysis troughs can contain agitators, cooling devices and devices for supplying and removing the aqueous electrolyte and for cleaning it. The brackets are of course connected to the respective current and voltage sources. These known apparatuses and plants can be designed for continuous or discontinuous operation, i.e. that the process according to the invention is carried out continuously or batchwise.

If the process according to the invention is carried out discontinuously, some or all of its process parameters change from a preselected initial state to a desired final state during its course. For example, the temperature of the aqueous electrolyte, the voltage, the current density and / or the acid and additive concentration are changed in a predetermined manner during the anodic oxidation in order to achieve a very particularly advantageous technical effect.

It is also possible to carry out the method according to the invention by forcibly keeping some or all of the method parameters constant.

However, the process according to the invention is also carried out continuously, the process parameters in the desired range being forced, as corresponds to the nature of a continuous process is kept constant and the plates, foils or strips of aluminum or aluminum alloys are continuously passed through the aqueous electrolyte.

Regardless of whether the process according to the invention is carried out continuously or batchwise, the temperature of the electrolyte to be used according to the invention is in the range from -2 to + 60.degree. The method according to the invention uses direct voltage, alternating voltage or direct voltage superimposed by alternating voltage of 1 to 75 V in both continuous and discontinuous operation. In both embodiments of the method according to the invention, amounts of electricity in the range from 2 to 100 kC / m² have proven to be advantageous. Particularly advantageous process results are obtained when the anodic oxidation lasts from 4 seconds to 5 minutes.

It is advantageous to select the predominant number of process parameters of the process according to the invention from the ranges specified above. It is particularly advantageous to select all process parameters from these areas. After the selection and setting of the process parameters, the majority of the process parameters in the process according to the invention are kept constant over the entire course of the anodic oxidation in the range specified above. Or these process parameters are selected and set, after which some or all of the process parameters change in the course of the anodic oxidation, starting from the initial state, until the desired final state is reached. This change is carried out according to a specific program or results automatically from the interaction of the changing process parameters with one another and with the changing nature of the surface to be oxidized. It is particularly advantageous if the process parameters are within the ranges specified above when the desired final state is reached.

The process according to the invention, in which the anodic oxidation is carried out at temperatures from -2 to + 60 ° C. with a direct voltage of 1 to 75 V and a current of 2 to 100 kC / m 2 within a period of 4 seconds to 5, delivers particularly excellent process results Minutes using an aqueous electrolyte which, based on its total amount, contains 0.05 to 50% by weight of the silanes I.

The process according to the invention can be preceded by a cleaning of the surface of the plates, foils or strips made of aluminum or aluminum alloys which is customary and known in this technical field. Examples Suitable cleaning methods are rinsing with water, aqueous alkaline solutions, acids and organic solvents. As is known, the known cleaning methods can also be combined with one another in a suitable manner. For this purpose, reference is made, for example, to DE-B-29 12 060.

The method according to the invention can also be preceded by a mechanical, chemical and / or electrochemical roughening of the surface of the plates, foils or strips made of aluminum or aluminum alloys which is customary and known in this technical field. This roughening usually follows the cleaning and is usually followed by a further cleaning step. Examples of suitable roughening methods are known from DE-A-25 57 222, DE-A-26 50 762 or DE-B-29 12 060.

The process according to the invention can be followed by customary and known aftertreatment processes for the surface layer essentially composed of aluminum oxides. Examples of suitable post-treatment methods are sealing, hardening and hydrophilizing the surface layer. As is known, treatment with hot steam is used for sealing, and chemical and electrochemical aftertreatment with halides and acids is known to be considered for hardening and / or hydrophilizing. For this, e.g. referred to DE-C-26 07 207. This aftertreatment can also be followed by a drying step.

Furthermore, after the process according to the invention has been carried out or after the aftertreatment carried out afterwards, silanes I can be applied to the surface layer then present, which is essentially composed of aluminum oxides, in order to further improve its already excellent profile of properties.

The process according to the invention has numerous special advantages which were not to be expected in this abundance.

The process according to the invention can be carried out in apparatuses and plants as are customary and known for anodic oxidation. Here, the method according to the invention reliably delivers method products with excellent application properties in a simple manner. The method according to the invention therefore does not require any new investments in equipment and systems to be specially developed for this.

The surface layers on the molded parts made of aluminum or aluminum alloys, which are essentially made of aluminum oxides and which are produced with the aid of the method according to the invention, have a good appearance, particularly high corrosion resistance, excellent hardness, very good wear resistance and very good dyeability, so that the relevant ones Molded parts also for architectural purposes, e.g. can be used with advantage as window frames, door panels or cover plates or for light machine construction. It proves to be a further very special advantage of the method according to the invention that the density and the structure of the surface layers concerned vary in a simple manner on the one hand broadly and on the other hand very precisely in a thickness range of 0.1 to 150 g / m², which is approximately Corresponds to 0.1 to 200 µm, can be set.

The method according to the invention is used with particular preference for the production of light-sensitive lithographic printing plates or offset printing plates, because its numerous advantages come to light in a particularly high degree.

Thus, the surface layers of the anodized plates, foils or strips made of aluminum or aluminum alloys, which are essentially made of aluminum oxides and are produced by the process according to the invention, have, in addition to the advantages listed above, a particularly high absorption capacity and adhesion for paints, synthetic resins and light-sensitive mixtures of the most varied compositions . In addition, the surface layers are hard, wear and abrasion-resistant and also very tough and unbreakable. In addition, they are very hydrophilic and have a high chemical and physical stability during storage and excellent color guide properties during printing. The density, thickness and structure of the surface layers can be varied widely and can be adapted to the light-sensitive mixtures to be applied and the printing requirements.

It should be emphasized that the 0.05 to 1.5 mm thick anodized plates, foils or strips made of aluminum and aluminum alloys which are produced with the aid of the method according to the invention, which are referred to below as "supports", with light-sensitive mixtures of various compositions in a thickness of 0.1 to 20 microns, in particular 0.5 to 5 microns can be covered and in this way provide photosensitive lithographic printing plates or offset printing plates, which both the rapid image-wise exposure with computer-controlled lasers, ie coherent actinic light, as well as conventional imagewise exposure with incoherent actinic light through a negative original are accessible.

• (a) in ihren belichteten Bereichen druckfarbenannehmend und/oder unlöslich werden, wobei ihre nicht belichteten Bereiche ggf. mit einer Entwicklerflüssigkeit ausgewaschen werden können,
  oder
• (b) in ihren belichteten Bereichen druckfarbenabstoßend und/oder löslich werden, wobei die belichteten Bereiche ggf. mit einer Entwickler­flüssigkeit ausgewaschen werden können,
  oder
• (c) in ihren belichteten Bereichen elektrisch leitfähig werden und in ihren nicht belichteten Bereichen ihre elektrisch isolierende Wirkung bewahren, so daß sie latente elektrostatische Bilder zu liefern vermögen.

Examples of photosensitive mixtures which can be applied to the supports anodically oxidized by the process according to the invention and form the photosensitive recording layer of the photosensitive lithographic printing plates or offset printing plates thereon are all those mixtures which are in the form of photosensitive recording layers by imagewise exposure to coherent or incoherent actinic light

• (a) become ink-accepting and / or insoluble in their exposed areas, it being possible for their unexposed areas to be washed out with a developer liquid,
  or
• (b) become ink-repellent and / or soluble in their exposed areas, the exposed areas possibly being washed out with a developer liquid,
  or
• (c) become electrically conductive in their exposed areas and retain their electrically insulating effect in their unexposed areas so that they are able to provide latent electrostatic images.

• (a₁) einem hydrophilen Polymeren wie Gelatine oder Leim und einem lichtempfindlichen Metallsalz,
• (a₂) einem hydrophilen Polymeren wie Gelatine, Fischleim, Gummi­arabikum, Polyvinylalkohol, Polyacrylamid, Carboxymethyl­cellulose, Hydroxyethylcellulose oder Copolymerisaten aus Poly­vinymethylether und Maleinsäureanhydrid und dem Tetrazoniumsalz einer Diaminoverbindung wie p-Aminodiphenylamin, Benzidin, Diamidin oder Toluidin,
• (a₃) einem Diazoharz, welches man im wesentlichen aus Formaldehyd und einem Diphenylamin-diazoniumsalz hergestellt hat,
• (a₄) einer Azidverbindung wie Natrium-4,4′-diazidostilben-2,2′-di­sulfonat, Natrium-1,5-diazidonaphthalin-3,7-disulfonat, Natrium-­3′-azido-4-azidobenzalacetophenon-2-sulfonat, Natrium-4,4′-­diazidostilben-α-carboxylat, Natrium-di-(4-azido-2′-hydroxy­benzal)-aceton-2-sulfonat, Natrium-4-azidobenzalacetophenon-2-­sulfonat oder Natrium-4,4′-diazidodiphenyl-3,3′-disulfonat und Polyacrylamid, Polyvinylpyrrolidon, Polyacrylsäure, Gelatine, Kasein, Albumin, Gummiarabikum, Carboxymethylcellulose, Hydroxy­ethylcellulose oder einem alkohollöslichen Polyamid,
• (a₅) einer Azidoverbindung wie 4,4′-Diazidostilben, 4,4′-Diazido­chalcon oder 4,4′-Diazidobenzalaceton und einem cyclisierten Kautschuk, synthetischem Kautschuk oder einem sonstigen in organischen Lösungsmitteln löslichen Polymeren,
• (a₆) einer Verbindung, welche beim Bestrahlen mit aktinischem Licht dimerisiert, wie z.B. Polyvinylcinnamat, Poly(vinylcinnamoyl­ethylether), Poly(ethylcinnamatacrylat), Poly(ethylcinnamat­methacrylat), Poly(p-vinylphenylcinnamat), Poly(vinylbenzal­acetophenon), Poly(vinylcinnamylidenacetat), Allylacrylat­präpolymere oder Derivate von Polyesterharzen von p-Phenylen­diacrylsäure und mehrwertigen Alkoholen,
• (a₇) mindestens einem in Entwicklerflüssigkeiten löslichen oder leicht dispergierbaren, polymeren Bindemittel, mindestens einem mit den jeweiligen Bindemitteln verträglichen, photopolymerisierbare olefinisch ungesättigte Gruppen enthaltenden Monomeren und mindestens einem Initiator der Photopolymerisation
  oder aus
• (a₈) mindestens einem Diazoharz, welches man im wesentlichen aus Formaldehyd und einem Diphenylamin-diazoniumsalz hergestellt hat, und mindestens einem in wäßrigen Entwickerflüssigkeiten löslichen oder leicht dispergierbaren Polymerisat als Bindemittel

bestehen.Typical examples of light-sensitive recording layers of light-sensitive lithographic printing plates or offset printing plates of the type mentioned under point (a) are those described in DE-C-26 07 207, which are primarily accessible to imagewise exposure to laser light. In addition, the usual and known recording layers come into consideration, which essentially consist of

• (a₁) a hydrophilic polymer such as gelatin or glue and a light-sensitive metal salt,
• (a₂) a hydrophilic polymer such as gelatin, fish glue, gum arabic, polyvinyl alcohol, polyacrylamide, carboxymethyl cellulose, hydroxyethyl cellulose or copolymers of polyvinymethyl ether and maleic anhydride and the tetrazonium salt of a diamine compound such as p-aminodiphenylamine, benzidine, diamidine or toluidine,
• (a₃) a diazo resin which has been prepared essentially from formaldehyde and a diphenylamine diazonium salt,
• (a₄) an azide compound such as sodium 4,4'-diazidostilbene-2,2'-disulfonate, sodium 1,5-diazidonaphthalene-3,7-disulfonate, sodium 3'-azido-4-azidobenzalacetophenone-2-sulfonate , Sodium 4,4'-diazidostilbene-α-carboxylate, sodium di- (4-azido-2'-hydroxybenzal) -acetone-2-sulfonate, sodium 4-azidobenzalacetophenone-2-sulfonate or sodium 4,4 '-Diazidodiphenyl-3,3'-disulfonate and polyacrylamide, polyvinylpyrrolidone, polyacrylic acid, gelatin, casein, albumin, gum arabic, carboxymethyl cellulose, hydroxyethyl cellulose or an alcohol-soluble polyamide,
• (a₅) an azido compound such as 4,4′-diazidostilbene, 4,4′-diazidochalcone or 4,4′-diazidobenzalacetone and a cyclized rubber, synthetic rubber or another polymer which is soluble in organic solvents,
• (a₆) a compound which dimerizes when irradiated with actinic light, such as, for example, polyvinyl cinnamate, poly (vinyl cinnamoyl ethyl ether), poly (ethyl cinnamate acrylate), poly (ethyl cinnamate methacrylate), poly (p-vinyl phenyl cinnamate), poly (vinyl benzalacetophenone), poly (vinyl cinnamyl), poly (vinyl cinnamyl), poly (vinyl cinnamyl), poly (vinyl cinnamyl) Allyl acrylate prepolymers or derivatives of polyester resins of p-phenylenediacrylic acid and polyhydric alcohols,
• (a₇) at least one polymeric binder which is soluble or easily dispersible in developer liquids, at least one photopolymerizable monomer containing olefinically unsaturated groups and compatible with the respective binders and at least one initiator of the photopolymerization
  or off
• (a₈) at least one diazo resin which has been prepared essentially from formaldehyde and a diphenylamine diazonium salt, and at least one polymer as a binder which is soluble or easily dispersible in aqueous developer liquids

consist.

The photosensitive recording layers (a₁) to (a₈) of photosensitive lithographic printing plates or offset printing plates are insoluble in the imagewise exposure to incoherent actinic light through a negative original or with laser light in their exposed areas and take therein the typical for offset printing Oil-in-water inks, whereas their unexposed areas can be washed out with developer fluids. Here, the hydrophilic and ink-repellent surface of the support of the lithographic printing plates or offset printing plates anodically oxidized by the method according to the invention is exposed, whereby the surface of the printing plates is differentiated into color-guiding image areas and color-repelling non-image areas.

• (b₁) einer Chinondiazidoverbindung wie Naphthochinon-1,2-diazido­sulfonatester, -sulfonsäure, -sulfonsäurechlorid oder -sulfon­säureamid und einem alkalilöslichen Bindemittel,
• (b₂) einer Verbindung, welche bei der Belichtung Säure abspaltet, einer monomeren oder polymeren Verbindung, welche mindestens eine durch Säure abspaltbare C-O-C-Gruppe, wie etwa eine o-Carbon­säureestergruppe oder eine Carbonsäureamidacetalgruppe, aufweist, und ggf. einem Bindemittel
  oder aus
• (b₃) einer Verbindung mit mindestens zwei aromatischen und/oder heteroaromatischen o-Nitrocarbinolestergruppierungen, einer vernetzend wirkenden Verbindung mit mindestens zwei reaktiven Gruppen, welche beim Erhitzen mit Carboxylgruppen zu reagieren vermögen, und einem diese Reaktion beschleunigenden Katalysator wie etwa Iodonium-, Sulfoxonium- oder Pyrryliumsalze.

Typical examples of photosensitive recording layers of photosensitive lithographic printing plates or offset printing plates of the type mentioned under point (b) essentially consist of

• (b₁) a quinonediazido compound such as naphthoquinone-1,2-diazidosulfonate ester, sulfonic acid, sulfonic acid chloride or sulfonic acid amide and an alkali-soluble binder,
• (b₂) a compound which splits off acid on exposure, a monomeric or polymeric compound which has at least one COC group which can be split off by acid, such as an o-carboxylic acid ester group or a carboxylic acid amidacetal group, and optionally a binder
  or off
• (b₃) a compound having at least two aromatic and / or heteroaromatic o-nitrocarbinol ester groups, a crosslinking compound having at least two reactive groups which are capable of reacting with carboxyl groups when heated, and a catalyst which accelerates this reaction, such as iodonium, sulfoxonium or Pyrrylium salts.

The photosensitive recording layers (b₁) to (b₃) of the photosensitive lithographic printing plates or offset printing plates become soluble in the exposed areas during imagewise exposure to incoherent actinic light or with laser light in their exposed areas, after which these can be washed out with developer liquids. As a result, the hydrophilic and therefore ink-repellent surface of the support of the lithographic printing plates or offset printing plates anodized by the process according to the invention is exposed. The unexposed areas, on the other hand, remain insoluble and take on the "oil-in-water" printing inks typical of offset printing, as a result of which here, too, the differentiation of the printing plate surfaces into color-guiding image areas and ink-repellent non-image areas is ultimately achieved.

Typical examples of photosensitive recording layers of photosensitive lithographic printing plates of the type mentioned under point (c) are generally referred to as electrophotographic recording layers and essentially consist of at least one readily dispersible binder which is soluble in developer liquids, at least one photoconductor and at least one sensitizer. These electrophotographic recording layers are loaded by means of a high-voltage corona with a surface potential of several hundred volts and then exposed imagewise with incoherent actinic light through a negative original or with laser light, as a result of which they become electrically conductive in their exposed areas, so that the surface potential is greater than that according to the invention Process anodized oxidized carrier can drain. In their unexposed areas, however, the electrically insulating effect of the electrophotographic recording layers is maintained, so that overall latent electrostatic images result, which can be made visible using conventional and known toners. The toner images produced in this way are fixed by heating. The exposed and therefore unstressed areas of the electrophotographic recording layers are then washed out, which, as described above, again results in the differentiation of the printing plate surface into color-guiding image areas and ink-repellent non-image areas, as described above.

No matter what kind of photosensitive recording layers are selected for the production of the photosensitive lithographic printing plates or offset printing plates and regardless of whether these photosensitive recording layers after their production

- Imaged through a negative original with short- or long-wave ultraviolet light or with visible light or with ultraviolet, visible or infrared laser light and afterwards
- washed out with organic, aqueous-alkaline or aqueous-alcoholic developer liquids or with water,

the special advantages of the supports anodically oxidized by the process according to the invention become apparent. The high sensitivity to light of the light-sensitive lithographic printing plates or offset printing plates, which enables even the finest and most critical image motifs of image originals (negative originals) to be reproduced completely faithfully, quickly and reliably.

The special advantages of the method according to the invention are thus not exhausted, but are also noticeable in the lithographic printing plates or offset printing plates which have been produced from the light-sensitive lithographic printing plates or offset printing plates. The printing plates in question are abrasion-resistant under printing conditions and deliver excellent printed products in an advantageously large number of copies.

The particular advantages of the method according to the invention are outstandingly evident from photosensitive lithographic printing plates which contain photosensitive recording layers (a₇), (a₈) or (c).

• (i) Herstellen eines Gemischs, welches aus den Komponenten der betreffenden lichtempfindlichen Aufzeichnungsschicht (a₇), (a₈) oder (c) besteht, mittels üblicher und bekannter Knet-, Misch- oder Lösungstechniken,
• (ii) Lösen des in dieser Weise hergestellten lichtempfindlichen Gemischs in einem geeigneten Lösungsmittel,
• (iii) Ausgießen der resultierenden Lösung auf die Oberfläche des nach dem erfindungsgemäßen Verfahren anodisch oxidierten Trägers, wodurch eine lösungsmittelfeuchte lichtempfindliche Aufzeichnungsschicht (a₇), (a₈) oder (c) auf dem Träger resultiert, und
• (iv) Trocknen der in dieser Weise hergestellten lösungsmittelfeuchten lichtempfindlichen Aufzeichnungsschicht, wodurch auf dem Träger die lichtempfindliche Aufzeichnungsschicht (a₇), (a₈) oder (c) resultiert.

These photosensitive recording layers are produced in a customary and known manner by

• (i) preparing a mixture which consists of the components of the light-sensitive recording layer (a₇), (a₈) or (c) in question, using customary and known kneading, mixing or dissolving techniques,
• (ii) dissolving the photosensitive mixture thus prepared in a suitable solvent,
• (iii) pouring the resulting solution onto the surface of the support anodically oxidized by the process according to the invention, whereby a solvent-moist photosensitive recording layer (a₇), (a₈) or (c) results on the support, and
• (iv) drying the solvent-moist photosensitive recording layer produced in this way, whereby the photosensitive recording layer (a₇), (a₈) or (c) results on the support.

The light-sensitive recording layer (a₇) or (a₈) produced in this way can then be matted in a customary and known manner, coated with a smooth or matt top layer which is soluble or easily dispersible in the developer solvents for (a₇) or (a₈), or with a easily removable, smooth or matt cover film are covered. As is known, the cover layer and the cover film can also be used together, the cover layer of the respective light-sensitive recording layer being directly in contact.

Examples of suitable binders for the production of the light-sensitive recording layers (a₇) are methyl methacrylate / methacrylic acid copolymers, styrene / methacrylic acid copolymers, methacrylic acid / acrylic acid copolymers, polyurethanes or unsaturated polyesters and polyester urethanes.

Examples of suitable monomers with photopolymerizable olefinically unsaturated groups for the preparation of the light-sensitive recording layers (a₇) are mono-, di- or poly (meth) acrylates as obtained by the esterification of monoalcohols, diols and polyols with acrylic acid and methacrylic acid or their derivatives .

Examples of suitable initiators of photopolymerization are benzoin, benzoin ethers, benzil acetals, acylphosphine oxides, Michler's ketone, anthraquinones, aryl-substituted imidazoles, acridines, phenazines or compounds which easily release halogen atoms on exposure.

In addition, inhibitors of thermal polymerization, dyes, pigments, photochromic compounds or systems, sensitometric regulators, plasticizers, flow control agents, matting agents or lubricants can also be used for the production of the light-sensitive recording layers (a₇).

All these components for the production of the light-sensitive recording layers (a₇) are used in the usual and known amounts. These amounts go e.g. from EP-A-0 089 802.

Examples of suitable diazo resins for the production of the light-sensitive recording layers (a₈) are the condensation products of diphenylamine-4-diazonium sulfate, -hexafluorophosphate, -tetrafluorophosphate or -tetrafluoroborate with formaldehyde or the condensation products of 3-methoxidiphenylamine-4-diazonium sulfate with 4,4'-ethyl-bismethyl -diphenyl ethers, which are isolated as mesitylene sulfonate or methanesulfonate salts.

Examples of suitable binders for the production of the light-sensitive recording layers (a₈) are copolymers of acrylic acid, methacrylic acid and / or crotonic acid as an essential component with acrylonitrile, alkyl (meth) acrylates such as ethyl methacrylate and with hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl methacrylate.

Examples of suitable solvents for the components of the light-sensitive recording layers (a₈) are those mentioned in DE-A-36 27 585, of which diacetone alcohol is very particularly preferred, contrary to the statements made there.

In addition, organic oligocarboxylic acids such as tartaric acids, dyes, pigments, flow control agents, plasticizers and the customary and known stabilizers for diazo resins can be used for the production of the light-sensitive recording layers (a₇).

All these components for the production of the light-sensitive recording layers (a₈) are used in the usual and known amounts. These amounts go e.g. from DE-A-36 27 585.

Examples of suitable binders for the production of the electrophotographic recording layers (c) are cellulose ethers, polyester resins, polyvinyl chlorides, polycarbonates or copolymers such as styrene / maleic anhydride, vinyl chloride / maleic anhydride, styrene / maleic anhydride / (meth) acrylic acid or styrene / (meth) acrylic acid Copolymers.

Examples of suitable photoconductors for the production of the electrophotographic recording layers (C) are the customary and known oxazoles, oxdiazoles, triazoles, azomethines, pyrazolines, imidazoles, arylamines, 1,3-dithiols, benzotriazoles, triazolylpyridines, pyrazolotriazoles, triphenyltriazoles, hydrazones, poly ( N-vinyl carbazole) or arylamine polymers.

Examples of suitable sensitizers for the preparation of the electrophotographic recording layers (c) are the dyes from the classes of triarylmethane, cyanine, xanthene, azo, phthalocyanine, naphtholactam or isoindolenine dyes.

In addition, leveling aids, plasticizers, adhesion promoters, fillers or metal complexes such as metal acetylacetonates can also be used for the production of the electrophotographic recording layers (c).

All of these components for the production of the electrophotographic recording layers (c) are used in the customary and known amounts. These amounts go e.g. from EP-A-0 131 215.

These photosensitive lithographic printing plates or offset printing plates with a support which has been anodically oxidized by the process according to the invention and the photosensitive recording layer (a₇), (a₈) or (c) provide excellent exposure and development, which are typical and customary for them lithographic printing plates or offset printing plates, which again document the particular advantages of the method according to the invention.

The exposure and development of photosensitive printing plates with the recording layer (a₇) is described in detail in EP-A-0 089 802.

The details of the exposure and development of photosensitive printing plates with the recording layer (a₈) can be found in DE-A-36 27 585.

The exposure and development of photosensitive printing plates with the recording layer (c) is known in all its features from EP-A-0 131 215.

These lithographic printing plates or offset printing plates which have been produced using the supports anodically oxidized by the process according to the invention are distinguished in particular by an excellent hydrophilicity in their non-image areas and by an excellent adhesion of their image areas to the supports. In addition, they deliver excellent print products in very large print runs.

Examples and comparative tests

• Note 1 (die Druckfarbe läßt sich vollkommen abspülen, es ist keinerlei Farbannahme in den Nichtbildbereichen erkennbar, die Offset­druckplatte genügt in dieser Hinsicht den höchsten Qualitäts­ansprüchen und ist für besonders schwierige Anwendungen beim Offsetdruck geeignet)
• Note 2 (in den Nichtbildbereichen sind nach dem Abspülen noch Farbreste erkennbar, die aber durch Reiben entfernt werden können, die Offsetdruckplatte ist für den Offsetdruck sehr gut verwendbar)
• Note 3 (die Farbreste in den Nichtbildbereichen lassen sich auch nicht mehr durch Reiben entfernen, die Offsetdruckplatte ist für den Offsetdruck nicht verwendbar)
• Note 4 (hinsichtlich der Farbannahme von Bild- und Nichtbildbereichen ist keine Differenzierung mehr erkennbar; die Druckplatte ist gleichmäßig eingefärbt und daher für den Offsetdruck völlig untauglich)

In the following examples and comparative experiments, the lithographic printing plates or offset printing plates were rubbed with an "oil-in-water" type offset printing ink to test their ink-guiding properties and the hydrophilicity of their non-image areas. After that, the offset printing ink was rinsed off again with water. It was then assessed visually whether and to what extent the respective hydrophilic non-image areas had accepted and retained the printing ink. The respective results of the visual assessment were graded as follows:

• Grade 1 (the printing ink can be completely rinsed off, there is no color acceptance in the non-image areas, the offset printing plate meets the highest quality standards in this regard and is suitable for particularly difficult applications in offset printing)
• Grade 2 (in the non-image areas, color residues can still be seen after rinsing, but these can be removed by rubbing, the offset printing plate can be used very well for offset printing)
• Note 3 (the color residues in the non-image areas can no longer be removed by rubbing, the offset printing plate cannot be used for offset printing)
• Grade 4 (with regard to the color acceptance of image and non-image areas, no differentiation is discernible; the printing plate is evenly colored and therefore completely unsuitable for offset printing)

Furthermore, in the following examples and comparative experiments, the lithographic printing plates or offset printing plates for testing the strength with which the image areas adhere to the supports were rubbed off with a tampon which was impregnated with an offset-typical, commercially available, aqueous-alkaline developer liquid. After that, it was visually assessed whether and to what extent the fine image motifs had been damaged. The visual evaluation results obtained were evaluated as follows:

example 1 The anodic oxidation of aluminum plates by the process according to the invention; Test specification:

Aluminum sheets measuring 280x250x0.3 mm were cleaned alkaline, electrochemically roughened in hydrochloric acid at a concentration of 20 g / l at a current density of 60 A / dm² for 15 seconds, then cleaned again alkaline and then anodized. For the anodic oxidation, an aqueous electrolyte consisting of 30% sulfuric acid was used, which contained 0.1% by weight of 3- (triethoxisilylpropyl) succinic anhydride, the amount of electricity was 20 kC / m², the electrolysis temperature was 30 ° C. and the electrolysis time was 40 seconds.

After this, the plates were covered with a dense, uniform, good-looking surface layer, which was mainly made up of aluminum oxides. Further advantages were evident when the plates were used as supports for offset printing plates.

Example 2 The anodic oxidation of aluminum plates by the process according to the invention; Test specification:

Example 1 was repeated, except that instead of (3-triethoxisilylpropyl) succinic anhydride (2-trimethoxisilylethyl) phosphonic acid was used. The same advantageous results as in Example 1 were obtained. Further advantages were evident when the plates were used as supports for offset printing plates.

Comparative experiment 1 The anodic oxidation of aluminum plates using a conventional method; Test specification:

Example 1 was repeated, except that 1% by weight of polyvinylphosphonic acid was used instead of 0.1% by weight of (3-triethoxisilylpropyl) succinic anhydride.

At first glance, the surface layer obtained in this way appeared to be of the same quality as the one produced by the process according to the invention, but its defects were revealed when the plates were used as supports for offset printing plates.

Comparative experiment 2 The anodic oxidation of aluminum plates using a conventional method; Test specification:

Example 1 was repeated without silane I and without polyvinylphosphonic acid.

The surface layer obtained in this way was less dense, non-uniform and less good-looking than that from example 1 or 2. Further defects were revealed when using the plates as supports for offset printing plates.

Examples 3 to 5 The use of the aluminum plates anodized according to Example 1 as a support for the light-sensitive recording layers of lithographic printing plates or offset printing plates; Test specification:

Three photosensitive mixtures (a₇), (a₈) and (c) were prepared by dissolving the relevant components in a suitable solvent. The solutions were poured onto the supports and then dried in such a way that the light-sensitive recording layers (a₇), (a₈) and (c) resulted in the desired thickness and the desired composition.

The light-sensitive lithographic printing plates or offset printing plates obtained in this way were exposed in the typical, customary and known manner for each of them imagewise to incoherent actinic light through a standard negative (UGRA test wedge) and then developed.

The quality of the lithographic printing plates or offset printing plates thus obtained was then tested and graded in the manner described above. The results in question are summarized in Table 1.

The offset printing plates were then clamped onto printing cylinders and used for continuous printing on a commercially available offset printing unit. The assessment of the quality of the printed products obtained and their circulation can also be found in Table 1.

For example 3, the photosensitive recording layer (a₇) was used. This consisted of the total amount 59% by weight a copolymer made from methyl methacrylate and methacrylic acid (binder), 30% by weight 1,4-butanediol diglycidyl ether diacrylate (monomer), 2% by weight Michler's ketone (photoinitiator), 6% by weight 2- (4′-methoxinaphth-1′-yl) -4,6-bis- (trichloromethyl) -s-triazine (coinitiator that releases chlorine atoms), 1% by weight Victorian pure blue (CI BB7) and 2% by weight Benzenesulfonic acid-n-butylamide (plasticizer).

The layer weight of the light-sensitive recording layer (a₇) was 2 g / m². It was exposed with the help of a high-pressure mercury lamp for 25 seconds (power consumption: 3 kW) and then with developed an aqueous alkaline developer in a developing machine of the brand ®nylolith 650-W2 from BASF AG.

For example 4, the photosensitive recording layer (a₈) was used. This consisted of the total amount 86% by weight a copolymer made from 2-hydroxyethyl methacrylate, acrylonitrile, ethyl methacrylate and methacrylic acid (binder), 2% by weight Tartaric acid, 11.9% by weight the condensation product of diphenylamine-4-diazonium hexafluorophosphate with formaldehyde (diazonium salt) and 0.1% by weight Victorian pure blue (CI BB7).

The layer weight of the light-sensitive recording layer (a₈) was 2.5 g / m². The exposure and development conditions correspond to those of Example 3, except that an exposure time of 45 seconds was selected (power consumption: 3 kW).

For example 5, the electrophotographic recording layer (c) was used. This consisted of the total amount 54.6% by weight a copolymer of styrene and methacrylic acid (binder), 45% by weight 2,5-bis (4'-N, N-diethylamino-phen-1'-yl) -1,3,4-oxdiazole (photoconductor) and 0.4% by weight CI Basis Red 1 (sensitizer).

The recording layer (c) was loaded with a surface potential of -850 V using a high-voltage corona of -6.75 kV from a distance of 1 cm. Afterwards, it was imaged with the help of a repro camera with four halogen spotlights of 1000 W each for 15 seconds, whereby a latent electrostatic charge image was generated, which was toned with a commercially available toner. This toner image was fixed by heating, and then the fixed toner image on the recording layer (c) was developed in the manner as in Example 3.

Examples 6 to 8 The use of the anodically oxidized aluminum plates according to Example 2 as a support for the light-sensitive recording layers of lithographic printing plates or offset printing plates; Test specification:

Examples 3 to 5 were repeated, except that those from example 2 were used instead of the supports from example 1.

The assessment of the quality of the offset printing plates from Examples 6 to 8 can also be found in Table 1.

Comparative experiments 3 to 5 The use of the aluminum plates anodized according to comparative experiment 1 as a support for the light-sensitive recording layers of lithographic printing plates or offset printing plates; Test specification:

Examples 3 to 5 were repeated, except that those from comparative experiment 1 were used instead of the supports from example 1.

The assessment of the quality of the offset printing plates from comparative experiments 3 to 5 can also be found in Table 1.

Comparative experiments 6 to 8 The use of the aluminum plates anodized according to comparative experiment 2 as a support for the light-sensitive recording layers of lithographic printing plates or offset printing plates; Test specification:

Examples 3 to 5 were repeated, except that those from comparative experiment 2 were used instead of the supports from example 1.

The assessment of the quality of the offset printing plates from comparative experiments 6 to 8 can also be found in Table 1.

Table 1, which summarizes the assessments of all of the offset printing plates obtained from Examples 3 to 8 and Comparative Experiments 3 to 8, clearly and practically documents that the method according to the invention for the anodic oxidation of plates, foils or strips made of aluminum or aluminum alloys is clearly the conventional method is superior. The examples and comparative tests can be compared directly as follows:

- Example 3 with Example 6, Comparative Experiment 3 and Comparative Experiment 6 (photosensitive recording layer a₇);
-Example 4 with Example 7, Comparative Experiment 4 and Comparative Experiment 7 (photosensitive recording layer a₈);
- Example 5 with Example 8, Comparative Experiment 5 and Comparative Experiment 8 (photosensitive recording layer c).

Claims (30)

1. A process for the anodic oxidation of the surface of plates, foils or strips made of aluminum or aluminum alloys in an aqueous electrolyte containing one or more acids and optionally one or more additives, characterized in that one as an additive or as one of the additives or as Acid or one or more silanes of the general formula I used as one of the acids,

X- (CH₂) _y -Si (R¹) _n (OR²) _3-n I,

where the indices and the variables have the following meaning:

y is an integer from 1 to 4;
n independently of y 0, 1 and 2;
R¹ u. R² is C₁ to C₉ alkyl and C₆ to C₁₂ aryl, where R¹ and R² are the same or different; and
X residues X¹ to X¹¹

where the variables have the following meaning:

R³ is hydrogen atom, C₁ to C₉ alkyl, alkane carboxylic acid residue having 1 to 9 carbon atoms and carboxylic acid anhydride ring formed from the alkane carboxylic acid residue having 1 to 9 carbon atoms and the methylene carboxylic acid group linked to R³

R⁴ u. R⁵ radical R¹;
R⁶ is hydrogen and R¹;
Z hydrogen atom and alkali metal cation;
Ar C₆ to C₁₂ arylene; and
Hal chlorine and bromine;

wherein the silanes of the general formula I (= silanes I) are present in the electrolyte solution in hydrolyzed and / or in condensed form. 2. The method according to claim 1, characterized in that the aqueous electrolyte, based on its total amount, contains 0.001 to 50% by weight of one or more of the silanes I. 3. The method according to claim 1 or 2, characterized in that one or more of the non-hydrolyzed and / or non-condensed silanes I is added to the aqueous electrolyte. 4. The method according to claim 1 or 2, characterized in that one or more of the silanes I is added to the aqueous electrolyte in hydrolyzed and / or condensed form. 5. The method according to any one of claims 1 to 4, characterized in that the aqueous electrolyte at least one acid from the group of inorganic mineral acids, the low molecular weight, mono- and polyfunctional organic carboxylic, sulfonic and phosphonic acids and the oligomeric and high molecular weight, polyfunctional Contains carbonic, sulfonic and phosphonic acids. 6. The method according to any one of claims 1 to 5, characterized in that the aqueous electrolyte contains one or more further additives from the group of inorganic and organic salts and the low molecular weight, oligomeric and high molecular weight, non-acidic organic compounds in molecularly dispersed or colloidal solution. 7. The method according to any one of claims 1 to 6, characterized in that the anodic oxidation of the surface of the plates, foils or strips made of aluminum or aluminum alloys at temperatures from -2 to + 60 ° C with a DC voltage of 1 to 75 V. a current of 2 to 100 kC / m² within a period of 4 seconds to 5 minutes and in an electrolyte which, based on its total amount, contains 0.05 to 50% by weight of one or more of the silanes I. 8. The method according to claim 7, characterized in that the anodic oxidation is carried out discontinuously, some or all of the process parameters changing from the preselected initial state in the course of the anodic oxidation until the desired final state is reached. 9. The method according to claim 7, characterized in that one carries out the anodic oxidation discontinuously, the majority of their process parameters are forcibly kept constant in the desired range over the entire course of the anodic oxidation. 10. The method according to claim 7, characterized in that the anodic oxidation is carried out continuously, the plates, foils or strips of aluminum or aluminum alloys in question being passed continuously through the aqueous electrolyte and the process parameters of the anodic oxidation being forcibly constant in the desired range being held. 11. The method according to any one of claims 1 to 10, characterized in that the plates, foils or strips of aluminum or aluminum alloys used here are cleaned before the anodic oxidation and then roughened mechanically, chemically and / or electrochemically. 12. The method according to any one of claims 1 to 11, characterized in that treating the surface of the anodized plates, foils or strips made of aluminum or aluminum alloys with hot steam. 13. The method according to any one of claims 1 to 12, characterized in that the surface of the anodized plates, foils or strips of aluminum or aluminum alloys is subjected to a hydrophilizing aftertreatment. 14. The method according to any one of claims 1 to 13 for the production of light-sensitive lithographic printing plates or offset printing plates, characterized in that here the hydrophilic, chemically and physically stable surface layer or 0.05 to 1.5 mm thick essentially made of aluminum oxides , anodized plates, foils or tapes made of aluminum or aluminum alloys covered with a light-sensitive recording layer. 15. The method according to claim 14, characterized in that the light-sensitive recording layer is produced by mixing its components, pouring from solution and drying. 16. The method according to claim 14 or 15, characterized in that the light-sensitive recording layer by the imagewise exposure to coherent or incoherent actinic light in its exposed areas is ink-accepting and / or insoluble. 17. The method according to claim 16, characterized in that the unexposed areas of the imagewise exposed recording layer are washed out with a developer liquid. 18. The method according to claim 17, characterized in that an aqueous alcoholic developer liquid is used here. 19. The method according to claim 17 or 18, characterized in that the light-sensitive recording layer consists essentially of a diazo resin and a polymer soluble or easily dispersible in aqueous developer liquids as a binder. 20. The method according to claim 15 and 19, characterized in that the light-sensitive recording layer is produced by casting from a solution of its components in diacetone alcohol. 21. The method according to claim 17 or 18, characterized in that the light-sensitive recording layer consists essentially of at least one polymer binder which is soluble or easily dispersible in developer liquids, at least one photopolymerizable monomer containing olefinically unsaturated groups which is compatible with the respective binder and at least one initiator of the There is photopolymerization. 22. The method according to claim 14 or 15, characterized in that the light-sensitive recording layer by the imagewise exposure to coherent or incoherent actinic light in its exposed areas becomes ink repellent and / or soluble. 23. The method according to claim 22, characterized in that the exposed areas of the imagewise exposed recording layer are washed out with a developer liquid. 24. The method according to claim 14 or 15, characterized in that the light-sensitive or electrophotographic recording layer becomes electrically conductive in its exposed areas by exposure to coherent or incoherent actinic light and retains its electrically insulating effect in its unexposed areas. 25. The method according to claim 24, characterized in that the electrophotographic recording layer consists essentially of at least one binder which is soluble or easily dispersible in aqueous alkaline developer liquids, at least one photoconductor and at least one sensitizer. 26. The method according to claim 25, characterized in that one (i) charges the electrophotographic recording layer by means of a high voltage corona with a surface potential of several hundred volts and (ii) then imagewise exposed to form a latent electrostatic image, after which (iii) toner the latent electrostatic image and (iv) the resulting toner image is fixed by heating, after which (v) Washes the unexposed and therefore unstressed areas of the electrophotographic recording layer with an aqueous alkaline developer. 27. The method according to any one of claims 16 to 23, characterized in that the surface of the light-sensitive recording layer is matted. 28. The method according to any one of claims 16 to 23 or according to claim 27, characterized in that the surface of the light-sensitive recording layer is coated with a smooth or matt cover layer which is soluble or easily dispersible in the developer liquid in question. 29. The method according to any one of claims 16 to 23 or according to claim 27, characterized in that the surface of the light-sensitive recording layer is covered with an easily removable, smooth or matt cover sheet. 30. The method according to claim 28, characterized in that the surface of the cover layer is covered with an easily removable, smooth or matt cover film.