JPH0154439B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for anodizing aluminum in an electrolyte containing special organic acids. In recent decades, there has been a trend towards continuous improvement of aluminum surfaces for various applications (e.g. for construction or for the production of printing plates), e.g. when processing aluminum or its alloys in the form of strips, sheets or plates. Remarkable. The various properties desired for the surface include, for example, corrosion resistance, appearance, density, hardness, abrasion resistance, adsorption and adhesion of paints or synthetic resin films, colorability, gloss, and the like. Starting from rolled aluminum, chemical, mechanical and electrochemical surface treatment methods are developed, and combinations of various methods are also used in practice. (lithography) Processing of strip, sheet or plate materials of aluminum or aluminum alloys used as substrates for printing plates usually involves mechanical or electrochemical roughening steps and subsequent surface roughening. The combination of anodized aluminum surfaces with a treatment step has reached a tentative conclusion in technological development. However, depending on the desired number of print runs of the printing plates to be treated, the aluminum material may be anodized without a separate roughening treatment, in which case the aluminum material will form a sufficiently adherent and strong aluminum oxide coating. The aluminum oxide film itself must have good adhesion to the photosensitive film to be applied. The anodized coating on the (lithographic) printing plate provides, inter alia, good dampening water guidance (=increased hydrophilicity) and increased abrasion resistance, thus reducing the image area of the printing plate, e.g. during the printing process. In addition, it has an increased adhesion strength to, for example, photoresist films. The following standard methods for anodizing aluminum in an aqueous electrolyte containing H ² SO ₄ are known from the prior art, e.g.
“Werkstoff Aluminum und seine anodische
Oxydation”, Francke Publishing House (Bern), 760
Page (1948); “Praktische Galvanotechnik”;
Eugen G. Leuze Publishers (Saulgau), pp. 395 et seq. and 518/519 (1970); W. Hu¨bner and CTSpeiser
Co-author, “Die Praxis der anodischen Oxidation
des Aluminiume”, Aluminum Verlag (Duyusseldorf), pp. 137 et seq., 3rd edition (1977)],
It has now become clear that H ² SO ₄ is an electrolytic acid that can be used in most applications: - direct current - sulfuric acid method, in which usually per solution
10-22 in an aqueous electrolyte consisting of approximately 230 g _of ^H2SO4
anodized at a current density of 0.5-2.5 A/ ^dm2 for 10-60 minutes. At this time, the sulfuric acid concentration in the aqueous electrolyte solution is 8 to 10% by weight of H ² SO ₄ (approximately 100 g of H ² SO ₄ /
) and 30% by weight (H ² SO ₄ 365g/
) or more. - “Hard anodization” is performed using an aqueous electrolyte containing H ² SO ₄ at a concentration of 166 g H ² SO ₄ / (or about 230 g H ² SO ₄ /) at a treatment temperature of 0 to 5 °C and a current density of 2 to 5 °C.
It is carried out for 30-200 minutes at 3 A/dm ² with an increasing voltage of about 25-30 V at the beginning and about 40-100 V at the end of the process. Known electrolytes other than sulfuric acid in the one-step oxidation process of metals, such as aluminum, or in the pre-treatment step prior to the actual oxidation, include in particular those described in the following publication: West German Patent No. 607 012 The book describes anodizing aluminum in an aqueous solution of oxalic acid or chromic acid. The oxidation product is later used as a base material for a photosensitive film (for example silver halide) which is to be filled into an oxide film to produce characters or pictures. A similar method is described in US Pat. No. 2,115,339. West German patent no.
No. 607474 also uses oxalic acid in aqueous solution as an electrolyte. In addition, further additives, such as organic acids, are mentioned, but are not described in detail. This oxidation product is suitable for coloring purposes. In addition to sulfuric acid, the electrolyte in the anodization of aluminum according to German Patent No. 623 847 contains sulfonated phenols. The pores formed during oxidation may be closed, for example with fat, and the reaction product is suitable for coloring purposes. West German patent no.
No. 825937 mentions aromatic hydrocarbon sulfonic acid as an additive to sulfuric acid or phosphoric acid during anodized bright coating treatment of aluminum. According to West German Patent No. 1251616, sulfuric acid and 1,8-dihydroxynaphthalene-3,6-
An aqueous electrolyte containing sulfonic acid is used for coloring aluminum by anodizing. West German Patent No. 1260266 (U.S. Patent No.
3227639), in addition to sulfuric acid, 4-
Obtained in an aqueous electrolyte containing sulfophthalic acid or 5-sulfoisophthalic acid. In German Patent Application No. 1 446 002, uniformly colored aluminum oxide coatings are obtained in aqueous electrolytes based on sulfuric acid and sulfosalicylic acid.
Similarly, according to German Patent Application No. 1521016, an aqueous electrolyte containing naphthalene disulfonic acid and sulfuric acid is used for anodizing aluminum. West German Patent Application Publication No. 2713985
The use of sulfofumaric acid for the same purpose is known from the publication no. U.S. Pat. No. 4,022,670 discloses that, in addition to sulfuric acid or phosphoric acid, polybasic aromatic sulfonic acids, such as sulfophthalic acid or The use of sulfosalicylic acid has been described. According to DE 1 671 614 (=U.S. Pat. No. 3,511,661), lithographic printing plates are produced by anodizing an aluminum substrate in aqueous phosphoric acid. The surface after oxidation is composed of cells with a pore size of 150-750·10 ^-10 m. Similar processes are described in US Pat. may also be present in the aqueous electrolyte. West German Patent Application Publication No. 2000227 (=
US Pat. No. 3,658,662) describes a process for anodizing aluminum in an aqueous sodium silicate solution, the material obtained being suitable as printing plate substrate material. It is known from U.S. Pat. No. 3,672,972 to simultaneously oxidize aluminum in an aqueous electrolyte and form boehmite in an oxide film, which electrolyte contains oxalic acid, sulfuric acid, phosphoric acid, malonic acid, sulfonic acid, etc. Contains salicylic acid/sulfuric acid mixture and aluminate ions. The surface has improved adhesion. US patent no.
Aluminum plates according to No. 3,915,811 are anodized in an aqueous ternary electrolyte containing phosphoric acid, sulfuric acid and an organic acid, such as acetic acid. US Pat. No. 3,988,217 describes a method in which aluminum is anodized and coated with resin simultaneously. The aqueous electrolyte includes an aliphatic amine or quaternary ammonium salt and a resin. The reaction product has a surface with improved adhesion and corrosion resistance. According to U.S. Pat. No. 4,115,211, an aqueous anodizing electrolyte for the pretreatment for the subsequent deposition of metal salts on aluminum contains water-soluble heavy metal salts as well as water-soluble acids such as oxalic acid, tartaric acid, citric acid, etc. acid,
Contains malonic acid, maleic acid, sulfuric acid, phosphoric acid, sulfamic acid or nitric acid. German Patent No. 647,427 describes a pre-anodizing treatment of aluminum before applying an oxide coating, in which the electrolysis is carried out mainly with monobasic organic acids, such as acetic acid, and also with sulfuric acid or phosphorus. It is carried out in an aqueous solution containing acid and optionally boric acid. According to German Patent No. 703 314, a pretreatment of the aluminum before applying the oxide coating by anodization is carried out in an electrolyte with a pH of 4 to 10.
The electrolyte includes an alkali salt of an organic acid, such as tartaric acid or citric acid. The use of such electrolytes for the production of printing plates filled with photosensitive films is described in US Pat. No. 3,756,826. An aqueous electrolyte for anodizing aluminum containing sulfuric acid and phosphoric acid is known from US Pat. No. 2,703,781. DE 2707810 (US Pat. No. 4,049,504) describes the use of this method in the production of printing plate substrates. The process according to DE 1178272 for coloring aluminum by anodizing the aluminum is carried out in an aqueous electrolyte containing primarily sulfosalicylic acid and additionally sulfuric acid and maleic acid or maleic anhydride.
DE 1 496 719 A1 uses electrolytes consisting of tartaric acid, sulfuric acid or sulfates and sulfamic acid, sulfosalicylic acid or sulfophthalic acid for the same purpose. An oxide film produced by hard anodizing on an aluminum alloy containing at least 1% copper is disclosed in West German Patent Application No. 2243178 (=U.S. Pat.
3804731), it is obtained in an electrolyte based on aromatic sulfonic acids and sulfuric acid, which may also contain oxalic acid or maleic acid. The anodic oxidation coloring of aluminum according to German Patent Application No. 1496722 is carried out using a) malonic acid, tartaric acid, citric acid, diglycolic acid, malic acid, succinic acid, glutaric acid, itaconic acid, maleic acid, pyromellitic acid (among others) benzetetracarboxylic acid), trimellitic acid (benzetricarboxylic acid), citraconic acid, acetylene dicarboxylic acid,
It is carried out in an aqueous electrolyte containing at least a dibasic organic carboxylic acid from the group of aconitic acid, glycosylic acid and phthalic acid and b) oxalic acid or glycosylic acid. Two-step and single-step oxidation methods or one-step oxidation methods with non-oxidizing after-treatment steps are also known from the prior art, including, for example: German Patent No. 629 629 describes a method for anodizing aluminum, in which the surface is first electrolytically treated in sulfuric acid and subsequently in an organic acid solution (malonic acid or oxalic acid). The printing plate base material is based on the West German Patent Application Publication No.
Publication No. 1471707 (=U.S. Patent No. 3181461 specification)
The aluminum oxide coating produced by anodization is further processed with fillers, such as silicates, dichromates, oxalates or dyes, in an aqueous solution. In DE 1621478 (=US Pat. No. 4,153,461) polyvinylphosphonic acid is used in aqueous solution for the same purpose. Electrochemical silicate treatment under anodizing conditions of already anodized printing plate substrates made of aluminum has been described in West German patent application no.
Publication No. 2532769 (= US Patent No. 3902976 specification)
It is described in. The method for anodizing aluminum according to West German Patent Application No. 1496874 uses a sulfuric acid-based aqueous electrolyte in the first step, and sulfuric acid, sulfosalicylic acid, sulfophthalic acid,
Use those based on ligninsulfonic acid or resorcinsulfonic acid. West German Patent Application No. 2211553 (=
^The aluminum oxide film obtained by anodization from U.S. Pat. Alternatively, it is known to carry out non-electrolytic post-treatment (sealing) using N,N,N-amino-trimethanephosphonic acid. According to West German Patent Application No. 2520955, the aluminum is first anodized and then a water bath containing 0.5 to 200 g of colored metal salt and phosphonic acid is used to electrolytically color the oxide film using alternating current. . Phosphonic acids include in particular amino-substituted mono- or polyphosphonic acids, such as aminomethanephosphonic acid, n-propylamino-di(methanephosphonic acid) or hydrazine-tetra(methanephosphonic acid). These compounds are used as "barrier film formers" for already anodized aluminum, and for this purpose also boric acid, citric acid or tartaric acid are often used. DE 2805219 (U.S. Pat. No. 4,090,880) describes a method for producing anodized metal (in particular aluminum) printing plate substrates, in which, before the oxidation step, In some cases, compounds that later have the effect of making the substrate hydrophilic in an aqueous solution, such as silicates, silicic acid,
Treated with polyacrylic acid, zirconium fluoride or zirconium fluoride. According to West German Patent Application Publication No. 2836878, the hydrophobic aluminum oxide film on hydrated aluminum is formed by ammonia and ammonia in the first anodizing step.
It is produced by treatment in an aqueous electrolyte based on citric acid and phosphoric acid and, in a second anodization step, in an aqueous electrolyte based on azelaic acid (1,9-nonanedioic acid). The reaction product is used as an electrolytic capacitor. A two-stage anodization of aluminum printing plate substrates is known from US Pat. No. 3,940,321, in which they are first treated in sulfuric acid and then in phosphoric acid. The previously known processes based on sulfuric acid give oxide films on aluminum that can be used in many fields of use, but have some drawbacks, for example when used for the production of substrates for printing plates. There is.
The disadvantages are, on the one hand, the increased sensitivity of the resulting coatings to alkalis and "haze formation", and on the other hand, the oxidation process used in particular in "hard anodizing",
The relatively high residence time of aluminum in the electrolyte is advantageous in the continuous anodization of aluminum, which is advantageous in terms of energy and economy to obtain and maintain a low electrolysis temperature. For industrially usable anodization processes, phosphoric acid as the sole electrolyte or in mixtures has hitherto been of no importance or of only secondary importance.
With this acid, only relatively thin films can be obtained by film growth. However, this thin film is not thick enough to compete with films made from borates or citric acid, for example, as conversion coatings for capacitors [M.Schenk, “Werkstoff
Aluminum und seine anodische Oxydation”,
See Flancke Verlag, Bern, p. 324 (1948)] This is the reason for the strong ability of phosphoric acid to redissolve aluminum oxide (Sienck, supra, p. 385).
provides a possible explanation not only for why thicker and wear-resistant oxide coatings are not produced under economically acceptable conditions, but only under difficult conditions. The coarse pore structure of the oxide films produced in phosphoric acid (Sienck, supra, p. 585) and the low abrasion resistance of the films are probably also attributable to this redissolution. Anodized coatings on aluminum belong to two main types. One type is a so-called barrier film, which occurs when the electrolyte used during anodization has only a small ability to dissolve oxides. Such coatings are mostly non-porous and their thickness is limited to approximately 13.10 ^-10 m/V. As soon as this critical thickness is achieved, an effective barrier to subsequent ion or electron flow generally exists. The current drops to a current corresponding to a low conductivity value and oxide film formation ceases. For example, boric acid and tartaric acid are used as electrolytes in this method. On the other hand, if the electrolyte exerts a sufficient dissolving effect on the oxide, the barrier film does not reach a critical thickness, i.e. the current continues to flow, and the effect results in a "porous" oxide structure. . The porous film is of considerable thickness, i.e. several
The thickness may be 10 ^-7 m, but the metal/
A thin oxide barrier film is always present at the oxidized metal interface. Electron microscopy reveals the presence of billions of closely packed amorphous oxide cells throughout the oxide film, generally aligned perpendicular to the metal/metal oxide interface. It is shown that there is. Sulfuric acid is the most commonly used electrolyte in this case, but phosphoric acid is also used. The aluminum oxide film formed by anodization is harder than the surface film oxidized in air. Anodized aluminum produced by the various aforementioned methods can be seen in action.
Substances which additionally influence adhesion and structure, especially after anodization, are also used in the printing plate sector, and improvements are nevertheless still desired. This includes, for example, the removal of defects that appear scattered in oxide films or during the application of photoresist films, the avoidance of unanticipated and early image collapse on the printing press, or the prevention of premature image collapse on the printing press. Fast and reliable inking on top. Even longer life on the printing press is desirable, as well as sealing or other forms of sealing or other forms of coating as a pre-step to later applying the photosensitive film to the substrate in a subsequent second and therefore additionally carried out processing step. An improved method of performing post-treatment that is more economical than conventional anodization would be desirable.
Improved corrosion resistance and economical production over known anodizing methods for protective and decorative purposes are desirable. The object of the present invention is therefore to provide an improvement in which an aluminum oxide coating is produced which is sufficient for practical use, and the pores of this coating are also modified (sealing), so that the product is on the one hand suitable for e.g. architectural applications. on the other hand, exhibits improved adhesion, gives high print runs, results in low wear on the press, has improved shelf life, and not to mention in terms of hydrophilicity. It is an object of the present invention to propose a particularly economical method for producing anodized aluminum, which can be used as an improved printing plate substrate. According to the invention, a plate-like, sheet-like or strip-like material made of aluminum or an aluminum alloy, optionally after mechanical, chemical and/or electrochemical roughening, is placed in an aqueous electrolyte containing at least one special organic acid. Starting from the anodizing method. The process according to the invention uses phytic acid, nitrilotriacetic acid, phosphoric acid mono(dodecyloxy-
polyoxyethylene) ester, tridecyl-benzenesulfonic acid, dinitro-stilbendisulfonic acid, dodecylnaphthalene disulfonic acid, dinonylnaphthalene disulfonic acid, di-n-butylnaphthalene disulfonic acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, or these It consists of using a mixture of two or more acids. Additionally, the aqueous electrolyte may contain an inorganic acid from the group consisting of phosphoric acid, phosphorous acid and mixtures of phosphoric acid and sulfuric acid or phosphorous acid. The method of the invention can be carried out continuously or batchwise. The aluminum materials treated by the method of the invention are generally first cleaned, for which purpose various organic solvents or aqueous alkaline solutions are used.
For alkaline degreasing, for example, sodium hydroxide, potassium hydroxide, trisodium phosphate and sodium silicate solutions are used, which may also contain surfactants. Environmental and health organic solvents, such as trichlorethylene, 1,1,1-
Degreasing with trichloroethane and perchlorethylene is less commonly used. “Pure Aluminum”, 1100, 3003 and A-19 aluminum alloys are used and advantageous for offset printing; typical analyzes (% by weight) of these alloys for offset printing are as follows: is:

[Table] The metal surface may be smooth or roughened. Conventional techniques can be used to roughen the surface. These include, among others, chemical etching in alkaline or acidic solutions, roughening by dry polishing with metal brushes, wet polishing with a suspension of brushes and abrasive particles, roughening with shots and/or Electrochemical roughening in hydrochloric acid or nitric acid may be mentioned. The surface roughness and structure differ in each of these areas. The average roughness R _Z is in the range of approximately 1 to 15 μm. The roughness is DIN (German Industrial Standard) 4768.
(October 1970 edition), roughness R _Z is 5
is the arithmetic mean of the individual roughness of each of the two adjacent reference lengths. The individual roughness is defined as the distance between two lines parallel to the average line that touch the highest and lowest points of the cross-sectional curve within each reference length. Each reference length is 1/5 of the length projected perpendicularly to the average line of the cross-sectional curve portion used for direct evaluation.
The mean line is a line parallel to the general direction of the cross-sectional curve of a geometrically ideal cross-sectional shape, and the mean line connects the cross-sectional curve with the total area of the material portion above this mean line. Divide so that the total area excluding material below is equal. Practical practice of the invention has shown that for best results, clean surfaces should be anodized immediately before air oxides form. The cleaned, degreased and optionally roughened plate may be additionally etched to remove air oxides before being treated with the method of the invention. This etching is carried out using known etchants, such as acidic and alkaline solutions, followed by rinsing. A method for removing air oxides is, for example, decoating the plate with a phosphoric acid/chloro acid solution. Metal surfaces should therefore advantageously be rinsed with water immediately after cleaning, roughening (if this step is required) and etching and anodizing while still wet, but this careful measure should not be strictly followed. Useful products can be obtained even if these rules are not followed. In addition to the acids mentioned above, the aqueous electrolyte contains polybasic organic acids 1
It may contain more than one species, and such acids are described in Japanese Patent Application No. 1983. Polybasic organic acids herein have at least five acid functions and belong to the group of phosphonic acids, sulfonic acids or carboxylic acids. A mixture of acids belongs. Possible electrolyte concentrations are from about 0.01% to saturation (but solutions above about 30% are often inappropriate due to viscosity) and do not depend significantly on chemical structure. Concentration At electrolyte concentrations of 1 to 5%, there is little difference in the properties of the products, and characteristic properties are obtained even at 30%, despite the often high viscosity of the electrolyte.
Furthermore, at constant voltage, increasing concentration results in a decrease in the rate of film thickness growth. A particularly advantageous concentration range is from about 0.8 to about 5%, considering the desired properties, ease of processing, film thickness achieved, and cost of the electrolyte. The relationship between the weight of the oxide film produced by anodization and the DC voltage used is approximately linear. The electrolytically applied coatings at all magnitudes of voltage above about 5 V provide corrosion resistance and printing properties superior to those of the prior art. When the voltage is 70V (DC), the stability of the oxide film will also increase due to the large film weight and large film thickness. When the voltage exceeds 70V, the film stability decreases again. This is believed to be due to a loss of film density, since the dielectric breakdown strength of the film was exceeded and pits formed in the film. This view is confirmed by examination under a transmission electron microscope, in which pits are visible. Corrosion resistance is therefore advantageous by working below 70V. With plates in which electrolysis is carried out using low voltages, printing tests last for a long time. 10, 20 and 40V
Comparative tests on diazo-coated aluminum plates electrolytically treated show that the press life is inversely proportional to the electrolytic voltage and the oxide film thickness. Printing test results demonstrate that low voltage promotes good adhesion to photosensitive films, especially diazo-based films, where 1
~30V, especially the 10-30V range is excellent. Direct current is suitable for this method, but alternating current may also be superimposed. A square wave of pulsed power supply is particularly suitable. The strength of the current is highest at the beginning of the method according to the invention and decreases over time, while an oxide layer forms on the metal surface and the current supply capacity decreases. The current supply capacity decreases within 30 seconds to a level that minimizes subsequent current consumption. This is an important factor for the economy of the process, since a useful film has already been formed. Current densities of 1 to 5, especially 1.3 to 4.3 A/dm ² represent advantageous process conditions and are excellent. The temperature at which the method is carried out may vary from about -2°C (near the freezing point of the electrolyte) to about 60°C. surface hardness test,
According to oxide film stability tests, streak adhesion, hydrophilicity and aging properties, best results are achieved at 10°C. However, the decrease in performance from 10°C to room temperature or up to 40°C is not significantly large. Working at very low temperatures requires expensive cooling capacities, and for this reason temperatures of about 10 to 35°C are advantageous, as they also offer the greatest economic efficiency and the least loss of capacity. Particularly good is processing at a working temperature of about 20-25°C. More than 60% of the aluminum oxide film is formed during the first 5 seconds (approximately 0.08 minutes) of anodization. For use in printing technology, no more than 5 minutes are used, since then no film is formed anymore. However, as discussed above, as long as the voltage is low, time is not a barrier. A time of 0.16 to 1 minute is excellent. From a methodological point of view, the process requires shorter (processing) times and lower temperatures (with little need for additional heating or cooling) compared to the conventional two-step method, which includes anodization followed by a characteristic hot immersion treatment. (no room temperature) and low overall current consumption are advantageous economic factors. In the embodiment of the process according to the invention, in which an inorganic acid is added in addition to at least one of the acids mentioned above, the following process parameters are preferably taken into account: The binary system of phosphoric acid and the acid mentioned has a concentration of
It has about 10 g/ to about 200 g/H ₃ PO ₄ . Preferably 20 g/~100 g/H ₃ PO ₄ is used and at least about 0.25%, preferably at least about 0.5% of the acid is added to ensure the above-mentioned properties and advantages of the anodized aluminum plate. Ru. In ternary systems in which sulfuric acid or phosphorous acid is added to phosphoric acid, such mixtures may vary over a whole range of compositions. If non-porosity is to be ensured, a high ratio of H ² SO ₄ to H ₃ PO ₄ requires a high proportion of said acid, ie about 1% or more. However, very high ratios of H ² SO ₄ to H ₃ PO ₄ can prevent the formation of non-porous films;
If the ratio of H ² SO ₄ to H ₃ PO ₄ is low, non-porosity is already achieved with a proportion of said acid of about 0.5%. Higher contents of said acids are in no case harmful. If the inorganic acid content is sufficiently low, the electrodeposition produces a non-porous coating in all cases, which is determined primarily by the concentration of the acid mentioned. The current supply capacity increases rapidly with increasing electrolyte concentration, resulting in shorter processing times and lower voltage requirements. The relationship between the weight of the aluminum oxide film produced and the DC voltage used is approximately linear. At all voltages above approximately 5 V, the electrodeposited coating provides corrosion resistance and print-technical properties superior to state-of-the-art products. The electrolytic voltage may be in the range of 5 to 75 V (DC) or higher. In the presence of strong inorganic acids, high weight electrodeposited oxide films can be easily obtained without the need for high voltages or long processing times. The desired products according to the invention are advantageously obtained using voltages of about 5 V to about 40 V in both binary and ternary systems. The strength of the current is the dependent variable, while the uniform composition of the electrolyte and the voltage are independent variables. Current density 0.2A/dm ² ~6A/d
m ² indicates favorable processing conditions and is excellent. The temperature at which the method is carried out may likewise vary from about -2°C (near the freezing point of the electrolyte) to about 60°C. It is also possible to carry out the anodization of the aluminum material by classical methods, in particular with aqueous sulfuric acid, even before applying the aluminum oxide coating by the method according to the invention (ie using the acids mentioned). In this case, the holes are sealed by the subsequent method according to the invention, so that a surface which is likewise improved in practice is produced. Applications of the materials anodized by the method according to the invention include, in particular, their use as substrates in the production of printing plates with photosensitive films. When the substrate is coated by the manufacturer of the presensitized printing plate or by the user, the substrate is coated with one of the following photosensitive materials: As a photosensitive film, the subsequent phenomenon may occur. In principle, all coatings are suitable which give a printable, image-like surface after exposure with and/or fixing. In addition to films containing silver halide, which are used in many areas, for example "Light-Sensitive Systems" (Jaromir Kosar, John Wiley & Sous, New York, 1965) ] are known: colloidal films containing chromates and dichromates (ibid., Chapter 2); films containing unsaturated compounds, in which the compounds are isomerized upon exposure to light. membranes containing photopolymerizable compounds, in which the monomers or prepolymers polymerize upon exposure, optionally with an initiator (ibid., Chapter 4); Chapter 5); and membranes containing O-diazo-quinones, such as naphthoquinone diazide, P-diazo-quinone or diazonium salt condensates (ibid., Chapter 7). Suitable films also include electrophotographic photosensitive films, such as those containing inorganic or organic photoconductors. Of course, in addition to the photosensitive material, these films may also contain other components, such as resins, dyes or softeners. In particular, the following photosensitive substances or compounds can be used for coating the substrates produced by the method according to the invention: US Pat. Nos. 3,175,906, 3,046,118
No. 2063631, No. 2667415 and No. 3867147
condensation products of iminoquinone diazide, 0-quinone diazide and aromatic diazonium compounds with suitable binders, as described in the patent specification, the substances described in the last-mentioned patent specification being generally superior. There is. Furthermore, photosensitive polymer systems based on ethylenically unsaturated monomers, which have a photopolymerization initiator and may also contain a polymeric binder, are suitable. Additionally, photodimeric systems, such as systems based on polyvinyl cinnamate and diallyl phthalate prepolymers, are suitable. Such systems are described, for example, in U.S. Pat. No. 3,497,356;
No. 3615435, No. 3926643, No. 2670286, No.
3376138 and 3376139. U.S. Pat. No. 3,902,976 describes the use of tin(2) chloride solution to measure the density and alkali resistance of oxide films. Visible hydrogen evolution is shown at the transition point with subsequent formation of black spots. Aluminum conventionally anodized with sulfuric and/or phosphoric acid as electrolyte is used in construction because of its excellent weather resistance. The tin chloride () test on such materials usually lasts about 4 to 10 seconds, whereas the test time on aluminum plates according to the invention is about 15 seconds, 5 seconds with the 0.1%-electrolyte solution used.
% - reaches more than 200 seconds in electrolyte solutions. It is assumed that the coating thickness is correlated with corrosion resistance, which is a crucial property of anodized coatings provided for the protection and decoration of metals. Due to its formation, “organic oxide metal complex (Organo-
The film weight of the oxide film, also referred to as ``metalloxid-komplex'', is approximately 82°C in an aqueous chromic acid/phosphoric acid standard solution (C ₂ O ₃ 1.95%, H ₃ PO ₄ 3.41% - 85%).
It can be quantitatively measured by removing the membrane in 15 minutes. The adhesion properties of the coatings produced by the method according to the invention are much better than those produced by immersion treatment in hot solutions, such as those carried out in the state of the art following anodization. The aqueous 1.0N NaOH solution removes most of the coating applied by immersion and heating. In contrast, coatings applied electrolytically are not substantially removed, ie they are insoluble in the same or less aggressive reagents. An offset printing plate with an aluminum oxide coating applied electrolytically and before being coated with a photosensitive film is tested. Plates can be inked wet or dry, the tests listed later being more rigorous (more problematic). After inking, rinse the plate under running water or spray with water and wipe gently. The ease and completeness of removal of printing ink is an indication of the hydrophilicity of the surface. Dry inking and post-drying in an oven at 100℃,
Printing ink can be completely rinsed off from plates produced according to the invention. Plates that are not anodized or that have been anodized in a conventional manner and then modified by non-electrolytic immersion methods exhibit "staining" even when aged under less severe conditions, which may be due to the original I couldn't go back. In the inking test, plates with and without a photosensitive coating are aged at different temperatures for different times and then tested for retention of hydrophilicity. Plates with various photosensitive diazo coatings are tested for substantial photosensitivity, resolution, retention of background hydrophilicity and ease of development by aging. Tests conducted using various voltages and times suggest that a film of what appears to be an organic oxidized metal complex on the metal surface acts as a capacitor. As long as the breakdown strength limit is not exceeded during electrolysis, there is no longer any weight gain over time, the film is not ruptured, and the tin chloride () test time remains constant. On the other hand, if the dielectric breakdown strength limit is exceeded, pits will form in the coating and the coating will lose its thickness. The tin chloride () test time corresponds to this pit. When the aluminum oxide coating produced according to the present invention is examined with a transmission electron microscope at a magnification of at least 55,000 times, no porosity is observed on the surface, whereas conventionally anodized aluminum is already
Typical porosity is shown at 5000x magnification. In the examples below and the description above, "%" refers to "% by weight" unless otherwise stated. Examples 1 to 10 Several aluminum alloy flat pieces having dimensions of 17.75 cm x 19.0 cm x 0.05 cm were prepared for electrolytic treatment. First, a commercially available aqueous solution containing a surfactant on both sides.
Treated with alkaline degreaser. The degreased aluminum piece was then heated to 1.0N at room temperature.
- Etched with NaOH aqueous solution for 20 seconds. After etching, the aluminum piece was thoroughly rinsed with water and immediately filled with a 1.0% aqueous solution of one of the acids mentioned above.
Placed in an electrically insulated container. Lead electrodes with dimensions corresponding to the dimensions of the aluminum plate were placed on both sides of the aluminum. The two electrodes each had a distance of 10 cm from the aluminum. A direct current power supply was used, with the aluminum connected as anode and the lead electrode as cathode. The bath temperature was maintained at 25°C and the voltage was 60V. The treatment lasted 30 seconds, and the plates were removed from the bath and rinsed well, followed by wiping dry. When a few drops of a saturated solution of SnCl ₂ are placed on the surface, the SnCl ₂ penetrates the film produced by the electrochemical process and immediately reacts with the aluminum. Scattered black specks of metallic tin indicate the end of the test. The weight of the aluminum oxide film was measured by removing the film with a chromic acid/phosphoric acid solution. The hydrophilicity of the surface was tested by applying a highly abrasive ink without water. A dry applicator was used for this purpose. The test results are obtained from the following table, where the abbreviations represent: C = can be rinsed completely clean and suitable for difficult offset printing T = lightly smudged or spotted S = smeared; Unsuitable for offset printing CT = Intermediate result between C and T

Table: Examples 11 to 16 Various mixtures of acids according to the invention with a total concentration of 1.0% were prepared and these mixtures were used as electrolytes in the process according to the invention. Electrolysis was carried out using 30 V DC for 30 seconds at bath temperature on an aluminum plate that had been previously degreased, grained with an abrasive suspension, and etched.The composition of the electrolyte, the film weight of the oxide film, The reaction time with SnCl ₂ and the behavior in the dry inking test are listed below. Corrosion resistance and hydrophilicity were very good in all examples. Example 11 Electrolyte 1: Hydroxyethyl-ethylenediaminetriacetic acid 0.75%, Electrolyte 2: Polystyrene sulfonic acid 0.25%, Film weight: 440mg/m ² , SnCl ₂ test: 107 seconds, Ink test: CT Example 12 Electrolyte 1: Ethylenediaminetetraacetic acid 0.75
%, electrolyte 2: polyvinylphosphonic acid 0.25%, film weight 401 mg/m ² , SnCl ₂ test: 112 seconds, ink test: C Example 13 Electrolyte 1: polyvinylphosphonic acid 0.5%, electrolyte 2: phytic acid 0.5%, film weight :392mg/ ^m2 ,
SnCl ₂ test: 123 seconds, ink test: C Example 14 Electrolyte 1: polyvinylphosphonic acid 0.75%, electrolyte 2: phytic acid 0.25%, film weight: 378 mg/m ² ,
SnCl ₂ test: 131 seconds, Ink test: C Example 15 Electrolyte 1: phytic acid 0.5%, Electrolyte 2: Vinyl methyl ether/maleic anhydride copolymer (hydrolyzed) 0.5%, Film weight: 388 mg/m ² , SnCl ₂
Test: 125 seconds, Ink test: C Example 16 Electrolyte 1: Polystyrene sulfonic acid 0.5%, Electrolyte 2: Phytic acid 0.5%, Film weight: 411mg/
m ² , SnCl ₂ test: 98 seconds, ink test: CT Example 17 An anodic oxide film was formed in a 1% phytic acid aqueous solution at 30 V DC within 60 seconds by a method similar to Example 1. When examined under a transmission electron microscope at 55,000x magnification, the insulating oxide film exhibited a smooth, apparently unpatterned surface with no visible porosity. Example 18 Flat specimens of aluminum alloy 3003 with dimensions 18.3 cm x 17.8 cm x 0.03 cm were prepared for electrolytic treatment as described in Example 1. After etching (10-15 seconds) the samples were washed with water and dried in a stream of air. The sample was pressed onto a conductive rail and suspended in an insulated bath between two lead plates, each with a distance of 20 cm. The bath contained an aqueous solution containing 100 g/H ₃ PO ₄ and 1% phytic acid. It was connected to a DC power source using aluminum as an anode and a lead electrode as a cathode. The bath had an ambient temperature of 22°C ± 2°C during the test. The current was switched on with a pre-adjusted DC voltage of 16 V and the electrolytic treatment lasted for 60 seconds. Contact was broken, the plate was removed from the bath, rinsed with water and finally wiped dry. To test the hydrophilicity of the surface, a highly abrasive printing ink was applied with a dry applicator without water. When immediately dry inked and washed with water, the plates were significantly cleaner than conventionally produced plates. The test time to reach the transition point when a few drops of potassium zincate solution was added to the surface was 100 seconds. Finally, a photosensitive solution containing pigment, polyvinyl formal binder and diazonium condensation product according to US Pat. No. 3,867,147 was applied to the plate. After exposure with a negative original and development with an aqueous-alcoholic developer, the background was clean and a clear image remained within the exposed area. 21 steps-
After development with an aqueous-alcoholic developer using a Stauffer step wedge, the 6 steps were exposed to full black. The insulating aluminum oxide coating showed a smooth surface with no visible porosity when examined under a transmission electron microscope at 55,000x magnification.

Claims (1)

[Claims] 1. A method for anodizing plate-like, sheet-like or strip-like materials made of aluminum or aluminum alloys in an aqueous electrolyte containing at least one special organic acid, in which phytic acid is used as the acid. , nitrilotriacetic acid, phosphoric acid mono(dodecyloxy-polyoxyethylene) ester, tridecyl-benzenesulfonic acid, dinitro-stilbene disulfonic acid, dodecylnaphthalene disulfonic acid, dinonylnaphthalene disulfonic acid, di-n-
Anodizing a plate-like, sheet-like or strip-like material made of aluminum or an aluminum alloy, characterized in that it uses butylnaphthalene disulfonic acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid or a mixture of two or more of these acids. Method. 2. The method according to claim 1, wherein the aqueous electrolyte contains 0.05 to 30% by weight of acid. 3. A method according to claim 1 or 2, wherein the aqueous electrolyte contains at least 0.5% by weight of acid. 4 Anodic oxidation using a voltage of 1 to 30 V and a current density of 1
4. A method according to any one of claims 1 to 3, which is carried out at ~5 A/ ^dm2 for 0.08 to 5 minutes at a temperature of -2 to 60<0>C. 5. Anodizing using a voltage of at least 5 V, a current density of 1.3-4.3 A/ ^dm2 and a temperature of 10-35 °C.
5. A method according to any one of claims 1 to 4, which is carried out for 0.16 to 1 minute. 6. A process for anodizing plate-like, sheet-like or strip-like materials made of aluminum or aluminum alloys in an aqueous electrolyte containing at least one special organic acid, in which the acids are phytic acid, nitrilotriacetic acid, phosphoric acid. Mono(dodecyloxy-polyoxyethylene) ester, tridecyl-benzenesulfonic acid, dinitro-stilbendisulfonic acid, dodecylnaphthalene disulfonic acid, dinonylnaphthalene disulfonic acid, di-n-
Butylnaphthalene disulfonic acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, or a mixture of two or more of these acids are used, and the aqueous electrolyte is additionally phosphoric acid, phosphorous acid, and phosphoric acid and sulfuric acid or phosphorous acid. A method for anodizing plate-like, sheet-like or strip-like materials made of aluminum or aluminum alloys, characterized in that they contain an inorganic acid of the group consisting of a mixture of aluminum and aluminum alloys. 7. The method according to claim 6, wherein the aqueous electrolyte contains 0.05 to 30% by weight of acid. 8. A method according to claim 6 or 7, wherein the aqueous electrolyte contains at least 0.5% by weight of acid. 9. The method according to any one of claims 6 to 8, wherein the aqueous electrolyte contains 10 to 200 g/inorganic acid. 10 Anodic oxidation using voltage 5-40V with current density
0.2~6A/ ^dm2 and temperature -2~60℃ 0.08~5
10. A method according to any one of claims 6 to 9, which is carried out for a minute. 11. A process for anodizing plate-like, sheet-like or strip-like materials made of aluminum or aluminum alloys in an aqueous electrolyte containing at least one special organic acid, in which the acids are phytic acid, nitrilotriacetic acid, phosphoric acid. Mono(dodecyloxy-polyoxyethylene) ester, tridecyl-benzenesulfonic acid, dinitro-stilbendisulfonic acid, dodecylnaphthalene disulfonic acid, dinonylnaphthalene disulfonic acid, di-n
- using butylnaphthalene disulphonic acid, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid or mixtures of two or more of these acids, and with the addition of aqueous sulfuric acid as electrolyte before anodization in the acid-containing electrolyte. A method for anodizing plate-like, sheet-like or strip-like materials made of aluminum or aluminum alloys, characterized in that the anodization is carried out in a solution. 12. The method according to claim 11, wherein the aqueous electrolyte contains 0.05 to 30% by weight of acid. 13. Claims 11 or 12, wherein the aqueous electrolyte contains at least 0.5% by weight of acid.
The method described in section. 14 Anodic oxidation using a voltage of 1 to 30 V and a current density of 1 to 5 A/dm ² for 0.08 to 5 minutes at a temperature of -2 to 60°C.
Claims 11 to 13, implemented in
The method described in any one of the preceding paragraphs. 15 Anodizing using a voltage of at least 5V,
At current density 1.3~4.3A/ ^dm2 and temperature 10~35℃
15. A method according to any one of claims 11 to 14, which is carried out for 0.16 to 1 minute.