EP0118740B1 - Plate, foil or web-like materials made of mechanically and electrochemically grained aluminium, process for their manufacture and their use as supports for lithographic printing plates - Google Patents

Abstract

Disclosed is a sheet, foil or strip material comprising aluminum or an alloy thereof, which is first mechanically and then electrochemically roughened on one or both surfaces to produce the following parameters: (a) from about 60 to 90% of the surface comprise a basic structure, in which the arithmetic mean of the distribution of diameters Da1 of the pits is in the range from about 1 to 5 microns, (b) from about 10 to 40% of the surface comprise a superimposed structure formed of elevations having an average base F from about 100 to 1,500 microns2, in which the arithmetic mean of the distribution of diameters Da2 of the pits is in the range from about 0.1 to 1.0 micron, (c) the center line average roughnesses Ra of the entire surface are at least 0.6 micron, and (d) the contact area tpmi of the entire surface is not more than about 20% at a stylus working depth of 0.125 micron and not more than about 70% at a stylus working depth of 0.4 micron. Also disclosed is a process for the production of this material and offset-printing plates which comprise a layer of this material provided with a radiation-sensitive coating.

Description

The invention relates to a plate, film or ribbon-shaped material made of aluminum or its alloys with a surface that is first mechanically roughened on both sides and then electrochemically roughened, a process for its production and its use as a carrier material in the production of offset printing plates.

Backing materials for offset printing plates are provided either by the consumer directly or by the manufacturer of precoated printing plates on one or both sides with a radiation-sensitive layer (reproduction layer), with the aid of which a printing image of a template is generated photomechanically. After this printing form has been produced from the printing plate, the layer support carries the image points which will guide the color during later printing and at the same time forms the hydrophilic background for the lithographic printing process at the non-image points (non-image points) during later printing.

• - Die nach der Belichtung relativ löslicher gewordenen Teile der lichtempfindlichen Schicht müssen durch eine Entwicklung leicht zur Erzeugung der hydrophilen Nichtbildstellen rückstandsfrei vom Träger zu entfernen sein, ohne daß der Entwickler dabei in größerem Ausmaß das Trägermaterial angreift.
• - Der in den Nichtbildstellen freigelegte Träger muß eine große Affinität zu Wasser besitzen, d. h. stark hydrophil sein, um beim lithographischen Druckvorgang schnell und dauerhaft Wasser aufzunehmen und gegenüber der fetten Druckfarbe ausreichend abstoßend zu wirken.
• - Die Haftung der lichtempfindlichen Schicht vor bzw. der druckenden Teile der Schicht nach der Belichtung muß in einem ausreichenden Maß gegeben sein.

The following requirements must therefore be placed on a layer support for reproduction layers for the production of offset printing plates:

• - The parts of the photosensitive layer that have become relatively more soluble after exposure must be easy to remove from the support without residues by development to produce the hydrophilic non-image areas, without the developer attacking the support material to a greater extent.
• - The carrier exposed in the non-image areas must have a great affinity for water, ie be highly hydrophilic, in order to absorb water quickly and permanently during the lithographic printing process and to be sufficiently repellent to the bold printing ink.
• - The adhesion of the light-sensitive layer before or the printing parts of the layer after exposure must be sufficient.

In principle, aluminum, steel, copper, brass or zinc, but also plastic films or paper can be used as the base material for such layer supports. These raw materials are modified by suitable modifications such. B. grain, matt chrome plating, surface oxidation and / or application of an intermediate layer in layer support for offset printing plates. Aluminum, which is probably the most frequently used base material for offset printing plates today, is roughened on the surface by known methods by dry brushing, wet brushing, sandblasting, chemical and / or electrochemical treatment. In order to increase the abrasion resistance, the roughened substrate can also be subjected to an anodization step to build up a thin oxide layer.

Additional requirements are imposed on the radiation-sensitive coated printing plate support, some of which interact with the requirements for the support material itself. These include, for example, a high sensitivity to radiation (light), good developability, clear contrasts after exposure and / or development, long print runs and reproduction that is as accurate as possible; increasingly play, especially in the case of printing plates with positive-working radiation-sensitive layers, a behavior of the radiation-sensitive layer that is as free of radiation as possible when irradiating (exposing) the printing plate and good (ie with as little water as possible and with the greatest possible fluctuation tolerance in the water requirement during printing) Water routing of the printing forms plays an important role. The following publications are known from the prior art, for example, which provide solution contributions for individual requirements; this includes, on the one hand, generating elevations in or on the radiation-sensitive layer and, on the other hand, a combination of several roughening stages for the carrier material.

DE-OS-2 512 043 (= US Pat. No. 4,168,979) describes a radiation-sensitive printing plate which has a matt coating on the surface of the radiation-sensitive layer which is removed during development. This matte layer generally is a layer of binder (for. Example, of a cellulose ether) with incorporated by dispersion therein, delustering particles, such as those made of Si0 _2, ZnO, Ti0 _2, Zr0 _2, glass, A1 ₂ 0 _3, starch or polymers. A printing plate constructed in this way is intended to shorten the time required to achieve the most extensive and uniform possible contact between the film template and the radiation-sensitive layer during the exposure stage of the printing form production process.

From DE-OS-2926 236 (= ZA-PS-80/3523) a radiation-sensitive reproduction material is known which contains particles in the positive-working radiation-sensitive layer, the smallest dimension of which is at least as large as the thickness of the layer itself, whereby the type of particles corresponds qualitatively to that described in the previously described DE-OS. Such a material is said to be suitable for all applications in which positive contact copies have to be made in a vacuum copying frame and in which high image resolution and faithful reproduction of the original are important; in particular, it should show a lower tendency to under-radiation when copying, i. H. As a result of a locally increased distance, under-radiation (lateral and oblique radiation incidence) can occur between the original and the radiation-sensitive layer, which then lead to inaccurate imaging of small picture elements such as halftone dots.

However, the application or introduction of particles with a binder onto or without a special binder in the radiation-sensitive layer is a complex process step that requires a great deal of care, particularly in modern, continuously running coating systems. They also set up brought or added particles during the development of the layer for the developing liquid and in particular also the automatically working developing devices are a kind of "foreign body" that can cause malfunctions in the functional sequence. The additives have no particular influence on the water flow of the printing form.

The process for the continuous production of a lithographic surface on a metal strip according to DE-PS-1 962 728 (= US-PS-3 691 030) by wet grinding and electrochemical treatment in an electrolyte uses the electrolyte during grinding for wetting and conducts the electrochemical Treatment after grinding through. Both the grinding and the electrochemical treatment can each have a roughening effect on z. B. Exercise aluminum.

The process for producing a support for lithographic printing plates according to DE-OS-3 012 135 (= GB-OS-2 047 274) is carried out in at least three stages, with a) the aluminum plate being mechanically roughened, b) from the roughened surface 5 to 20 g / m ^{2 are} removed and c) an electrochemical roughening with an electric current of alternating waveform is carried out in an aqueous acid solution, and this current must have certain parameters. After the electrochemical roughening, further ablation treatment and also anodic oxidation of the roughened surface can follow. The surface topography of the support must look such that the surface in the primary structure shows even hills, overlaid by a secondary structure that shows pinholes, the respective bisecting axis of which is approximately perpendicular to the tangent to the outer surface of the hill. The statistical distribution of the diameter of the pinholes is approximately such that 5% of the holes have a diameter D ₅ of at most 3 µm and 95% of the holes have a diameter D ₉₅ of at most 7 µm, ie the majority of the holes are in the range between 3 and 7 ₁ 1m, in particular between 5 and 7 microns. The density of the pinholes is approximately 10 ⁶ to 10 ⁸ holes per cm ² . It is mentioned that in the mechanical roughening stage - in addition to the preferred method of roughening with a rotating nylon brush using an aqueous pumice stone dispersion - which is also carried out in the only example - wire brushing or the spherical grain size of the surface is also possible, but this statement becomes possible not specified further. The average roughness value R of the mechanically roughened aluminum is 0.4 to 1.0 µm before the ablation treatment stage.

JP-OS-123 204/78 (application no. 38238/77, published October 27, 1978) also describes the combination of mechanical roughening by nylon brushes and aqueous pumice stone dispersion and electrochemical roughening for printing plate support materials made of aluminum. Ablative treatment is performed after both roughening stages have been completed, but not between them.

From GB-PS-1 582 620 the combination of a) mechanical roughening of printing plate support materials and b) electrochemical roughening with alternating current in aqueous HCI and / or HN0 ₃ containing solution is known. The topography of the surface is not qualified or quantified. In the examples, only mechanical roughening of aluminum with oscillating nylon brushes is carried out using an aqueous dispersion containing pumice and quartz; however, the description also mentions wire brushing as an alternative, but without further specification. The mechanically roughened aluminum surface is chemically cleaned between the two roughening stages.

The aluminum printing plate support material according to US Pat. No. 2,344,510 is first roughened mechanically, in particular by wire brushing, and then roughened chemically or electrochemically. The finer roughening pattern of the chemical or electrochemical roughening should overlap the medium-fine roughening pattern of the mechanical roughening. Between the mechanical and the preferred electrochemical roughening, a cleaning stage is switched on, which is carried out with a 5% strength aqueous NaOH solution at 95 ° C. The roughening electrolyte is an aqueous solution containing NaCl and HCl. After roughening, the material can also be anodized.

US Pat. No. 3,929,591 describes an aluminum printing plate carrier material which is produced in three stages, namely a) mechanical roughening using a moist particle mass based on silicates, oxides or sulfates, b) electrochemical roughening Alternating current in an aqueous electrolyte containing phosphates or H ₃ PO ₄ , and c) anodic oxidation with direct current in an aqueous electrolyte containing H ₂ SO ₄ . Level b) should lead to an increased reflection behavior of the surface of at least 5%. The topography of the surface is not qualified or quantified.

The combination of mechanical and electrochemical roughening can contribute to an improvement in the water flow, but no influence on the behavior of radiation-sensitive printing plates produced therewith which is as free of radiation as possible is mentioned or suggested in the prior art at any point. In addition, the comparative experiments described below show that not every mechanically roughened - even not every wire brushed - aluminum printing plate support is suitable after the electrochemical roughening and possibly anodic oxidation of the surface, on the one hand good water flow and on the other hand an at least reduced tendency to under radiation when printing with these printing forms or in the manufacture of the printing forms.

The object of the present invention is to propose a material made of aluminum, with the aid of which it is possible to produce offset printing plates which have radiation-sensitive layers and which show as little or no tendency to under radiation during the irradiation process in the copying frame and, moreover, good water flow when printing printing plates made from the plates exhibit.

• a) 60 bis 90 % der Oberfläche eine Grundstruktur aufweisen, in der das arithmetische Mittel der Verteilung der Lochdurchmesser D_a1 im Bereich von 1 bis 5 µm liegt,
• b) 10 bis 40 % der Oberfläche eine überlagerte Struktur aus Erhebungen einer mittleren Grundfläche F von 100 bis 1500 µm² aufweisen, in der das arithmetische Mittel der Verteilung der Lochdurchmesser D_a2 im Bereich von 0,1 bis 1,0 um liegt,
• c) die Mittenrauhwerte R, der gesamten Oberfläche mindestens 0,6 µm betragen, und
• d) der Traganteil t_pmi der gesamten Oberfläche bei einer Schnittiefe von 0,125 um maximal bei 20 % und bei einer Schnittiefe von 0,4 µm maximal bei 70 % liegt.

The invention is based on a plate-shaped, sheet-like or band-shaped material made of aluminum or its alloys with a surface that is first mechanically roughened and then electrochemically roughened on one or both sides. The material according to the invention is then characterized in that

• a) 60 to 90% of the surface have a basic structure in which the arithmetic mean of the distribution of the hole diameters D _{a1 is} in the range from 1 to 5 μm,
• b) 10 to 40% of the surface have a superimposed structure of elevations of an average base area F of 100 to 1500 μm ² , in which the arithmetic mean of the distribution of the hole diameters D _{a2 is} in the range from 0.1 to 1.0 μm,
• c) the average roughness values R of the entire surface are at least 0.6 μm, and
• d) the bearing component t _{pmi of} the entire surface is a maximum of 20% at a depth of cut of 0.125 µm and a maximum of 70% at a depth of cut of 0.4 µm.

In a preferred embodiment, the parameters a) D _{a1 are} in the range from 2 to 4 μm, b) D _a2 in the range from 0.3 to 0.8 μm with an average base area F from 200 to 1200 μm ² , c) R _a in the range of 0.8 to 1.2 µm and d) tp _m ; (0.125) maximum at 15% and tp _m ; (0.4) maximum at 60%. Some of these parameters can already lie in the specified ranges in the case of commercially available carrier materials for offset printing plates, but no carrier material has yet been found which matches all of these parameters with the material according to the invention. This applies in particular to the “double structure” claimed according to the invention and its effects on the behavior of the printing plate or printing form. The parameters characterizing the material according to the invention are defined as follows:

The roughening of the surface can be measured and analyzed using various methods. Standard methods include observation under a scanning electron microscope and instrument measurements such as with a roughness measuring device (profilometer), which scans a linear path on the plate with a highly sensitive needle.

The diameter of the holes created by the roughening or the base area of the elevations are determined on the basis of photos which are taken, for example, with 240, 1200 or 6000 times magnification by means of a scanning electron microscope with an electron beam incident obliquely to the aluminum surface. A representative area with at least 1000 holes is selected for the measurement for each sample. The diameter of each hole is measured in the plane of the surface both parallel and perpendicular to the rolling axis or strip direction of the aluminum. The arithmetic mean of the diameters in the parallel and vertical directions are calculated separately. The arithmetic mean D _{a of} the distribution of the hole diameters is calculated from the arithmetic mean of the hole diameters in a parallel and perpendicular direction. D _a1 is the arithmetic mean of the distribution of the hole diameters in the basic structure, D _a2 accordingly in the superimposed structure. The percentages of the basic structure and the superimposed structure from the surveys of the entire surface are also determined from these representative surface sections.

The surface roughness (see for example DIN 4768 in the version from October 1970 or DIN 4762 in the version from May 1978) is measured with a roughness measuring device (profilometer, stylus device with electrical transmission) over a representative measuring distance of at least 2 mm both parallel and perpendicular to Roll axis measured. The mean roughness values are determined and calculated from the two measurements as the arithmetic mean of the absolute distance of all points on the surface of the roughness profile from the center line of the profile. The average roughness value R _a is then the average value of the average roughness values in the parallel and perpendicular directions. The load share tp _m ; is the ratio of the load-bearing length of the roughness profile to the measuring section of the roughness profile in the respectively selected depth of cut of 0.125 µm or 0.4 µm in%, ie in the present case tp _mi (0.125) is less than tpm (0.4); the load share tp _mi is also the average value of the load shares in the parallel and vertical direction; The roughness profile is the difference between the palpated profile and the envelope line (path of the center of a center point of a ball rolling over the profile, which is generally formed electronically in a stylus device); the depth of cut indicates the distance from the envelope line of the bearing component is determined. A curve drawn up from the load components (load component curve, Abbott curve) can, for example, provide information about the behavior in use, too high, ie load components above the claimed values lead to less suitable materials in the present field of application. The load share curve not only takes the profile depths into account, but also the profile shapes.

The parameters characterizing the invention are thus the hole diameter and its size distribution in the basic structure and the superimposed structure from elevations, the average base area of the elevations, the percentages of the basic structure and the superimposed structure on the entire roughened surface, and the surface roughness, characterized by the Average roughness values and the load share.

Suitable base materials for the material according to the invention include those made of aluminum or one of its alloys, which have, for example, a content of more than 98.5% by weight of Al and proportions of Si, Fe, Ti, Cu and Zn. The base material is roughened on one or both sides first mechanically and then electrochemically, if appropriate after a preliminary cleaning, any type of mechanical and electrochemical roughening being suitable in principle, the combination of which results in the “double structure” according to the invention. In addition to the wire, mechanical roughening processes can be used, for example brushing can also be counted a brushing with rotating, plastic bristle brushes using aqueous abrasive suspensions. The electrochemical roughening step is generally carried out in aqueous acids as electrolytes, but neutral or acidic aqueous salt solutions can also be used, each of which can also contain additives with corrosion inhibitors. After the mechanical roughening has been carried out, the mean roughness value R should not be less than 0.5 μm and the load _fraction t _pmi (0.125) should not be more than 20%.

To produce the materials according to the invention, a process is used in particular in which the base material, if appropriate after a preliminary cleaning, is mechanically roughened on one or both sides by wire brushing, and then, if appropriate after a removal intermediate treatment in an alkaline or acidic aqueous solution, electrochemically in a hydrochloric acid and / or electrolyte containing nitric acid is roughened using alternating current. Pre-cleaning includes, for example, treatment with aqueous NaOH solution with or without degreasing agent and / or complexing agents, trichlorethylene, acetone, methanol or other commercially available aluminum stains. Wire brushing has been used in the relevant field for years and requires no further explanation. The ablating intermediate treatment, which can optionally also be carried out electrochemically, is generally carried out using an aqueous alkali metal hydroxide solution or the aqueous solution of an alkaline salt or an aqueous acid solution based on HN0 ₃ , H ₂ S0 ₄ or H ₃ P0 ₄ at a removal rate of 5 g / m ² .

Electrochemical roughening has also been used in practice for years. The aqueous electrolyte, preferably based on aqueous solutions containing HCl and / or HN0 ₃ , can contain corrosion-inhibiting or other additives such as HyS0 ₄ , Hy0 ₂ , H ₃ P0 ₄ , H ₂ Cr0 ₄ , HgBOg, gluconic acid, amines, diamines, surfactants or aromatic aldehydes can be added.

In general, the process parameters in the roughening stage, in particular in the case of continuous process control, are in the following ranges: the temperature of the electrolyte between 20 and 60 ° C., the active substance (acid, salt) concentration between 2 and 100 g / l (in the case of salts also higher), the current density between 25 and 250 A / dm ² , the residence time between 3 and 100 sec and the electrolyte flow rate in continuous. Method on the surface of the workpiece to be treated between 5 and 100 cm / sec; AC is usually used as the type of current, but modified types of current such as AC with different amplitudes of the current strength are also possible for the anode and cathode currents. In this process with the previous wire brushing, the distribution of the hole sizes is generally more uniform than in processes without prior mechanical roughening. This stage is carried out in such a way that the basic topography of the mechanically roughened surface, characterized by the mean roughness value and the load-bearing component, changes only relatively little, but a hole structure that is as closed as possible, caused by the electrochemical roughening, is additionally formed, so that the external appearance shows a basic structure for 60 to 90% of the surface with the hole diameter distribution given above and a structure which appears as a superimposed structure from elevations for 10 to 40% of the surface. The frequency of the surveys is on average around 200 to 500, in particular 250 to 450, per mm ² , but it can also vary up and down. The electrochemical roughening can additionally be followed by a removal treatment with one of the solutions indicated in the intermediate treatment, in particular a maximum of 2 g / m ² removal.

• - Das Gleichstrom-Schwefelsäure-Verfahren, bei dem in einem wäßrigen Elektrolyten aus üblicherweise ca. 230 g H₂S0₄ pro 1 I Lösung bei 10° bis 22°C und einer Stromdichte von 0,5 bis 2,5 Aldm² während 10 bis 60 min anodisch oxidiert wird. Die Schwefelsäurekonzentration in der wäßrigen Elektrolytlösung kann dabei auch bis auf 8 bis 10 Gew.-% H₂SO₄ (ca. 100 g H₂S0_4/1) verringert oder auch auf 30 Gew.-% (365 g H₂S0₄/1) und mehr erhöht werden.
• - Die "Hartanodisierung" wird mit einem wäßrigen, H₂S0₄ enthaltenden Elektrolyten einer Konzentration von 166 g H₂S0₄/1 (oder ca. 230 g H₂S0₄/1) bei einer Betriebstemperatur von 0° bis 5°C, bei einer Stromdichte von 2 bis 3 A/dm², einer steigenden Spannung von etwa 25 bis 30 V zu Beginn und etwa 40 bis 100 V gegen Ende der Behandlung und während 30 bis 200 min durchgeführt.

After the roughening process, an anodic oxidation of the aluminum usually follows in a further process step, for example in order to improve the abrasion and adhesion properties of the surface of the carrier material. The usual electrolytes such as H ₂ S0 ₄ , H ₃ P0 ₄ , H ₂ C ₂ 0 ₄ , amidosulfonic acid, sulfosuccinic acid, sulfosalicylic acid or mixtures thereof can be used for anodic oxidation. Reference is made, for example, to the following standard methods for the use of aqueous electrolytes containing H ₂ S0 ₄ for the anodic oxidation of aluminum (see, for example, BM Schenk, material aluminum and its anodic oxidation, Francke Verlag - Bern, 1948, page 760; Practical electroplating, Eugen G. Leuze Verlag - Saulgau, 1970, page 395 ff and pages 518/519; W. Hübner and CT Speiser, The practice of anodic oxidation of aluminum, Aluminum Verlag - Düsseldorf, 1977, 3rd edition, pages 137 ff):

• - The direct current sulfuric acid process, in which in an aqueous electrolyte from usually approx. 230 g H ₂ S0 ₄ per 1 I solution at 10 ° to 22 ° C and a current density of 0.5 to 2.5 Aldm ² during 10 is anodized up to 60 min. The sulfuric acid concentration in the aqueous electrolyte solution can also be reduced to 8 to 10 wt .-% H ₂ SO ₄ (approximately 100 g of H ₂ S0 _4/1), or even to 30 wt .-% (365 g of H ₂ S0 ₄ / 1) and more can be increased.
• - The "hard anodising" is reacted with an aqueous H ₂ S0 ₄ electrolyte containing a concentration of 166 g H ₂ S0 _4/1 (or about 230 g H ₂ S0 _4/1), at an operating temperature of 0 ° to 5 ° C , at a current density of 2 to 3 A / dm ² , a rising voltage of about 25 to 30 V at the beginning and about 40 to 100 V towards the end of the treatment and for 30 to 200 min.

In addition to the processes for anodic oxidation of aluminum already mentioned in the previous paragraph, the following processes can also be used, for example: the anodic oxidation of aluminum in an aqueous electrolyte containing H ₂ SO ₄ , the Al ^{3 +} ion content of which is present Values of more than 12 g / l are set (according to DE-OS-2 811 396 = US-PS-4 211 619), in an aqueous electrolyte containing H ₂ S0 ₄ and H ₃ P0 ₄ (according to DE- OS-2 707 810 = US-PS-4 049 504) or in an aqueous H _z S0 ₄ , H ₃ P0 ₄ and A) 3 + ions containing electrolytes (according to DE-OS-2 836 803 = US-PS -4 229 266). Direct current is preferably used for the anodic oxidation, but alternating current or a combination of these types of current (eg direct current with superimposed alternating current) can also be used; the electrolyte is in particular an aqueous solution containing H ₂ S0 ₄ and / or H ₃ P0 ₄ . The layer weights of aluminum oxide range from 0.5 to 10 g / m ² , corresponding to a layer thickness of approximately 0.15 to 3.0 µm.

The stage of anodic oxidation of the aluminum printing plate support material can also be followed by one or more post-treatment stages. Aftertreatment means in particular a hydrophilizing chemical or electrochemical treatment of the aluminum oxide layer, for example an immersion treatment of the material in an aqueous polyvinylphosphonic acid solution according to DE-PS-1 621 478 (= GB-PS-1 230 447), an immersion treatment in one aqueous alkali silicate solution according to DE-AS-1 471 707 (= US-PS-3 181 461) or an electrochemical treatment (anodization) in an aqueous alkali-silicate solution according to DE-OS-2 532 769 (= US-PS -3 902 976). These post-treatment stages serve in particular to additionally increase the hydrophilicity of the aluminum oxide layer, which is already sufficient for many areas of application, the remaining known properties of this layer being at least retained.

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

• positiv-arbeitende, o-Chinondiazide, insbesondere o-Naphthochinondiazide wie Naphthochinon-(1,2)-diazid-(2)-sulfonsäureester oder -amide, die nieder- oder höhermolekular sein können, als lichtempfindliche Verbindung enthaltende Reproduktionsschichten, die beispielsweise in den DE-PSen 854 890, 865 109, 879 203, 894 959, 938 233, 1 109 521, 1 144 705, 1 118 606, 1 120 273, 1 124 817 und 2 331 377 und den EP-OSen 0 021 428 und 0 055 814 beschrieben werden;
• negativ-arbeitende Reproduktionsschichten mit Kondensationsprodukten aus aromatischen Diazoniumsalzen und Verbindungen mit aktiven Carbonylgruppen, bevorzugt Kondensationsprodukte aus Diphenylamindiazoniumsalzen und Formaldehyd, die beispielsweise in den DE-PSen 596 731, 1 138 399, 1 138 400, 1 138 401, 1 142 871, 1 154 123, den US-PSen 2 679 498 und 3 050 502 und der GB-PS-712 606 beschrieben werden;
• negativ-arbeitende, Mischkondensationsprodukte aromatischer Diazoniumverbindungen enthaltende Reproduktionsschichten, beispielsweise nach der DE-OS-2 024 244, die Produkte mit mindestens je einer Einheit aus a) einer kondensationsfähigen aromatischen Diazoniumsalzverbindung und b) einer kondensationsfähigen Verbindung wie einem Phenolether oder einem aromatischen Thioether, verbunden durch ein zweibindiges, von einer kondensationsfähigen Carbonylverbindung abgeleitetes Zwischenglied wie einer Methylengruppe aufweisen;
• positiv-arbeitende Schichten nach der DE-OS-2 610 842, der DE-PS-2 718 254 oder der DE-OS-2 928 636, die eine bei Bestrahlung Säure abspaltende Verbindung, eine monomere oder polymere Verbindung, die mindestens eine durch Säure abspaltbare C-O-C-Gruppe aufweist (z. B. eine Orthocarbonsäureestergruppe oder eine Carbonsäureamidacetalgruppe) und gegebenenfalls ein Bindemittel enthalten;
• negativ-arbeitende Schichten aus photopolymerisierbaren Monomeren, Photoinitiatoren, Bindemitteln und gegebenenfalls weiteren Zusätzen; als Monomere werden dabei beispielsweise Acryl- und Methacrylsäureester oder Umsetzungsprodukte von Diisocyanaten mit Partialestern mehrwertiger Alkohole eingesetzt, wie es beispielsweise in den US-PSen 2 760 863 und 3 060 023 und den DE-OSen 2 064 079 und 2 361 041 beschrieben wird;
• negativ-arbeitende Schichten gemäß der DE-OS-3 036 077, die als lichtempfindliche Verbindung ein Diazoniumsalz-Polykondensationsprodukt oder eine organische Azidoverbindung und als Bindemittel ein hochmolekulares Polymeres mit seitenständigen Alkenylsulfonyl- oder Cycloalkenylsulfonylurethan-Gruppen enthalten.

In addition to the layers containing silver halides used in many fields, various others are also known, such as e.g. As described in "Light-Sensitive Systems" by Jaromir Kosar, John Wiley & Sons Verlag, New York 1965: the colloid layers containing chromates and dichromates (Kosar, Chapter 2); the layers containing unsaturated compounds in which these compounds are isomerized, rearranged, cyclized or crosslinked during exposure (Kosar, Chapter 4); the layers containing photopolymerizable compounds, in which monomers or prepolymers optionally polymerize during exposure by means of an initiator (Kosar, Chapter 5); and the layers containing o-diazo-quinones such as naphthoquinonediazides, p-diazo-quinones or diazonium salt condensates (Kosar, Chapter 7). The suitable layers also include the electrophotographic layers, ie those which contain an inorganic or organic photoconductor. In addition to the light-sensitive substances, these layers can of course also other components such. B. contain resins, dyes or plasticizers. In particular, the following light-sensitive compositions or compounds can be used in the coating of the carrier materials produced by the process according to the invention:

• positive-working, o-quinonediazides, in particular o-naphthoquinonediazides such as naphthoquinone- (1,2) -diazid- (2) -sulfonic acid esters or amides, which can be of low or higher molecular weight, as a photosensitive compound-containing reproduction layers, for example in the DE-PSen 854 890, 865 109, 879 203, 894 959, 938 233, 1 109 521, 1 144 705, 1 118 606, 1 120 273, 1 124 817 and 2 331 377 and EP-OSen 0 021 428 and 0 055 814;
• Negative-working reproduction layers with condensation products from aromatic diazonium salts and compounds with active carbonyl groups, preferably condensation products from diphenylamine diazonium salts and formaldehyde, which are described, for example, in DE-PS 596 731, 1 138 399, 1 138 400, 1 138 401, 1 142 871, 1 154 123, U.S. Patents 2,679,498 and 3,050,502 and GB Patent 712,606;
• Negative working, mixed condensation products of aromatic diazonium compounds containing reproduction layers, for example according to DE-OS-2 024 244, the products with at least one unit each from a) a condensable aromatic diazonium salt compound and b) a condensable compound such as a phenol ether or an aromatic thioether by a double bonded intermediate derived from a condensable carbonyl compound such as a methylene group;
• positive-working layers according to DE-OS-2 610 842, DE-PS-2 718 254 or DE-OS-2 928 636, which is a compound which splits off when irradiated, a monomeric or polymeric compound which passes through at least one Has acid-releasable COC group (z. B. an orthocarboxylic acid ester group or a carboxylic acid amidacetal group) and optionally contain a binder;
• negatively working layers made of photopolymerizable monomers, photoinitiators, binders and optionally other additives; the monomers used here are, for example, acrylic and methacrylic acid esters or reaction products of diisocyanates with partial esters of polyhydric alcohols, as described, for example, in US Pat. Nos. 2,760,863 and 3,060,023 and DE-OSes 2,064,079 and 2,361,041;
• Negative-working layers according to DE-OS-3 036 077, which contain a diazonium salt polycondensation product or an organic azido compound as the photosensitive compound and a high molecular weight polymer with pendant alkenylsulfonyl or cycloalkenylsulfonylurethane groups as the binder.

It can also be photoconductive layers such as z. B. in DE-PS 1 117 391, 1 522 497, 1 572 312, 2 322 046 and 2 322 047 are described, applied to the carrier materials produced according to the invention, whereby highly light-sensitive, electrophotographic printing plates are formed. Of the specified layers, the positive-working radiation-sensitive layers are preferred.

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

The materials according to the invention are characterized in that, after application of a radiation-sensitive coating, a reproduction material is produced which shows very little under-radiation during the irradiation process in the copying frame and, moreover, good water flow (good water storage capacity and low water requirement, fast) during the printing process with printing forms made from the reproduction material Free running when printing). In addition, a variety of the requirements of a practical reproductive material described at the outset can also be met, in particular this applies to the requirements for the interaction of carrier material / radiation-sensitive coating, so that a practical carrier material can also be produced for the highest demands if the parameters according to the invention are observed, which is also continuously possible in modern strip treatment plants. The special advantages also include increased mechanical resistance of the material, which can be demonstrated, for example, by increased print runs.

• Fig. 1 ein Ausschnitt aus der Oberfläche eines erfindungsgemäßen Materials in Draufsicht in 2 verschiedenen Maßstäben (1a, 1b),
• Fig. 2 ein Ausschnitt aus der Oberfläche eines erfindungsgemäßen Materials im Schnitt in Höhe der Linie I - I in Fig. 1,
• Fig. 3 ein Ausschnitt aus der Oberfläche eines nur mechanisch aufgerauhten Materials aus dem Stand der Technik im Schnitt senkrecht zur Grundfläche des Materials und
• Fig. 4 ein Ausschnitt aus der Oberfläche eines mechanisch und elektrochemisch aufgerauhten Materials aus dem Stand der Technik im Schnitt senkrecht zur Grundfläche des Materials.

In the accompanying drawing it is shown in

• 1 shows a detail from the surface of a material according to the invention in plan view in two different scales (1a, 1b),
• 2 shows a section of the surface of a material according to the invention in section at the line I-I in FIG. 1,
• Fig. 3 shows a section of the surface of a mechanically roughened material from the prior art in section perpendicular to the base of the material and
• Fig. 4 shows a section of the surface of a mechanically and electrochemically roughened material from the prior art in section perpendicular to the base of the material.

1a and 1b (approximately in 240- or 1200-fold magnification), which are made after scanning electron microscope recordings, show the different orders of magnitude and the distribution of the holes 2 in the basic structure of the feature a) or the elevations 1 in the superimposed structure of feature b); FIG. 2 shows a section through the surface, which is not to scale, from which an approximate size relationship between the holes 3 in the elevations 1 of the superimposed structure and the holes 2 in the basic structure can also be seen. 3 and 4 were prepared in accordance with DE-OS-3 012 135 and show in FIG. 3 the primary structure of the surface with uniform hills 4 and the holes 5 in these hills, the respective bisecting axis of the holes approximately is perpendicular to the base surface of the material, and in Fig. 4 the comparable primary structure of the surface with uniform hills 4 and holes 6, which overlap the primary structure as a secondary structure and whose respective bisecting axis is approximately perpendicular to the tangent to the outer surface of the hill.

Unless otherwise stated, percentages in the following examples relate to the weight, parts by weight relate to parts by volume such as kg to dm ³ .

example 1

eines Polykondensationsprodukts, hergestellt aus 1 Mol 3-Methoxy-diphenylamin-4-diazo- niumsulfat und 1 Mol 4,4'-Bismethoxymethyl-diphenylether in 85-%-iger H₃P0₄ und isoliert als Mesitylensulfonat
so beschichtet, daß das Schichtgewicht nach dem Trocknen 0,4 g/m² beträgt. Nach der bildmäßigen Belichtung von einer anspruchsvollen Vorlage wird mit einer Lösung eines Gehalts an 89 Vol.-Teilen Wasser, 5 Gew.-Teilen Natriumundecanoat, 3 Gew.-Teilen eines nichtionogenen Tensids (Blockpolymerisat aus 80 % Propylen- und 20 % Ethylenoxid) und 3 Gew.-Teilen Tetranatriumdiphosphat entwickelt. Die Bildwiedergabe beim Drucken ist ausgezeichnet, die Wasserführung gut, es können etwa 120.000 Drucke in praxisgerechter Qualität erhalten werden.An aluminum strip is mechanically roughened continuously on one side by wire brushing, whereby a surface is created whose average roughness value R _a = 0.90 µm and whose load share tp _mi (depth of cut 0.125 µm) = 13%. The mechanically roughened tape is treated for 3 seconds in a 4% aqueous NaOH solution at 70 ° C. in such a way that about 3 g / m ² are removed from the surface. The electrochemical roughening is also carried out continuously in a 0.9% aqueous HNO ₃ solution containing 4% of Al (NO ₃ ) ₃ at 40 ° C., a residence time of 10 seconds and with an alternating current with a current density of 170 A. / dm ² carried out. The mechanically and electrochemically roughened carrier shows the following parameters: D _a1 = 2.8 µm, D _a2 = 0.8 µm, basic structure = 75%, superimposed structure = 25%, F = 500 µm ² , R _a = 1.0 µm , tp _mi (0.125) = 18%, tp _mi (0.4) = 67%. The subsequent anodic oxidation is carried out in 10% aqueous H ₃ PO ₄ solution at 60 ° C. using direct current until the oxide layer weight is approximately 0.6 g / m ² . A carrier material produced in this way is cut in the plates and one of these plates is coated with a negative-working radiation-sensitive layer

of a polycondensation product, prepared from 1 mol of 3-methoxy-diphenylamine-4-diazonium sulfate and 1 mol of 4,4'-bismethoxymethyl-diphenyl ether in 85% strength H ₃ PO ₄ and isolated as mesitylene sulfonate
coated so that the layer weight after drying is 0.4 g / m ² . After imagewise exposure of a demanding original, a solution containing 89 parts by volume of water, 5 parts by weight of sodium undecanoate, 3 parts by weight of a nonionic surfactant (block polymer composed of 80% propylene and 20% ethylene oxide) and Developed 3 parts by weight of tetrasodium diphosphate. The image reproduction when printing is excellent, the water flow is good, about 120,000 prints can be obtained in practical quality.

Comparative Example V1

The procedure of Example 1 is followed, but the mechanical roughening and the alkaline intermediate treatment are omitted. The topography of the surface ("double structure") that can be achieved in Example 1 is not achieved, but rather only an unevenly roughened carrier, penetrated by scars, is obtained. Image reproduction, water flow and print run are considerably worse than in example 1.

Comparative example V2

The procedure of Example 1 is followed, but the wire brushing is carried out in such a way that the R _a value of the mechanically roughened surface is 0.39 μm and the tp _mi (0.125) value is 37%. After the electrochemical roughening, this carrier material is roughened more uniformly than in comparative example V1, but does not reach the claimed parameter ranges, in particular not in the R _a and tp _mi values, and does not yet have a “double structure”. Image reproduction, water flow and print run are a little better than in V1, but still significantly worse than in example 1.

Example 2

An aluminum strip is continuously roughened mechanically by wire brushing, creating a surface whose Ra value = 0.65 µm and whose tp _mi (0.125) value = 15%. The mechanically roughened tape is treated as indicated in Example 1. The electrochemical roughening is carried out in a 1.5% aqueous HN0 ₃ solution containing 5% Al (N0 ₃ ) ₃ at 30 ^° C., a residence time of 15 seconds and with an alternating current with a current density of 100 A / dm ² carried out. The mechanically and electrochemically roughened carrier shows the following parameters: D _a1 = 3.7 µm, D _a2 = 0.6 µm, basic structure = 80%, superimposed structure = 20%, F = 720 µm ² , R _a 0.95 µm, t _pmi (0.125) = 17%, t _pmi (0.4) = 60%. After a further ablation treatment of the surface for 2 seconds in 2% aqueous NaOH solution at 35 ° C., about 0.6 g / m ^{2 being} removed from the surface, a 25% aqueous H ₂ S0 ₄ solution anodized at 50 ° C with direct current until the oxide layer weight is about 2 g / m ² . The radiation-sensitive layer to be applied according to Example 1 additionally contains 5.5 parts by weight of a reaction product of a polyvinyl butyral (containing vinyl butyral, vinyl acetate and vinyl alcohol units) and propenylsulfonyl isocyanate. Development takes place in a weakly alkaline aqueous solution with a content of 1% sodium metasilicate, 3% nonionic surfactant and 5% benzyl alcohol. Image reproduction and water flow correspond to that of Example 1, the print run is about 50,000 prints higher.

Example 3

• 8,50 Gew.-Teilen des Veresterungsprodukts aus 1 Mol 2,3,4-Trihydroxybenzophenon und 3 Mol Naphthochinon-(1,2)-c
• 6,60 Gew.-Teilen des Veresterungsprodukts aus 1 Mol 2,2'-Dihydroxynaphthyt-(1,1')-methan und 2 Mol des vorher bes
• 2,10 Gew.-Teilen Naphthochinon-(1,2)-diazid-(2)-4-sulfonsäurechlorid,
  
  das nach dem Trocknen ein Schichtgewicht von 2,5 g/m² ergibt. Die Entwicklung nach der Belichtung wird mit einer wäßrigen Lösung eines Gehalts an 5,3 % Natriummetasilikat . 9 H₂0, 3,4 % Na₃P0₄ . 12 H₂0 und 0,3 % NaH₂P0₄ durchgeführt. Die Bildwiedergabe beim Drucken ist ausgezeichnet, die Wasserführung gut, es können etwa 400.000 Drucke (nach Durchführung eines Einbrennvorgangs) in praxisgerechter Qualität erhalten werden.

The procedure of Example 2 is followed, but after the anodic oxidation the surface of the support material is additionally anodized in a 17% aqueous sodium silicate solution at 70 ° C. for 15 seconds with 36 V and then with a 1.5 -% aqueous H ₃ P0 ₄ solution rinsed off. The radiation-sensitive coating is made with a positive working mixture

• 8.50 parts by weight of the esterification product from 1 mol of 2,3,4-trihydroxybenzophenone and 3 mol of naphthoquinone- (1,2) -c
• 6.60 parts by weight of the esterification product from 1 mol of 2,2'-dihydroxynaphthyt- (1,1 ') - methane and 2 mol of the previously bes
• 2.10 parts by weight of naphthoquinone- (1,2) -diazide- (2) -4-sulfonic acid chloride,
  
  that results in a layer weight of 2.5 g / m ² after drying. Development after exposure is carried out with an aqueous solution containing 5.3% sodium metasilicate. 9 H ₂ 0, 3.4% Na ₃ P0 ₄ . 12 H ₂ 0 and 0.3% NaH ₂ P0 ₄ performed. The image reproduction during printing is excellent, the water flow is good, and about 400,000 prints (after carrying out a baking process) can be obtained in practical quality.

Comparative Example V3

The procedure of Example 3 is followed, but the mechanical roughening and the alkaline intermediate treatment are omitted. The topography of the surface ("double structure") that can be achieved in Example 3 is not achieved, but rather only a rather unevenly roughened carrier with several scars is obtained. Image reproduction, water flow and print run are considerably worse than in example 3.

Comparative Example V4

The procedure of Example 3 is followed, but the wire brushing is carried out such that the R _a value of the mechanically roughened surface is 0.40 μm and the tp _mi (0.125) value is 35%. After the electrochemical roughening, this carrier material is roughened more uniformly than in comparative example V3, but does not reach the claimed parameter ranges, in particular not in the R _a and tp _mi values, and does not yet have a “double structure”. Image reproduction, water flow and print run are better than in V3, but still significantly worse than in example 3.

Comparative Example V5

The procedure of Example 3 (in connection with Example 2) is followed, but the wire brushing is replaced by brushing with oscillating nylon brushes using an aqueous abrasive dispersion, a surface being formed before the electrochemical roughening, the Ra value of which is 0. 60 µm and whose tp _mi (0.125) value = 20%. After the electrochemical roughening, the carrier material is roughened relatively uniformly, but the surface does not have a “double structure”, ie the parameters which are caused by this special structure are not present or are not in the ranges claimed according to the invention. After the printing form has been produced, it is found that the water flow and the print run are better than in V4, but have not yet reached Example 3, in particular the practically not improved tendency to under radiation has remained.

Examples 4 and 5

The procedure of Example 3 is followed, but either a matt coating according to DE-OS-2 512 043 is applied to the radiation-sensitive layer or an additive of particles is mixed into the radiation-sensitive layer according to DE-OS-2 926 236. These modifications of the layer should lead to a reduction in the tendency to under radiation (see introduction to the description). The image reproduction of printing forms produced therewith is practically unchanged from those which are produced according to Example 3 without modification of the layer, i. H. when using a "double structure" material according to the invention as a support for offset printing plates, this type of special modification of the radiation-sensitive layer can be dispensed with.

Example 6

An aluminum strip is mechanically roughened continuously on one side by wire brushing, producing a surface whose Ra value = 1.0 µm and whose t _pmi - (0.125) value = 10%. The mechanically roughened strip is subjected to an intermediate treatment in a 3% strength aqueous NaOH solution at 50 ° C. for 10 seconds in such a way that about 2.5 g / m ² are removed from the surface. The electrochemical roughening is also carried out continuously in a 1% aqueous HCl solution containing 2% AlCl ₃ . 6 H ₂ 0 at 40 ° C, a residence time of 20 sec and with alternating current with a current density of 70 A / dm ² . The mechanically and electrochemically roughened carrier shows the following parameters: D _a1 = 3.0 µm, D _a2 = 0.8 µm, basic structure = 87%, superimposed structure = 13%, F = 300 µm ² , R _a = 1.7 µm , tp _mi (0.125) = 8%, t _pmi (0.4) = 40%. Anodic oxidation and radiation-sensitive coating are carried out according to the instructions in Example 1. Image reproduction and water flow are rather better than in Example 1, the print run is around 100,000 prints.

Claims (10)

1. A material in the form of a sheet, a foil or a strip, comprising aluminum or alloys thereof, which has first been mechanically and then electrochemically roughened on one or both surfaces, wherein

a) 60 to 90 % of the surface comprise a basic structure, in which the arithmetic mean of the distribution of pit diameters D_a1 is in the range from 1 to 5 µm,

b) 10 to 40 % of the surface comprise a superimposed structure formed of elevations having an average base F from 100 to 1,500 µm², in which the arithmetic mean of the distribution of pit diameters D_a2 is in the range from 0.1 to 1.0 µm,

c) the center line average roughnesses R_a of the entire surface are at least 0.6 µm, and

d) the contact area tp_mi of the entire surface is not more than about 20 % at a working depth of stylus of 0.125 µm and not more than about 70 % at a working depth of stylus of 0.4 µm.

2. A material as claimed in claim 1, wherein the parameters are as follows: a) D_a1 is in the range from 2 to 4 um, b) D_a2 is in the range from 0.3 to 0.8 µm, at an average base F from 200 to 1,200 µm², c) R_a is in the range from 0.8 to 1.2 µm and d) tp_mi (0.125) is not more than about 15 % and tp_mi (0.4) is not more than about 60 %.

3. A material as claimed in claim 1 or claim 2, wherein the surface of the material additionally comprises an aluminum oxide layer which has been generated by anodic oxidation.

4. A material as claimed in claim 3, wherein the aluminum oxide layer has been post-treated to render it hydrophilic.

5. A process for the production of a material as claimed in any of claims 1 to 4, wherein the aluminum in the form of a sheet, a foil or a strip, optionally after precleaning, is mechanically roughened on one or both sides by wire-brushing and is thereafter, optionally after an etching intermediate treatment in an alkaline or acidic aqueous solution, electrochemically roughened in an electrolyte containing hydrochloric acid and/or nitric acid, with the application of an alternating current.

6. A process as claimed in claim 5, wherein the etching intermediate treatment of the mechanically roughened material comprises removing not more than 5 g/m² of material from the surface.

7. A process as claimed in claim 5 or claim 6, wherein after electrochemical roughening an etching treatment in an alkaline or acidic aqueous solution is additionally carried out.

8. A process as claimed in claim 7, wherein the etching post-treatment of the electrochemically roughened material comprises removing not more than 2 g/m² of material from the surface.

9. Use of the material as claimed in any of claims 1 to 4 as a support material in the manufacture of offset-printing plates provided with a radiation-sensitive coating on one or both sides.

10. Use as claimed in claim 9, wherein the offset-printing plate is provided with a positive-working radiation-sensitive coating.

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