Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F3/00—Electrolytic etching or polishing
  • C25F3/02—Etching
  • C25F3/04—Etching of light metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/03—Chemical or electrical pretreatment
  • B41N3/034—Chemical or electrical pretreatment characterised by the electrochemical treatment of the aluminum support, e.g. anodisation, electro-graining; Sealing of the anodised layer; Treatment of the anodic layer with inorganic compounds; Colouring of the anodic layer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S205/00—Electrolysis: processes, compositions used therein, and methods of preparing the compositions
  • Y10S205/921—Electrolytic coating of printing member, other than selected area coating

Definitions

• the invention relates to a process for the bilateral electrochemical roughening of plate, foil or tape-shaped material made of aluminum with three-phase alternating current and the use of the material in the production of printing plates.
• Printing plates generally consist of a support and at least one radiation-sensitive reproduction layer arranged thereon, this layer either from the consumer (in the case of non-precoated plates) or from the industrial one Manufacturer (for pre-coated boards) is applied to the substrate.
• Aluminum or one of its alloys has established itself as a layer material in the printing plate field.
• these substrates can also be used without a modifying pretreatment, but they are generally modified in or on the surface, for example by mechanical, chemical and / or electrochemical roughening (sometimes also called grain or etching in the literature), a chemical or electrochemical oxidation and / or treatment with H ydrophil michsmitteln.
• a combination of the above-mentioned types of modification is often used, in particular a combination of electrochemical roughening and anodic oxidation, optionally with a subsequent hydrophilization step.
• the roughening is carried out, for example, in aqueous acids such as aqueous HCl or HN0 3 solutions or in aqueous salt solutions such as aqueous NaCl or Al (NO 3 ) 3 solutions using alternating current.
• the roughness depths that can be achieved in this way are in the range from about 1 to 15 ⁇ m, in particular in the range from 2 to 8 pm.
• the roughness depth is determined in accordance with DIN 4768 in the version from October 1970, the roughness depth R is then the arithmetic mean of the individual roughness depths of five adjacent individual measuring sections.
• a process for the electrochemical roughening of aluminum in which an aluminum foil strip is guided as a central conductor through an aqueous electrolyte containing HC1 and treated with alternating current, the n phases ( preferably has 3 phases R, S and T). At least as many electrodes are alternately arranged in succession in the electrolyte as the alternating current has phases, i. H. usually 3.6 etc. electrodes. When roughening on one side, the electrodes all face the same hinge side, alternatively on both sides of the hinge on both sides.
• the object of the present invention is therefore to propose a method for electrochemical roughening of aluminum materials on both sides, which can be used in particular as a carrier material for printing plates and in which the energy of the current to be used can be used as far as possible for the roughening.
• the invention is based on the known method for electrochemical roughening on both sides of plate, sheet or strip material made of aluminum or its alloys in an aqueous electrolyte solution and three-phase alternating current.
• the method according to the invention is then characterized in that two of the three phases are conductively connected with electrodes arranged on both sides of the material and the rest of the phase with the material to be roughened.
• a three-phase alternating current is to be understood as a current which has three phases (R, S and T) with the same amplitude, but with a phase shift of 120 ° each; if these three phases are equally loaded, a neutral conductor would not carry any current (see, for example, Dorn, Physik - Oberissue - Issue A, Hermann Schroedel Verlag - Hanover, 1966, 10th edition, pp. 256 to 258).
• consumers are connected to the power grid of the power plant either in a star connection or in a delta connection.
• the materials to be roughened are, for example, those with an aluminum content of? 99.5, from 99.2, from? 98.5 or 98.3 used, which contain Fe, Si, Cu and optionally Zn, Ti, Mn and / or Mg as admixtures; these are traded for example with the designation "pure aluminum", "1100", "3003" or "A-19".
• the thickness of these materials is generally in the range of about 0.1 to 0.65 mm.
• one pole of a three-phase alternating current source is connected to one of two electrodes which are located in front of and behind the aluminum material in the preferred vertical material guide or are arranged above and below the aluminum material with a horizontal material guide, while the third pole is Three phase AC power source is connected to the aluminum material itself, the aluminum material and the electrodes being in an aqueous electrolyte solution.
• This arrangement makes it possible to roughen both sides of the aluminum material at the same time, both a discontinuous procedure with aluminum sections and preferably a continuous procedure with aluminum strips being possible. It has been shown that the total energy requirement of the current for a material to be roughened on both sides at the same time is substantially less than if each side were roughened individually.
• the roughening when used of the method according to the invention results in a very uniform roughening image, since the degree of roughening in the regions of the material near the edges is essentially the same as that in the middle of the material. This is not the case with roughened surfaces in two separate steps.
• the surface obtained according to the invention also has a uniform hole structure and has little pitting.
• Typical aqueous electrolyte solutions which can be used are those known from the prior art which, in addition to water, generally contain one or more electrolytes, such as acids or salts; These include, for example, hydrochloric acid, nitric acid, aluminum salts of mineral acids and compounds containing chloride or phosphate ions; in addition, these aqueous electrolyte solutions may also contain modifiers such as gluconic acid, tartaric acid, boric acid or hydrogen peroxide in a known manner. The exact parameters of the conditions under which the electrochemical roughening can be carried out are variable, they are directed u. a. according to the desired results and the composition of the aqueous electrolyte solution.
• the concentration of the aqueous electrolyte solution can in principle be in a range from about 1 g / l to the saturation of the solution on the electrolyte or electrolytes.
• the concentration of the electrolyte is preferably between 3 and 20 g / 1, in particular between 8 to 20 g / 1, and particularly preferably between 10 and 15 g / l.
• the aluminum material to be roughened is usually connected to the S-pole of a three-phase variable transformer in the practical implementation of the method according to the invention, the R-pole and the T-pole are conductively connected, for example, to two graphite plates serving as electrodes. The graphite plates are then set up on both sides of the support, the preferred distance being 1.5 cm.
• the material to be roughened can be conductively connected to the S pole in a known manner, for example via a contact roller or contact cell.
• the electrodes are preferably made of graphite, but other conductive materials such as lead or stainless steel can also be used.
• the distance between the electrodes and the aluminum material is in particular less than 10 cm, preferably less than 5 cm and particularly preferably less than 3 cm.
• the three-phase alternating current used coming from the network can be, for example, 60 A and 480 V, but these values are not mandatory. This current can then be converted into a current of 1320 A and about 20 to 25 V via a variable transformer. These values are not critical and can be tailored to the respective requirements by a person skilled in the art, on the other hand the current density is of greater importance.
• the current flow from the electrodes to be roughened material should be such that on each side of the A luminiummaterials a current density of about 30 to 120 A / dm 2, preferably from 40 to 100 A / dm 2, and in particular from 60 to 75 A / dm 2 is reached.
• an anodic oxidation of the aluminum can then follow in a further process step to be used, for example to improve the abrasion and adhesion properties of the surface of the material.
• the usual ones for anodic oxidation 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.
• the layer weights of aluminum oxide range from 1 to 10 g / m 2 , corresponding to a layer thickness of approximately 0.3 to 3.0 ⁇ m.
• a modification can also be applied which causes surface abrasion from the roughened surface, as described, for example, in DE-OS 30 09 103.
• Such a modifying intermediate treatment can, among other things, enable the build-up of abrasion-resistant oxide layers and a lower tendency to tone during later printing.
• the step of anodic oxidation of the aluminum material can also be followed by one or more post-treatment steps.
• all layers are suitable as light-sensitive reproduction layers which, after exposure, optionally with subsequent development and / or fixation, provide an image-like area from which printing can take place and / or which represent a relief image of an original. They are applied either by the manufacturer of presensitized printing plates or by so-called dry resists or directly by the consumer to one of the usual carrier materials.
• the light-sensitive reproduction layers include such as z. B.
• 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.
• An aluminum plate with a content of more than 99.5% aluminum is immersed together with a graphite electrode arranged at a distance of 1.5 cm in an aqueous electrolyte solution which contains 13 parts by weight of HN03 and 65 parts by weight in 1000 parts by volume Contains aluminum nitrate.
• One side of the plate is roughened by the action of a single-phase alternating current of 300 A for 60 seconds, so that the power consumption is 6.6 kW.
• the plate is then turned over and the other side roughened in the same way, so that the total power consumption is 13.2 kW.
• the power required to achieve a roughening, which can already meet printing requirements is 91.1 kW / m 2 , but the roughening does not have the uniformity of roughening according to the method according to the invention.
• a further aluminum plate of the same quality is immersed in the same electrolyte together with 2 graphite electrodes, which are located on both sides of the plate at a distance of 1.5 cm each. Both sides are caused by the action of 300 A from two phases (R and T) of the three-phase alternating current roughened, the rest of the phase (S) lies on the aluminum plate; only 52.8 seconds are required for the roughening process.
• the total power consumption to achieve a substantially uniform roughening of both plate surfaces suitable for printing purposes is thus 11.6 kW. This corresponds to a power consumption of 80 kW / m 2 aluminum surface or a saving of 12% compared to the conventional processes.
• An aluminum plate containing 99.2% aluminum is degreased in a conventional aqueous-alkaline solution and rinsed well with water.
• the plate treated in this way is placed wet in an aqueous electrolyte solution which contains 13 parts by weight of HNO 3 and 65 parts by weight of aluminum nitrate in 1000 parts by volume.
• the aluminum plate is firmly connected to a pole of an AC power source, being held in place by a non-conductive bracket.
• a graphite electrode is placed opposite the aluminum plate at a distance of 1.5 cm, which is connected to the second pole of the single-phase AC power source. With constant stirring of the electrolyte solution between the graphite electrode and the aluminum plate, a voltage of 22 V (60 Hz) with a current flow of 600 A is applied for 60 seconds.
• the plate After the treatment, the plate is rinsed well and dried. A microscopic examination shows that due to the extensive effect of the current, all four edges of the opposite side are roughened about 1 cm wide. The treated side shows an even, weak in the middle roughening, the roughening is coarser near the edge, and a slight aluminum dissolution is found on the edge. In order to be able to use a printing plate carrier produced in this way, one would have to use an oversized plate format and cut off the edges after the treatment. A microscopic evaluation using a scanning electron microscope (SEM) in 1000, 2000 and 5000 times magnification confirms the visual impression. The middle part looks even but undertreated, which means the roughening is too flat.
• SEM scanning electron microscope
• a roughened plate is produced according to the information in comparative example V2. After the treatment steps described above, the plate is removed from the bath, turned over and immersed again in the bath, so that its untreated side now faces the electrode, this side is handled in the same way as the first side.
• both the visual inspection and the examination with the scanning electron microscope confirm that the plate obtained is a rather undertreated central zone and a roughened edge area.
• the first treated side shows no changes, ie, it will receive a both sides roughened plate which can not be accepted ruck plate area for practice on the D.
• a plate is degreased as described in comparative example V2 and immersed in a solution of the composition given there. It is connected to a pole (S) of a three-phase variable transformer.
• the existing graphite electrode is connected to a second pole (R), in addition a graphite electrode of the same type is attached to the opposite side of the plate and connected in the same way to the third remaining pole (T).
• the two electrodes are 1.5 cm apart from the aluminum plate attached between them.
• a voltage of 22 V (60 Hz) and 530 A is applied for 60 seconds and the plate is thus electrochemically roughened.
• the plate is removed from the bath, rinsed and wiped dry.
• the plate has on both sides a very uniform appearance, ie, see both sides exactly the same 'out, they show no signs of insufficient roughening in the middle, coarse roughening the edges or etched-aluminum edges.
• the examination with the scanning electron microscope (1000, 2000 and 5000 times magnification) confirms that the entire surface is roughened very uniformly, and it essentially no measurable difference in the hole diameter can be determined, nor can undesirable pitting be detected.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Printing Plates And Materials Therefor (AREA)

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• 1981
  • 1981-12-21 US US06/332,392 patent/US4396468A/en not_active Expired - Fee Related
• 1982
  • 1982-12-13 EP EP82111543A patent/EP0082452B1/fr not_active Expired
  • 1982-12-13 DE DE8282111543T patent/DE3266243D1/de not_active Expired
  • 1982-12-17 JP JP57220411A patent/JPS58157997A/ja active Granted

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