Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
  • B41C1/00—Forme preparation
  • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
  • B41C1/1041—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by modification of the lithographic properties without removal or addition of material, e.g. by the mere generation of a lithographic pattern

Definitions

• the invention relates to a one-stage imaging and development or stripping process for reproduction layers in an aqueous electrolyte solution.
• Reproduction layers sensitive to radiation are used, for example, in the production of offset printing forms or photoresists (both hereinafter referred to as copying materials). H. they are generally applied to a substrate by the consumer or by the industrial manufacturer. Metals such as zinc, magnesium, chromium, copper, brass, steel, silicon, aluminum or combinations of these metals, plastic films, paper or similar materials are used as layer supports in these copying materials. These supports can be modified with the radiation-sensitive reproduction layer without a modifying pretreatment, but preferably after carrying out a surface modification such as mechanical, chemical and / or electrochemical roughening, oxidation and / or treatment with hydrophilizing agents (e.g. in the case of supports for offset printing plates) be coated.
• a surface modification such as mechanical, chemical and / or electrochemical roughening, oxidation and / or treatment with hydrophilizing agents (e.g. in the case of supports for offset printing plates) be coated.
• the usual radiation-sensitive reproduction layers usually also contain an organic binder (resins or the like) and, if appropriate, also plasticizers, pigments, dyes, wetting agents, sensitizers, adhesion promoters, indicators and other customary auxiliaries.
• organic binder resins or the like
• plasticizers pigments, dyes, wetting agents, sensitizers, adhesion promoters, indicators and other customary auxiliaries.
• reproduction layers are developed after their irradiation (exposure) in order to produce an image from them, for example a printing form or a photoresist is thus obtained; in the case of electrophotographic layers, the development corresponds to the stripping.
• the term “reproduction layers” is also to be understood as meaning those which do not contain a radiation-sensitive compound but contain the rest of the listed components, i. H. especially an organic binder.
• a solution which has a pH of 2.0 to 10.0 and contains at least one salt in a concentration of 0.1% up to the saturation limit of the solution on the respective salt.
• the electrolyte can also contain a surfactant in a concentration of 0.1 to 5%.
• DE-A 27 34 508 describes a process for the production of a planographic printing plate in which a hydrophilic layer which is arranged on an electrically conductive oleophilic layer is decomposed imagewise by the action of electric current by means of a needle electrode and is thereby made soluble. The soluble layer areas are then washed out.
• JP-A 58 5295 a conductive layer containing a diazonium salt is cross-linked reductively by imagewise exposure to direct current, so that a water-insoluble oleophilic image is formed, which is then developed by washing with water.
• JP-A 58/5294 describes a similar process in which a bichromate / polymer layer filled with graphite, carbon black or the like is used and the image is hardened and oleophilized.
• JP-A 58/11154 a polyvinyl alcohol layer is crosslinked in the same way by direct current using a metal electrode.
• the method should enable digitally available information to be applied directly to a material to be used later as printing form without a detour via irradiation (imaging), so that the otherwise conventional imaging and development stages coincide.
• the invention is based on a method for electrochemical image formation on a multilayer sheet material with at least one electrically conductive layer by the action of electric current via at least one needle-shaped electrode, the multilayer sheet material having a reproduction layer which may contain at least one radiation-sensitive compound, at least a needle-shaped electrode acts from the side of the multilayer sheet material which carries the reproductive layer.
• the method according to the invention is then characterized in that both the electrode (s) and the multilayer sheet material are arranged in interaction with an aqueous electrolyte solution.
• the aqueous electrolyte solution generally has a pH in the range from 1 to 14, in particular from 2.0 to 10.0, and in addition to the main constituent contains water as a dissociated compound, in particular at least one salt of an organic or inorganic acid in a concentration from 0.1% by weight to the saturation limit of the solution on the respective salt.
• These salt solutions can also be in the form of a buffer system and then, in addition to the salt content, can also contain weak acids (such as acetic acid) or weak bases (such as ammonia); it can also be expedient to shift the pH of the salt solutions by adding acids or bases, but the pH values stated above should not be exceeded or undershot.
• the aqueous electrolyte can also contain acids (such as acetic acid or boric acid) in the specified pH range instead of the salts preferably used.
• the salts which can be used in the aqueous electrolyte in the process according to the invention include, in particular, those which are cations Li + , Na + , K + , NH 4 + , Al 3+ , Fe 2+ , Fe 3+ , V S + , Ca 2+ , Mg 2+ Sr 2+ or Ba2 + and as anions SO 4 2- , S 2 O 3 2- , SCN-, CO 3 2- , CH 3 COO - , NO 3 - , NO 2 - , PO 4 3- , B0 2 - , Polyphosphate, polyborate, F-, CL-, Br-, BF 4 - , N 3 -, V0 3 -, anions of alkyl sulfates (sulfuric acid monoalkyl ester anions) from C 7 to C 16 or their corresponding hydrogen salts.
• the aqueous electrolyte solution can also contain a surfactant which is different from the dissociated compounds listed above and is preferably added in a concentration of 0.1 to 5% by weight.
• a surfactant which is different from the dissociated compounds listed above and is preferably added in a concentration of 0.1 to 5% by weight.
• Both nonionic and anionogenic or cationogenic surfactants can be used; however, especially when the method according to the invention is carried out in processing machines, they should be of slightly foaming type.
• Suitable surfactants have been found to be, for example: alkali metal or ammonium salts of sulfuric acid monoalkyl esters with alkyl groups from C 7 to C 16 , ethoxylated alcohols and phenols, ethoxylated fatty amines or block polymers based on alkylene oxides (especially based on ethylene and propylene oxide).
• the method according to the invention it is possible to differentiate image-wise different types of unexposed reproduction layers in aqueous solutions which do not contain any organic solvent or other large amounts of environmentally harmful auxiliaries.
• the resolution that can be achieved corresponds to that of conventional, non-electrochemical irradiations and developments.
• the concentration of the dissociated compound in the aqueous electrolyte solution can be between 0.1% by weight, in particular 1% by weight, and the respective saturation concentration of the dissociated compound; in general, concentrations of up to 5% by weight are sufficient. If the concentration of the aqueous electrolyte is less than 0.1% by weight, the conductivity of the solution is usually too low, so that the resulting current density becomes too low to achieve rapid development.
• the temperature of the aqueous electrolyte can range from room temperature to the boiling point of the electrolyte system, but a temperature of 20 ° to 70 ° C. is preferred. It is generally not necessary to mix the aqueous electrolyte while the process according to the invention is being carried out.
• the method according to the invention is carried out with direct current or alternating current of different frequency and modulation, and pulsed direct current can also be used.
• the current density can in principle also be outside a range from 1 to 100 Aldm 2 , but this range is preferred, since otherwise the heating of the aqueous electrolyte solution becomes too strong and / or the duration or quality of the image formation can be negatively influenced.
• the current density increases at the beginning of the electrochemical imaging, remains at a level for a certain time and increases again slightly towards the end of the treatment.
• H + (H 3 + ) ions During electrochemical imaging, hydrogen is usually released at the cathode by discharging H + (H 3 + ) ions. It is assumed that this causes the pH to increase locally and causes the image-differentiating detachment. Due to the occasionally high pH value, the support of the reproduction layer can be attacked in places in some aqueous electrolyte solutions; however, the actual image formation is not affected by this, and this attack can - if necessary at all - be reduced by adding corrosion inhibitors.
• needle-shaped electrode is to be understood as an elongated body made of a material which is as inert as possible (ie which does not degrade during the process according to the invention), such as graphite, gold or platinum, and which has the smallest possible tip in order to achieve the best possible resolution and To achieve the finest image or non-image points. This electrode or these electrodes are guided as close as possible over the flat material to be imaged.
• a plurality of needle-shaped electrodes can also be used to image larger areas; this can also be possible to accelerate the method. Like just one electrode, these electrodes are controlled by a device which contains the image information in digitized form (for example a "computer-to-plate" system).
• the counter electrode is the electrically conductive layer of the multilayer sheet material.
• the aqueous electrolyte solution must be arranged in relation to the multilayer sheet material and the needle-shaped electrode (s) in such a way that, in interaction with the two bodies acting as electrodes, it can bring about an imagewise differentiation in the reproduction layer, for example by immersing the body in the solution.
• the reproduction layers include not only the customary (see below) known radiation-sensitive layers, but also those of a comparable composition which, however, do not contain any radiation-sensitive compound; d. H. reproduction layers are to be understood as those layers which enable imagewise differentiation in the method according to the invention.
• the reproduction layer to be treated which is part of the multilayer sheet material with at least one electrically conductive layer, is contacted by immersion with the aqueous electrolyte solution.
• An edge of the flat material should protrude from the surface of the electrolyte bath, a power connection can then be attached to this part.
• Another way of supplying power is to make contact via the material back, which has no reproduction layer.
• the needle-shaped electrode should, in particular, be arranged at a uniform distance from the flat material, so that a uniform current density can be set at any point on the flat material to be imaged.
• the advantage of the method is that the size of the non-image points can be controlled by varying the current density and time by generating them point by point.
• the control pulses can, for. B. come directly from a computer-to-plate system.
• the uncoated back of the flat material to be treated should preferably be in contact with a non-conductive material in order to avoid unnecessary consumption of electrical energy. Another possibility is to seal off the back of the material, with the plate being guided in tight grooves in the electrolyte bath container.
• the needle-shaped electrode (s) should suitably be largely insulated.
• the reproduction layer to be treated is present, in particular, as part (radiation-sensitive layer) of an offset printing plate or as a resist (photoresist layer) applied to a carrier material; it generally contains a polymeric binder which dissolves under the action of the electrical current from the needle-shaped electrode and releases the underlying part of the flat material.
• a polymeric binder which dissolves under the action of the electrical current from the needle-shaped electrode and releases the underlying part of the flat material.
• coatings based on a polymeric binder which do not contain any radiation-sensitive compound are also understood to be covered by the invention, but are preferably used as radiation-sensitive layers.
• Electrically conductive carrier materials are suitable as carrier materials, which include, for example, those based on zinc, chromium, magnesium, copper, brass, steel, silicon, aluminum or combinations of these metals.
• this coating is preferably only carried out after surface modification such as mechanical, chemical or electrochemical roughening, oxidation and / or treatment with hydrophilizing agents (in particular in the case of supports for offset printing plates).
• the particularly suitable substrates for the production of offset printing plates include those made of aluminum or one of its alloys, which for example have a content of more than 98.0% by weight, in particular more than 98.5% by weight, of A1 and proportions of Si , Fe, Ti, Cu, Zn, Mn and / or Mg.
• the aluminum support materials for printing plates which are very common in practice, are generally mechanically (e.g. by brushing and / or with abrasive treatments), chemically (e.g. by etching agents) or electrochemically (e.g. through change current treatment in aqueous HCI or HN0 3 solutions) roughened.
• the average roughness depth R z of the roughened surface is in the range from about 1 to 15 pm, in particular in the range from 1.5 to 10 ⁇ m.
• the surface roughness is determined in accordance with DIN 4768 in the version from October 1970, the surface roughness R z is then the arithmetic mean of the individual surface roughnesses of five adjacent individual measuring sections.
• the aluminum strip can be pre-cleaned before roughening; it includes, for example, treatment with aqueous NaOH solution with or without degreasing agents and / or complexing agents, trichlorethylene, acetone, methanol or other commercially available aluminum stains.
• an abrasive treatment can additionally be carried out, in particular a maximum of 2 g / m 2 being removed (up to 5 g / m 2 between the stages);
• aqueous solutions of alkali metal hydroxide or aqueous solutions of alkaline salts or aqueous acid solutions based on HN0 3 , H 2 SO 4 or H 3 PO 4 are used as abrasive solutions.
• non-electrochemical treatments are also known which essentially have only a rinsing and / or cleaning effect and, for example, for removing deposits formed during roughening ("Schmant") or simply for removal serve from leftovers; For example, dilute aqueous alkali hydroxide solutions or water are used for these purposes.
• an anodic oxidation of the aluminum connect, for example, the abrasion resistance and the adhesion properties of the surface to improve the carrier material.
• the usual electrolytes such as H 2 S0 4 , H 3 P0 4 , H 2 C 2 0 4 , amidosulfonic acid, sulfosuccinic acid, sulfosalicylic acid or mixtures thereof can be used for anodic oxidation; in particular, H 2 S0 4 and H 3 PO 4 are used alone, in a mixture and / or in a multi-stage anodizing process.
• 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.
• the stage of anodic oxidation of the aluminum support material can also be followed by one or more post-treatment stages.
• These post-treatment stages serve in particular to additionally increase the hydrophilicity of the aluminum oxide layer, which is often sufficient, while at least the other known properties of this layer are retained.
• Reproduction layers sensitive to radiation are to be understood in principle as those which - in the otherwise customary methods which, however, are not required according to the invention - provide an image-like area after irradiation (exposure), optionally with subsequent development and / or fixation that can be printed.
• photoconductive layers such as z. B. in DE-C 11 17 391, 15 22 497, 15 72 312, 23 22 046 and 23 22 047 are used.
• the layers described above and containing at least one radiation-sensitive compound can also be used in the process according to the invention, provided they contain at least one binder, without the presence of the radiation-sensitive compound.
• the following organic polymers which are soluble in the aqueous electrolyte solution are particularly suitable: polyamides, polyesters, alkyd resins, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, polyacetals, gelatin and / or cellulose ethers.
• the thickness of the reproduction layer can range from about 0.1 ⁇ m to about 1 mm or more.
• the reproduction layers contain radiation-sensitive compounds which result in a negative working system
• the positive working ones are preferred in the method according to the invention.
• the% data - unless otherwise stated - are based on the weight. Parts by weight relate to parts by volume like g to cm 3 .
• the reproduction layers to be treated are located on conductive supports and - unless otherwise described - are connected as a cathode in a direct current circuit, the needle-shaped electrode (s) then as an anode (s).
• the electrolyte temperature is 25 to 30 ° C., the distance of the material to be treated from the counterelectrode is kept as short as possible without causing a short circuit.
• the course of the current density can generally be represented as follows: the current density initially rises to a certain value during a few msec, remains at this level for a few msec and can increase slightly again towards the end of the electrolytic development. If no special comments are given, the treated materials are practical.
• this plate is imaged in an aqueous solution containing 3% lithium sulfate and 1% sodium octyl sulfate (sodium salt of sulfuric acid monooctyl ester) at pH 3.5 with a needle electrode with a voltage which changes depending on the non-image point size .
• This plate is electrochemically imaged with a needle electrode in an aqueous solution containing 3% lithium sulfate and 1% sodium octyl sulfate at a pH of 7.5 at about 60 V depending on the spot size.
• the electrochemical dot-like imaging takes place in an aqueous solution containing 1.5% lithium carbonate and 1% sodium octyl sulfate at a pH of 8 with about 60 V. After rubbing out and drying at 220 ° C., one is used in practice receive sufficient printing form.
• Example 5 The electrophotographically working layer from Example 5 is applied to an aluminum support which has been mechanically roughened by dry brushing and processed further according to the instructions in Example 5.
• the imagewise stripping takes place in the same electrolyte under the same conditions, but without a previous non-electrochemical exposure phase.
• the electrochemical image treatment is carried out in an aqueous solution containing 3% sodium phosphate and 3% of an ethoxylated isotridecyl alcohol with 8 ethylene oxide units at a pH of 7 by applying about 20 V depending on the point size (the pH becomes set with H 3 P0 4 ).
• the plate is imaged and then dried at 220 ° C or hardened by post-exposure.
• the print run of a plate treated in this way is 80,000 prints.
• the plate from Example 3 is electrochemically treated in 6% aqueous sodium lauryl sulfate solution at a pH of 4.
• This coated film is treated electrochemically in an aqueous solution containing 3% ammonium phosphate and 1% sodium octyl sulfate at a pH of 7.5 (adjusted with H 3 PO 4 ).
• this plate is imaged in an aqueous solution containing 3% lithium sulfate and 1% sodium octyl sulfate (sodium salt of monoocyte sulfuric acid) at pH 3.5 with a needle electrode with a voltage which changes depending on the point size.
• This plate is electrochemically imaged with a needle electrode in an aqueous solution containing 3% lithium sulfate and 1% sodium octyl sulfate at a pH of 7.5 at about 60 V depending on the spot size.
• the layer from example 13 is applied to an aluminum support which has been mechanically roughened by dry brushing and processed further as described in example 13.
• the imagewise stripping takes place in the same electrolyte under the same conditions, but without a previous non-electrochemical exposure phase.
• the electrochemical treatment is carried out in an aqueous solution containing 3% ammonium sulfate and 1% sodium octyl sulfate at a pH of 4 and at about 40 V.
• Example 66 The plate of Example 66 is electrochemically treated in an aqueous solution containing 3% sodium nitrate and 3% ethoxylated isotridecyl alcohol with 8 ethylene oxide units at a pH of 4.
• the imagewise stripping takes place electrochemically in an aqueous solution containing 3% ammonium phosphate and 3% of an ethoxylated isotridecyl alcohol with 8 ethylene oxide units at a pH of 8.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Printing Plates And Materials Therefor (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)

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• 1984
  • 1984-05-08 DE DE19843416867 patent/DE3416867A1/de not_active Withdrawn
• 1985
  • 1985-04-30 DE DE8585105257T patent/DE3579737D1/de not_active Expired - Fee Related
  • 1985-04-30 EP EP85105257A patent/EP0160920B1/de not_active Expired - Lifetime
  • 1985-05-06 US US06/730,632 patent/US4614570A/en not_active Expired - Fee Related
  • 1985-05-08 JP JP60096152A patent/JPS60244597A/ja active Pending

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