EP0054165B1 - Laminated printing cylinder - Google Patents

Description

The invention relates to a gravure cylinder according to the preamble of the main claim and comprises a method for producing a composite body therefor.

So far, it has been customary to produce printing rollers, such as those used in particular in gravure printing technology, but also in copiers and the like, by mechanically machining, polishing and balancing steel cylinders of relatively large length, since they have to rotate at high speed during operation. Such rollers are essentially very thick-walled cylinders, since the mechanical requirements at the high printing speeds are considerable.

A copper layer approximately 1 mm thick is electrolytically deposited on the circumference of the steel cylinder as a carrier. In order to keep the layer smooth and to compact it at the same time, it is compacted by a moving agate roller during a layer growth lasting about 15 hours. A silver layer is then placed on this copper layer as a separating layer. A further copper layer is then also electrolytically deposited over the silver layer.

After the usual photolythographic operations, the gravure pits are etched with a chemical etchant. The depth of the gravure pits is about 20 to 30 wm.

In operation, in front of the printing roller, after the required edition of a magazine or the like has been printed, the outer jacket is removed mechanically from the printing roller, in particular with the aid of pliers, a new layer of silver is applied and a copper layer is deposited thereon again, so that the gravure cylinder for the Photo exposure and the etching of another cliché template is available again.

The main disadvantage of this method, which has been practiced for many decades, is above all that it is not easy to remove the outer jacket and that damage to the roller carrier often occurs. This in turn requires reworking of the printing roller in the manufacturing plant, removal and reinstallation at the location of the printing press, transport costs and other costs.

From US-PS-3, 677, 975 it is known to provide a carrier body with a hard, tightly sealing and electrically conductive sheathing by flame spraying. A mixture of esters or salts of a valve metal and a noble metal salt is converted by spraying in an oxidizing flame into a valve metal oxide-noble metal oxide mixture which forms a coherent coating. Titanium is preferably used as the valve metal, while ruthenium is used as the noble metal. Such coatings have been used in fuel cell technology and chlor-alkali electrolysis.

The object of the invention is to provide a pressure roller with a composite structure in such a way that the outer jacket can be removed easily and without damage to the roller by anyone.

The object is achieved according to the invention in a gravure cylinder of the type mentioned at the outset by the features of the characterizing part of claim 1.

• Eine wesentliche Zeitersparnis für den Schichtaufbau, was der Tiefdrucktechnik neue Anwendungsgebiete eröffnet.

The main advantages of the invention are:

• This saves a significant amount of time for layer build-up, which opens up new areas of application for rotogravure technology.

The outer layer no longer has to be removed mechanically; there is no risk of damage to the roller carrier.

High material cost savings, especially on expensive precious metals.

The invention is explained below on the basis of exemplary embodiments, without being restricted thereto. In one embodiment of the invention, a pressure roller in composite construction was produced with a conventional steel cylinder as a support and thereon without an intermediate layer such as silver, a layer deposited from a matrix of substoichiometric TiO _1.94-1.96 with 3% platinum in the form of fine particles in one Amount of 0.1 to 10%, preferably 1 to 5%, based on the matrix mass, uniformly mixed and attached to the titanium oxide separation and then applied in a plasma spraying process. The noble metal was evenly distributed on the grains of the titanium oxide throughout the layer. The layer is dense and has a smooth, high surface quality with a roughness depth of less than 25 pm, approximately 5-15 pm, and the layer thickness produced was in the range of approximately 100 μm, particularly after mechanical processing such as grinding and polishing. However, their thickness can be 50 μm to 1 mm, in particular between 50 and 150 μm, preferably approximately between 80 and 120 μm. The roller was operated with good success and it has been found that copper can be deposited on the roller very quickly and easily cathodically and then anodically detached again by electrical polarity reversal.

It has been found that a pressure roller in this composite construction can withstand more than 125 cycles for the application and removal of copper layers.

Manufacturing example

The matrix material such as titanium oxide is e.g. B. in a fluidized bed by spraying, the salt being sprayed in a mist in countercurrent onto the fluidized bed. The particles of the matrix material are covered very homogeneously with active material, ie the particles of the active material are regularly distributed on the Surface of the matrix grains. The method therefore uses the matrix material such as titanium oxide in the form of powder (grain size), the active material consisting of noble metal such as platinum being dissolved in the form of a salt in an easily distillable solvent.

example

2.5 g of hexachloroplatinate are dissolved in 120 ml of methanol. 100 g of non-stoichiometric titanium oxide with grain size - 100 + 37 mym are weighed out in an evaporation dish. The solution is then added to this titanium oxide and then the methanol is evaporated off with constant stirring over a water bath. When the powder is almost dry, continue drying in a drying cabinet at a temperature of 105 ° C. After two hours, the powder is then removed from the oven and lightly crushed using a mortar, so that the conglomerate formed is brought back to the original grain size. Now the powder is heated in a crucible in a muffle furnace to 550 ° C for 4 hours. When the powder comes out of the oven and has cooled, it is lightly ground with a mortar to the original grain size. Then the powder is sieved and used with a grain size - 100 + 37 mym as a spray powder for coating.

A steel cylinder with a diameter of about 200 to 400 mm and a length of up to about 2,000 mm is after conventional pretreatment, such as. B. sandblasting using a plasma torch, type F 4 (company Plasmatechnik), with the activated powder, d. H. Titanium oxide coated with platinum attached to it. Instead of platinum, iridium or ruthenium was also mixed as oxide with the valve metal oxide and deposited evenly distributed. The other platinum group precious metals and gold and silver are also suitable. They also fulfill the requirement of being well electrically conductive and electrochemically active, which also applies to the oxides mentioned in the platinum metal group. The electrical conductivity usually increases with increasing percentage of precious metal in the mixed or combined powder: matrix plus active particles. On the other hand, one will be tempted to limit the share because of the high price of the precious metals. The valve metal oxide is of a conventional type, e.g. B. as the commercially available titanium oxide under the trade name "Amperit" (Starck).

The conditions of the plasma spraying process were current 400 A, voltage 70 V, plasma gas nitrogen 26 per minute, hydrogen 2 I per minute, spraying distance 150 mm.

Instead of the plasma spraying process, a conventional light sample spraying process can also be used.

• Temperatur: Raumtemperatur 20 °C
• Stromstärke 100 Alm²

A copper layer is then galvanically deposited on the spray layer, e.g. B. with an electrolyte of 0.5 N copper sulfate solution in 5% sulfuric acid. The electrolysis conditions were chosen as follows:

• Temperature: room temperature 20 ° C
• Current 100 Alm ²

Electrolysis time: cathodic 20 min. Anodic 25 min.

The chosen production has brought the advantages mentioned in the description.

For the success, the inventors see it above all that the electrochemically active particles are connected to the inert and electrically conductive matrix material in the respective electrolyte before application by one of the thermal spray processes mentioned.

In the accompanying drawing, a pressure roller is shown in composite body construction, which has a carrier I and a layer 2, which is composed according to the main claim.

Claims (7)

1. Intaglio cylinder comprising a metal base member and at least one galvanically deposited electrically conductive layer into which is inset the printing block or plate, characterised in that the base member has thereon a chemically inert and electrochemically active composite particle layer formed from a matrix of sub-stoichiometric titanium oxide in the form Ti0_2-x, x = 0.04 to 0.06, with particles of precious metals of the platinum group being deposited thereon in uniform distribution.

2. Intaglio cylinder according to claim 1, characterised in that the precious metal particles are platinum particles.

3. Intaglio cylinder according to claim 2, characterised in that the platinum particles are deposited on the matrix layer in a quantity of 0.1 to 10 %, preferably 1 to 5 %, related to the matrix composition.

4. Intaglio cylinder according to one of the claims 1 to 3, characterised in that the layer is dense with respect to the operating electrolyte and that its thickness amounts to between 50 µm and 1 mm, in particular to 50 to 150 µm, and preferably between say 80 and 120 µm.

5. Method for production of an intaglio cylinder, in which a layer is placed on a carrier, characterised in that inert electrically conductive particles of sub-stoichiometric titanium oxide of the form TiO_2-x, with x = 0.04 to 0.06, are initially prepared, which then have deposited on them electrochemically active particles of the platinum group, and that the composite particles so obtained are deposited on the carrier by means of a heat spraying process, for forming the layer.

6. Method according to claim 5, characterised in that a plasma jet method is utilised as a heat spraying process.

7. Method according to claim 5, characterised in that an arc deposition method is utilised as a heat spraying process.

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