EP1816006A1 - Inking roller for a rotary printing machine. - Google Patents

Abstract

A printing machine colour roller comprises a metallic core (7.1) and a surface coating (7.3) applied by plasma immersion ion implantation. The plasma coating contains Ti, Mb, Zr and/or other group 4 or 6 metals. The coating consists of at least two layers, and the composition is chosen so the total surface energy is a maximum of 35mN/m. A further metallic layer is located between the core and the plasma coating, and consists of Ni, Cr, Fe, B, and Si.

Description

The invention relates to a ink ductor roller of a web-fed printing machine according to the preamble of claim 1.

Ink fountain rollers of web presses pick up the ink from a film inking unit and usually transfer it to the printing plate cylinder via further ink transfer rollers, which transfer the ink to a blanket cylinder and finally to the subject.

For the printing result, it is essential that the ink absorption of the ink ductor roller is homogeneous and the ink film does not tear on the ductor roller or the ductor roller runs blank or dry.

Herein, blank running or ink film cracking on the ductor roller surface depends on the composition of the ink, the concentration of dampening solution used in printing, or any impurities adhering to the ductor roller surface.

Ink roller rollers with a ceramic surface are known from the prior art, which usually consist of a mixture of chromium oxide (Cr ₂ O ₃ ) and titanium oxide (TiO ₂ ), which, however, achieve only unsatisfactory results with regard to the blank running properties.

An improvement in blank running properties was achieved by ink ductor rollers with a metallic sprayed layer applied to the ink ductor roller by high velocity flame spraying. There is the metallic Spray coating, preferably of a metal alloy, such as nickel (Ni), chromium (Cr), iron (Fe), boron (B) and silicon (Si). Although this metallic surface can be used to improve the level of cold running in relation to the ceramic surfaces, complete prevention can not be achieved with this coating. So far, it has been used to prevent the Farbduktorblanklaufens additional anti-adhesive pastes, but showed only a temporary effect.

In addition to the blank running of the ink ductor occurs in the inking the problem of dirt. These soiling, such as paper dust, get into the color of the inking unit and are absorbed by the ink fountain roller. Whereby superficially adhering dirt on the ink ductor, in turn, favor the infiltration of paint and thus the free running.

On this basis, the present invention is based on the problem to provide a ductor roller of a web-fed printing press, which has a surface in which the phenomenon of blank or color film break even further reduced or completely prevented, the surface should also be designed such that contamination less or not sticking to it.

This problem is solved by a ink fountain roller of a web printing machine according to claim 1.

The inventors have recognized that first of all the surface energy, in this case above all the polar fraction, of the ink ductor roller surface is decisive for its oleophilic or hydrophobic properties. The lower the surface energy is, the more "color friendly" and "water hostile" is the surface. By this means, it can also be explained that the metallic high-speed flame sprayed layer on the ink fountain roller surface having a higher density and a lower surface energy than the ceramic ink duct roller surface, also has a better ink receptivity and thus lower Blanklaufeigenschaften.

The inventors have further recognized that the morphology or the topography of the surface also has an influence on the bright running properties of the ink ductor roller surface. For example, within pores and microcracks in the ink ductor roll surface, contaminants, especially of calcium carbonate and kaolin, which due to their hydrophilic properties act as germ cells for the unwanted spreading of dampening water on the ductor roll surface, cause the color to submerge and possibly run over the ductor roller causes.

From the DE 195 16 032 C2 For example, there is known a method of refining the surface of a paint transfer roller wherein a metal layer is applied by ion implantation to the ink transfer roller surface provided with a corrugation or depressions. The ink transfer roller rotates with the high rotational speed of the printing machine of up to 60,000 revolutions / minute and is thus subject to increased abrasion and increased wear. With the aid of the metal coating applied by ion implantation, the service life of the ink transfer roller is to be increased by minimizing the abrasion and at the same time improving the corrosion property.

By contrast, the ink fountain roller rotates at a rotation speed that is approximately 60 times lower. This low rotational speed is necessary to ensure a homogeneous absorption of the color from the ink fountain and to avoid whirling up of the paint. Due to the much lower rotational speed, the wear problem on the ink fountain roller occurs only to a lesser extent than in the ink transfer roller. So far, the use of a plasma coating on the surface appeared on the ink fountain roller a Farbduktorwalze, the coating means a not inconsiderable cost, not to be useful.

From the findings gained, the inventors propose to improve a ink ductor roller of a web-fed printing press according to the preamble of claim 1 such that the roller surface has a coating applied by means of plasma immersion ion implantation.

With the help of plasma immersion ion implantation, also referred to as ion implantation or vacuum plasma technology, the benefits of conventional ion implantation can be transferred to large, complex geometries. In this case, the plasma immersion ion implantation differs from the plasma coating by means of thermal spraying. In the plasma immersion ion implantation, the workpiece to be treated is enveloped in a vacuum chamber by a plasma generated by a suitable plasma source. By applying negative high voltage pulses with very short pulse rise times, which are in the range of less than one microsecond, the more mobile electrons of the plasma are then pushed back and accelerated or implanted the remaining positive ions on the workpiece. The acceleration voltages are below the acceleration voltages of conventional ion implantation, which are in the order of 30 kilovolts. Due to the improvement of the mechanical load capacity of metal components, the method is used in the space sector and in the medical implantation / field. As a further advantage of the plasma immersion ion implantation, a structure modification can take place in addition to a coating.

By the invention it is achieved that on the one hand microcracks on the surface of the ink ductor roller, which have a diameter in the sub-micron range, are reduced and thus the surface becomes smoother and less contamination can adhere. Furthermore, especially this plasma coating has favorable values with regard to the polar and disperse fraction of the surface energy.

For example, metals such as titanium, molybdenum, zirconium and / or other 4 or 6-valent metals are suitable for the plasma coating.

The plasma coating can also be multi-layered, preferably at least two-layered.

The composition of the plasma coating should be chosen such that the lowest possible total surface energy of about 35 mN / m results. The total surface energy σ _total is additively composed of the polar σ _polar and the disperse fraction σ _{dispers of} the surface energy: $${\sigma }_{\mathrm{total}}={\sigma }_{\mathrm{polar}}+{\sigma }_{\mathrm{disperse}}$$

The sessile drop method, which involves applying at least three test liquids to the surface, is suitable for determining the surface energy.

Furthermore, the composition of the plasma coating should be chosen such that a polar fraction of the surface energy of not more than 7 mN / m results. With a polar fraction of the surface energy of 7 mN / m at maximum and a total surface energy of 35 mN / m, a disperse fraction of the surface energy of at most 28 mN / m results.

Thus, the respective proportions in the polar and in the disperse fraction of the surface energy values are largely adapted to the values of typical offset printing inks.

In addition, the composition of the plasma coating should be chosen so that water has a wetting angle of at least 70 degrees on the surface.

Between the metallic core and the plasma coating, a thermal sprayed layer, preferably of metal and / or ceramic, can be applied. In this case, the intermediate layer can preferably be applied by high-speed flame spraying on the core. The metallic intermediate layer should contain at least nickel, chromium, iron, boron and silicon. Depending on the composition of the metal, the effect and the adhesion of the plasma coating are different.

The total layer thickness of the metallic plasma coating can be between 100 nm and 3 μm.

Fig. 1:

eine Prinzipdarstellung einer rasterelektronische Aufnahme einer Duktorwalzenoberfläche, die aus einer Keramikbeschichtung besteht, mit 500-facher Vergrößerung;

Fig. 2:

eine Prinzipdarstellung einer rasterelektronische Aufnahme einer Duktorwalzenoberfläche, die aus einer metallischen Spritzschicht besteht, mit 500-facher Vergrößerung;

Fig. 3:

Ausschnitt aus der Oberfläche aus Figur 2 mit darunter befindlichem Diagramm einer EDX-Analyse,

Fig. 4:

Diagramm mit Kaelblekreisen von verschiedenen Duktorwalzenoberflächen;

Fig. 5:

Zweischichtiger Aufbau einer Farbduktorwalze;

Fig. 6:

Dreischichtiger Aufbau einer Farbduktorwalze.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

Fig. 1:

a schematic representation of a raster electronic recording of a Ductor roller surface, which consists of a ceramic coating, with 500-fold magnification;

Fig. 2:

a schematic representation of a grid electronic recording of a Ductor roller surface, which consists of a metallic sprayed layer, with 500-fold magnification;

3:

Section from the surface of FIG. 2 with underlying diagram of an EDX analysis,

4:

Diagram with Kaelble circles of different ductor roll surfaces;

Fig. 5:

Two-layer construction of a ink ductor roller;

Fig. 6:

Three-layer construction of a ink ductor roller.

Hereinafter, the present invention will be described in more detail with reference to FIGS. 1 to 6.

1 shows a schematic diagram of a scanning electronic recording of a ceramic coating a Ductor roller surface with 500-fold magnification. In this schematic representation topographical height differences were outlined. The ceramic coating consists of a mixture of chromium oxide (Cr ₂ O ₃ ) and titanium oxide (TiO ₂ ). The illustrated section of the ceramic surface corresponds approximately to a width of 250 microns and a height of 180 microns, where one microns corresponds to 10 ^-6 meters. Wells 1 (circled area) can be clearly seen on this surface, some of which have diameters of approximately 20 μm. The inventors have recognized that unwanted contaminants can accumulate in these depressions. In the ink fountain roller according to the invention, among other things, the surface should be made smoother.

FIG. 2 shows a schematic representation of a scanning electronic recording of a metallic spray layer of a ductor roller surface with a magnification of 500 times. The size dimensions of the cutout correspond to those of FIG. 1. As can be clearly seen, the number of depressions 1 in the case of a metallic ink ductor roller surface is considerably lower than in the case of a ceramic coating. As described above, contaminations, especially of calcium carbonate and kaolin, which due to their hydrophilic properties can accumulate within these recesses in the ink duct roller surface as germ cells for the unwanted spreading of fountain solution on the ductor roller surface, which causes an infiltration of the color and possibly a run over the ink ductor roller.

The metallic ink duct roller surface with its lower surface energy and reduced number of recesses substantially reduces the likelihood of contamination on the ink duct surface.

FIG. 3 shows a partial section from the surface of FIG. 2 with a diagram of an EDX analysis underneath. In this case, the occurrence of certain substances and their concentration is determined with the EDX analysis, in which an energy-dispersive X-ray fluorescence analysis is performed. In the elliptically framed area of the left EDX diagram, in addition to the metal components of the ink fountain roller surface, a significantly increased concentration of carbon (first peak) in the region of the recesses can be recognized. In comparison, the "carbon peak" of the smooth roll surface in the elliptically framed area of the right EDX plot is of lesser height. This suggests that organic contaminants preferentially deposit in the wells.

aufgetragen. Die Wechselwirkung einer Oberfläche und der Farbe auf der Farbduktorwalze wird im Diagramm als Kreis aufgetragen, wobei die beiden Wertepaare von Oberflächen 6.1 und Farbe 6.2 Punkte auf dem Durchmesser der Kreislinie sind, womit dieser vollständig charakterisiert ist. Mit Hilfe der Kreise kann nun beantwortet werden, ob eine Flüssigkeit die Farbe auf der Oberfläche verdrängen kann oder nicht. Hierzu werden drei Fälle unterschieden:

• a: Die Oberflächenspannung der Flüssigkeit liegt außerhalb des Kaelblekreises. Dies bedeutet, dass die Flüssigkeit die Farbe nicht von der Oberfläche der Farbduktorwalze verdrängen kann.
• b: Die Oberflächenspannung der Flüssigkeit liegt innerhalb des Kaelblekreises. Dies bedeutet, dass die Flüssigkeit die Farbe von der Oberfläche der Farbduktorwalze verdrängen kann.
• c: Die Oberflächenspannung der Flüssigkeit liegt auf dem Kaelblekreis. Dieser Grenzfall bedeutet, dass geringe Schwankungen der Eigenschaft der Flüssigkeit, wie zum Beispiel Temperatur, Verunreinigungsgrad etc, beeinflussen können, ob die Flüssigkeit Farbe von der Oberfläche des Farbduktorwalze verdrängen kann oder nicht.

FIG. 4 shows a diagram with Kaelble circles of different ductor roll surfaces. Concerning the Kaelbletheorie is on the publication " Surface Analysis of Lithography "from Polymer Science Technology (1975), pages 735 to 761, by DH Kaelble, PI Dynes and D. Pav , whose contents are incorporated into this document. In this diagram, on the abscissa, the root value of the polar component of the surface energy and on the ordinate the root value of the disperse component of the surface energy are respectively in $\sqrt{\mathrm{mN}\mathrm{/}\mathrm{m}}$

applied. The interaction of a surface and the color on the ink ductor roller is plotted in the diagram as a circle, whereby the two value pairs of surfaces 6.1 and color are 6.2 points on the diameter of the circular line, thus fully characterizing it. With the help of circles can now be answered whether a liquid can displace the color on the surface or not. There are three different cases:

• a: The surface tension of the liquid is outside the Kaelblekreises. This means that the liquid can not displace the paint from the surface of the ink ductor roller.
• b: The surface tension of the liquid is within the Kaelblekreises. This means that the liquid can displace the paint from the surface of the ink ductor roller.
• c: The surface tension of the liquid is on the Kaelblekreis. This limiting case means that small variations in the property of the liquid, such as temperature, impurity level, etc., can affect whether or not the liquid can displace paint from the surface of the ink ductor roll.

In the diagram of Figure 4 are now three Kaelbekreise of three different surface materials of ink ductor rollers and three different dampening 5.1 to 5.3 shown. The circle 2 corresponds to the Kaelblekreis a ceramic layer consisting of chromium oxide (Cr ₂ O ₃ ) and titanium oxide (TiO ₂ ). The circle 3 corresponds to the Kaelblekreis a metal layer consisting of nickel (Ni), chromium (Cr), iron (Fe), boron (B) and silicon (Si), which was applied by high-speed flame spraying. The circle 4 corresponds to the Kaelblekreis a metal layer, which was then additionally coated plasma. The first fountain solution 5.1 is outside all Kaelblekreise 2 to 4 and can not displace the color of the ink fountain roller surface. The second fountain solution 5.2 is outside the Kaelblekreise 3 and 4, with the metallic coating and the metallic plasma coating. On these two surfaces, the ink can not be displaced by the second dampening solution 5.2 from the ink duct roller surface. However, the second dampening solution displaces the 5.2 Color on the ceramic surface, as it lies within the Kaelblekreises 2. From the diagram of Figure 4 it can be seen that the metallic plasma coating with respect to all three dampening 5.1 to 5.3 proves to be favorable. None of these dampening solutions 5.1 to 5.3 can displace the paint on the metallic plasma coating.

FIG. 5 shows a possible two-layer construction of a ink ductor roller. In this embodiment, the plasma coating is 7.3 applied directly to the Duktorwalzenkern 7.1.

FIG. 6 shows a possible three-layer construction of a ink ductor roller. In comparison to the two-layer structure of FIG. 5, a metallic intermediate layer 7.2 of nickel (Ni), chromium (Cr), iron (Fe), boron (B) and silicon (Si) is applied between plasma coating 7.3 and duct roller core 7.1. As an alternative to the metallic intermediate layer, this intermediate layer could also consist of ceramic material.

The ink duct roller according to the invention generally further reduces or prevents the problem of blank running. In addition, the new ductor roller allows far more dampening solution to be used, which does not displace the ink from the ink duct roller surface.

It is understood that the abovementioned features and the features of the claims can be used not only in the particular combinations indicated, but also in other combinations or in isolation, without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

1

deepening

2

Kaelble circle of a ceramic layer (Cr ₂ O ₃ / TiO ₂ )

3

Kaelble circle of a metal layer (NiCrFeBSi)

4

Kaelble circle of a metallic plasma coating

5.1

First dampening solution

5.2

Second fountain solution

5.3

Third dampening solution

6.1

Disperser and polar component of the surface energy of the ceramic layer

6.2

Disperser and polar component of the surface energy of the paint

7.1

Duktorwalzenkern

7.2

Metal layer (NiCrFeBSi)

7.3

plasma coating

Claims (11)

Ink ductor roller of a web-fed printing machine with at least one inking unit, from which the ink fountain roller picks up ink, wherein the ink fountain roller has a metallic core (7.1), characterized in that the ink fountain roller on the roller surface has a coating (7.3) applied by means of plasma immersion ion implantation is. Ink fountain roller according to claim 1, characterized in that the plasma coating (7.3) contains at least titanium, molybdenum, zirconium and / or other 4 or 6-valent metals. An ink fountain roller according to one or both of claims 1 and 2, characterized in that the plasma coating (7.3) has a multilayer structure, preferably at least two layers. Ink fountain roller according to one or more of claims 1 to 3, characterized in that the composition of the plasma coating (7.3) is selected such that a total surface energy of at most 35 mN / m results. Ink ductor roller according to one or more of claims 1 to 4, characterized in that the surface energy values of the treated surface in and polar and in the disperse fraction are largely adapted to values of typical offset printing inks. An ink fountain roller according to claim 5, characterized in that the composition of the plasma coating (7.3) is selected such that the polar component of the surface energy results in a maximum of 7 mN / m. Ink duct roller according to claim 5 and 6, characterized in that the composition of the plasma coating (7.3) is selected such that the disperse fraction of the surface energy results in a maximum of 28 mN / m. Ink fountain roller according to one or more of claims 1 to 7, characterized in that the composition of the plasma coating (7.3) is selected such that water has a wetting angle of at least 70 degrees. Ink fountain roller according to one or more of claims 1 to 7, characterized in that between the metallic core (7.1) and plasma coating (7.3), a further metallic intermediate layer (7.2) is applied, which is preferably made by high-speed flame spraying. Ink duct roller according to claim 9, characterized in that the further metallic intermediate layer (7.2) contains at least nickel, chromium, iron, boron and silicon. Ink ductor roller according to one or more of claims 1 to 10, characterized in that the total thickness of the plasma coating is between 100 nm and 3 microns.

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