EP0748701A2 - Ion implanted inking roll - Google Patents

Abstract

Ink transfer roller (1) has a surface structure, mechanically applied or applied by laser, made of saucers (N) in a microporous, metallic or (metal)-ceramic hard material layer (HS). The novelty is that source microcracks (M) and pores are closed by ion implantation material (H) applied by high voltage plasma. The ion implantation material (H) is made of Ti and Mo, and is coated with a wear resistant thin layer covering layer (D) made of a hard material, esp. a metal oxide and/or metal nitride so that the covering layer has a predetermined affinity to the printing ink to be applied by the roller. The covering layer is made of ZrO2. The hard layer (HS) consists of polished Cr2O3 in a thickness of 100-150 mu m, or consists of plasma-deposited Ni-Cr alloy in a thickness of 100 mu m, or consists of steel, copper or nickel coated with metal matrix. The roller is produced by subjecting it to turbulent heavy metal implantation at 50-80 degrees C in a gas discharge plasma using a voltage of 1000 V. Ti and Mo ions are used in a wt. ratio of 70/30 to 90/10. ZrO2 is implanted from the gas discharge plasma.

Description

The invention relates to an ink transfer roller with a mechanically or by laser surface structure made of ink transfer cups in a microporous, metallic or ceramic or metal-ceramic hard material layer, and a method for the production thereof.

Such an ink transfer roller is known for example from DE 40 07 130 A1. In this case, wells are embossed into a metallic surface, and a burr which arises is removed, and the well surface is covered with hard materials, e.g. with hard chrome or with silicon carbide grains, in a nickel matrix, galvanically coated to increase the abrasion resistance. In addition, a thin layer of hard chrome can be applied. However, these upper layers are always traversed by fine microcracks, and fine pores with micrometer dimensions are found, in particular at the boundaries of the embedded hard material grains, as a result of which there is only limited adhesion thereof.

Furthermore, from the magazine: Flexo, 1985, Vol. 10, No. 10; 45-50, inking rollers are known, the cells of which are lasered into a plasma-sprayed hard ceramic layer, for example chromium oxide (Cr203). With selective high-temperature treatment with the laser beam and the subsequent rapid cooling, microcracks and micropores and strong distortions and tension in the structure arise, which reduce the abrasion resistance and Corrosion resistance reduced.

It is an object of the invention to improve the ink transfer roller mentioned at the outset in such a way that it has a longer service life, less abrasion and less susceptibility to corrosion.

The solution is that superficial microcracks and pores are closed by an ion implant material applied with a high-voltage plasma.

A method according to the invention for treating the known rollers for plasma-assisted implantation of the closure material is specified in claims 13 to 17.

All previously known microstructured ink transfer rollers are suitable for the treatment of the surface with implant material according to the invention, both in the case of new production and for post-treatment. The material layers applied during the implantation have a thickness of 1 to 2 μm, which is comparatively small compared to the cell dimensions, so that the cell volume remains practically unchanged.

Combinations of tetravalent substances with heavy metals, in particular the tetravalent titanium and the hexavalent molybdenum in a weight ratio of 70/30 to 90/10, preferably 80/20, have proven successful as substances for filling and closing the cracks and pores. These metal ions penetrate deep into the interior of microcracks and the boundary layer, which often occur at the grain boundaries of electrolytically applied layers or in sputtered layers or after lasering. The closure and the filling of the cracks provides especially an increase in corrosion resistance, since the surface becomes smooth and dense.

The implantation of the metal ions takes place in a nitrogen atmosphere, so that the metals combine with it in part as nitrides and form very hard crystalline structures.

Another abrasion-resistant cover layer of 0.05-1 µm, preferably 0.1 µm, of a hard material is advantageously implanted in a similar manner. Hard metal oxides or nitrides are provided for this. Zirconium oxide (Zr02) has proven particularly useful, for which the implantation is carried out in an oxygen plasma. This cover layer is chosen in particular in such a way that a desired surface affinity for the printing ink to be transported and dosed arises.

In addition to finishing the surface with zirconium oxide, silicon oxide, silicon and carbon layers have also been successfully produced and used. The carbon coating has shown a smear effect that reduces abrasion.

The surfaces tempered in this way show a higher hardness of 1400 - 166 HV compared to that of the paint particles, which is below 1200 HV. The untreated surfaces of chrome have a hardness of 600 - 800 HV, and surfaces of the ceramics have a hardness of 900 - 1000 HV. They are therefore generally under that of the paint particles, and there is constant wear.

The implantations are carried out under high voltage with a turbulent flow of the plasma, preferably in nitrogen and / or oxygen. As tension will be a thousand to ten thousand volts are applied, and the current strength is selected so that, with moderate heating, a sufficient penetration depth of the ions and anchoring of the implant takes place in the surface without burning or thermally destroying it.

A gas pressure of approximately 1 mbar has proven to be favorable. The impact voltage of the ions is preferably in the range between 600 V and 2 kV.

The operating heat is kept so low by appropriate control of the current intensity and the high voltage that no noticeable thermal stresses occur after cooling in the layer near the surface. Temperatures of 50 - 80 ° C are planned. Therefore, such novel rollers according to DE 44 26 485 can also be coated with an implant, the hard material layer of which is supported by a plastic substructure. Esp. the hard material layer is applied over a metal layer on an elastic plastic jacket, which consists of plastic reinforced with plastic fiber inserts and is interchangeably mounted on a solid metallic roller core with an elastic substructure.

Fig. 1

zeigt eine vergrößerte Aufsicht auf eine gerasterte Walzenoberfläche;

Fig. 2

zeigt einen 1000-fach vergrößerten Schnitt durch das Gefüge unter einem geprägten Näpfchen;

Fig. 3

zeigt einen hochvergrößerten Schnitt durch ein Näpfchen mit einer Hartstoff-Metallmatrix-Beschichtung;

Fig. 4

zeigt in 100-facher Vergrößerung Mikrorisse entlang der Korngrenzen einer Walzenbeschichtung;

Fig. 5

zeigt eine Aufsicht 150-fach vergrößert auf eine gelaserte Hartkeramikoberfläche;

Fig. 6

zeigt einen Querschnitt zu Fig. 5 in 350-facher Vergrößerung;

Fig. 7

zeigt einen schräg in die Tiefe verlaufenden Anschliff zu Fig. 5.

Advantageous embodiments are shown with reference to Figures 1 to 7.

Fig. 1

shows an enlarged plan view of a rastered roller surface;

Fig. 2

shows a 1000 times enlarged section through the structure under an embossed cell;

Fig. 3

shows a highly enlarged section through a well with a hard material-metal matrix coating;

Fig. 4

shows microcracks in 100x magnification along the grain boundaries of a roll coating;

Fig. 5

shows a plan 150 times enlarged on a lasered hard ceramic surface;

Fig. 6

shows a cross section to Figure 5 in 350-fold magnification;

Fig. 7

shows a bevel at an angle to the depth of FIG. 5.

Figure 1 shows an enlarged plan view of a section of the surface of a roller 1, which is provided in a predetermined grid R with truncated pyramidal cups N. A small web S remains between the wells and the inclined walls W end in a flat bottom B.

Figure 2 shows a thousandfold enlargement of a small section of the wall W and the bottom B of a well N, which is made of a hard material HS, e.g. Steel, existing structure is provided by a micrometer-thick doping with an ion implant material H and an overlying cover layer D. It is clear that the hard material HS is very badly destroyed in its structure by the mechanical processing and has a high surface roughness and porosity, although the surface has been electrolytically polished before the ion implantation. The layer thicknesses of the implants H, D are shown exaggerated; in particular, the implanted oxide cover layer D is generally much thinner than the nitrified metallic implantation H.

Figure 3 shows an enlarged cross section in the Roll surface into, the well N consists in a known manner with an oxidic hard material HS from a nickel matrix with carbide insert, on which a hard chrome layer is applied. The chrome surface is then provided with the implant material H and the cover layer D by the ion implantation.

FIG. 4 shows an enlarged surface of the hard material layer HS, which is provided with hard chrome. The grain boundaries, which form small microcracks M, are clearly shown. These micro cracks are closed by the high voltage implant.

Figure 5 shows another type of the known roller surfaces in high magnification. Here, a ceramicized surface, for example made of chromium oxide, is provided with a N cup by lasering. The laser beam is guided from well to well and melts the material with high energy and evaporates part of it, so that the wells N are formed. As the drawing after a photo shows, the crater edges have solidified unevenly from the melt, and many microcracks M are visible there.

As shown in FIG. 6 in a deep section, the microcracks M extend into a deep depth of the solidified well surface relative to the well structure. These microcracks M are filled with the implant H. The cover layer D is shown on the implant H, which in particular has a favorable influence on the compatibility of the color with the surface and gives it a predetermined adhesion to the printing ink. The strengths of layers H and D are shown exaggerated.

Figure 7 shows one from left to right at an angle Deep grinding of a lasered hard material layer HS. It can be seen that the microcracks M also extend approximately radially from the wells N in the lower regions. These microcracks are filled up and sealed by the ion implantation. In addition, the implant material H, D results in a relatively smooth cell surface.

Claims (17)

Ink transfer roller (1) with a mechanical or laser-made surface structure made of ink transfer cups (N) in a microporous, metallic or ceramic or metal-ceramic hard material layer (HS),
characterized in that superficial microcracks (M) and pores are closed by an ion implant material (H) applied with a high-voltage plasma. Ink transfer roller according to claim 1, characterized in that the ion implant material (H) consists of a tetravalent substance and at least one heavy metal. Ink transfer roller according to claim 2, characterized in that the ion implant material (H) consists of titanium and molybdenum in a ratio of 70/30 to 90/10. Ink transfer roller according to one of the preceding claims, characterized in that the ion implant material (H) is coated with a wear-resistant, thin cover layer (D) made of a hard material, in particular a metal oxide and / or metal nitride, by an ion implantation in such a way that the cover layer (D) has a predetermined affinity for a printing ink to be dosed with the printing roller. Ink transfer roller according to Claim 4, characterized in that the cover layer (D) has a thickness of 0.05-1 µm, preferably 0.1 µm. Ink transfer roller according to claim 4 or 5, characterized in that the cover layer (D) consists of zirconium oxide, silicon oxide, silicon or carbon. Ink transfer roller according to Claim 1, characterized in that the urea layer (HS) consists of ground and finished chrome oxide (Cr2O3) with a thickness of 100-150 µm and the cells (N) are introduced and finished by laser engraving and then the ion implant material (H) inserted pore-closing. Ink transfer roller according to claim 1, characterized in that the hard material layer (HS) consists of a plasma-deposited nickel-chromium alloy 80/20 with a thickness of approximately 100 µm. Ink transfer roller according to claim 1, characterized in that the hard material layer (HS) consists of steel, copper or nickel, which is thinly coated with hard chrome (HC) after the insertion of the wells (N) and electrolytic polishing. Ink transfer roller according to claim 1, characterized in that the hard material layer (HS) consists of steel, copper or nickel, which after the insertion of the cups (N) is electrolytically coated with a metal matrix with the incorporation of hard material grains. Ink transfer roller according to claim 10, characterized in that the hard material grains consist of silicon carbide and are embedded in a nickel matrix. Ink transfer roller according to one of the preceding claims, characterized in that the hard material layer (HS) on a thin metallic Intermediate layer is applied, which is sputtered onto a plastic jacket that contains plastic fiber inserts. Process for producing a highly abrasion-resistant and highly corrosion-resistant ink transfer roller, in particular according to one of the preceding claims, characterized in that the roller (1) after the insertion of the wells (N) in a first implantation step in a gas discharge plasma at a voltage of one thousand volts up to ten thousand Volt is exposed to a turbulent heavy metal ion implantation at a temperature between 50 - 80 ° C until microcracks (M) and micropores of the surface are filled and the ion implant material (H) has grown on the free surface in a layer thickness of less than 1 µm. Process according to Claim 13, characterized in that tetravalent and hexavalent substances, in particular titanium and molybdenum, are added to the plasma as ions in a weight ratio of 70/30 to 90/10. A method according to claim 13 or 14, characterized in that the gas discharge burns in nitrogen or oxygen at a pressure of about 1 mbar. Method according to one of claims 13 to 15, characterized in that the first implantation step is followed by a second, in which the roller (1) in a gas discharge plasma at a voltage of one thousand to ten thousand volts with an impact energy of 600-2000 eV at a temperature between 50 - 80 ° C a turbulent metal ions, metal oxide and / or metal nitride implantation is exposed until the oxide or nitride to a layer thickness of 0.05 to 1 µm the surface grew up. A method according to claim 16, characterized in that zirconium oxide (Zr02), silicon oxide, silicon or carbon dioxide is implanted from the gas discharge plasma.

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