EP2331329B1 - Diamond-coated doctor blade - Google Patents

Description

Technical area

The invention relates to a doctor blade, in particular for doctoring off printing ink from a surface of a printing form and / or for use as a paper doctor blade, comprising a flat and elongate base body with a working edge region formed in a longitudinal direction, wherein at least the working edge region having a first coating on the base a nickel-phosphorus alloy is coated. Furthermore, the invention relates to a method for the production and the use of a doctor blade.

State of the art

In the printing industry, scrapers are used, in particular, for scraping off excess printing ink from the surfaces of printing cylinders or printing rollers. Especially with intaglio and flexographic printing, the quality of the squeegee has a decisive influence on the print result. Unevenness or irregularities of the standing with the impression cylinder working edges of the doctor blade lead z. B. to incomplete stripping of the ink from the webs of the printing cylinder. This can lead to an uncontrolled release of ink on the print carrier.

The working edge portions of the doctor blade are pressed against the surfaces of the printing cylinders or printing rollers during stripping and are moved relative thereto. Thus, the working edges, especially in rotary printing machines, exposed to high mechanical loads, which bring a corresponding wear. Squeegees are therefore basically consumables, which must be replaced periodically.

Squeegees are usually based on a steel body with a specially shaped working edge or working edge area. To improve the life of the doctor blade, the working edges of the doctor blade can also be provided with coatings or coatings of metals and / or plastics. Metallic coatings often contain nickel or chromium, which may be mixed or alloyed with other atoms and / or compounds. The material properties of the coatings in particular have a significant influence on the mechanical and tribological properties of the doctor blade

In the WO 2003/064157 (Nihon New Chrome Co. Ltd.) are z. B. squeegee for printing described, which have a first layer of chemical nickel having dispersed therein hard material particles and a second layer with a low surface energy. The second layer preferably consists of a coating of chemically nickel with fluorine-based resin particles or of a purely organic resin. Such coated doctor blades have an improved wear resistance compared to uncoated doctor blades. However, the lifetime is still not completely satisfactory. In addition, it has been shown that it can come with the use of such squeegee, especially in the run-in phase to uncontrolled banding, which is also undesirable.

There is therefore still a need for an improved squeegee, which in particular has a longer life and at the same time allows optimal wiping.

Presentation of the invention

The object of the invention is to provide a squeegee associated with the technical field mentioned above, which has an improved wear resistance and during the entire life of a precise scraping, in particular of ink allows.

The solution of the problem is defined by the features of claim 1. According to the invention, monocrystalline and / or polycrystalline diamond particles are dispersed in the first coating, with a particle size of the diamond particles measuring at least 5 nm and less than 50 nm.

Under a nickel-phosphorus alloy, which forms the basis for the first coating, is understood in this context, a mixture of nickel and phosphorus, wherein the phosphorus content of the alloy is in particular 1-15 wt .-%. Such alloys can in particular be deposited without current and are then also referred to as chemically nickel. The expression "based on a nickel-phosphorus alloy" means that the nickel-phosphorus alloy is the main constituent of the first coating. In this case, in the first coating in addition to the nickel-phosphorus alloy quite other types of atoms and / or chemical compounds may be present, which have a smaller proportion than the nickel-phosphorus alloy. The nickel-phosphorus alloy and any other types of atoms and / or chemical compounds present form a matrix for the monocrystalline and / or polycrystalline diamond particles. The proportion of the nickel-phosphorus alloy in the matrix is preferably at least 50% by weight, particularly preferably at least 75% by weight and very particularly preferably at least 95% by weight. Particularly advantageous is the matrix of the first coating except for unavoidable impurities exclusively of a nickel-phosphorus alloy. Ideally, the first coating is correspondingly, except for unavoidable impurities, exclusively of a nickel-phosphorus alloy having dispersed therein monocrystalline and / or polycrystalline diamond particles.

According to the invention, the monocrystalline and / or polycrystalline diamond particles are dispersed in the first coating. This means, in particular, that the diamond particles are present substantially uniformly distributed in the first coating.

In this context, the particle size is understood to mean, in particular, a maximum dimension and / or external dimension of the monocrystalline and / or polycrystalline diamond particles. With regard to the particle size, the diamond particles generally also have a certain distribution or a scattering width. Therefore, diamond particles with different particle sizes are especially present at the same time in the first coating.

As has been shown, the monocrystalline and / or polycrystalline diamond particles dispersed in the first coating based on a nickel-phosphorus alloy with the particle sizes of at least 5 nm and less than 50 nm according to the invention substantially improve the wear resistance of the working edges or working edge regions of the doctor blade , This brings in particular a long life of the inventive doctor blade with it.

At the same time, the working edges are optimally stabilized by the first coating based on a nickel-phosphorus alloy with the diamond particles dispersed therein. This results in a sharply defined contact zone between the doctor blade and the printing cylinder or the pressure roller, which in turn allows a very precise scraping or doctoring off of ink. The contact zone remains over the entire life of the doctor blade or over the entire printing process largely stable.

Furthermore, the doctor blade according to the invention has extremely favorable sliding properties on the printing cylinders or printing rollers commonly used. As a result, when the doctor blade according to the invention is used for deburring, wear on the printing cylinders or printing rollers is also reduced.

In order to achieve the improvement of the wear resistance and the optimum stabilization of the working edges of the doctor blade, monocrystalline and / or polycrystalline diamond particles with a particle size of at least 5 nm and less than 50 nm have proven to be the best possible choice. Diamond with a mono- and / or polycrystalline structure has proven to be an optimal material for the particles according to the invention, in particular because of its high hardness and its chemical inertness with respect to a multiplicity of potential reaction partners. In this case, diamond with mono- and / or polycrystalline structure is not to be confused with other forms of carbon, such as. Example, graphite, glassy carbon, graphene, carbon black or the diamond-like carbon diamond ("DLC"). These forms of carbon bring the inventive advantages only limited or not at all.

In the case of the particle sizes according to the invention, the proportion of the particle surface in relation to the particle volume is very large in comparison with particle sizes in the micrometer range. Accordingly, the particle surface, which also contacts and interacts with the surrounding nickel-phosphorus alloy, has a not insignificant influence on the properties of the diamond particles, which apparently has a positive effect on the properties of the doctor blade according to the invention.

When using diamond particles with particle sizes smaller than 5 nm, in particular, the wear resistance of the working edge of the doctor decreases, which shortens the life of the doctor blade. With particle sizes of 50 nm and more, in particular, the stabilization of the working edge of the doctor reduces, which worsens the exact ink coating.

The addition of diamond particles with a particle size of at least 5 nm and less than 50 nm therefore results in interaction with nickel-phosphorus alloys novel coatings for doctor blade with superior mechanical and tribological properties.

A phosphorus content of the nickel-phosphorus alloy is preferably 7-12% by weight. Coatings of this kind have proven particularly suitable in combination with the monocrystalline and / or polycrystalline diamond particles according to the invention, since in particular a higher wear resistance is obtained during the entire service life of the doctor blade. A phosphorus content of 7 - 12% by weight also improves the corrosion resistance, the tarnish resistance and the inertness of the nickel-phosphorus alloy. A phosphorus content of 7 to 12% by weight also has a positive effect on the sliding properties of the doctor blade as well as the stability of the working edge, which makes it possible to paint or scrub off printing ink very precisely. Furthermore, at a phosphorus content of 7 - 12 wt% on the commonly used primers for doctor blade, such. As steel, given a good adhesion.

In principle, however, it is also possible to provide a lower phosphorus content than 7% by weight or a greater phosphorus content than 12% by weight. However, the above-mentioned positive effects are reduced or even completely eliminated.

A layer thickness of the first coating is advantageously 1-10 μm. Such thicknesses of the first coating provide optimum protection of the working edge of the doctor blade. In addition, such sized first coatings have a high intrinsic stability, which effectively reduces the partial or total delamination of the first coating, for example during the doctoring of printing ink from a printing cylinder.

Although thicknesses of less than 1 μm are possible, the wear resistance of the working edge or the doctor blade decreases rapidly. Greater thicknesses than 10 μm are also feasible. On the one hand, these are less economical and have a negative impact on the quality of the working edge.

In particular, a volume density of the monocrystalline and / or polycrystalline diamond particles in the first coating is 5-20%, particularly preferably 15-20%. Squeegees with such volume densities show a very good wear resistance and a long service life. At the same time, there is also an optimally sharply defined contact zone between the doctor blade and the pressure cylinder or pressure roller, wherein the contact zone remains substantially constant or stable over the entire service life of the doctor blade.

It is also possible in principle to provide monocrystalline and / or polycrystalline diamond particles with larger or smaller volume fractions. However, under certain circumstances, the wear resistance and / or the stability of the doctor during the printing process may be impaired.

In a further advantageous embodiment, additional hard material particles are contained in the first coating. The term hard material particles in this context, in particular metal carbides, metal nitrides, ceramics and intermetallic phases, which preferably have a hardness of at least 1000 HV, understood. These include, for example, cubic boron nitride (BN), boron carbide (BC), chromium oxide (Cr ₂ O ₃ ), titanium diboride (TiB ₂ ), zirconium nitride (ZrN), zirconium carbide (ZrC), titanium carbide (TiC), silicon carbide (SiC), titanium nitride ( TiN), aluminum oxide or corundum (Al ₂ O ₃ ), tungsten carbide (WC), vanadium carbide (VC), tantalum carbide (TaC), zirconium dioxide (ZrO ₂ ) and / or silicon nitride (Si ₃ N ₄ ).

If additional hard material particles are present in the first coating, in particular the wear resistance of the working edge can be further improved. Ideally, the additional hard material particles comprise aluminum oxide particles or particles of corundum (Al ₂ O ₃ ) with a particle size of 0.3-0.5 μm. Such hard particles are characterized in particular by their hardness, mechanical strength, chemical resistance and good sliding properties. By the aluminum oxide particles, in particular at a particle size of 0.3 - 0.5 microns, the stability of the first coating or the nickel-phosphorus alloy in combination with the monocrystalline and / or polycrystalline diamond particles is further increased, which improves the quality of the working edge and a over the entire life of the doctor blade allows particularly uniform and accurate doctoring.

In principle, however, it is also possible to use other hard material particles as particles of aluminum oxide and / or particle sizes of less than 0.3 μm and / or provide more than 0.5 microns. Under certain circumstances, however, this is at the expense of the wear resistance and / or stability of the doctor blade. Whether and which type of additional hard material particles of the first coating is added, may also depend on the intended use of the doctor and is z. B. determined by the material and the surface finish of the printing cylinder and / or pressure rollers.

According to the invention, a second coating based on a further nickel-phosphorus alloy is arranged on the first coating. A second coating based on a further nickel-phosphorus alloy can serve in particular as a protective layer for the first coating, whereby the wear resistance and stability of the working edge of the doctor blade can be further increased. In addition, a second coating can serve as a stable matrix for further additives which positively influence doctoring off with the doctor according to the invention.

According to the invention, a phosphorus content of the further nickel-phosphorus alloy of the second coating is smaller than a phosphorus content of the nickel-phosphorus alloy of the first coating. The combination of coatings with different proportions of phosphorus in particular a higher wear protection of the working edge is achieved while maintaining a further stabilization of the working edge. A phosphorus content of the further nickel-phosphorus alloy of the second coating of 6-9% by weight has proven to be particularly suitable.

In principle, however, the phosphorus content of the further nickel-phosphorus alloy of the second coating can also be less than 6% or more than 9%. It is also possible in principle to provide a comparable phosphorus content in the first coating and the second coating or to form a higher phosphorus content in the second coating than in the first coating. However, this can be at the expense of the quality of the working edge of the doctor blade.

A layer thickness of the second coating measures in particular 0.5-3 μm. Such layer thicknesses guarantee, in particular, a high intrinsic stability of the second coating and at the same time a good protective effect for the first coating, which benefits the stability of the working edge as a whole.

However, it is also within the scope of the invention to realize a second coating with a layer thickness of less than 0.5 .mu.m or more than 3 .mu.m. However, under certain circumstances this reduces the stability and wear resistance of the working edge of the doctor blade.

In a particularly preferred embodiment, the second coating contains polymer particles. The polymer particles advantageously contain polytetrafluoroethylene (PTFE) and in particular have a particle size of 0.5-1 μm. Advantageously, the polymer particles, except for unavoidable impurities, completely made of polytetrafluoroethylene.

In particular, polymer particles in the second coating can produce a lubricating effect, which in turn improves the sliding properties of the working edge of the doctor during doctoring. Polymer particles comprising polytetrafluoroethylene and especially polymer particles, which consist entirely of polytetrafluoroethylene, have proved to be particularly advantageous, especially at a particle size of 0.5-1 μm. In particular, in conjunction with a nickel-phosphorus alloy having a phosphorus content of 6 - 9%, such polymer particles contribute to a high-quality working edge, which allows a very precise and gentle for a printing cylinder and / or a pressure roller buffing.

In principle, polymer particles containing polytetrafluoroethylene may also contain additional polymeric materials. It is likewise possible to use polymer particles without polytetrafluoroethylene or to provide particle sizes of less than 0.5 or more than 1 μm. It is also possible to completely dispense with polymer particles in the second coating. However, the advantages mentioned above are at least partially eliminated.

To produce a doctor blade, in particular a doctor blade according to the invention, a first coating based on a nickel-phosphorus alloy can be deposited on a working edge region of the doctor blade which is formed in a longitudinal direction of a flat and elongated base body. In this case, monocrystalline and / or polycrystalline diamond particles having a particle size of at least 5 nm and less than 50 nm are dispersed in the first coating.

Advantageously, the deposition of the first coating is carried out by an electroless deposition or coating process. For the deposition of the first coating based on a nickel-phosphorus alloy, no electric current is used in this case, as a result of which such deposition processes clearly differ from the electrodeposition techniques. For electroless deposition or coating, the working edge or optionally the entire base body of the doctor blade is immersed in a suitable electrolyte bath with monocrystalline and / or polycrystalline diamond particles suspended therein and coated in a manner known per se. The monocrystalline and / or polycrystalline diamond particles suspended in the electrolyte bath are incorporated into the nickel-phosphorus alloy during the coating or deposition process and are thus dispersed in the deposited nickel-phosphorus alloy essentially randomly distributed. Due to the relatively small particle size of at least 5 nm and less than 50 nm and the associated relatively large ratio of surface area to volume, the diamond particles are distributed evenly despite their considerable density in the entire electrolyte solution. Since the frictional forces occurring between the surface of the diamond particles and the liquid in the electrolyte bath are generally greater than the gravitational force acting on the diamond particles, a drop in the diamond particles during the deposition process is largely prevented. This ultimately leads to an extremely uniform incorporation of the diamond particles in the first coating.

By an electroless deposition process, therefore, a high-quality first coating can be produced, which in particular has a high contour accuracy with respect to the working edge of the doctor blade or with respect to the main body of the doctor blade and a very uniform layer thickness distribution. In other words, an extremely uniform nickel-phosphorus alloy with particularly uniformly distributed monocrystalline and / or polycrystalline diamond particles is formed by the electroless deposition, which optimally follows the contour of the working edge of the doctor blade or the base body, which decisively contributes to the quality of the doctor blade.

Due to the electroless deposition of the nickel-phosphorus alloy, in principle, plastics can also be used as the basic body for the doctor blade and in a simpler manner Be provided manner with the first coating of the nickel-phosphorus alloy.

In principle, however, it is also conceivable to deposit the first coating by means of a galvanic process on the base body. However, it has been found that such deposited first coatings are less uniform and overall have a reduced stability and adhesion to the base body.

If a second coating based on a further nickel-phosphorus alloy is applied to the first coating, it can be deposited both by an electroless plating process and by a galvanic plating process. However, in particular for the deposition of a second coating based on a further nickel-phosphorus alloy with polymer particles dispersed therein, the electroless deposition has proven to be particularly suitable.

More preferably, the first coating for curing a heat treatment, in particular at a temperature of 100 = 500 ° C, in particular 170-300 ° C, subjected. If present, the second coating is advantageously also subjected to this heat treatment. The heat treatment induces solid state reactions in the nickel-phosphorus alloys which increase the hardness of the nickel-phosphorous alloys in the first coating, and optionally also in the second coating. The temperatures of 100-500.degree. C., in particular 170-300.degree. C., are preferably maintained during a holding time of 0.5-15 hours, more preferably 0.5-8 hours. Such temperatures and hold times have been found to be optimal to achieve sufficient hardness of the nickel-phosphorus alloys.

Temperatures of less than 100 ° C are also possible here. In this case, however, very long and mostly uneconomical holding times are required. Higher temperatures than 500 ° C, depending on the material of the body, in principle also feasible, but the curing process of the nickel-phosphorus alloy is more difficult to control.

In principle, however, can be completely dispensed with a heat treatment. However, this is at the expense of the wear resistance and life of the doctor blade.

If two coatings are arranged on the base body, the heat treatment advantageously takes place only after the deposition or application of the second coating on the first coating. As a result, in particular, oxide formation on the surface of the first coating, which is covered by the second coating, is prevented. On the one hand, this results in better adhesion between the first coating and the second coating, and on the other hand, the overall uniformity of the doctor blade in the region of the working edge is improved.

If a second coating is provided, it is deposited on all sides, in particular on a jacket region of the base body present with respect to the longitudinal direction, preferably on the entire base body. In this case, the jacket region of the main body, which is present with respect to the longitudinal direction, or preferably the entire main body, is covered on all sides with the second coating. Apart from the fact that the body of the doctor blade is best protected against environmental influences and in particular the partially chemically aggressive inks, thereby simplifying the coating process. The main body can z. B. be completely immersed in the electrolyte bath. This is not possible with the sole coating of the working edge provided with the first coating, since the basic body may then have to be aligned in a complicated manner with respect to the liquid surface of the electrolyte bath.

In principle, however, only the working edge provided with the first coating can also be provided with the second coating.

From the following detailed description and the totality of the claims, further advantageous embodiments and feature combinations of the invention result.

Brief description of the drawings

Fig. 1

Einen Querschnitt durch einen ersten Lamellenrakel mit einer Beschichtung im Bereich der Arbeitskante;

Fig. 2

Einen Querschnitt durch eine erfindungsgemässe Lamellenrakel mit einer Zweifachbeschichtung im Bereich der Arbeitskante;

Fig. 3

Eine schematische Darstellung eines Verfahrens zur Herstellung einer Rakel.

The drawings used to explain the embodiment show:

Fig. 1

A cross section through a first sipe blade with a coating in the working edge;

Fig. 2

A cross section through a slat doctor according to the invention with a double coating in the region of the working edge;

Fig. 3

A schematic representation of a method for producing a doctor blade.

Basically, the same parts are provided with the same reference numerals in the figures.

Ways to carry out the invention

In Fig. 1 is a first slat blade 100 shown in cross section. The lamella blade 100 includes a base body 111 made of steel, which on the in Fig. 1 left side has a rear portion 112 with a substantially rectangular cross-section. A doctor blade thickness, measured from the top 112.1 to the bottom 112.2 of the rear area, is about 0.2 mm. A length of the main body 111 or the lamella blade 100 measured perpendicular to the plane of the sheet is, for example, 1000 mm.

On the in Fig. 1 Right side of the base body 111 is tapered step-like to form a working edge portion 113 and a working edge of the upper side 112.1 of the rear portion 112 ago. An upper side 113.1 of the working edge 113 lies on a plane below the plane of the upper side 112.1 of the rear region 112, but is essentially parallel or plane-parallel to the upper side 112.1 of the rear region 112. Between the rear portion 112 and the working edge 113 is a concave shaped transition region 112.5 before. The lower side 112.2 of the rear region 112 and the lower side 113.2 of the working edge 113 lie in a common plane, which is plane-parallel to the upper side 112.1 of the rear region 112 and plane-parallel to the upper side 113.1 of the working edge 113. A width of the main body 111, measured from the free end of the rear region to the end face 114 of the working edge 113 measures, for example, 40 mm. A thickness of the working edge 113, measured from the top 113.1 to the bottom 113.2 of the working edge, is for example, 0.060 - 0.150 mm, which corresponds to about half the blade thickness in the rear area 112. A width of the working edge region 113, measured at the upper side 113.1 of the working edge 113 from the front side 114 to the transitional region 112.5, is for example 0.8-5 mm.

A free end face 114 of the right-hand free end of the working edge 113 extends from the upper side 113.1 of the working edge 113 obliquely downwards to the lower side to the lower side 113.2 of the working edge 113. The front side 114 has an angle of approximately 45 ° or 135 ° with respect to the upper side 113.1 of the working edge 113 or with respect to the lower side 113.2 of the working edge 113. An upper transition region between the top 113.1 and the end face 114 of the working edge 113 is rounded. Likewise, a lower transition region between the end face 114 and the bottom 113.2 of the working edge 113 is rounded.

The working edge 113 of the lamella blade 100 is further surrounded by a first coating 120. In this case, the first coating 120 completely covers the upper side 113.1 of the working edge 113, the concave transition region 112.5 and a subregion of the upper side 112.1 of the rear region 112 of the main body 111 adjoining this. Likewise, the first coating 120 covers the end face 114, the underside 113.2 of the working edge 113 and a subregion of the underside 112.2 of the rear region 112 of the base body 111 adjoining the underside 113.2 of the working edge 113.

The first coating 120 is z. B. essentially from a currentless deposited nickel-phosphorus alloy with a phosphorus content of z. B. 10 wt .-%. Therein polycrystalline diamond particles 120.1 having a particle size of, for example, 15-40 nm are dispersed. The volume fraction of the polycrystalline diamond particles 120.1 is z. 18%. The layer thickness of the first coating 120 measures in the region of the working edge 113 z. B. 5 microns. In the region of the upper side 112.1 and the lower side 112.2 of the rear region 112, the layer thickness of the first coating 120 decreases continuously, with the result that the first coating 120 ends in a wedge shape in a direction away from the working edge 113.

In Fig. 2 a slat blade 200 according to the invention is shown in cross-section. The lamellae blade 200 includes a base body 211 made of steel, which is formed substantially identical to the base body 111 of the first sipe blade 100 from Fig. 1 ,

The working edge 213 of the second fin blade 200 is surrounded by a first coating 220. In this case, the first coating 220 completely covers the upper side 213.1 of the working edge 213, the transition region 212.5 and a subregion of the upper side 212.1 of the rear region 212 of the base body adjoining this. Likewise, the first coating 220 covers the front side 214, the underside 213.2 of the working edge 213 and a subregion of the lower side 212.2 of the rear region 212 of the base body 211 which adjoins the underside 213.2 of the working edge 213.

The first coating 220 of the second Lammellenrakel 200th consists, for example, essentially of a currentless deposited nickel-phosphorus alloy with a phosphorus content of z. B. 12 wt .-%. In the first coating are polycrystalline diamond particles 220.1 (in Fig. 2 symbolized by circles) and adhesive particles 220.2 of aluminum oxide (Al ₂ O ₃ ) (in Fig. 2 symbolized by pentagons) dispersed. The diamond particles 220.1 have a particle size of, for example, 15-40 nm, while the hard material particles 220.2 or the particles of aluminum oxide have a particle size of 0.4 μm. The volume fraction of polycrystalline diamond particles 220.1 is z. For example 15%. The layer thickness of the first coating 220 measures in the region of the working edge 213 z. B. 5 microns. In the region of the upper side 212.1 and the lower side 212.2 of the rear region 212, the layer thickness of the first coating 220 continuously decreases, so that the first coating 220 ends in a wedge shape in a direction away from the working edge 213.

The first coating 220 and the remaining regions of the main body 211, which are not covered by the first coating 220, are completely surrounded by a second coating 221. Thus, the upper side 212.1 and the lower side 212.2 of the rear region 212 and the rear end side of the main body 211 are covered with the second coating 221. The jacket region of the main body 211 with respect to the plane perpendicular to the plane longitudinal direction of the main body 211 and the second blade bar 200 is thus completely and completely surrounded by at least one of the two coatings 220, 221. The plane parallel to the leaf level and in Fig. 2 invisible front and rear side surfaces of the main body 211 may also be covered with the second coating 221.

The second coating 221 consists of a further electrolessly deposited nickel-phosphorus alloy with a phosphorus content of about 7%. The phosphorus content of the first coating 210 is thus greater than the phosphorus content of the second coating 220. The layer thickness of the second coating 221 is, for example, 1.8 μm. In addition, polymer particles 221.1 are dispersed in the second coating 221. The polymer particles 221.1 consist z. Example of polytetrafluoroethylene (PTFE) and have a particle size of, for example, 0.6 - 0.8 microns.

In Fig. 3 is a method 300 for producing a doctor blade, as z. Tie Fig. 1 and 2 are shown schematically shown. In a first step 301, the working edges 113, 213 of the base bodies 111, 211 to be coated are immersed in a suitable and known aqueous electrolyte bath with polycrystalline and / or monocrystalline diamond particles 120.1, 220.1 having a particle size of, for example, 10 to 40 nm suspended therein , If, as with the Lammellenrakel out Fig. 2 additional hard material particles 220 are to be installed in the coating, the additional hard particles 220 are also suspended in the electrolyte bath. During the subsequent deposition process, among other nickel ions from a nickel salt, z. For example, nickel sulfate, by a reducing agent, for. As sodium hypophosphite, reduced in aqueous environment to elemental nickel and deposited on the working edges 113, 213 to form a nickel-phosphorus alloy and embedding the polycrystalline and / or monocrystalline diamond particles 120.1, 220.1 and, if present, the additional hard particles 220.2. This is done without the application of an electrical voltage or completely de-energized under moderately acidic conditions (pH 4 - 6.5) and at elevated temperatures of for example 70 - 95 ° C. The phosphorus content in the first coatings 120, 220 can be controlled in a manner known per se by the concentrations and mixing ratios of the educts in the electrolyte bath.

If as in the second blade squeegee 200 off Fig. 2 In addition, a second coating 220 is provided, in a second step 302, the base body 211 with the first coating 210 in another and known per se aqueous electrolyte bath with polymer particles 220.1 suspended therein, z. B. of polytetrafluoroethylene with a particle size of 0.6 - 0.8 microns, immersed. The subsequent deposition process proceeds in the same way as described in the first step 301 for the first coatings 120, 220. In the event that like the first lamella blade off Fig. 1 no second coating is provided, the second step 302 is omitted and, if desired, the third step 303 is performed directly.

In a third step 303, the coated base bodies 111, 211 are subjected to a heat treatment during, for example, two hours and at a temperature of 300 ° C. Thus, the first coatings 120, 220 and, if present, the second coating 221 cure. Finally, the finished lamellae 100, 200 are cooled and ready for use.

As has been shown in test experiments, the in Fig. 1 depicted first lamellae 100 a very high wear resistance and stability over the entire life. For comparison, in a lamellar blade, as in Fig. 1 is shown dispensed in a first comparative experiment on the introduction of diamond particles 120.1 in the first coating 120. It has been found that such doctor blade without diamond particles have a lower wear resistance and correspondingly shorter life than the inventive lamellae 100 from Fig. 1 ,

In a second comparative experiment, in a lamellar squeegee, as in Fig. 1 is shown, instead of the diamond particles 120.1, which have a particle size of about 10-40 nm, larger diamond particles used with a particle size of about 100 nm. However, in this case, the working edge of the squeegee was less stable than the squeegee blade 100 considered over the entire life of the squeegee Fig. 1 ,

The second lamellae 200 off Fig. 2 has proved to be even more stable and wear-resistant in further test trials compared to the first lamella blade 100.

The above-described embodiments as well as the production methods are to be understood as illustrative examples only, which may be modified as desired within the scope of the invention.

Thus, the main body 11 in Fig. 1 also from another material, such. As stainless steel or carbon steel, be made. In this case, it may be advantageous for economic reasons to attach the second coating 21 only in the region of the working edge 13 in order to reduce the material consumption in the coating. In principle, the base body 11 but also made of a non-metallic material such. As plastics exist. This may be advantageous in particular for applications in flexographic printing.

But it is also possible, instead of the main body 111, 211 from the Fig. 1 and 2 To use basic body with other shapes. In particular, the basic body can have a wedge-shaped working edge or a non-tapered cross-section with a rounded working edge. The free end faces 114, 214 of the right-hand free ends of the working edges 113, 213 may for example also be formed completely rounded.

Furthermore, the inventive doctor blades 100, 200 from the Fig. 1 and 2 also be different dimensions. For example, the thicknesses of the working areas 113, 213, measured from the upper sides 113.1, 213.1 to the lower sides 113.2, 213.2 of the working areas 113, 213, can vary within a range of 0.040-0.200 mm.

Likewise, all coatings 120, 220, 221 of the two blade squeegee 100, 200 more alloy components and / or additional substances such. As metal atoms, non-metal atoms, inorganic compounds and / or organic compounds.

In the two in the Fig. 1 and 2 It is also possible to surround the jacket areas of the base bodies 111, 211 completely and completely with the first coatings 120, 220 with respect to the longitudinal direction of the base bodies 111, 211 perpendicular to the plane of the sheet.

In summary, it should be noted that a novel construction has been created for doctor blades, which brings a high wear resistance and stability of the doctor blade. With the doctor blades according to the invention, a more exact inking, in particular of printing ink on printing cylinders or printing rollers, becomes possible, in particular during the entire service life.

Claims (15)

1. A doctor blade (100, 200), In particular for doctoring off printing ink from a surface of a printing form and/or for use as a paper doctor knife, comprising a flat and elongated main body (111, 211) having a working edge region (113, 213) formed in a longitudinal direction, wherein at least the working edge region (113, 213) is covered with a first coating (120, 220) on the basis of a nickel-phosphorus alloy, and monocrystalline and/or polycrystalline diamond particles (120.1, 220.1) are dispersed in the first coating (120, 220), wherein the particle size of the diamond particles (120.1, 220.1) measures at least 5 nm and less than 50 nm, and wherein a second coating (221) on the basis of a further nickel-phosphorus alloy is arranged on the first coating (120, 220), characterized in that a phosphorus content of the further nickel-phosphorus coating of the second coating (221) is less than a phosphorus content of the nickel-phosphorus coating of the first coating,
2. The doctor blade (100, 200) as claimed in claim 1, characterized in that the phosphorus content of the nickel-phosphorus alloy in the first coating (120, 220) is 7-12% by weight.
3. The doctor blade (100, 200) as claimed in either of claims 1-2, characterized in that the layer thickness of the first coating (120, 220) is 1-10 µm.
4. The doctor blade (100, 200) as claimed in one of claims 1-3, characterized in that the volume density of the diamond particles (120.1, 220.1) in the first coating is 5-20%, in particular 15-20%.
5. The doctor blade (100, 200) as claimed in one of claims 1-4, characterized in that additional hard material particles (220.2) are present in the first coating (220).
6. The doctor blade (100, 200) as claimed in claim 5, characterized in that the additional hard material particles (220.2) comprise aluminum oxide particles having a particle size of 0.3-0.5 µm.
7. The doctor blade (100, 200) as claimed in one of claims 1 - 6, characterized in that the phosphorus content of the further nickel-phosphorus alloy of the second coating (221) is 6-9% by weight.
8. The doctor blade (100, 200) as claimed in either of claims 1 - 7, characterized in that the layer thickness of the second coating (221) measures 0.5-3 µm.
9. The doctor blade (100, 200) as claimed in one of claims 1 - 8, characterized in that the second coating (221) contains polymer particles (221.1).
10. The doctor blade (100, 200) as claimed in claim 9, characterized in that the polymer particles (221.1) contain polytetrafluoroethylene and, in particular, have a particle size of 0.5-1 µm.
11. A process (300) for producing a doctor blade, in particular a doctor blade (100, 200) as claimed in one of claims 1-10, wherein a first coating (120, 220) on the basis of a nickel-phosphorus alloy is deposited on a working edge region (113, 213) of the doctor blade (100, 200) formed in a longitudinal direction of a flat and elongated main body (111, 211), and monocrystalline and/or polycrystalline diamond particles (120.1, 220.1) having a particle size of at least 5 nm and less than 50 nm are dispersed in the first coating (120, 220), and wherein a second coating (221) on the basis of a further nickel-phosphorus alloy is arranged on the first coating (120, 220), characterized in that a phosphorus content of the further nickel-phosphorus coating of the second coating (221) is less than a phosphorus content of the nickel-phosphorus coating of the first coating.
12. The process (300) as claimed in claim 11, characterized in that the first coating (120, 220) is deposited by an electroless coating process.
13. The process (300) as claimed in either of claims 11-12, characterized in that the second coating (221) with polymer particles (221,1) dispersed therein, is deposited.
14. The process (300) as claimed in one of claims 11-13, characterized in that the first coating (120, 220) is subjected to heat treatment for hardening purposes, in particular at a temperature of 100-500°C, in particular 170-300°C.
15. The use of a doctor blade (100, 200) as claimed in one of claims 1-10 for doctoring off printing Ink from a surface of a printing form, in particular a printing form for flexographic printing, gravure printing and/or decorative gravure printing.

Images