EP2525984B1 - Doctor blade - Google Patents

Description

Technical area

The invention relates to a squeegee, in particular for doctoring ink from a surface of a printing form, comprising a flat and elongated base body having a working edge region formed in a longitudinal direction, the working edge region coated with at least one first nickel-phosphorus alloy-based coating is. Furthermore, the invention relates to a method for producing 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 printing cylinder in contact with working edges of the doctor blade lead z, B, to an 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 edges of the doctor are pressed during stripping to the surfaces of the impression cylinder or pressure rollers and are moved relative to these. 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. 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 physical 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 described, for example, printing technique squeegees having a first layer of chemically nickel with particles dispersed therein and a second layer having 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.

The WO 2006/112522 A2 (Nihon New Chrome Co. Ltd.) describes steel squeegee for paint stripping in the gravure printing process used to improve abrasion resistance z, B is coated with a nickel-phosphorus alloy. Particles selected from the groups consisting of metal oxides, metal carbides, metal nitrides, diamond and the like may be embedded in this alloy.

The WO 2010/040236 A1 (Daetwyler SwissTec AG) describes doctor blades whose base body is surrounded by a first coating of a nickel-phosphorus alloy. This layer contains monocrystalline and / or polycrystalline diamond particles as hard material particles. Optionally, further hard material particles may be incorporated in the first layer. The WO 2010/040236 A1 represents prior art under Art. 54 (3) EPC.

The WO 2010/037240 A1 (Daetwyler SwissTec AG) describes doctor blade for printing ink from a surface of a printing form welohe coated in the working edge area with a first coating on the basis of electroless deposited nickel-phosphorus alloy. These are hard material particles, z, B. of SiC, Al ₂ O ₃ , diamond and / or BN. The WO 2010/037240 A1 represents prior art under Art. 54 (3) EPC.

However, such coated squeegee are still not completely satisfactory in terms of service life and wear resistance. It has also been shown that uncontrolled banding may occur when using such a doctor blade, especially in the running-in phase, which is likewise undesirable.

There is therefore still a need for an improved doctor blade, which in particular has both a longer life and also allows optimal scraping.

Presentation of the invention

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

The solution of the problem is defined by the features of claim 1. According to the invention, the first coating contains at least one additional component for improving the wear behavior of the doctor blade, wherein the at least one additive component comprises hard material particles, and the hard material particles comprise both SiC and diamond, and wherein the average particle size of the SiC is greater than the average particle size of the diamond ,

An additional component for improving the wear behavior of the doctor blade is understood in particular in the first coating to be dispersed particles and / or mixed chemical substances.

In the case of an additional component in the form of dispersed particles, the first coating has a heterogeneous structure, which in particular contains the dispersed particles in the nickel-phosphorus alloy as matrix. Such coatings can also be referred to as a mixture. Advantageously, the particles are distributed substantially uniformly in the first coating. In addition to the hard material particles according to claim 1, the dispersed particles may moreover comprise, in particular, metals, metal oxides, metal carbides, metal nitrides, metal carbonitrides, metal borides, ceramics and / or intermetallic phases several representatives from the series of Al, Cu, Pb, W, Ti, Zr, Zn Cu, Mo, steel, WSi ₂ , Al ₂ O ₃ , Cr ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , ZrO ₂ , ThO ₂ , SiO ₂ , CeO ₂ , BeO ₂ , MgO, CdO, UO ₂ , TiC, WC, VC, ZrC, TaC, Cr ₃ C ₂ , B ₄ C, BN, ZrB ₂ , TiN, Si ₃ N ₄ , ZrB ₂ and / or TiB ₂ . But there are others, z. B, completely non-metallic and / or organometallic particles as Additional component for improving the wear of the doctor possible. Completely non-metallic particles are z. B. in the form of diamond.

In this context, the particle size is understood in particular to mean a maximum dimension and / or external dimension of the particles. With regard to the particle size, the particles generally have a certain distribution or a spread. If particle sizes are used in the present context, in particular mean particle sizes are meant.

Additional components in the form of blended chemical substances are present in particular as homogeneous mixtures and / or alloys. The blended chemical substances may, for example, be metals. Examples of metals include Al, Cu, Pb, W, Tl, Zr and / or Zn. However, it is basically also conceivable to mix organometallic and / or nonmetallic components into the first coating.

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 is in particular 1-15% by weight.

The expression "based on a nickel-phosphorus alloy" means that the Niokel-phosphorus alloy forms the main constituent of the first coating. In the first coating, in addition to the nickel-phosphorus alloy and the additional component for improving the dispensing behavior of the doctor blade, there may well be other types of atoms and / or chemical compounds which have a smaller proportion than the nickel-phosphorus alloy. The proportion is preferred the nickel-phosphorus alloy in the first coating at least 50 wt .-%, particularly preferably at least 70 wt .-% and most preferably at least 80 wt .-%. [deallike, the first coating, except for unavoidable impurities, consists exclusively of the nickel-phosphorus alloy and one or more additional components to improve the doctoring performance of the doctor blade.

It has been found that the inventive doctor blades have a high wear resistance and, correspondingly, a long service life. Furthermore, the Working edges of the inventive doctor blade optimally stabilized. This results in a sharply defined contact zone between the doctor blade and the printing cylinder or the pressure roller, which in turn allows extremely accurate ink stripping. The contact zone remains largely stable over the entire printing process.

In addition, it has been found that the doctoring devices according to the invention form significantly less streaks during the break-in phase in the printing process or otherwise cause effects impairing the printing process. The doctor according to the invention therefore makes it possible to achieve a substantially constant printing quality during the entire printing process.

Furthermore, the doctor blades according to the invention have extremely favorable sliding properties on the printing cylinders or printing rollers commonly used. As a result, the use of the doctor blade according to the invention for doctoring also reduces wear on the printing cylinders or printing rollers.

In a preferred variant of the invention, the first coating is an electrolessly deposited nickel-phosphorus alloy. Electrolessly deposited nickel-phosphorus alloys, which are deposited without supply of electric current or without external current, can also be referred to as chemical nickel. Such nickel-phosphorus alloys can be formed, in particular, with 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. As a result, the first coating can optimally follow the contour of the working edge of the doctor blade or the base body, which decisively contributes to the quality of the doctor blade. Electrolessly deposited nickel-phosphorus alloys also differ in particular with respect to the microstructure and elasticity of electrodeposited nickel-phosphorus alloys. Electroless deposited nickel-phosphorus alloys are also both with basic plastic bodies as well as with basic bodies of metal, eg. As steel, compatible and adhere well to different basic bodies.

Depending on the application, it may also be advantageous if the first coating is a galvanically deposited nickel-phosphorus alloy. In this case, the first Coating deposited galvanically by means of electricity from an electrolyte bath on the working edge and / or the body of the doctor blade. In the case of electrodeposited layers, in particular the layer thickness can be controlled very precisely, which is advantageous especially with thin layers.

Preferably, a phosphorus content of the first coating is 7-12% by weight. Such coatings have proven to be particularly suitable in combination with the additional components for improving the wear behavior, since in particular an even 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 of the first coating. 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 and / or plastics, 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 can be reduced thereby. In the case of special additional components and / or embodiments of the coatings, however, such contents of phosphorus can also bring about advantages.

Advantageously, the first coating has a hardness of 750-1400 HV. As a result, in particular the wear resistance of the doctor is increased. Although lower hardnesses than 750 HV are also possible, the wear resistance of the doctor blade decreases. If the hardness is greater than 1400 HV, the printing cylinder or the printing cylinder may be damaged, which may result in a lower print quality.

A layer thickness of the first coating is advantageously 1 - 30 microns. More preferably, the thickness of the first coating is 5-20 μm, more preferably 5-10 μm. Such thicknesses of the first coating provide optimum protection of the working edge the squeegee. 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 30 microns are also feasible. However, these are generally less economical and may also negatively affect the quality of the working edge. However, thicknesses of less than 1 .mu.m or more than 30 .mu.m can be quite advantageous for special application areas of the doctor blade.

In a further advantageous variant, a second nickel-based coating is arranged on the first coating. A second nickel-based coating may in particular serve 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. A second coating can also serve as a stable matrix for other additives and positively influence the doctoring with the doctor blade according to the invention.

The term "nickel-based" means that nickel is the major component of the second coating. In this case, in addition to nickel, other types of atom and / or chemical compounds may still be present in the second coating which have a smaller proportion than nickel. The proportion of nickel in the second coating is preferably at least 50% by weight, particularly preferably at least 75% by weight and very particularly preferably at least 95% by weight. In a particularly suitable embodiment, the second coating consists exclusively of nickel except for unavoidable impurities.

In principle, however, a differently composed second coating may be present, for. B. with another metal as the main component, or it can be completely dispensed with the second coating.

In a preferred variant, the second coating is a nickel-based electrodeposited coating. Such coatings form a relatively soft Protective coating for the first coating, whereby the friction and wear in the contact zone area of the doctor blade can be reduced in many applications. The reduction in friction and the associated lower resistance during doctoring leads in many applications to a particularly high wear resistance and stability of the working edge of the doctor blade.

For other applications, however, it may also be advantageous to provide a current-deposited coating as the second coating.

More preferably, the second coating is based on a further nickel-phosphorus alloy. As already explained in connection with the first coating, the expression "based on another nickel-phosphorus alloy" means that the further nickel-phosphorus alloy forms the main constituent of the second coating. In this case, in the second coating, in addition to the further nickel-phosphorus alloy, there may well be other types of atoms and / or chemical compounds which have a smaller proportion than the further nickel-phosphorus alloy. The proportion of the further nickel-phosphorus alloy in the second coating is preferably at least 50% by weight, particularly preferably at least 70% by weight and very particularly preferably at least 80% by weight. Ideally, the second coating, except for unavoidable impurities, consists exclusively of the nickel-phosphorus alloy and, if appropriate, one or more additional components for improving the wear behavior of the doctor blade.

In an advantageous variant, the second coating comprises a galvanically deposited nickel-phosphorus alloy. This is particularly advantageous in combination with a first coating based on electroless nickel-phosphorus alloy. The working edges are optimally stabilized by the combination of the first coating of electroless nickel-phosphorus alloy with the at least one additional component to improve the Verschleissverhaltens the doctor and the second coating based on the electrodeposited nickel-phosphorus alloy. This results in a particularly sharply delimited contact zone between the doctor blade and the printing cylinder or the pressure roller, which in turn allows extremely accurate ink stripping. The contact zone remains largely stable over the entire printing process.

The further nickel-phosphorus alloy of the second coating has, in an advantageous variant, a phosphorus content of 12-15%. This in particular, if the second coating consists, except for unavoidable impurities, essentially exclusively of the further nickel-phosphorus alloy and is electrodeposited.

In particular, if the second coating is based on a further nickel-phosphorus alloy and also contains at least one additional component for improving the wear behavior of the doctor, the phosphorus content of the second coating is advantageously lower than the phosphorus content of the first coating. In other words, with advantage, therefore, 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. This may even be advantageous depending on the intended use of the doctor blade.

A layer thickness of the second coating is in particular less than the layer thickness of the first coating and advantageously measures 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. It is also possible in principle to choose a layer thickness of the second coating equal to or greater than the layer thickness of the first coating.

Whether and with what composition a second coating is to be arranged depends essentially on the intended use of the doctor blade. This plays z. B, the material and the surface finish of the printing cylinder or the pressure roller an essential role. A second coating comprising a nickel-phosphorous alloy is generally somewhat harder and more corrosion resistant than a nickel-based coating which is substantially free of phosphorus.

• In einer ersten bevorzugten Ausgestaltung der Erfindung umfasst die erfindungsgemässe Rakel eine erste Beschichtung auf der Basis einer stromlos abgeschiedenen Nickel-Phosphor-Legierung mit darin dispergierten Hartstoffpartikeln, wobei die Hartstoffpartikel sowohl SiC als auch Diamant umfassen und die gemittelte Partikelgrösse des SiC grösser ist als die gemittelte Partiketgrösse des Diamants, und insbesondere einer an die erste Beschichtung angrenzenden zweiten Beschichtung auf der Basis von galvanisch abgeschiedenem Nickel oder einer zweiten Beschichtung auf der Basis einer galvanisch abgeschiedenen Nickel-Phosphor-Legierung.

In the case of rakein with two or more coatings, in particular the following different embodiments have proven to be advantageous:

• In a first preferred embodiment of the invention, the doctor according to the invention comprises a first coating based on an electrolessly deposited nickel-phosphorus alloy with hard material particles dispersed therein, wherein the hard material particles comprise both SiC and diamond and the average particle size of the SiC is greater than the averaged one Particle size of the diamond, and in particular a second coating on the basis of electrodeposited nickel or a second coating based on a galvanically deposited nickel-phosphorus alloy adjacent to the first coating.

In a further advantageous embodiment, the doctor has a first coating based on a current-free deposited nickel-phosphorus alloy with a first type of dispersed therein hard material particles, wherein the first type of hard material particles include both SiC and diamond and the average particle size of the SiC greater than the average particle size of the diamond, and a second coating adjacent to the first coating based on a current-free deposited nickel-phosphorus alloy with a second type of hard material particles dispersed therein. The two types of hard material particles differ in particular by their material compositions and / or their particle sizes, In addition, embodiments have proven to be particularly suitable in which the doctor blade a first coating based on an electrolessly deposited Nlckel-phosphorus alloy having dispersed therein hard material particles, wherein the hard material particles both SiC and diamond and the average particle size of the SiC is greater than the average particle size of the diamond, as well as a second coating adjacent to the first coating, based on a currentless deposited nickel-phosphorus alloy having dispersed therein lubricant particles, in particular particles of hexagonal BN comprises. In the first coating can also be present more types of different hard particles.

The wear resistance of the doctor blade in these embodiments can optionally be further improved by admixing alloy components, eg metals, such as W, with the first and / or the second coating.

If the additional component contains lubricants, in particular lubricating particles, the lubricants are preferably arranged in the outermost coating. Thus, a constant improvement in wear in the inventive doctor blades is achieved in particular from the beginning.

In another preferred embodiment, the second coating comprises a base layer of pure nickel adjacent to the first coating and a covering layer of nickel and / or a nickel-phosphorus alloy arranged above it. The base layer of pure nickel is, except for unavoidable impurities, preferably exclusively of nickel. A thickness of the base layer is preferably 0.2-0.8 μm, in particular 0.4-0.6 μm. In particular, if the cover layer consists of pure nickel, the cover layer advantageously also contains saccharin and / or a saccharin salt.

On the one hand, such a second coating has high adhesion to the first coating and possibly also to the main body. In addition, in the case of a cover layer with saccharin and / or a saccharin salt, the second coating has a very even surface with a low surface roughness, which favors the formation of a sharply delimited contact zone between doctor blade and impression cylinder or pressure rollers.

In principle, however, it is possible with the second coating to dispense with the formation of a base layer and a cover layer and to provide only a single and substantially homogeneous layer.

In the following, details of preferred additional components are made.

In a preferred variant, the hard material particles comprise metal particles. Suitable z. As metal particles of W, Ti, Zr, Mo, and / or steel, the metal particles can be used in combination with other metal particles and / or in combination with other additional components.

Metal particles of metallic molybdenum have proven particularly suitable. Squeegees with a first coating according to claim 1 and / or a second coating based on a nickel-phosphorus alloy with metal particles of molybdenum dispersed therein have a very high wear resistance and, correspondingly, a long service life. The working edges of such doctor blade in this case have a sharply defined contact zone between the doctor blade and the printing cylinder or the pressure roller, which allows a more accurate ink stripping. In a welter preferred variant, the metal particles have a particle size of 1 - 2 microns and a volume fraction in the first coating of 5 - 30%, particularly preferably 15-20%, on.

According to another advantageous embodiment, the hard particles, in place of or in addition to the metal particles, may include metal oxides, metal carbides, metal nitrides, metal carbonitrides, metal borides, ceramics and / or intermetallic phases. This can z. B. one, two or more representatives from the series WSi ₂ , Al ₂ O ₃ , Cr ₂ O ₃ , Fe ₂ O ₃ , TiO ₂ , ZrO ₂ , ThO ₂ , SiO ₂ , CeO ₂ , BeO ₂ , MgO, CdO , UO ₂ , SiC, TiC, WC, VC, ZrC, TaC, Cr ₃ C ₂ , B ₄ C, cubic BN, ZrB ₂ , TiN, Si ₃ N ₄ , ZrB ₂ , TiB ₂ . Although B ₄ C (boron carbide) is not a metal carbide in the strict sense, B ₄ C in the present context is attributed to the metal carbides due to the similar material properties.

Squeegees with a first coating and / or a second coating based on a nickel-phosphorus alloy with metal oxides, metal carbides, metal nitrides, metal carbonitrides, metal borides, ceramics and / or intermetallic phases dispersed therein have a high wear resistance and, accordingly, a long duration Life on, Such hard particles can be embedded extremely stable in the first coating and form a hard-wearing composite with the nickel-phosphorus alloy of the first coating. As a result, the strength of the first coating as a whole can be improved, and at the same time the working edges of such doctor blade on a sharply defined contact zone between the doctor blade and the pressure cylinder or the pressure roller, which in turn allows a more accurate ink stripping.

In particular, the following metal carbides and / or metal nitrides have been found to be particularly suitable: B ₄ C, cubic BN, TiC and / or WC. In the case of metal oxides, Al ₂ O ₃ is particularly advantageous.

However, apart from SiC and diamond, which are present in the at least one first coating, the hard material particles need not necessarily be in the form of metal particles, metal oxides, metal carbides, metal nitrides, metal carbonitrides, metal borides, ceramics and / or intermetallic phases. Basically come as hard particles and particles of other materials in question.

According to the invention, the hard material particles in the at least one coating comprise diamond. Preference is given to using diamond with mono- and / or polycrystalline structure. Hard diamond particles made of diamond have proven to be particularly advantageous in the inventive doctor blades and, in particular, bring about a further improvement in the wear resistance and stabilization of the working edges of the doctor blade. This is probably due to the high hardness and the chemical and mechanical stability of diamond. However, diamond should not be confused with other forms of carbon, such as carbon. As graphite, glassy carbon, graphene or soot. These forms of carbon bring the inventive advantages only limited or not at all.

As has been shown, however, it is in principle possible to use particles of amorphous diamond-like carbon ("DLC") in addition to hard material particles of diamond with mono- and / or polycrystalline structure. Advantageously however, the amorphous diamond-like carbon has a high sp3 hybridization content to provide sufficient hardness. Depending on

Use of the squeegee may even have advantages in amorphous diamond-like carbon. In general, amorphous diamond-like carbon is also less expensive than diamond.

Particularly suitable are hard material particles having an average particle size of between 5 nm and 4 μm, in particular 0.9 and 2.5 μm, particularly preferably 1.4 and 2.1 μm. With such particle sizes, the tribological properties of the inventive doctor blade can be further improved.

The particle size of the hard material particles is advantageously adapted to the particular material of the hard material particles.

For example, hard material particles in the form of metal particles particularly preferably have an average particle size of 0.5-2.5 μm, in particular 1-2 μm. With metal oxides, metal carbides, metal nitrides, metal carbonitrides, metal borides, ceramics and / or intermetallic phases, average particle sizes of 1.0-2.5 μm, in particular 1.5-2.0 μm, have proven to be particularly advantageous.

Diamond particles as hard material particles advantageously have an average particle size of 5 nm-1.1 μm. More preferably, the average particle size of diamond particles is less than 300 nm. In particular, the average particle size of diamond particles is in a range of 100-200 nm. However, such particle sizes are not mandatory. In special embodiments and / or uses of the doctor blades, diamond particles having averaged particle sizes of 5 to 50 nm have also proven to be advantageous.

When using hard particles with smaller average particle sizes than 5 nm, in particular the wear resistance of the working edge of the doctor usually decreases, which shortens the life of the doctor. For larger average particle sizes than 4 μm, there is the possibility that the doctor blade has an increased surface roughness, which is generally undesirable. For special purposes and / or doctor blade assemblies but in particular larger particle sizes may be suitable.

A volume fraction of the additional component for improving the wear properties is, in particular in the case of particulate additional components, preferably 5-30%, more preferably 15-20%. With such proportions, a significant improvement in terms of intermeshing properties and edge stability is achieved.

While lower volume percentages are also possible, they generally show a less satisfactory improvement in wear resistance. Too high a volume fraction of the additional component can also have a negative effect on properties of the doctor blade. For special applications but may also higher volumes than 30% are suitable.

The hard material particles in the at least one first coating include different particles of at least two different materials. As it has been shown, this synergetic effects can be caused, which improve the wear resistance and quality of the doctor much more than expected.

The hard material particles in the at least one first coating include both SiC and diamond, wherein an average particle size of the SiC is greater than an average particle size of the diamond. In particular, the hard material particles comprise SiC having an average particle size of 1.4-2.1 μm and diamond having an average particle size of 5 nm-1.1 μm, preferably 200-300 nm.

But it is also possible to choose the particle sizes of SiC and diamond differently, In addition, other combinations of hard particles are possible, with more than two, z. B. three, four or even more different hard material particles are combined.

In another preferred variant of the invention, the hard material particles additionally include, for example, cubic BN, wherein preferably an average particle size of the BN corresponds approximately to the average particle size of the SiC. Particularly preferably, the average particle sizes of the SiC and the cubic BN measure about 1.4-2.1 μm.

Furthermore, it has proved to be advantageous if the additional component for improving the wear resistance comprises lubricants, in particular lubricating particles. As a result, a lubricating effect can additionally be achieved during doctoring, which reduces wear. As lubricant or lubricant particles are basically substances in question, which cause a reduction in the sliding friction between doctor blade and impression cylinder and are particularly stable enough, so that no impairment or contamination of the printing cylinder occurs.

In question are, for example, polymeric thermoplastics, z, B, perfluoroalkoxylalkane and / or polytetrafluoroethylene, and graphite, molybdenum disulfide and / or soft metals, such as aluminum, copper and / or lead.

As a lubricant particularly advantageous hexagonal BN has been found. This particular in particle form. It has been found that lubricants, particularly hexagonal BN lubricating particles, have improved the blade's wear resistance in a variety of different cylinder applications. This particular largely independent of the process parameters when doctoring. In other words, hexagonal BN has proven to be an extremely versatile and effective lubricant.

Another suitable lubricant is, for example, polytetrafluoroethylene (PTFE). Also polytetrafluoroethylene is preferably used in the form of lubricating particles.

Lubricating particles, in particular lubricating particles of hexagonal BN, advantageously have an average particle size of 50 nm-1 μm, preferably 80-300 nm, more preferably 90-110 nm. As a result, an optimal effect is achieved for a large number of applications. In principle, however, other particle sizes may be suitable for specific applications.

In a particularly preferred embodiment, lubricants, in particular lubricating particles, as well as hard material particles are present in the first coating and / or any second coating as additives for improving the wear resistance. Ideally, lubricant particles of hexagonal BN are used together with hard material particles of SiC.

In a further preferred embodiment of the invention, the additional component comprises an additional alloying component in the first and / or any second coating. As a result, the physical and chemical properties of the first and / or the second coating can be further adapted specifically to the conditions present during the doctoring process. Due to the additional alloy component, which in particular is completely mixed with the first and / or second coating, the properties of the coatings can be modified without affecting the homogeneity. As the alloying component, z, B, metals can be used. Examples of metals include Al, Cu, Pb, W, Ti, Zr and / or Zn. In principle, however, it is also conceivable to mix organometallic and / or nonmetallic components into the first and / or the second coating.

Particularly preferably, the additional alloying component includes a transition metal, in particular tungsten (W). In particular, by the admixture of W, the wear resistance of the doctor can be improved. At the same time, a sharply defined contact zone between the working edge and the printing cylinder is obtained when using such a doctor blade, which allows a particularly accurate ink stripping. For example, for special applications but other alloy components can be used.

Advantageously, a proportion of the alloying component in the first coating is 0.0001 - 12 wt .-%. The proportion of the alloying component is more preferably 0.5-5% by weight. In a further preferred embodiment, the proportion of the alloying component is 1-3% by weight.

It is also advantageous if both an additional alloy component and hard material particles are present as additional component. As a result, the advantages according to the invention can be further improved.

In this case, the additional component preferably comprises metallic W as the alloying component as well as SIC and diamond as hard material components. At least in the at least one first coating, the average particle size of the SiC is greater than the average particle size of the diamond.

Particular preference is given to SiC having an average particle size of 1.4-2.1 μm and diamond having an average particle size of 10 nm-1.1 μm, preferably 200-300 nm.

In principle, however, other combinations of alloy components and hard material particles are possible.

In a preferred embodiment, the Gruhdkörper the doctor is made of metal, especially steel. Steel has proved to be a particularly robust and suitable material for the doctor according to the invention in mechanical terms.

In this case, at least one jacket region of the main body which is present with respect to the longitudinal direction is completely and completely covered with the first, the second and / or a further coating. As a result, at least the working edge, the upper side, the lower side and the rear edge of the main body opposite the working edge are covered with at least one coating. The side surfaces of the main body that are perpendicular to the longitudinal direction may be uncoated. However, it is also within the scope of the invention that the second coating covers the base body completely and on all sides, that is to say that the side surfaces of the base body which are perpendicular to the longitudinal direction are also covered with one of the coatings. In this case, at least one of the coating surrounds the base body all around.

As a result of the fact that at least the jacket region of the main body which is present with respect to the longitudinal direction is covered completely and completely with at least one coating, the essential regions of the main body which do not belong to the working edge are also provided with the second coating. This is particularly advantageous in order to protect the main body from the water-based or slightly acidic printing inks and / or other mlt of the squeegee coming into contact liquids, In particular bel basic bodies made of steel so optimal rust protection for the doctor blade is created. Thus, the constancy of print quality during the printing process is further improved because of the during the printing process with the squeegee in Contact standing pressure cylinder or the pressure roller, for example, is not contaminated by rust particles. Furthermore, the basic body is characterized by an im Coat area applied second coating also during storage and / or transport best possible protection against rust formation.

However, instead of steel, for example, other metals or metal alloys can be used as the main body.

In a further preferred embodiment, the base body consists of a plastic material. For special applications, plastic base bodies have proved to be more advantageous than steel base bodies because of their different mechanical and chemical properties. For example, some of the plastics in question have sufficient chemical stability or inertness to typical water-based and slightly acidic printing inks, which means that the base body does not need to be specially protected, as in the case of a steel base body.

As plastic material z. B. polymer materials in question. These may be, inter alia, thermoplastic, thermosetting and / or elastomeric polymer materials. Suitable plastics are, for example, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyethylene terephthalate, polyamide, polyacetal, polycarbonate, polyarylate, polyether ether ketone, polyimide, polyester, polytetrafluoroethylene and / or polyurethane. Composite structures with fibers to reinforce the polymer matrix are also possible.

In principle, however, basic body can be used which z. B. consist of both metal, especially steel, as well as plastic. Also basic body with other materials, eg, ceramics and / or composite materials, may be suitable for special applications.

In an advantageous method for producing a doctor blade, in particular a doctor blade according to the invention, a first coating based on a nickel-phosphorus alloy is deposited in a first step on a working edge region of the doctor blade formed in a longitudinal direction of a flat and elongate body at least one additional component for improving the wear behavior of the doctor blade is admixed with the first coating, the at least one additional component comprising hard material particles, and the hard material particles both SiC and Also include diamond, wherein the average particle size of the SiC is greater than the average particle size of the diamond.

The deposition of the first coating takes place in particular without current and advantageously from an aqueous solution. By such a deposition of the nickel-phosphorus alloy with admixture of the additional component to improve the wear behavior, 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, the electroless deposition an extremely uniform nickel-phosphorus alloy is formed with a uniformly distributed additional component, which optimally follows the contour of the working edge of the doctor blade or the body, which contributes significantly to the quality of the doctor. Furthermore, a first coating can be formed by the electroless deposition, which is particularly compatible with a second and on the first coating to be applied second coating based on nickel as possible. This ensures sufficient adhesion of the second coating on the first coating. For electroless plating, the working edge or optionally the entire body of the doctor blade is immersed in a suitable electrolyte bath with admixed additional component and coated in a manner known per se. The added in the electrolyte bath additional component is incorporated during the coating or deposition process in the nickel-phosphorus alloy and is substantially randomly distributed in the formed nickel-phosphorus alloy.

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

In principle, it is also possible to choose a different deposition method. For example, the first coating can also be deposited galvanically or by a gas phase process, if appropriate.

The deposition of the first coating is advantageously carried out in aqueous solution and preferably with air injection. By the air injection is in particular a achieved improved mixing of the substances to be deposited, which has a positive effect on the quality of the first coating.

Instead of or in addition to air injection, however, other measures can be taken to increase the mixing. This can be z. B, done by a mechanical agitator,

In an advantageous variant, an alloying component is admixed as an additional component, which is preferably a metal and / or a metal salt. Particularly preferably, a tungsten salt is used as the metal salt. Advantageously, the deposition of the first coating is carried out electrolessly from an aqueous solution being preferred tungsten salt is sodium tungstate dihydrate having the empirical formula Na ₂ WO ₄ - 2 H ₂ O is used. If necessary, additional complexing agents known per se may be added together with the tungsten salt.

Advantageously, the tungsten salt is present in the aqueous solution in a proportion of about 5 to 20 g / liter, preferably 10 to 12 g / liter. This corresponds to a proportion of about 2.7 to 10.9 g / liter, in particular 5.5 to 6.5 g / liter, of the element tungsten in the aqueous solution.

By adding the tungsten salt is achieved in particular that tungsten is incorporated as an alloying component in the nickel-phosphorus alloy. As a result, an extremely uniform nickel-phosphorus alloy can be obtained which has improved wear resistance. In particular, the hardness and corrosion resistance of the nickel-phosphorus alloy can be improved by the incorporation of tungsten.

In addition to or instead of the alloy component, other additional components may be added, such. B. additional hard particles and / or lubricating particles.

The aqueous solution preferably has a pH of 8-9 during the deposition. Such high pH values surprisingly have a positive influence on the quality of the deposited coating, in particular during the deposition of alloying grain components. The wear resistance of the doctor blade can thereby be significantly improved and the contact area between the working edge of the doctor blade and the printing cylinder remains extremely constant during the entire life of the doctor blade. This in turn is the exact painting of ink to good.

If a second coating is provided, in a second step preferably a second coating based on nickel, at least on a partial area of the first coating, is deposited. Preferably, the first coating is completely covered with the second coating.

According to a first advantageous variant, the second coating is deposited in the second step by a galvanic process. This has proven to be expedient in particular for second coatings without particulate additional components. Second coatings, which except for unavoidable impurities consist exclusively of nickel or a nickel-phosphorus alloy, are therefore advantageously electrodeposited.

The possibly performed in the second step galvanic process can be carried out in a conventional manner. The areas of the doctor blade to be coated, that is to say in particular the working edge provided with the first coating, are immersed, for example, in a suitable galvanic electrolyte bath. The areas to be coated act as a cathode, while for example a soluble consumable electrode with nickel serves as the anode. It is, depending on the material to be deposited, but in principle also possible to use insoluble anodes. By applying a suitable electrical voltage between the cathode and anode, an electric current flows through the galvanic electrolyte bath, whereby elemental nickel or, for example, a nickel-phosphorus alloy is deposited on the areas of the doctor blade to be coated and forms the second coating. The second coatings produced by the galvanic process are pure and of high quality. In principle, in order to further improve the quality of the second coating, an additional component for improving the wear resistance and / or other additives may be added to the electrolyte bath, which may also be incorporated into the second coating.

The galvanic deposition of a nickel-phosphorus alloy also has process engineering advantages over electroless plating. For example, the phosphorus content is very easy to control and the deposits can be carried out at high deposition rates. Likewise, the galvanic deposition of a nickel-phosphorus alloy over the galvanic deposition of nickel has the advantage that even insoluble anodes can be used.

In a second advantageous variant, the deposition of the second coating takes place without current, in particular from an aqueous solution. This procedure is particularly advantageous if particulate additional components, eg. B. hard material particles and / or lubricating particles, are integrated into the second coating. In particular, a uniform distribution of the particulate additional components to be integrated into the second coating is achieved by the electroless deposition.

Advantageously, in a third step, which is carried out after the first and / or the second step in time, a heat treatment is carried out to cure the first, if appropriate, also of the second coating. The heat treatment induces solid state reactions in the nickel-phosphorus alloys which increase the hardness of the nickel-phosphorus alloys. Since the heat treatment takes place only after the deposition or the application of a possible second coating, in particular an oxide formation on the surface of the first coating is prevented. On the one hand, this entails high adhesion between the first coating and the optionally present second coating, and on the other hand, the overall uniformity of the doctor blade in the region of the working edge is improved.

In principle, however, can also be dispensed with a heat treatment. However, this is possibly at the expense of the wear resistance or service life of the doctor blade produced according to the invention.

In particular, during the heat treatment, the coated base body is heated to a temperature of 100-500 ° C, particularly preferably to a temperature of 170-300 ° C. In particular, these temperatures are held for a holding time of 0.5 to 15 hours, preferably 0.5 to 8 hours. Such temperatures and Holding 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. 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 another advantageous variant, during the galvanic process in the second step, first a base layer of nickel is deposited at a pH of less than 1.5, in particular at a pH of less than 1, by a galvanic process. In a further step, a covering layer of nickel, for example, can subsequently be deposited using saccharin at a pH of 2-5, in particular at a pH of 3.4-3.9.

Due to the acidic conditions, the surface of the working edge or the first coating to be coated is chemically activated, so that the base layer forms an extremely stable adhesive bond with the working edge. The base layer provides an optimal base for the topcoat to be deposited over it. Maintaining a pH of 2-5 and the use of saccharin provide an optimal topcoat with a smooth and even surface.

In principle, however, the base layer and the outer layer can also be deposited under other conditions.

In particular, it is also possible to deposit a base layer of nickel at a pH of less than 1.5, in particular at a pH of less than 1, by a galvanic process and then z. B. to apply a cover layer in the form of a nickel-phosphorus alloy. In this case, the nickel-phosphorus alloy may, for example, also contain an additional component for improving the wear behavior of the doctor blade.

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 eine erste Lamellenrakel, wobei eine Arbeitskante der Lamellenrakel mit einer Nickel-Phosphor-Legierung und darin dispergierten Hartstoffpartikeln beschichtet ist;

Fig. 2

Einen Querschnitt durch eine zweite Lamellenrakel, wobei eine Arbeitskante der Lamellenrakel mit einer Nickel-Phosphor-Wolfram-Legierung beschichtet ist;

Fig. 3

Einen Querschnitt durch eine dritte Lamellenrakel, welche im Bereich der Arbeitskante mit einer ersten Beschichtung mit darin dispergierten Hartstoffpartikeln und einer darauf angeordneten und die Rakel vollständig umgebenden zweiten Beschichtung aus reinem Nickel beschichtet ist;

Fig. 4

Eine Variante der Rakel aus Fig. 3, wobei die zweite Beschichtung lediglich im Bereich der ersten Beschichtung vorliegt;

Fig. 5

Einen Querschnitt durch eine fünfte Lamellenrakel, welche im Bereich der Arbeitskante mit einer ersten Beschichtung mit darin dispergierten Hartstoffpartikeln und einer darauf angeordneten zweischichtigen zweiten Beschichtung aus Nickel beschichtet ist;

Fig. 6

Einen Querschnitt durch eine sechste Lamellenrakel, welche im Bereich der eine Arbeitskante mit einer ersten Beschichtung mit darin dispergierten Hartstoffpartikeln und einer darauf angeordneten zweiten Beschichtung mit darin dispergierten Schmierpartikeln aus hexagonalem Bornitrid beschichtet ist;

Fig. 7

Einen Querschnitt durch eine siebte und erfindungsgemässe Lamellenrakel, welche im Bereich der eine Arbeitskante mit einer ersten Beschichtung mit zwei unterschiedlichen Arten von darin dispergierten Hartstoffpartikeln und einer darauf angeordneten zweiten Beschichtung mit darin dispergierten Schmierpartikeln beschichtet ist;

Fig. 8

Eine schematische Darstellung eines erfindungsgemässen Verfahrens zur Herstellung einer Rakel.

The drawings used to explain the embodiment show:

Fig. 1

A cross-section through a first blade squeegee, wherein a working edge of the lamellar blade is coated with a nickel-phosphorus alloy and dispersed therein hard material particles;

Fig. 2

A cross-section through a second blade squeegee, wherein a working edge of the lamellar blade is coated with a nickel-phosphorus-tungsten alloy;

Fig. 3

A cross section through a third blade squeegee, which is coated in the region of the working edge with a first coating having dispersed therein hard material particles and a second coating of pure nickel disposed thereon and completely surrounding the squeegee;

Fig. 4

A variant of the squeegee Fig. 3 , wherein the second coating is present only in the region of the first coating;

Fig. 5

A cross section through a fifth blade squeegee, which is coated in the region of the working edge with a first coating with dispersed therein hard material particles and a two-layered second nickel coating disposed thereon;

Fig. 6

A cross section through a sixth lamella blade, which in the region of a working edge with a first coating having dispersed therein hard material particles and arranged thereon second coating having dispersed therein hexagonal boron nitride lubricating particles;

Fig. 7

A cross section through a seventh and inventive blade squeegee, which is coated in the region of a working edge with a first coating with two different types of dispersed therein hard material particles and a second coating disposed thereon with lubricant particles dispersed therein;

Fig. 8

A schematic representation of a method according to the invention 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 non-inventive slat blade 100 shown in cross section. The lamella blade 100 includes a base body 110 made of steel, which on the in Fig. 1 left side has a rear portion 120 having a substantially rectangular cross-section. The rear region 120 is provided as a fastening region in order to hold the lamellar blade, for example in a corresponding receiving device of a printing press. A doctor blade thickness, measured from the top 121 to the bottom 122 of the rear area, is about 0.2 mm. A length of the base body 110 or the lamella blade 100 measured perpendicularly to the plane of the sheet is, for example, 1000 mm.

On the in Fig. 1 right side is the main body 110 to form a working edge 130 of the top 121 of the rear portion 120 ago tapers step-like. An upper side 131 of the working edge 130 lies on a plane below the plane of the upper side 121 of the rear region 120, but is substantially parallel or plane-parallel to the upper side 121 of the rear region 120. Between the rear region 120 and the working edge 130 lies a concave shape Transition region 125 before. The bottom 122 of the rear portion 120 and the Bottom 132 of the working edge 130 lie in a common plane, which is plane-parallel to the top 121 of the rear portion 120 and plane-parallel to the top 131 of the working edge 130 is formed. A width of the main body 110, measured from the end of the rear area to the front side 140 of the working edge 130 measures, for example, 40 mm. A thickness of the working area 130, measured from the upper side 131 to the lower side 132 of the working area, is for example 0.060-0.150 mm, which corresponds to approximately half the thickness of the squeegee in the rear area 120. A width of the working area 130, measured at the upper side 131 of the working area 130 from the end face 140 to the transition area 125, is for example 0.8-5 mm.

A free end face 140 of the free end of the working edge 130 extends from the top 131 of the working edge 130 obliquely down to the bottom 132 of the working edge 130 back. The end face 140 has an angle of approximately 45 ° or 135 ° with respect to the upper side 131 of the working edge 130 or with respect to the lower side 132 of the working edge 130. An upper transition region between the upper side 131 and the front side 140 of the working edge 130 is rounded. Likewise, a lower transition region between the end face 140 and the bottom 132 of the working edge 130 is rounded.

The working edge 130 of the lamella blade 100 is further surrounded by a first coating 150. The first coating 150 completely covers the upper side 131 of the working edge 130, the transition region 125 and a subregion of the upper side 121 of the rear region 120 of the base body 110 adjoining this. Likewise, the first coating 150 covers the end face 140, the underside 132 of the working edge 130 and a subregion of the underside 122 of the rear region 120 of the base body 110 adjoining the underside of the working edge 130.

The first coating 150 is z. B. from a nickel-phosphorus alloy with a phosphorus content of 9 wt. Therein are hard material particles 160, z. B. of silicon carbide (SiC), dispersed. The volume fraction of the hard material particles 160 is for example 16% and an average particle size of the hard material particles 160 is approximately 1.6 μm. The layer thickness of the first coating 150 measures in the region of the working edge 130 z. B. 15 microns, while the hardness z. B. 1200 HV. In the area of the top 121 and the underside 122 of the rear region 120 continuously decreases the layer thickness of the first coating 150, so that the first coating 150 terminates in a wedge shape in a direction away from the working edge 130.

Fig. 2 shows a second non-inventive slat blade 200 in cross section. The second lamella blade 200 has a main body 210 with a rear region 220 and a working edge region 230 and is substantially identical in construction to the first lamella blade 100 Fig. 1 , Similarly, in the second sipe blade 200, the upper side 231 of the working edge 230, the transition region 225 and an adjoining thereto portion of the top 221 of the rear portion 220 of the body 210 and the end face 240, the bottom 232 of the working edge 230 and one to the bottom 232nd the working edge 230 subsequent portion of the bottom 222 of the rear portion 220 of the body 210 with a coating 250 coated.

The second coating consists of a nickel-phosphorus alloy with a mixed alloying component in the form of tungsten (W). The phosphorus content is e.g. 10 wt .-% and the proportion of tungsten, for example, 5 wt .-%, each measured on the total weight of the coating 250. The layer thickness of the coating 250 measures in the region of the working edge 130 z. B. 15 microns, while the hardness z. B. 1200 HV.

Fig. 3 shows a third non-inventive slat blade 300 in cross section. The third squeegee 300 has a main body 310 which protrudes in the region of the working edge 330 in the same way as the first squeegee Fig. 1 coated with a first coating 350. Correspondingly, the upper side 331 of the working edge 330, the transition region 325 and an adjoining subregion of the upper side 321 of the rear region 320 of the base body 310 and the end face 340, the bottom 332 of the working edge 330 and a subsequent to the bottom 332 of the working edge 330 portion the underside 322 of the rear portion 320 of the base body 310 coated with the coating 350.

The first coating 350 of the third lamella blade 300 is composed and constructed the same as the coating 150 of the first lamella blade 100 and contains corresponding hard particles 360. z. B. of silicon carbide.

In addition, in the case of the third lamella blade there is a second coating 370 which completely surrounds the lamella blade 300. In other words, the second coating 370 completely covers both the first coating 350 and the upper side 321 as well as the lower side 322 of the rear region 320 of the main body 310.

The second coating 370 is formed, for example, by a galvanically deposited nickel layer with a thickness of, for example, approximately 2 μm. The second coating 370 is in the present case except for unavoidable impurities exclusively of nickel.

Fig. 4 shows a fourth non-inventive slat blade 400 in cross section. The fourth sipe blade 400 is substantially identical to the third sipe blade Fig. 3 , However, unlike the third squeegee 300, the fourth squeegee 400 has a second coating 470 covering only the first coating 450. The second coating 470 thus surrounds only the upper side 431 of the working edge 430, the transition region 425 and a subregion of the upper side 421 of the rear region 420 of the base body 410 adjoining it, the front side 440, the underside 432 of the working edge 430 and an underside 432 The rear region 420 of the main body 410 is corresponding blank and covered with neither the first coating 450 nor the second coating 470.

In the region of the upper side 421 and the lower side 422 of the rear region 420, the layer thickness of the second coating 470 continuously decreases, so that the second coating 470 terminates in a wedge shape in a direction away from the working edge 470.

In Fig. 5 a fifth non-inventive blade squeegee 500 is shown in cross section. The main body 510 with the rear end 520 and the working edge 530 is essentially identical to the lamella blade 300 Fig. 3 , Likewise, the fifth doctor 500 has a first coating 550, which is the same design as the Coating 350 of the third doctor blade 300. Accordingly, the first coating 550 of the fifth doctor blade 500 covers the upper side 531 of the working edge 530, the transitional region 525 and a subsequent subregion of the upper side 521 of the rear region 520 of the main body 510, and the lower side 540 532 of the working edge 530 and a subsequent to the bottom 532 of the working edge 530 portion of the bottom 522 of the rear portion 520 of the body 510.

As with the third sipe blade 300, the fifth squeegee 500 also has a second coating 570 completely surrounding the sipe blade 500 so that the second coating 570 covers both the first coating 550, the top 521, and the bottom 522 of the back Area 520 of the base body 410 completely surrounds. In contrast to the second coating 370 of the third doctor blade, however, the second coating 570 of the fifth doctor blade 500 has a two-layer structure. The second coating 570 has a base layer 571 which is applied directly to the first coating 550 and the rear region 520 of the base body 510 and which, except for unavoidable impurities, consists exclusively of pure nickel. A thickness of the base layer 571 is for example about 0.5 microns. The cover layer 572 applied to the base layer 571 likewise consists of an electrodeposited pure nickel, which, however, is additionally mixed with saccharin. A layer thickness of the second coating 570, ie the layer thickness of the base layer 571 and the layer thickness of the cover layer 572 together, is for example approximately 4 .mu.m in the region of the working edge 530, while the layer thickness in the rear region 520 z. B. measures about 2 microns.

Fig. 6 shows a sixth non-inventive blade squeegee 600 in cross section. The main body 610 with the rear region 620 and the working edge 630 provided with a first coating 650 are substantially identical in construction to the third doctor 300 Fig. 3 , Unlike the third squeegee 300 off Fig. 2 however, the second coating 670 completely surrounds the sixth doctor blade 600 but consists of an electrolessly deposited nickel-phosphorus alloy having dispersed therein hexagonal boron nitride (hex-BN) lubricating particles 680. The phosphorus content of the second coating 670 is z. B. 7% by weight while a thickness of the second coating measures about 2 microns. The lubricating particles 680 have a particle size of about 100 nm and a volume fraction of about 17%.

Fig. 7 shows a seventh and inventive fin blade 700, which is a variant of the sixth blade 600 from Fig. 6 represents, in cross-section. The arrangement of the first coating 750 and the second coating 770 on the main body 710 of the seventh doctor blade 700 is substantially the same as in the sixth doctor blade 600 Fig. 6 , However, the sixth squeegee 600 and the seventh squeegee 700 are different in the composition of the coatings.

The first coating 750 of the seventh blade 700, which substantially surrounds the working edge 730, is based on a nickel-phosphorus electroless alloy deposited with a first additive component in the form of mixed tungsten (W). In other words, the first coating 750 is therefore based on a nickel-phosphorus-tungsten alloy. The layer thickness of the first coating 750 measures in the region of the working edge 730, for example, about 12 microns and the phosphorus content is about 12 wt .-%. In addition, additional additional components in the form of a first hard material component 760 and a second hard material component 761 are dispersed in the first coating 750. The first hard component 760 is z. For example, diamond particles with a particle size of, for example, 100-200 nm and a volume fraction of about 10%. The second hard material component consists for example of silicon carbide (SiC) having a particle size of 1.5 to 2.0 microns and a volume fraction of about 10%. The particle size of the second hard material component 761 (SiC) is thus larger than the particle size of the first hard material component 760 (diamond). The hardness of the first coating 750 is about 1300 HV.

The second coating 770, which completely surrounds the seventh blade squeegee 700, is based on, for example, FIG. B. on a de-energized nickel-phosphorus alloy with dispersed therein lubricant particles 780 hexagonal BN (hex-BN). A phosphorus content of the second coating is about 6% by weight while the layer thickness measures about 2 μm and the volume fraction of the lubricating particles 780 is about 18%. The particle size of the lubricating particles 780 is about 100 nm. The phosphorus content of the nickel-phosphorus alloy The second coating 770 is thus smaller than the phosphorus content of the nickel-phosphorus alloy of the first coating 750.

The above-described and in the Fig. 1-7 The lamella blades shown are only to be understood as illustrative examples of a multiplicity of realizable embodiments according to the invention and not according to the invention. Further concrete inventive and non-inventive embodiments are listed in Table 1 below. To understand the table, the following: The abbreviation "Chem. Ni-P" stands for a chemically or electrolessly deposited nickel-phosphorus alloy. Correspondingly, the abbreviation "Galv." Galvanically deposited and "Galv. Ni-P" is to be understood as a galvanically deposited nickel-phosphorus alloy. "P content" stands for the phosphorus content in a nickel-phosphorus alloy. <b> Table 1: </ b> No. 1. coating 2. coating Base additional component Base additional component - P content - particle size - P content - particle size - thickness - Vol. Antell thickness - Vol. Share A * Chem. NI-P SiC none none ( Fig.1 ) -9% -1.6 μm -15 μm -16% B * Chem. Ni-P TiC none none -12% -1.9 μm - 25 microns -20% C * Chem. Ni-P WC none kelne -8th% - 1.8 μm - 25 microns -15% D * Chem. Ni-P cubic BN none none -8th% -1.8 μm - 25 microns -15% e * Chem. Ni-P cubic B ₄ C none none -8th% -1.8 μm - 25 microns -15% F * Chem. NI-P Molybdenum (particles) none none -10% 1.5 μm -10 μm -17% G* Chem. Ni-P hexagonal BN none none -8th% -1.8 μm -20 μm -15% H* Chem. Ni-P tungsten none None ( Fig. 2 ) -10% - none, because alloy -15 μm -5% I * Chem. Ni-P SiC Galv. nickel none ( Fig. 3 ) -9% - 1.6 μm -0% -15 μm -16% - 2 μm J * Chem. Ni-P Al ₂ O ₃ Galv. nickel none -9% -1.6 μm -0% - 15 μm -16% - 2 μm K * Chem. Ni-P SiC Galv. nickel None ( Fig. 5 ) - 9% -1.6 μm (Base coat / topcoat with saccharin) - 15 μm -16% -0% - 2 - 4 μm L * Chem. Ni-P SiC Galv. Ni-P none -9% -1.6 μm -13% -15 μm -16% -2 μm M * Chem. Ni-P Al ₂ O ₃ Galv. Ni-P none -9% -1.6 μm -13% -15 μm -16% - 2 μm N * Chem. Ni-P SiC Chem. Ni-P hexagonal BN ( Fig. 6 ) -9% -1.6 μm -7% - 100 nm -15 μm -16% - 2 μm -17% O* Chem. Ni-P SiC Chem, Ni-P cubic BN -9% -1.6 μm - 6% -1.5 μm - 15 μm -16% - 2 μm -18% P Chem. Ni-P tungsten Chem. Ni-P hexagonal BN ( Fig. 7 ) -12% - none, because alloy -6% - 100 nm -12 μm -5% -2 μm -18% SiC -1.5 μm -10% diamond -150 nm -10% * = not according to the invention

The embodiment designated in the table with "A" corresponds to that in FIG Fig. 1 The embodiments "B" - "G" have, apart from the stated and sometimes different additional components, particle sizes, volume fraction and / or layer thicknesses, a construction analogous to the lamella blade 100.

The embodiment labeled "H" corresponds to the second sipe blade 200 Fig. 2 while the embodiment labeled "I" of the third fin blade 300 is made Fig. 3 equivalent. The embodiment "J" is except for the different additional component in the first coating substantially identical to the third blade squeegee 300 Fig. 3 ,

In the Fig. 5 shown blade blade 500 is indicated in the table as embodiment "K" and accordingly has a two-layer electrodeposited second nickel-based coating. The embodiments "L" and "M" represent variants of embodiment "K", which instead of the second nickel-based coating have a second coating in the form of a galvanically deposited nickel-phosphorus alloy.

Embodiment "N" corresponds to FIG Fig. 6 Embodiment "O" differs from embodiment "N" in particular by cubic boron nitride (cubic BN) instead of hexagonal boron nitride (hexBN) in the second coating. It should be noted that the particle size of the cubic boron nitride is much larger than the particle size of the hexagonal boron nitride.

Finally, embodiment "P" corresponds to the seventh lamella blade 700 Fig. 7 ,

Fig. 8 illustrates a method 800 for producing a lamellar blade, as z. In Fig. 5 is shown. In this case, in a first step 801, the working edge 530 of the main body 510 to be coated with the nickel-phosphorus alloy or the first coating 550 is immersed, for example, in a suitable and known aqueous electrolyte bath with hard material particles 560 suspended therein, nickel ions consisting of a nickel salt , z. For example, nickel sulfate, by a reducing agent, for. B.

Sodium hypophosphite, reduced in aqueous environment to elemental nickel and deposited on the working edge 530 with the formation of a nickel-phosphorus alloy and simultaneous embedding of the hard material particles 560. 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.

In a second step 802 z. For example, first a first galvanic electrolyte bath on an aqueous basis with nickel chloride and hydrochloric acid at a pH of about 1 presented. Subsequently, the main body 510 with the first coating 550 already applied in the first step is completely immersed in the electrolyte bath in a manner known per se with externally supplied electrical current, a base layer 571 of the second coating 570 is deposited. Subsequently, in a second galvanic electrolyte bath on an aqueous basis with nickel, nickel sulfate, nickel chloride, boric acid and saccharin, a covering layer 572 is deposited in a manner known per se at a pH of 3.7.

In a third step 803, the main body 510 provided with the first coating 550 and the second coating 570 is subjected to a heat treatment during, for example, two hours and at a temperature of 300 ° C. Finally, the finished lamella blade 500 is cooled and is ready for use.

If a doctor blade is produced without a second coating, the second step 802 is omitted and the third step is carried out without the second coating. In order to produce a doctor blade which has a second coating based on electrolessly deposited nickel-phosphorus alloy, in the second step 802 a coating analogous to the first step 801 is carried out. If tungsten (W) is provided as an additional component for improving the wear behavior, the deposition of the relevant coating according to the first step 801 takes place in particular at a pH of 8-9.

As has been shown in test experiments, have in the Fig. 1-7 lamella blades 100, 200, 300, 400, 500, 600, 700 and the lamellar blade additionally shown in Table 1 have a very high wear resistance and stability on and allow extremely accurate painting, especially of printing ink. The latter over the entire life of the doctor blades.

For comparison, an identical base body as in the lamellae blade 100 was made Fig. 1 described in a first comparative experiment in the region of the working edge only provided with a first coating of a pure nickel-phosphorus alloy and thereby dispensed with the additional component to increase the wear resistance in the form of hard particles of SiC. As has been shown, such squeegees have a significantly lower wear resistance and stability than those in the Fig. 1-7 shown squeegee.

In further test experiments, the lamellar squeegee 300, 500, 600, 700 were made from Fig. 3 . 5 . 6 and 7 each waived the additional components to improve the wear behavior. Such squeegees have a significantly lower wear resistance than those in the Fig. 3 . 5 . 6 and 7 shown squeegee.

However, the above-described embodiments and the manufacturing method are to be understood as illustrative examples only, which may be arbitrarily modified within the scope of the invention.

Thus, the main body 110, 210, 310, 410, 510, 610, 710 of the doctor blade from the Fig. 1-7 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 coatings only in the region of the working edges 130, 230, 330, 430, 530, 630, 730 in order to reduce the material consumption in the coating. Basically, the main body of the squeegee from the Fig. 1-7 but also from a non-metallic material, such. As plastics exist. This may be advantageous in particular for applications in flexographic printing.

It is also possible, instead of in the Fig. 1-7 shown basic bodies each base body to use a different shape. 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 140, 240, 340, 440, 540, 640, 740 of Working edges 130, 230, 330, 430, 530, 630, 730 may for example also be formed completely rounded.

Furthermore, the inventive doctor blade from the Fig. 1-7 also be different dimensions. For example, the thicknesses of the working areas 130, 230, 330, 430, 530, 630, 730 measured from the respective tops 131 ... 731 to the respective bottoms 132, 232, ... 732 may be in a range of, for example, 0.040 - 0.200 mm vary.

Similarly, the coatings of the doctor blade from the Fig. 1-7 other alloying components and / or additional substances, such. As metal atoms, non-metal atoms, inorganic compounds and / or organic compounds. The additional substances can also be particulate.

All of the in the FIGS. 1-7 For example, the doctor blades shown can be coated with further coatings. The further coatings may be present in the region of the working edges and / or the rear regions and z. B. improve the wear resistance of the working edges and / or protect the rear area from influences by aggressive chemicals. In principle, these can also be coatings made of plastics.

At the squeegee 200 off Fig. 2 Furthermore, it is also possible to apply a second coating on the already existing first coating 250 and in the second coating additional components to improve the wear behavior, eg. As particulate additional components to bring.

In summary, it has been found that novel doctor blades have been created, which are characterized by an extremely high level of wear resistance and enable uniform and streak-free ink stripping during the entire service life. At the same time, the squeegees according to the invention can be realized in a wide variety of embodiments, so that they can be specifically adapted to specific uses.

Claims (29)

1. A doctor blade (100, 200, ..., 700), in particular for scraping printing ink from a surface of a printing plate, which comprises a flat and longitudinal base element (110, 210, ..., 710) having a working edge region (130, 230, ..., 730) formed in a longitudinal direction, where the working edge region (130, 230, ..., 730) is coated with at least a first coating (150, 250, ..., 750) based on a nickel-phosphorus alloy, where the first coating (150, 250, ..., 750) contains at least one additive component (160, 360, 460, 660, 760, 761) for improving the wear behavior of the doctor blade, where the at least one additive component (160, 360, 460, 660, 760, 761) comprises hard material particles, characterized in that the hard material particles comprise both SiC and diamond, with the average particle size of the SiC being greater than the average particle size of the diamond.
2. The doctor blade as claimed in claim 1, characterized in that the hard material particles have average particle sizes in the range 5 nm - 4 µm, in particular 0.9 - 2.5 µm, particularly preferably 1.4 - 2.1 µm.
3. The doctor blade as claimed in claim 2, characterized in that the hard material particles comprise SiC having an average particle size of 1.4 - 2.1 µm and diamond having a particle size of 10 nm - 1.1 µm.
4. The doctor blade as claimed in any of claims 1 - 3, characterized in that the first coating (150, 250, ..., 750) comprises a nickel-phosphorus alloy deposited by an electroless method.
5. The doctor blade as claimed in claim 4, characterized in that the phosphorus content of the first coating (150, 250, ..., 750) is 7 - 12% by weight.
6. The doctor blade as claimed in any of claims 1 - 5, characterized in that the first coating (150, 250, ..., 750) has a hardness of 750 - 1400 HV.
7. The doctor blade as claimed in any of claims 1 - 6, characterized in that the thickness of the first coating (150, 250, ..., 750) is 1 - 30 µm, in particular 5 - 10 µm.
8. The doctor blade as claimed in any of claims 1 - 7, characterized in that a second coating (370, 470, 570, 670, 770) based on nickel is present, where the second coating has, in particular, been applied directly on top of the first coating (150, 250, ..., 750).
9. The doctor blade as claimed in claim 8, characterized in that the second coating (370, 470, 570, 670, 770) is an galvanically deposited coating.
10. The doctor blade as claimed in either of claims 8 - 9, characterized in that the second coating (370, 470, 570, 670, 770) is based on a nickel-phosphorus alloy.
11. The doctor blade as claimed in claim 10, characterized in that the nickel-phosphorus alloy of the second coating (370, 470, 570, 670, 770) has a phosphorus content of 12 - 15%.
12. The doctor blade as claimed in any of claims 8 - 11, characterized in that the layer thickness of the second coating (370, 470, 570, 670, 770) is 0.5 - 3 µm.
13. The doctor blade as claimed in any of claims 1 - 12, characterized in that the hard material particles comprise metal particles, in particular metal particles of metallic molybdenum.
14. The doctor blade as claimed in any of claims 1 - 13, characterized in that the hard material particles comprise metal carbides, metal nitrides and/or metal carbonitrides.
15. The doctor blade as claimed in claim 14, characterized in that the hard material particles contain B₄C, cubic BN, TiC, and/or WC.
16. The doctor blade as claimed in any of claims 1 - 15, characterized in that the hard material particles contain metal oxides, in particular Al₂O₃.
17. The doctor blade as claimed in any of claims 1 - 16, characterized in that the hard material particles additionally comprise cubic BN, with the average particle size of the BN preferably corresponding approximately to the average particle size of the SiC and the average particle sizes of the SiC and of the cubic BN more preferably being 1.4 - 2.1 µm.
18. The doctor blade as claimed in any of claims 1 - 17, characterized in that the additive component (160, 360, 460, 660, 760, 761) comprises lubricating particles.
19. The doctor blade as claimed in claim 18, characterized in that the lubricating particles comprise hexagonal BN and/or polytetrafluoroethylene.
20. The doctor blade as claimed in claim 19, characterized in that the lubricating particles comprise hexagonal BN having an average particle size of 50 nm - 1 µm, preferably 80 - 300 nm, more preferably 90 - 110 nm.
21. The doctor blade as claimed in any of claims 1 - 20, characterized in that the additive component (160, 360, 460, 660, 760, 761) comprises an additional alloying component.
22. The doctor blade as claimed in claim 21, characterized in that the additional alloying component comprises tungsten.
23. The doctor blade (1) as claimed in any of claims 1 - 22, characterized in that the base element (110, 210, ..., 710) consists of steel.
24. The doctor blade (1) as claimed in any of claims 1 - 22, characterized in that the base element (110, 210, ..., 710) consists of plastic.
25. A process (800) for producing a doctor blade (100, 200, ..., 700), in particular a doctor blade as claimed in any of claims 1 - 24, where, in a first step (801), at least one first coating (150, 250, ... , 750) based on a nickel-phosphorus alloy is deposited on a working edge region (130, 230, ..., 730) of the doctor blade formed in a longitudinal direction of a flat and elongated base element (110, 210, ..., 710), where at least one additive component (160, 360, 460, 660, 760, 761) for improving the wear behavior of the doctor blade is mixed into the first coating, where the at least one additive component (160, 360, 460, 660, 760, 761) comprises hard material particles, characterized in that the hard material particles comprise both SiC and diamond, with the average particle size of the SiC being greater than the average particle size of the diamond.
26. The process as claimed in claim 25, characterized in that the deposition of the at least first coating (150, 250, ..., 750) is carried out in aqueous solution and preferably with blowing in of air.
27. The process as claimed in claim 26, characterized in that an alloying component which is a tungsten salt is mixed in as additive component.
28. The process as claimed in either of claims 26 - 27, characterized in that the aqueous solution in the deposition has a pH of 8 - 9.
29. The process as claimed in any of claims 25 - 28, characterized in that, in a second step (802), a second coating (370, 470, 570, 670, 770) based on nickel is deposited at least on the first coating (150, 250, ..., 750).

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