Sieve

Abstract

Screen (4) for rotary screen printing made of a planar screen material (1) for use in screen printing, in particular in rotary screen printing, with strands (5, 5.1, 5.2) forming a woven screen structure, arranged at angles to each other and intersecting at intersection points (10), wherein the strands (5, 5.1, 5.2) form undercuts (11) there, and wherein the strands form a screen structure with openings and the strands (5, 5.1, 5.2) consist at least on their surfaces of metal (3), in particular of nickel, which was deposited on the strands (5, 5.1, 5.2) in an electroplating process, wherein the screen (4) has the form of a cylindrical sleeve and the planar screen material (1) is coated in particular on one side with a polymer layer (2), e.g. B. with a photopolymer layer, characterized in that in the area of ​​intersection points of the strands (5, 5.1, 5.2) whose undercuts (11) have at least partially a filling (12) of the metal applied in the electroplating process.

Description

[0001] The invention relates to a sieve with the features outlined in claim 1. State of the art

[0002] The industrial application of sieves and fabrics is known from various fields.

[0003] In filtration applications, the square mesh pattern is the standard design. This mesh pattern has also been adopted for printing applications. With available photographic coatings and established application methods, a reasonable image resolution can only be achieved with a large number of "supports." Therefore, fabrics with high mesh counts are increasingly being used.

[0004] In electronics printing, the thinnest possible screens or fabrics with the thinnest possible wire are used to ensure good paste flow and to enable the finest image motifs.

[0005] Solar cell coating requires a high paste application rate and precise, fine image resolution. This is particularly important for applying conductive traces as current fingers with minimal coverage of the solar cells, thus ensuring high solar cell efficiency.

[0006] The screens or fabrics used for electronics printing are very expensive and delicate to process, making them unsuitable for producing screen printing plates for rotary screen printing. This unsuitability is further compounded by the fact that rotary screens can only tension the screen fabrics in one direction, namely along the cylinder's longitudinal axis, whereas flat screen printing allows tension in two dimensions.

[0007] In rotary screen printing, the ink is transported through the screen by the hydrodynamic pressure generated by the rotation of the screen and the angled squeegee in front of the squeegee blade. Due to design limitations, only open or semi-open squeegee systems can be used, meaning the dynamic pressure is influenced by many factors such as viscosity, ink volume, and rotation speed. The hydrodynamic pressure can be easily increased by increasing the rotation speed or the ink volume.

[0008] Such a rotary screen printing machine is described, for example, in WO 99 / 19146 A1.

[0009] According to current technology, stainless steel mesh with a plain weave is used as the basic structure for screen materials. The ratio of screen opening, contact area, and mesh thickness has proven suitable. The thickness of the structure, i.e., the mesh thickness (initial dimension before calendering), corresponds approximately to twice the wire diameter. The basic structure is then processed in a calendering process to achieve the desired raw mesh thickness. This also results in a smoother screen surface and thus reduced wear on the screen and doctor blade. In the subsequent nickel plating process, the mesh is typically reinforced uniformly, i.e., symmetrically to the axis of the threads, to increase wear resistance, and the support points at the intersections are enlarged. However, methods for targeted plating in only one direction, perpendicular to the surface of the mesh, are also known.According to EP 0049022 A1, targeted metal deposition is achieved by adjusting the flow rate and adding chemical additives.

[0010] A complete process for the production of such sieve materials is described, for example, in EP 0 182 195 A2.

[0011] DE 40 200 46 A1 describes a screen printing stencil support fabric made of stretchable and movable threads, which should be able to be stretched in the direction of the longitudinal threads without constricting.

[0012] DE 197 38 874 A1 describes a method for producing a fabric web for use as a screen printing stencil from a plastic fabric which is provided with a metal coating.

[0013] US 4,285,274 describes a method for manufacturing a seamless cylindrical screen printing cylinder from metal wires, which is said to have higher resistance.

[0014] DE 29 18 063 A1 describes a method for manufacturing drums for rotary screen printing which are intended to have increased durability, whereby plating processes can be used.

[0015] It is known from the prior art that stainless steel fabrics, e.g. for rotary screen printing, are metallized by means of galvanic processes.

[0016] The current state of the art for nickel plating involves the preferred use of sulfamate nickel baths or electroless nickel plating processes. The advantage of these processes is a uniform geometric layer distribution in all spatial planes. The disadvantage lies in the formation of a so-called angular weakness, also referred to as an undercut, at the intersection point. This undercut negatively affects the flow behavior, for example, during cleaning processes and the flow of ink in printing, as well as the stability of the metallized fabric.

[0017] It is also known that multi-layer nickel coatings are deposited using Watt's nickel sulfate electrolytes for corrosion protection and / or decorative purposes. These processes can be applied in a wide range of applications for refining diverse components in various industries.

[0018] Various additives, preferably organic, are added to Watt's nickel sulfate baths. These additives are divided into primary and secondary brighteners. Primary brighteners, which can also exhibit properties of secondary brighteners, are used to achieve homogeneous metal deposition with a specific base gloss over the widest possible current density range. Secondary brighteners significantly influence the leveling behavior and gloss level.

[0019] Furthermore, the combination of first and second class brighteners has other effects on the deposited nickel layer: luster, ductility, hardness, leveling behavior and electrochemical potential of the deposited layers to each other.

[0020] Commercially available mixtures of organic additives must meet a wide range of technical requirements. These mixtures and nickel baths are essentially designed for the metallization of individual items in barrel plating lines.

[0021] These baths can only be used to a limited extent for nickel plating fabrics in reel-to-reel plating systems. In metallization, it is common practice for the surface to be finished to face the anode during the process (e.g., by rotation in barrel plating systems). This, in combination with the addition of additives, ensures a uniform coating distribution.

[0022] In a reel-to-reel system, this could theoretically be achieved by guiding the tape between two anodes. However, woven fabrics, especially fine fabrics, have the property of expanding extremely rapidly due to current input and their low mass, leading to waviness and internal stresses. Furthermore, the mixtures mentioned above are formulated in such a way that either an undercut remains at the intersection point or the mesh openings become too tightly closed.

[0023] To ensure the stability of the sieve material, a close-meshed structure with many support points is chosen. These sieve materials and sieves, known from the prior art, have the following disadvantages: At the intersection points of the fabric threads, there are angular weaknesses, i.e., undercuts. In other words, the stability of woven sieves is limited by the notch effect in the area of ​​the intersection points of the fabric threads. Reinforcing the coating using the well-known electroplating process is not a solution, as the openings in the fabric can become clogged, and in screen printing, this can lead to ink particles blocking the openings. This then impairs the print quality. Task

[0024] The object of the present invention is therefore to provide a screen material and a screen which do not exhibit the disadvantages of screen materials and screens known from the prior art and are particularly suitable for rotary screen printing. The screen materials, in particular steel mesh, should exhibit higher stability and a longer service life for use in rotary screen printing.

[0025] This problem is solved by a screen with the features of claim 1. These features are particularly advantageous because they meet the specific requirements of rotary screen printing and exhibit greater stability compared to conventional screen materials and screens. The planar screen material according to the invention is intended for use in screen printing, especially rotary screen printing. The screen material has strands arranged at angles to one another and intersecting at their intersection points, forming a woven screen structure, the invention being independent of the weave type and mesh shape. At the intersection points, the strands form undercuts, whereby undercuts are understood to be the inner edges of adjacent surfaces of the intersecting strands, for example, warp and weft threads. These thus exhibit an angular weakness, which is also referred to as inner edge weakness.The strands are arranged to form a sieve structure with openings. At least on their surfaces, the strands consist of metal, in particular nickel, which was deposited onto the strands in an electroplating process. According to the invention, the planar sieve material is designed such that, in the area of ​​the strand intersections, the undercuts of the strands have at least a partial filling of the metal applied in an electroplating process. In other words, the electroplating process reduced or eliminated the undercuts by selectively depositing additional metal in the area of ​​the undercuts.

[0026] This type of sheet-like screen material has the advantage that the metallic infill reduces flow resistance and turbulence when used for screen printing, resulting in improved ink flow. Furthermore, ink cannot dry in the undercuts. The cleaning process is also simplified, as direct flow of cleaning fluid is possible, leading to shorter cleaning times and reduced fluid consumption. Another advantage is the increased stability of the sheet-like screen material, since the metallic infill reduces the notch effect of the undercuts.

[0027] In a particularly advantageous and therefore preferred embodiment of the screen material for the screen according to the invention, each infill forms an inner edge transition with a rounded edge. The metal infill is thus designed such that no sharp edges or chamfers are present in the area of ​​the undercuts. It is particularly advantageous if the infills have a radius of at least 1 µm or at least one-tenth of the mean radius of the strands (average of the warp and weft radii). This ensures that, in screen printing applications, the ink can flow through the screen material without difficulty, that there are no significant deposits in the area of ​​the undercuts, that the screen material is easy to clean, and that it exhibits high stability.

[0028] In a first embodiment of the planar sieve material for the sieve according to the invention, a curve along the surface of the sieve material – viewed in a cross-sectional plane perpendicular to the sieve material and through one of the strands – describes a smooth curve. A smooth curve is understood here to be a smooth curve in the mathematical sense, i.e., a curve that is continuous and differentiable, thus a curve without corners or abrupt turns.

[0029] In a second embodiment of the planar screen material for the screen according to the invention, a curve along the surface of the screen material—viewed in a cross-sectional plane parallel to the screen material and through all strands—describes a smooth curve. A smooth curve is understood here to be a smooth curve in the mathematical sense, i.e., a curve that is continuous and differentiable, i.e., a curve without corners or abrupt turns. For the first embodiment, the undercuts on the top and / or bottom of the screen material each have a metallic filling. For the second embodiment, however, the undercuts in the plane of the screen material each have a metallic filling. In an advantageous further development, both embodiments are combined to form a particularly stable and flow-optimized planar screen material.

[0030] In an advantageous further development of the planar sieve material with smooth curves between two intersection points, the curve along the surface of the sieve material has two inflection points, with the inflection points defining the filling area. An inflection point is understood here as an inflection point in the mathematical sense, i.e., a point on the surface curve at which the sign of the first derivative changes. The inflection points can, in particular, have a distance from each other of at least 1 µm and a maximum distance corresponding to the division. The division is defined as the distance between the central axes of two adjacent, parallel strands. In particular, however, the inflection points are spaced 10 to 20 µm apart.Fillings that fall into this category are, on the one hand, easy to manufacture and, on the other hand, meet the expectations for higher stability and better flow properties of the flat sieve material.

[0031] In an alternative embodiment to the rounded filling, a parabolic filling is provided, each section of which itself has an undercut. With the parabolic filling, the screen material is particularly densely filled and reinforced in the area of ​​each undercut.

[0032] In another alternative embodiment, the fillings are designed such that their surfaces lie almost in the same plane on the surface and / or underside of the screen material. In other words, the metallic filling ensures that the strands are completely embedded in it.

[0033] In a further development of this or the previously described sieve materials, the sieve material exhibits a sieve structure with calendered surfaces, thinned through a calendering process. A calendering process, also known as a rolling process, is generally understood to be a rolling process that causes the sieve structure to flatten.

[0034] Such a calendering process is described, for example, in DE 691 08 040 T2.

[0035] The sheet-like sieve material is formed by a fabric, e.g., a plastic mesh or a metal wire mesh. The structure has the form of so-called meshes, e.g., rectangular or square meshes.

[0036] The strands consist of metal on their surfaces, with nickel being particularly advantageous and therefore preferred. The metal was deposited onto the strands in an electroplating process.

[0037] To produce the sieve material described above for the sieve according to the invention, a fabric structure with one or more layers, particularly those containing nickel, is preferably metallized in a single electrolyte bath. Organic additives can be selectively added to the electrolyte bath to strengthen the intersection points. The formation of the nickel layer is further influenced by moving the fabric past non-conductive bodies, i.e., insulators, on the side facing away from the anode. These insulators alter the field and thus influence the nickel deposition. During this movement, the fabric structure rests on the insulator. The anodes can also be arranged such that they have varying distances from the fabric along their length. This allows the nickel layer distribution at the intersection points on the front and back of the fabric to be optimized.Depolarized pure nickel plates or nickel pellets in baskets can be used as anodes.

[0038] By means of such a process and the combination of a surface nickel plating process, specific dosage of first and second class brighteners, and targeted flow through the electrolyte, the streamlines of the electric field can be influenced in such a way that more nickel can be deposited on the side of the fabric facing away from the anode at the intersection points.

[0039] This also makes it possible to achieve eccentric nickel plating of a single strand of the fabric, with a stronger coating on the side facing away from the anode.

[0040] With ideal coordination of all components, the coating can be carried out in a single process step. This is particularly advantageous when applying thin nickel layers of just a few micrometers.

[0041] If thicker layers above 2 µm need to be deposited, it is advantageous to divide the layer deposition into several process steps, although different electrolyte baths can be dispensed with.

[0042] The tissue can be cleaned between the deposition of the individual nickel layers.

[0043] The invention relates to a screen for rotary screen printing, which is made from a flat screen material as described above and wherein the screen has the form of a cylindrical sleeve.

[0044] In an advantageous further development of the sieve according to the invention, the planar sieve material is provided on one side with a polymer layer, in particular with a photopolymer layer, so that imaging according to a method known to the skilled person is made possible.

[0045] The described invention and the described advantageous embodiments of the invention also represent advantageous embodiments of the invention in any combination with one another.

[0046] Regarding further advantages and structurally and functionally advantageous embodiments of the invention, reference is made to the dependent claims and the description of exemplary embodiments with reference to the accompanying drawings. Example of implementation

[0047] The invention will be explained in more detail using an exemplary embodiment. The schematic representation shows... Fig. 1 a sieve according to the invention Fig. 2a a sieve material before nickel plating Fig. 2b a sieve material after nickel plating Fig. 3a a sectional view with a section perpendicular to the screen material Fig. 3b a detailed presentation of the Fig. 3a Fig. 3c a detailed representation of the Fig. 3a before filling Fig. 4a Alternative filling of the undercuts Fig. 4b Filling of undercuts of calendered tissue Fig. 5 a sectional view with a section in the plane of the screen material Fig. 6 a sieve for rotary screen printing

[0048] Corresponding elements and components are provided with the same reference symbols in the figures.

[0049] The following describes, by way of example, a method for producing the sieve material 1 for the sieve 4 according to the invention and, by way of example, a required bath composition. It is assumed that nickel 3 is to be applied to the fabric structure 5 during electroplating.

[0050] A Watt nickel electrolyte bath can serve as the basis for nickel plating, to which primary and secondary brightening agents are preferably added: Nickel 60 - 90 g / l Chloride 12 - 45 g / l Boric acid 30 - 50 g / l Bathroom temperature 45 - 70°C, pH value 3.5 to 4.8,

[0051] For deposition, gloss additives are preferably added, so-called secondary gloss formers, such as butynediol derivatives, quaternary pyridinium derivatives, propargyl alcohol, propynol propoxylates, in particular butynediol, as well as primary gloss formers such as benzenesulfonic acids, alkylsulfonic acids, alylsulfonic acids, sulfonimides, sulfonamides or benzoic acid sulfimide.

[0052] Secondary glazing agents are used in this application for the defined enhancement of the intersection points 10, whereby these are added in a content of 0 to 0.15 g / l, depending on the desired enhancement, and primary glazing agents between 0 and 8 g / l.

[0053] The tissue structure 5, pre-treated as is usual in electroplating, is nickel-plated using the bath described above.

[0054] Tissue 5 is transported in the nickel bath over an electrically non-conductive support surface.

[0055] The electrically non-conductive contact surface can be provided with segments perpendicular to the transport direction of the tissue 5, which are also filled with electrolyte during operation and ensure a permanent electrolyte exchange.

[0056] Nickel deposition 3 is hindered on the contact surface by the absence of electrolyte.

[0057] By adding a secondary brightener, the metal deposition 3 is additionally concentrated specifically in the intersection points 10.

[0058] In the segmented zone, deposition also occurs on the reverse side of the fabric. By strategically distributing the segments across the contact surface, combined with the appropriate amount of secondary brightener, nickel deposition can be distributed across the intersection points or the entire reverse side.

[0059] An ideal electrolyte flow between the anode and the tissue structure (acting as the cathode) reduces the deposition rate on the tissue at the anode side. This arrangement has been shown to result in increased deposition on the side facing away from the anode.

[0060] An ideal anode distance lies between 1 cm and 40 cm from the cathode. This distance is advantageous because the tissue 5 can still be sufficiently supplied with fresh electrolyte, while the electrical voltage losses due to the increased anode distance remain at an acceptable level.

[0061] Nickel plating can generally be carried out in a single nickel plating cell. However, it is also conceivable to arrange several nickel plating cells in series.

[0062] Fig. Figure 1 shows a flat screen material 1 for the screen 4 according to the invention, which is provided on one side with a photopolymer coating 2 (direct stencil). In an alternative embodiment not shown, a pre-imaged film can be applied to the screen structure 1 (indirect stencil). The nickel-plated flat screen material 1 is made of a woven fabric.

[0063] In Fig. Figure 2a shows a planar screen material 1, which is formed from interwoven strands 5. The strands 5 are arranged at right angles to each other and spaced apart, so that openings 6 are created in the planar screen material 1. The area where the perpendicular strands 5 meet or slide against each other is called the intersection point 10. A metal coating 3, e.g., nickel, which is applied to the strands 5 in an electroplating process, connects the strands 5 at the intersection points 10. Since the metal coating 3 is applied essentially uniformly to the surface of the strands 5, so-called undercuts 11 are formed where the surfaces of the strands 5 meet. In other words, the adjacent surfaces of the strands 5, for example, warp thread 5.1 and weft thread 5.2, form inside edges at their lines of contact.This results in an inner edge weakness, also known as angular weakness, which negatively affects the stability, flow properties and cleanability of the flat sieve material 1.

[0064] In Fig. Figure 2a shows a Cartesian coordinate system xyz, where the planar sieve material 1 lies in the xy-plane. The z-axis is orthogonal to this plane.

[0065] Fig. Figure 2b shows the flat sieve material 1 made of Fig. 2a. According to the invention, the undercuts 11 at the intersection points 10 were each provided with a filling 12 by targeted deposition. This targeted deposition can be carried out, in particular, during the electroplating of the metal coating 3. By filling the undercuts 11 with 12, the properties of the planar screen material 1 are significantly improved, especially with regard to stability, ink flow, and cleanability.

[0066] In Fig. Figure 3a shows a section through the planar screen material 1 in the xz-plane and the yz-plane: the warp threads 5.1 and weft threads 5.2 are each provided with a metal coating 3. As in Fig. As indicated in Figure 3c, the thickness of the metal coating a, b, c on the upper surface (top side 28) and the lower surface (bottom side 29) of warp threads 5.1 and weft threads 5.2 can be uniform or different. Different thicknesses a, b, c of the metal coating 3 can influence the properties of the sheet screen material 1. The diameters 26, 27 of warp threads 5.1 and weft threads 5.2 can also be either the same size or different sizes. This, too, can influence the weave structure and thus the properties of the sheet screen material 1. Further geometric dimensions are described in Figure 3c. Fig. 3a The neutral fiber 20 is represented by the wire longitudinal section and the division 21, which describes the distance between two central axes of strands 5 (here 5.1). At the intersection points 10, the undercuts 11, which in Fig. 3c are still recognizable, according to Fig. 3a is provided with a filler 12 by targeted deposition. This results in an inner edge transition with a rounding 12.1, where the rounding has a radius 25. Inner edges, chamfers, incisions or undercuts were thus eliminated and the surface exhibits a smooth transition between the strands 5.

[0067] In the detailed presentation of Fig. 3b the fillings 12 of the undercuts 11 are more clearly visible: when viewed in the embodiment according to Fig. 3b. The curve along the surface of the screen material 1 reveals two inflection points 22 in the area of ​​each infill 12, which are inflection points in the mathematical sense. These inflection points 22 are spaced 23 apart and define the infill 12. In other words: between the inflection points 22, there is an infill 12 of the undercut 11, while outside the inflection points 22, the warp thread 5.1 or the weft thread 5.2 is provided with the usual metal coating 3 of layer thickness a, b, c. The infill 12 produced by targeted deposition has its greatest infill thickness 24 approximately midway between the two inflection points 22, which is measured between the surface of the infill 12 and the theoretical apex of the undercut 11.

[0068] In Fig. Figure 4a shows alternative electroplated coatings i, ii, iii, iv. According to alternative i, the filling 12 is parabolic in shape. Thus, the filling thickness of the filling 12 is particularly large in the area of ​​the original undercut 11. However, the filling 12 is designed in such a way that the filling still has an undercut, forming an inner edge.

[0069] According to alternative ii, a particularly thick electroplated coating was applied to fill 12 the undercut 11. The filling 12 is so extensive that the surface of the filling 12 lies in a plane 30 and the warp threads 5.1 and the weft threads 5.2 are completely embedded in the metal coating 3, 12. This creates a flat screen material 1 which has a flat surface lying in plane 30.

[0070] In accordance with variant iii, the undercut 11 was also provided with a particularly thick filling 12. As already shown in Fig. As described in 3a, the filling 12 has an inner edge transition with a rounded section 12.1. In contrast to the embodiment according to Fig. However, in 3a the rounding has a particularly large radius.

[0071] The coating alternative iv can be used alternatively or in combination with the coating alternatives described above. In this case, a reinforced metal coating 3 is applied in the area of ​​a respective warp thread 5.1 or weft thread 5.2, so that the metal coating 3 has a particularly high layer thickness on one side, i.e., that the coating is applied eccentrically.

[0072] In Fig. Figure 4b shows a highly calendered, flat screen material 1. Before the fabric, consisting of warp threads 5.1 and weft threads 5.2, was coated with the metal coating 3, it was rolled and thus flattened. This created calendered surfaces 5.3, i.e., flattened surfaces. Since undercuts 11 also occur in the area of ​​the intersection points 10 in a calendered fabric after the metal coating 3, the previously described alternatives to electroplating can be used here as well. As shown, the undercuts 11 on the underside 29 of the flat screen material 1 were left in their original state, while on the top side 28 of the flat screen material 1, the undercuts 11 were each filled with a material 12.

[0073] Fig. Figure 5 shows a section through the planar sieve material 1 in the xy-plane, i.e., in the plane of the planar sieve material 1. As in the upper half of the Fig. As shown in Figure 5, the planar screen material 1 also has undercuts 11 in the area of ​​the intersection points 10 of warp threads 5.1 and weft threads 5.2. These undercuts 11 can be, as described above, and in the lower area of ​​the Fig. Figure 5 shows that the area can also be provided with fillings 12, i.e., targeted deposits. Here too, the fillings 12 can have an inner edge transition with a rounding 12.1, wherein the filling 12 can be bounded by two inflection points 22 and can have a radius 25.

[0074] In Fig.Figure 6 indicates a screen 4 with a flat screen material 1 in a cylindrical sleeve shape for rotary screen printing. The screen material 1 is held in its cylindrical shape by end pieces that are not specified. Inside the screen 4 is a squeegee (not visible here) to press ink through the screen material. The squeegee can be oriented parallel to the axis of rotation of the screen 4. The rotation U of the screen 4 during printing is indicated by a double arrow. Reference symbol list 1. Flat sieve material 2. Polymer coating 3. Metal coating (e.g. nickel) 4 sieves in cylindrical tube shape 5 strand 5.1 Warp thread 5.2 Weft thread 5.3 calendered area 6 Opening 10 Intersection point 11 Undercut 12 Replenishment (targeted separation) 12.1 Inner edge transition with rounding 20 neutral fiber through wire longitudinal section 21 division 22 Turning Point 23 Distance between turning points 24 Filling Strength 25 radius 26 radius warp thread 27 Radius weft thread 28 Top 29 Underside Level 30 i, ii, iii, iv Alternative electroplating x, y, z axes of a coordinate system a, b, c Layer thicknesses of the metal coating U Rotation of the sieve

Claims

[1] Screen (4) for rotary screen printing made of a planar screen material (1) for use in screen printing, in particular in rotary screen printing, with strands (5, 5.1, 5.2) forming a woven screen structure, arranged at angles to each other and intersecting at intersection points (10), wherein the strands (5, 5.1, 5.2) form undercuts (11) there, and wherein the strands form a screen structure with openings and the strands (5, 5.1, 5.2) consist at least on their surfaces of metal (3), in particular of nickel, which has been deposited on the strands (5, 5.1, 5.2) in an electroplating process, wherein the screen (4) has the shape of a cylindrical sleeve and the planar screen material (1) is in particular coated on one side with a polymer layer (2), e.g. with a photopolymer layer, characterized by, that in the area of ​​intersection points of the strands (5, 5.1, 5.2) their undercuts (11) have at least partially a filling (12) of the metal applied in the electroplating process. [2] Sieve (4) according to claim 1, characterized by , that each filling (12) forms an inside edge transition with rounding (12.1). [3] Sieve (4) according to any of the preceding claims, characterized by , that the filling (12) has a radius (25) of at least 1 µm or of 1 / 10 of the mean radius (26, 27) of the strands (5, 5.1, 5.2). [4] Sieve (4) according to any of the preceding claims, characterized by , that a curve along the surface of the sieve material (1) - viewed in a section plane (xz, yz) perpendicular to the sieve material (1) and through one of the strands (5, 5.1, 5.2) - describes a smooth curve. [5] Sieve (4) according to any of the preceding claims, characterized by, that a curve along the surface of the sieve material (1) - viewed in a section plane (xy) parallel to the sieve material (1) and through all strands (5, 5.1, 5.2) - describes a smooth curve. [6] Sieve (4) according to one of claims 4 or 5, characterized by , that the curve along the surface of the sieve material (1) between two intersection points (10) has two inflection points (22), wherein the inflection points (22) limit the filling (12). [7] Sieve (4) according to claim 6, characterized by , that the inflection points (22) have a distance (23) from each other of at least 1 µm and at most the division (21), but in particular a distance (23) of 10 to 20 µm. [8] Sieve (4) according to any of the preceding claims, characterized by , that the undercuts (11) on the top (28) and / or on the bottom (29) of the sieve material (1) and / or in the plane (xy) of the sieve material (1) each have a filling (12). [9] Sieve (4) according to claim 1, characterized by , that the filling (12) is parabolic and the filling (12) has an undercut (i). [10] Sieve (4) according to any of the preceding claims, characterized by , that the surfaces of the filling (12) on the top (28) and / or on the bottom (29) of the sieve material (1) are each almost in a plane (30) (ii), and / or that the sieve material (1) has a sieve structure (1) that has been thinned in a calendering process.

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