EP2879882B1 - Flat screen material and screen - Google Patents

Description

The invention relates to a sieve material with the preamble features of claim 1 and a sieve with the preamble features of claim 8.

State of the art

The industrial application of fabrics and fabrics is known from various fields.

When used in the field of filtration, the square mesh is the usual embodiment. For the printing application, this mesh has been adopted. With the available photo layers and the well-known application methods, a reasonable image resolution can only be achieved with a large number of "supports". Therefore, increasingly high mesh fabrics are being used.

When electronic printing as thin as possible sieves or fabrics are used with the thinnest possible wire to ensure a good flow of pastes and to allow the finest of fine images.

The solar cell coating requires a high paste application and a precise and fine image resolution. For example, for applying printed conductors as current fingers with the smallest possible coverage of the solar cells, in order to ensure a high efficiency of the solar cells.

The screens or fabrics used for electronic printing are very expensive and delicate to process, making them unsuitable for the production of screen printing plates for rotary screen printing. The lack of suitability is also due to the fact that the screen fabric in the rotary screen can be stretched in one direction only, namely the cylinder longitudinal axis, in flat screen printing, however, in two dimensions.

In rotary screen printing, the color is transported through the screen by the hydrodynamic pressure generated by the rotation of the screen and by the squeegee in front of the squeegee. By design, only open or semi-open squeegee systems can be used, so that the dynamic pressure is influenced by many factors such as viscosity, filling quantity and rotational speed. By increasing the speed of rotation or the amount of ink, the hydrodynamic pressure can be easily increased.

Such a rotary screen printing unit is for example in the WO 99/19146 A1 described.

As basic structures for screen materials, state-of-the-art stainless steel cloths are used. The ratio of sieve opening, contact area and fabric thickness has proven to be suitable. The thickness of the structure, ie the fabric thickness (initial dimension before calendering) corresponds approximately to twice the wire thickness. The basic structure is processed in a further step in a calendering process, also referred to as a calendering process, and thus brought to the desired raw fabric thickness. Also, a higher smoothness of the screen and thus a lower screen and blade wear is achieved. In the subsequent Vemickelungsvorgang the fabric for the purpose of a higher wear resistance is generally uniform, ie symmetrical to the axis of the fabric threads, reinforced and increases the support points in the region of the crossing points. However, methods are also known for selective deposition only in one direction, perpendicular to the surface of the tissue. Thus, according to the EP 0049022 A1 By adjusting the flow rate and the addition of chemical additives targeted metal deposition achieved.

A complete process for producing such screen materials is for example in EP 0 182 195 A2 described.

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

The state of the art for nickel plating is that preferably sulphamate nickel baths or chemical nickel processes (external powerless) are used. Of the The advantage of this method is a uniform geometric layer distribution in all spatial planes. The disadvantage of this method is that at the crossing point a so-called angle weakness, hereinafter also referred to as an undercut, arises. The undercut has the property that the flow behavior, for example in cleaning processes and of ink in the print, as well as the stability of the metallized fabric are adversely affected.

It is also known that multiple nickel layers are deposited as corrosion protection and / or for decorative purposes with Watt's nickel sulphate electrolytes. These methods can be applied in a wide range of applications for refining various components in different industries.

The Watt's nickel sulphate baths are mixed with a wide variety of, preferably organic, additives. The additives are subdivided into gloss additives (so-called glossy carrier) first (primary) and second (secondary) class. Primary glossy supports, which incidentally may also have properties of second-class luster carriers, are used to achieve homogeneous metal deposition with a specific base luster over as wide a current density range as possible. Secondary glosses have a large influence on the leveling and gloss level.

Furthermore, the first and second class gloss supports have, in combination, other effects on the deposited nickel layer: gloss, ductility, hardness, flattening behavior and electrochemical potential of the deposited layers with each other.

Mixtures of organic additives available on the market must meet a variety of technical requirements. These mixtures and nickel baths are mainly adapted to the metallization of general cargo in drum systems.

For the nickel-plating of tissue, these baths can only be used to a limited extent in Reel to Reel systems (roll-to-roll). A common feature of metallization is that the surface to be refined faces the anode during the metallization process (eg in drum systems by turning).

This, in combination with the addition of additives, allows a uniform layer distribution.

In a reel to reel system, this could theoretically be achieved by a tape guide between two anodes. Tissue, in particular micro-fabric, however, has the property of expanding extremely rapidly due to power supply and its low mass, which leads to wave formation and internal stresses. In addition, the mixtures listed above are tuned so that either an undercut remains in the crossing point or close the mesh openings too much.

In order to ensure the stability of the screening material, a close-meshed structure with many support points is chosen. These screen materials and screens known from the prior art have the following disadvantages:
In the crossing points of the fabric threads are angle weaknesses, ie undercuts. In other words, the stability of woven fabrics is limited by the notch effect in the region of the crossing points of the fabric threads.

Increased coating by the well-known galvanic coating process is not a solution, since the openings of the tissue grow in the process and when used by screen printing, clogging of the openings by color particles can occur. This will affect the print quality.

US 3,482,300 describes a screen for a screen printing machine which is electrolytically coated with metal for reinforcement.

US 4,285,274 describes a seamless screen printing cylinder and a manufacturing method therefor. The described screen-printing cylinder has a metal net substrate, in which the crossing points are provided with a galvanic coating.

task

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

This object is achieved by a sieve material with the features of claim 1 and by a sieve with the features of claim 8. These are particularly advantageous since They meet the specific requirements of rotary screen printing and have a greater stability compared to conventional screen materials and screens. The flat screen material according to the invention is used in screen printing, in particular in rotary screen printing. The screen material has strands arranged at an angle to one another and crossing at points of intersection, which form a woven screen structure, the invention being independent of the weave and the stitch form. At the points of intersection, the strands form undercuts, wherein undercuts mean the inner edges of adjacent surfaces of the intersecting strands, for example of warp threads and weft threads. These thus have an angular weakness, which is also referred to as inner edge weakness. The strands are arranged so that a screen structure is formed with openings. Throughout their surfaces, the strands have a coating of approximately constant thickness of metal, particularly nickel, which has been deposited on the strands in a plating process. According to the invention, the areal sieve material is designed in such a way that, in the region of crossing points of the strands, their undercuts, in addition to the coating, at least partially have a filling of the metal applied in a plating process. In other words, the undercuts were reduced or eliminated by the plating process by depositing additional metal in the area of the undercuts. This creates a surface without sharp edges and chamfers.

Such a flat screen material has the advantage that flow resistances and turbulences are reduced by the metallic fillings when using the screen material for the screen printing, which leads to a better flow behavior of the paint. Furthermore, no ink can dry in the undercut. It also further simplifies the cleaning process by permitting a direct flow of cleaning fluid, which contributes to a shorter cleaning time and a lower consumption of cleaning fluid. Another advantage is the increased stability of the flat screen material, since the notch effect of the undercuts is reduced by the metallic filling.

In a particularly advantageous and therefore preferred development of the screening material according to the invention, a respective filling forms an inner edge transition with a rounding. The metal filling is thus designed so that there are no sharp edges or chamfers in the area of the undercuts. It is particularly advantageous if the fillings have a radius of at least 1 μm or at least one tenth of the mean radius of the strands (mean value of radius warp thread and radius weft thread). This ensures that in screen-printing applications, the ink can easily flow through the screen material and there are no significant deposits in the area of the undercuts, and the screen material is easy to clean, with high stability.

In a first variant of the inventive planar sieve material according to the invention, a curve along the surface of the sieve material - viewed in a sectional plane perpendicular to the sieve material and viewed through one of the strands - describes a smooth curve. A smooth curve is understood to mean a smooth curve in the mathematical sense, i. a curve that is continuous and differentiable, ie a curve without corners or abrupt turns.

In a second variant of the inventive planar sieve material according to the invention, a curve along the surface of the sieve material - in a sectional plane parallel to the sieve material and viewed through all the strands - describes a smooth curve. A smooth curve is understood to be a smooth curve in the mathematical sense, ie a curve which is continuous and differentiable, ie a curve without corners or abrupt turns. For the first variant, the undercuts at the top and / or at the bottom of the screen material each have a metallic padding. For the second variant, however, the undercuts in the plane of the screen material each have a metallic filling. In an advantageous development of the invention, both embodiments of the invention are combined with each other, so that a particularly stable and flow-optimized planar sieve material is formed.

In an advantageous embodiment of the flat screen material with smooth curves between two crossing points, the curve along the surface of the screen material has two

Turning points on, with the turning points limit the replenishment. By a turning point is meant a turning point in the mathematical sense, i. a point on the surface curve in which a sign change of the second derivative takes place. The turning points may in particular have a distance from each other of at least 1 micron and a maximum of a distance corresponding to the pitch. By division, the distance between the center axes of two adjacent, mutually parallel strands is called. In particular, however, the inflection points are 10 to 20 microns apart. Fillings that fall into this area, on the one hand production technology well produced and meet the other hand, the expectations of higher stability and better flow properties of the sheet material.

In a non-inventive, alternative embodiment for filling with rounding a parabolic filling is provided, which in each case has an undercut itself. In the case of the parabolic filling, the sieve material in the region of a respective undercut is filled up to a particularly high degree and reinforced.

In a further alternative embodiment, the fillings are designed in such a way that the surfaces of the fillings on the surface and / or on the underside of the sieve material are in each case almost in one plane. In other words, the metal fill causes the strands to be completely embedded in the metallic padding.

In a further development of this or of the screen materials described above, the screen material has a screen structure with calendered surfaces that has been diluted in a calendering process. A calendering process, also referred to as a calendering process, is understood to mean a process which generally rolls and which causes a flattening of the sieve structure.

Such a calendering process is used for example in the DE 691 08 040 T2 described.

The flat screen material is formed by a tissue, for. B. by a plastic fabric or a metal wire mesh. The structure has the form of so-called meshes, e.g. B. of rectangular mesh or square mesh.

The strands are made of metal at their surfaces, with nickel being particularly advantageous and therefore preferred. The metal was deposited on the strands in a galvanization process.

To produce the sieve material according to the invention described above, a fabric structure with one or more, in particular nickel-containing, layers of only one electrolyte bath is preferably metallized, it being possible to purposefully add organic additives to the electrolyte bath to reinforce the crossing points. The formation of the nickel layer is further influenced by the tissue is moved past the non-anode side of the fabric on non-conductive bodies, ie insulators, which change the field and thus influence the nickel deposition. During the passage, the fabric structure rests on the insulator. Also, the anodes can be arranged so that they have a different distance to the tissue over their extent. Thus, the nickel layer distribution in the crossing points on the front and back of the fabric can be optimized. As anodes, depolarized pure nickel plates or nickel pellets can be used in baskets.

By means of such a method and the combination of overlying nickel plating process, specific dosage of brighteners first and second class and targeted flow through the electrolyte, the electric field current lines can be influenced so that specifically more nickel can be deposited on the anode-facing side of the fabric in the crossing points.

As a result, it can furthermore be achieved that a single strand of the fabric is nickel-plated eccentrically, with a stronger coating also taking place here on the side facing away from the anode.

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 a few micrometers.

If thicker layers over 2 microns must be deposited, so it is advantageous to Subdivide layer order into several process steps, but can be dispensed with different electrolyte baths.

Between the deposition of the individual nickel layers, the tissue can be cleaned between.

The invention also relates to a screen for rotary screen printing, which is made of a flat screen material, as described above, and wherein the screen has the shape of a cylindrical sleeve.

In an advantageous 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 is made possible by methods known to the person skilled in the art.

The described invention and the described advantageous developments of the invention are also in any combination with each other advantageous developments of the invention.

With regard to further advantages and constructive and functional aspects of advantageous embodiments of the invention, reference is made to the dependent claims and the description of embodiments with reference to the accompanying drawings.

embodiment

Fig.1

ein erfindungsgemäße Sieb

Fig. 2a

ein Siebmaterial vor Vernickelung

Fig. 2b

ein Siebmaterial nach Vernickelung

Fig. 3a

eine Schnittdarstellung mit einem Schnitt senkrecht zum Siebmaterial

Fig. 3b

eine Detaildarstellung der Fig. 3a

Fig. 3c

eine Detaildarstellung der Fig. 3a vor Auffüllung

Fig. 4a

Alternative Auffüllungen der Hinterschnitte

Fig. 4b

Auffüllungen der Hinterschnitte eines kalandrierten Gewebes

Fig. 5

eine Schnittdarstellung mit einem Schnitt in der Ebene des Siebmaterials

Fig. 6

ein Sieb für den Rotationssiebdruck

The invention will be explained in more detail with reference to an embodiment. It show in a schematic representation

Fig.1

a sieve according to the invention

Fig. 2a

a screen material before nickel plating

Fig. 2b

a screen material after nickel plating

Fig. 3a

a sectional view with a section perpendicular to the screen material

Fig. 3b

a detailed view of the Fig. 3a

Fig. 3c

a detailed view of the Fig. 3a before replenishment

Fig. 4a

Alternative fillings of the undercuts

Fig. 4b

Fillings of the undercuts of a calendered fabric

Fig. 5

a sectional view with a section in the plane of the screen material

Fig. 6

a screen for rotary screen printing

Corresponding elements and components are provided in the figures with the same reference numerals.

In the following, a method for producing the screen material 1 according to the invention and, by way of example, a required bath composition will be described by way of example. It is assumed that in the galvanization nickel 3 is to be applied to the fabric structure 5.

• Nickel 60 - 90 g/l
• Chlorid 12 - 45 g/l
• Borsäure 30 - 50 g/l
• Badtemperatur 45 - 70°C,
• pH Wert 3.5 bis 4.8,

The basis for the nickel plating may be a Watt nickel electrolytic bath to which preferably primary and secondary brighteners are added:

• Nickel 60 - 90 g / l
• Chloride 12-45 g / l
• Boric acid 30 - 50 g / l
• Bath temperature 45 - 70 ° C,
• pH value 3.5 to 4.8,

For deposition, brightener additives are preferably added, so-called secondary luster agents, e.g. Butynediol derivatives, quaternary pyridinium derivatives, propargyl alcohol, propynol propoxylates, especially butynediol, and primary brighteners, e.g. Benzenesulfonic acids, alkylsulfonic acids, Alylsulfonsäuren, sulfonimides, sulfonamides or Benzoesäuresulfimid.

Secondary brighteners are used in this application for the defined reinforcement of the crossing points 10, these being added depending on the desired reinforcement in a content of 0 to 0.15 g / l, primary brightener between 0 and 8 g / l.

The fabric structure 5, which is pretreated as usual in electroplating, is nickel-plated with the bath described above.

The fabric 5 is transported in the nickel bath via an electrical non-conductive support surface.

The electrically non-conductive support surface can be provided transversely to the transport direction of the fabric 5 with segments which are also filled with electrolyte during operation and ensure a permanent exchange of electrolyte.

On the surface lying on the nickel deposition 3 is hindered by non-existent electrolyte.

By appropriate addition of secondary gloss support, the metal deposit 3 additionally concentrates specifically into the points of intersection 10.

In the segmented zone, deposition also takes place on the back of the fabric. By a clever distribution of the segments to the resting surface, combined with the corresponding amount of secondary gloss carrier, the nickel deposition 3 can be distributed over the crossing points or the entire back.

Due to an ideal electrolyte flow between the anode and the tissue structure as the cathode, the deposition rate on the tissue is reduced on the anode side. It has been shown in this arrangement that an increased deposition can take place on the side facing away from the anode.

An ideal anode distance is between 1 cm and 40 cm to the cathode. This distance is advantageous in that the tissue 5 can still be flowed through sufficiently strongly with fresh electrolyte, but the electrical voltage losses due to the increased anode distance remain at a tolerable level.

The nickel plating can basically take place in a single nickel cell. However, it is also conceivable to arrange several nickel cells one behind the other.

Fig. 1 shows an inventive sheet-like screen material 1, which is provided on one side with a photo-polymer coating 2 (direct template). In a not shown Alternatively, an already imaged film can be applied to the screen structure 1 (indirect template). The nickel-plated planar screen material 1 is constructed from a fabric.

In Fig. 2a is a sheet-like material 1 shown, which is formed from interwoven strands 5. The strands 5 are arranged at right angles to each other and at a distance, so that openings 6 are formed in the flat screen material 1. The region in which the strands 5 arranged at right angles to one another meet or push against one another is referred to as the intersection point 10. By a metal coating 3, z. As nickel, which is applied in a galvanic process on the strands 5, the strands 5 are connected to each other in the crossing points 10. Since the metal coating 3 is applied substantially evenly to the surface of the strands 5, so-called undercuts 11 occur where the surfaces of the strands 5 meet. In other words, the adjoining surfaces of the strands 5, for example of warp thread 5.1 and weft thread 5.2, form inside edges in their lines of contact. This has an inner edge weakness, also referred to as an angle weakness, the result, which has a negative effect on stability, flow properties and cleanability of the flat screen material 1.

In Fig. 2a is given a Cartesian coordinate system xyz, wherein the flat screen material 1 is in the xy plane. The z-axis is oriented orthogonal to this plane.

Fig. 2b shows the flat screen material 1 from Fig. 2a , In this case, the undercuts 11 were provided in the intersection points 10 according to the invention by selective deposition each with a padding 12. The targeted deposition can be carried out in particular in the context of the galvanic production of the metal coating 3. By filling 12 of the undercuts 11, the properties of the flat screen material 1 in particular with regard to stability, color flow and cleaning ability are substantially improved.

In Fig. 3a is a section through the flat screen material 1 in the xz plane or in the yz plane shown: the warp threads 5.1 and weft threads 5.2 are each provided with a metal coating 3. As in Fig. 3c indicated, the layer thickness of the metal coating a, b, c on the upper surface (top 28) and the lower surface (bottom 29) of warp yarns 5.1 and weft yarns 5.2 may be uniform or different. By different layer thicknesses a, b, c of the metal coating 3, the properties of the flat screen material 1 can be influenced. Also, the diameters 26, 27 of warp yarns 5.1 and weft yarns 5.2 can be either of the same size or of different sizes. Here too, influence can be exerted on the weave structure and thus on the properties of the flat sieve material 1. As further geometric variables, in 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). In the points of intersection 10, the undercuts 11, which were in Fig. 3c can still be seen, according to Fig. 3a provided by selective deposition with a padding 12. This results in an inner edge transition with rounding 12.1, wherein the rounding has a radius 25. Inner edges, chamfers, cuts or undercuts were thus eliminated and the surface has a smooth transition between the strands 5 on.

In the detailed representation of Fig. 3b the fillings 12 of the undercuts 11 can be seen more clearly: in the embodiment according to FIG Fig. 3b the curve along the surface of the screen material 1, so two turning points 22 can be seen in the region of a respective filling 12, which are turning points in the mathematical understanding. Stated another way: between the turning points 22 there is a filling 12 of the undercut 11, outside the turning points 22, however, the warp thread is 5.1 or the weft 5.2 with the usual metal coating 3 of layer thickness a, b, c provided. The filling 12 produced by targeted deposition has - approximately in the middle between the two turning points 22 - the largest filling strength 24, which is measured between the surface of the filling 12 and the theoretical vertex of the undercut 11.

In Fig. 4a are shown alternative galvanic coatings i, ii, iii, iv. According to the alternative i, the padding 12 is parabolic (not according to the invention). Thus, the Auffüllstärke the padding 12 in the region of the original undercut 11 is particularly large. However, the padding 12 is designed such that through the filling further has an undercut, which is formed by the filling of an inner edge.

According to the alternative ii, a particularly strong galvanic coating was applied to fill 12 of the undercut 11. The padding 12 is so extensive that the surface of the padding 12 lies in a plane 30 and the warp threads 5.1 and the weft threads 5.2 completely into the metal coating. 3 , 12 are embedded. As a result, a flat screen material 1 is created, which has a flat surface which lies in the plane 30.

Also, according to the variant iii, the undercut 11 was provided with a particularly strong padding 12. As already on the basis of Fig. 3a described, the padding 12 has an inner edge transition with rounding 12.1. In contrast to the embodiment according to Fig. 3a However, the rounding has a particularly large radius.

The coating alternative iv can be used alternatively or in combination with the previously described coating alternatives. In this case, in the region of a respective warp thread 5.1 or weft thread 5.2, a reinforced metal coating 3 takes place, so that the metal coating 3 has a particularly high layer thickness on one side, that is, the coating is applied eccentrically.

In Fig. 4b is a heavily calendered sheet sieve material 1 shown. Before the fabric of warp yarns 5.1 and weft yarns 5.2 with the metal coating 3, the fabric was rolled and thus flattened. This calendered surfaces 5.3, ie flattened areas were created. Since even with a calendered fabric after the metal coating 3 undercuts 11 result in the region of the crossing points 10, For example, the previously described alternatives to electroplating can be used equally here. As shown, the undercuts 11 were leave on the bottom 29 of the sheet material 1 in its original state, while at the top 28 of the flat screen material 1, the undercuts 11 were each provided with a padding 12.

Fig. 5 shows a section through the flat screen material 1 in the xy plane, ie in the plane of the flat screen material 1. As in the upper half of Fig. 5 represented, the flat screen material 1 in the region of the intersections 10 of warp yarns 5.1 and weft yarns 5.2 also undercuts 11. These undercuts 11, as described above, and in the lower part of the Fig. 5 represented, also with fillings 12, ie targeted deposits are provided. Again, the fillings 12 may have an inner edge transition with rounding 12.1, wherein the padding 12 may be limited by two turning points 22 and may have a radius 25.

In Fig. 6 is a sieve 4 indicated with a flat screen material 1 in a cylindrical sleeve shape for rotary screen printing. The screen material 1 is held by unspecified tails in its cylindrical shape. Inside the screen 4 is a - not visible here - squeegee to squeeze paint through the screen material. The orientation of the doctor blade may be 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.

LIST OF REFERENCE NUMBERS

1

Flat screen material

2

polymer coating

3

Metal coating (e.g., nickel)

4

Sieve in cylindrical sleeve shape

5

strand

5.1

warp

5.2

weft

5.3

calendered area

6

opening

10

intersection

11

undercut

12

Replenishment (targeted separation)

12.1

Inner edge transition with rounding

20

neutral fiber by wire-cutting

21

division

22

turning point

23

Distance turning points

24

Auffüllstärke

25

radius

26

Radius warp thread

27

Radius weft

28

top

29

bottom

30

level

i, ii, iii, iv

Alternative galvanic coatings

x, y, z

Axes of a coordinate system

ABC

Layer thickness of the metal coating

U

Rotation of the sieve

Claims (8)

1. Flat screen material (1) for use in screen printing, in particular in rotary screen printing, including threads (5, 5.1, 5.2) forming a woven screen structure, arranged at angles relative to one another, and intersecting at intersections (10) where said threads (5, 5.1, 5.2) form undercuts (11), said threads forming a screen structure with openings and the surfaces of said threads (5, 5.1, 5.2) having a coating of approximately constant thickness and made of a metal (3), in particular nickel, that has been deposited on the threads (5, 5.1, 5.2) in an electroplating process,
   wherein in the region of intersections of the threads (5, 5.1, 5.2), in addition to the coating, the undercuts (11) at least partly have a filling (12) made of the metal and applied in the electroplating process, and
   wherein the respective filling (12) does not have any sharp edges and ridges on its surface,
   characterized in
   that - as viewed in a section plane (xz, xy) perpendicular to the screen material (1) and through one of the threads (5, 5.1, 5.2) - a curve along the surface of the screen material (1) describes a smooth curve and/or that - as viewed in a section plane (xy) parallel with the screen material (1) and through all threads (5, 5.1, 5.2) - a curve along the surface of the screen material (1) describes a smooth curve.
2. Flat screen material according to claim 1,
   characterized in
   that a respective filling (12) forms an inner edge transition with a rounding (12.1).
3. Flat screen material according to any one of the preceding claims,
   characterized in
   that the filling (12) has a radius (25) of at least 1 µm or of 1/10 of the average radius (26, 27) of the threads (5, 5.1, 5.2).
4. Flat screen material according to any one of the preceding claims,
   characterized in
   that between two intersections (10), the curve along the surface of the screen material (1) has two (22) inflection points, said inflection points (22) limiting the filling (12).
5. Flat screen material according to claim 4,
   characterized in
   that the inflection points (22) are spaced apart from one another by a distance (23) of 1 µm at the minimum and of the pitch (21) at the maximum, preferably of 10 to 20 µm.
6. Flat screen material according to any one of the preceding claims,
   characterized in
   that the undercuts (11) have a respective filling (12) at the top side (28) and/or at the bottom side (29) of the screen material (1) and/or in the plane (xy) of the screen material (1).
7. Flat screen material according to any one of the preceding claims,
   characterized in
   that the surfaces of the filling (12) at the top side (28) and/or at the bottom side (29) of the screen material (1) respectively are (ii) approximately in one plane (30) and/or that the screen material (1) has a screen structure (1) that has been thinned in a calendering process.
8. Screen (4) for rotary screen printing made of a flat screen material (1) according to at least one of claims 1 to 7, wherein the screen has the form of a cylindrical sleeve and wherein the flat screen material (1), in particular one side thereof, is coated with a polymer layer (2), e.g. a photopolymer layer.

Images