EP2115217B1 - Dewatering screen and method for the production thereof - Google Patents

Description

The invention relates to a dewatering screen for the production of paper with multi-level watermark, with a carrier screen which has a multi-level relief in the form of the watermark to be generated in a partial area. The invention further relates to a method for producing such a dewatering screen and to a method for producing a paper having a multi-level watermark using such a dewatering screen.

In papermaking on round screening or screening machines, pulp accumulates continuously on a moving dewatering screen and is solidified to the extent that it can be removed as a wet paper web for further processing of the dewatering screen. Above all, security papers for banknotes, identity documents and the like are often equipped with watermarks for security purposes, which permit verification of the authenticity of the security paper and which at the same time serve as protection against unauthorized reproduction.

In the production of paper with watermarks, a distinction is made between two-level watermarks with a strong light-dark effect and multi-level watermarks with smooth transitions between light and dark and detailed representation of a motif. The term "multi-level" is to be understood in contrast to two-stage light-dark watermark and includes all watermarks with more than two brightness levels and includes in particular watermarks with continuous light-dark transitions.

To produce two-stage watermarks, metal wires or metal moldings, so-called electrotypes, are typically applied to the screen structure soldered to completely close the drainage screen at these locations. For the production of multi-level watermarks, a three-dimensional relief is embossed in the dewatering screen, so that the paper thickness of the finished paper varies according to the relief and, in transmitted light, reveals soft, gradual transitions between lighter and darker areas.

In the EP 1122 360 A1 a watermark paper is described, wherein the watermark is designed as a multi-tone watermark and has lighter areas, which are arranged like a raster image. In the US 6,911,115 B2 there is disclosed a security paper having a security zone, the security zone comprising cells whose thickness differs from the thickness of the paper around the cells.

Based on this, the present invention seeks to provide a Entwässerungssieb of the aforementioned type, which avoids the disadvantages of the prior art. In particular, the dewatering screen should enable the production of paper with multi-level watermarks with high level of detail and, if possible, can also be used on wire or oblique screen paper machines.

This object is achieved by the dewatering screen having the features of the independent claims. A method for producing inventive drainage screens, a watermark insert, an injection mold for the production of a watermark insert, a method for producing a paper, a security paper and a value document with multi-level watermark are specified in the independent claims. Further developments of the invention are the subject of the dependent claims.

According to a first aspect of the invention, in a dewatering screen of the type mentioned above, the multi-level relief is formed by an injection-molded, perforated watermark insert. The use according to the invention of the injection molding method allows the production of multi-level watermark inserts with extremely detailed relief representations.

In a preferred variant of the invention, the watermark insert is welded or glued to the carrier screen. For this purpose, the watermark insert may advantageously have a knobbed edge on which it is connected to the carrier screen. In an alternative, likewise advantageous variant of the invention, the watermark insert is injected directly into the carrier screen.

In both variants, the watermark insert can be arranged in a cut-out region of the carrier screen and connected to it only in an edge region. The watermark insert can then be lowered, in particular, so that the maximum height of the watermark insert essentially corresponds to the screen level.

The watermark insert is expediently formed from a hydrophobic plastic, for example from polyoxymethylene. To reduce wear during operation, the plastic may be added with wear-reducing additives. Preferably, the additives are glass fibers, glass beads or carbon fibers.

The carrier screen advantageously has a screen fabric with at least one system of interwoven, longitudinally running warp threads and weft threads extending transversely thereto. The screen fabric may include a metal fabric, in particular a bronze fabric, a metal-plastic mixed fabric, in particular a bronze-plastic blended fabric, or a pure plastic fabric.

In the latter two cases, the metal-plastic mixed fabric or the plastic fabric as plastic preferably polyester, a high temperature resistant thermoplastic material from the group of polyether ketones, in particular polyetheretherketone, or a other higher quality plastic. Polyethylene terephthalate (PET) is particularly preferred. The plastic of the watermark insert and the plastic of the mesh fabric are matched with advantage in terms of their melting or glass transition temperatures matched. Thus, in certain embodiments, the melting or glass transition temperature of the screen mesh plastic by more than 40 °, preferably more than 60 °, more preferably lie more than 80 ° above the melting or glass transition temperature of the watermark insert plastic. In other embodiments, it may again be advantageous that the melting or glass transition temperatures of the plastics used are substantially equal.

In order to conceal the transition from watermark insert to carrier screen in the finished paper or to include it in the motif design, the transition region between the watermark insert and the carrier screen is preferably designed in the form of a motif or a pattern. In particular, the edge of the watermark insert may be designed in the form of a motif or a pattern. Furthermore, the edge of the watermark insert may be shaped such that there is no hard edge in the transition region but a soft transition.

Preferably, the watermark insert has indentations on its rear side which make it possible to bend the watermark insert in at least one direction. The notches thus have a kind of hinge effect. This has the advantage that the flexibility of the insert can be adapted to the flexibility of the screen. Especially for round screens or screens in long or oblique screen paper machines, which are guided over rollers with narrower radii, increased flexibility in use watermark inserts.

Further, the watermark insert preferably has a plurality of perforations that ensure dewatering in papermaking. The dimensions of these drainage perforations are chosen so small that they do not adhere to fibers during papermaking. The perforations preferably taper towards the upper design surface of the watermark insert. The perforations can take any shape, such as dots, stars, lines, etc. The dimensions of the perforations can also be chosen so large that they are visually recognizable in the finished paper as dark marks, preferably marking points. In this case, it is advisable to arrange the perforations and thus the resulting markings in the form of characters, patterns or a coding.

Within a watermark insert different perforations may be present in different areas. From area to area, the perforations may differ in the density of the breadboard and / or hole size. By means of the differently perforated areas areas with different brightness can be generated in the watermark. For example, the watermark becomes darker, the tighter the breadboard is. A tighter hole pattern leads to better drainage and consequently to the attachment of more fibers. The watermark thus becomes darker.

The perforations are preferably produced by means of a laser beam, in particular by means of an infrared laser, such as a CO ₂ laser. Preferably, the watermark insert is thereby acted upon by its rear side facing away from the design surface with laser radiation, so that the design surface of the watermark insert tapered perforations arise. The plastic can also be added additives that the Lasering the perforation easier. For example, the additives can absorb the wavelength of the laser radiation particularly well.

1. a) ein Trägersieb bereitgestellt wird,
2. b) ein separater Wasserzeicheneinsatz mit einem mehrstufigen Relief in Form des zu erzeugenden Wasserzeichens im Spritzgussverfahren hergestellt und perforiert wird, und
3. c) der Wasserzeicheneinsatz mit dem Trägersieb verschweißt oder verklebt wird.

The invention also includes a process for producing a dewatering screen for papermaking, in which

1. a) a carrier screen is provided,
2. b) a separate watermark insert with a multi-level relief in the form of the watermark to be produced by injection molding and perforated, and
3. c) the watermark insert is welded or glued to the carrier screen.

1. a) ein Trägersieb bereitgestellt,
2. b) ein Wasserzeicheneinsatz mit einem mehrstufigen Relief in Form des zu erzeugenden Wasserzeichens im Spritzgussverfahren in das Trägersieb eingespritzt, und
3. c) der in dem Trägersieb integrierte Wasserzeicheneinsatz perforiert.

According to another inventive method for producing a dewatering screen for papermaking with multi-level watermark is

1. a) a carrier screen is provided,
2. b) a watermark insert with a multi-level relief in the form of the watermark to be generated by injection molding injected into the support, and
3. c) perforated in the support screen integrated watermark insert.

The screen mesh of the carrier screen is preferably squeezed into an injection mold and sealed, and the plastic is then in the sealed injection molding tool is injected with the carrier screen. Suitably, the screen fabric is clamped for the injection process in order to reduce the effects of different shrinkages during the cooling process. In this variant of the method, the carrier screen can also be perforated together with the watermark insert.

Preferably, the hot runner technique is used as injection molding.

The invention further includes a watermark insert for a dewatering screen of the type described, wherein the watermark insert is an injection molded, perforated plastic insert having a multi-level relief in the form of the watermark to be generated.

The invention also includes an injection mold for the production of a watermark insert for a dewatering screen of the type described, which has a multi-level relief in the form of the watermark to be generated.

In a second aspect of the invention, the invention includes a dewatering screen of the type mentioned, in which the multi-level relief is formed by a deep-drawn, perforated watermark insert. According to yet a further aspect of the invention, a dewatering screen of the type mentioned in the beginning has a multi-level relief, which is formed by a hot embossed, perforated watermark insert. The more detailed embodiments of watermark insert and carrier screen and the connection of the two elements can be carried out in these two aspects of the invention analogous to the above-described manner, taking into account the peculiarities of the respective manufacturing process accordingly.

In both additional aspects, a separate watermark insert with a multi-level relief in the form of the watermark to be produced by deep-drawing or hot embossing can first be produced and perforated, and the separately produced watermark insert then connected to the support, in particular welded or glued.

Alternatively, in both aspects, a plastic plate can first be inserted into the carrier screen, and a watermark insert having a multi-level relief in the form of the watermark to be produced can be produced from the plastic plate used in the deep-drawing method or in the hot stamping method. In a subsequent method step, the watermark insert integrated in the carrier screen is perforated, optionally together with the carrier screen. When using a deep-drawing process, an already pre-perforated plastic plate can also be used so that the subsequent perforating step can be dispensed with.

The described drainage screens may be round screens or wire screens or inclined screens.

The invention further includes a method for producing a paper, in particular a security paper, with a multi-level watermark, in which the paper attachment takes place on one of the above-described dewatering screens with injection-molded, deep-drawn or hot stamped watermark inserts.

Finally, the invention also includes a security paper produced by the process according to the invention or value document with multi-level watermark. Especially if the watermark is very bright and rich in contrast, the paper in the watermark area but is very thin, it is advisable to provide the security paper or the document of value in the area of the multi-level watermark with a transparent, preferably stabilizing film. By way of example, such a multi-level watermark can be arranged in the region of a covering film of a banknote with a through opening and stabilized by the covering film. In a further embodiment, the film may be provided with security elements, such as diffraction structures, liquid crystal layers, thin-film structures, fluorescent substances, magnetic, conductive and / or metallic layers.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem mehrstufigen Wasserzeichen hoher Detailschärfe,

Fig. 2

in (a) eine Spritzgussform für die Herstellung eines Wasserzeicheneinsatzes, und in (b) einen spritzgegossenen Wasserzeicheneinsatz in Aufsicht,

Fig. 3

im Querschnitt: in (a) den Wasserzeicheneinsatz der Fig. 2(b), in (b) den Wasserzeicheneinsatz mit laserstrahlgebohrten Perforationen und in (c) den mit dem Siebgewebe eines Trägersiebs verbundenen, perforierten Wasserzeicheneinsatz,

Fig. 4

in (a) ein Sicherheitspapier mit einem mehrstufigen Wasserzeichen und mit als dunkle Markierungspunkte sichtbaren Perforationen, wobei die dunklen Markierungspunkte in (b) und (c) als zusätzliches Sicherheitsmerkmal und/oder als Erkennungsmerkmal ausgestaltet sind,

Fig. 5

einen Querschnitt durch ein Entwässerungssieb, bei dem der Wasserzeicheneinsatz gegenüber dem Ausführungsbeispiel der Fig. 3(c) soweit abgesenkt ist, dass seine maximale Höhe dem Siebniveau entspricht,

Fig. 6

in (a) eine speziell angepasste Spritzgussform für die Direkteinspritzung eines Wasserzeicheneinsatzes in das Trägersieb, in (b) das Trägersieb mit einem direkt eingespritzten Wasserzeicheneinsatz in Aufsicht und in (c) Trägersieb und Einsatz im Querschnitt,

Fig. 7

einen Wasserzeicheneinsatz mit einem künstlerisch in Form eines Musters gestalteten Rand,

Fig. 8

in (a) bis (c) drei Zwischenschritte bei der Herstellung eines Wasserzeicheneinsatzes mittels Tiefziehen, und

Fig. 9

in (a) bis (c) drei Zwischenschritte bei der Herstellung eines Wasserzeicheneinsatzes mittels Heißprägen.

Show it:

Fig. 1

a schematic representation of a banknote with a multilevel watermark of high detail,

Fig. 2

in (a) an injection mold for the production of a watermark insert, and in (b) an injection-molded watermark insert in supervision,

Fig. 3

in cross-section: in (a) the watermark insert of Fig. 2 (b) , in (b) the watermark insert having laser drilled perforations, and (c) the perforated watermark insert connected to the screen fabric of a carrier screen,

Fig. 4

in (a) a security paper with a multi-level watermark and with perforations visible as dark marking dots, the dark marking dots in (b) and (c) being designed as an additional security feature and / or as a distinguishing feature,

Fig. 5

a cross section through a dewatering screen, wherein the watermark insert with respect to the embodiment of Fig. 3 (c) as far as it is lowered, that its maximum height corresponds to the sieve level,

Fig. 6

in (a) a specially adapted injection mold for the direct injection of a watermark insert into the carrier screen, in (b) the carrier screen with a directly injected watermark insert in top view and in (c) carrier screen and insert in cross section,

Fig. 7

a watermark insert with an artistically shaped border in the form of a pattern,

Fig. 8

in (a) to (c) three intermediate steps in the manufacture of a watermark insert by means of deep drawing, and

Fig. 9

in (a) to (c) three intermediate steps in the production of a watermark insert by means of hot stamping.

The invention will be explained below using the example of a banknote. Fig. 1 shows a schematic representation of a banknote 10, the multi-level watermark 12 high detail sharpness in the form of an in Fig. 1 just implied portraits. The production of banknotes with such detail-sharp, multi-level watermarks is carried out according to the invention using one of the following described drainage sieves with injection-molded watermark inserts.

In a first, with respect to the FIGS. 2 to 5 described variant variant first separate watermark inserts are produced by injection molding and perforated. The finished watermark inserts are then connected to the carrier screen, for example, welded or glued.

Fig. 2 (a) shows an injection mold 20 for producing a watermark insert 30, which has a multi-level relief 22 in inverted form of the watermark to be generated. An injection-molded, hydrophobic plastic, for example, polyoxymethylene added with wear-reducing additives, is melted, pressed at high pressure into the injection mold 20 and then cooled again. The resulting watermark insert 30, which is in Fig. 2 (b) in supervision and in Fig. 3 (a) is shown in cross-section, shows a very detailed impression 32 of the given by the injection mold 20 image motif 22nd

For the attachment of the watermark insert 30 on the carrier screen, an edge of nub-shaped recesses 24 is provided in the injection mold 20, which form a circumferential knob edge 36 with raised fastening nubs 34 in the finished watermark insert 30.

The injection molding process allows the production of extremely detailed relief images 32 in the watermark inserts 30. Although only the design surface 46 with a shape is always shown in the figures, can with an appropriate design of the injection mold 20, of course, the back have a shape, so that, for example, a watermark insert with constant material thickness is formed.

For further explanation is in the cross sections of Fig. 3 and the following figures, the detailed relief each represented only schematically by a curved line.

In order to ensure dewatering in papermaking, the injection molded watermark insert 30 is provided with a plurality of perforations 40 by laser radiation 42, as in FIG Fig. 3 (b) shown. The dimensions of the perforations are chosen so small that they do not adhere to fibers in paper production.

In specific embodiments, in areas with a high local material thickness, the perforation can be dispensed with, at least in part, so that in these areas, in principle, only little or no dehydration takes place, and only very few or no paper fibers are deposited. In these areas, a two-level watermark or a hole is thus generated. The non-perforated areas with high material thickness act in this case as electric types. With such an application, detailed watermarks can be combined with two-level watermarks.

The dewatering perforations are advantageously drilled with a laser beam 42, for example, with the beam of a CO ₂ laser of a wavelength of 10.6 microns. The focus diameter of the laser corresponds to the desired maximum perforation diameter and is for example 500 microns. The laser irradiation preferably takes place from the rear side 44 of the watermark insert 30, so that due to the Gaussian energy distribution or the beam shape of the laser beam to the front side surface 46 of the insert tapering perforations 40 arise, as in Fig. 3 (b) shown.

In the embodiment of Fig. 3 For example, the diameter of the perforations on the back side 44 of the watermark insert is approximately 500 μm, and its diameter on the design surface 46 depends on the local material thickness of the insert due to the tapering of the perforations. How out Fig. 3 (b) As can be seen, the perforation diameter at the design surface 46 in regions of large material thickness 50 is smaller than in regions of low material thickness 52. For example, the perforation diameters at the design surface 46 are between 150 .mu.m with high material thickness and 350 .mu.m with low material thickness.

The perforations 40 tapering towards the design surface 46 offer two advantages over straight-line perforations. First, they create a freewheel in the direction of flow 48 of the fiber suspension during papermaking and thus effectively prevent a permanent clogging of the drainage perforations 40.

On the other hand, the areas of large material thickness 50 serve to produce thin spots in the paper. Since the smaller perforation diameters in these regions inhibit drainage more than in the low gauge regions 52, thinning in the regions 50 is further assisted by the tapered perforations 40.

The spacing of the perforations 40 depends on the desired dewatering effect and is for example about 500 μm.

The perforation diameters may also be chosen to be large enough to be recognized as paper marks 60 in addition to the watermark 62 as dark marks 64, as shown in an exaggerated illustration in FIG Fig. 4 (a) shown. The hole diameter for producing dark marking points is preferably at least 300 μm.

These dark spots 64 can serve as an additional security feature and / or as a recognition feature for the manufacturing process used. The perforations 40 and thus the marking points 64 can also be arranged in a predetermined pattern. For example, the perforations, as in Fig. 4 (b) be shown in a portion 66 in a square grid, be arranged in another portion 68 in a hexagonal grid, wherein the portions 66, 68 form a motif, such as a parent pattern or an encoding. The perforations 40 and the resulting marking dots 64 may also themselves form a pattern 70 to increase anti-counterfeiting security, as exemplified in FIG Fig. 4 (c) shown.

Coming back to the explanation of the manufacturing process of Fig. 3 After the perforation, the watermark insert 30 is connected to the screen mesh 54 of a carrier screen. The screen fabric has at least one system each of interwoven, longitudinally extending warp threads 56 and weft threads 58 extending transversely thereto. In the context of the invention, the screen fabric may contain a metal fabric, in particular a bronze fabric, a metal-plastic mixed fabric, in particular a bronze-plastic mixed fabric, or even a pure plastic fabric. For example, the mesh can be a blended fabric composite from weft (Reference 58) 1: 1 bronze / polyester and chain (reference numeral 56) in bronze.

At the in Fig. 3 (c) In the exemplary embodiment shown, the screen mesh 54 is cut out in the area of the watermark and overlaps the watermark insert 30 only in the area of the knob edge 36. The connection of the watermark insert and screen mesh can be effected, for example, by ultrasonic welding, whereby the knobs 34 are firmly connected to the mesh screen 54 in the overlapping area.

In order to reduce the wear of the watermark insert 30 in papermaking, the watermark height d, which in the embodiment of FIGS Fig. 3 (c) about 1.0 mm. As in Fig. 5 shown, the watermark insert 30 can be lowered so far that its maximum height 38 just corresponds to the screen level. In addition to a reduced wear of the watermark inserts, this reduction leads to watermarks, which at a consistently high contrast to the design of the Fig. 3 (c) have a slightly darker visual appearance.

Instead of initially producing the watermark inserts separately and subsequently connecting them to the carrier screen, the inserts can also be injected directly into the carrier screen, as is now described with reference to FIGS Fig. 6 explained.

For direct injection into the carrier screen, a specially adapted, in Fig. 6 (a) schematically shown injection mold 80 used in which the screen fabric of the support wire 90 for the injection process along a sealing edge 82 is squeezed and sealed. The liquid plastic can then not escape laterally during injection molding.

In this way, after the injection molding step, the in Fig. 6 (b) in supervision and in Fig. 6 (c) Cross-section shown carrier beam 90 with integrated watermark insert 92. Again, the watermark insert 92 shows due to the injection molding technique used a very detailed impression of the predetermined by the injection mold 80 image motif.

In a further method step, the integrated watermark insert 92 is provided with dewatering perforations by means of a laser beam, as described above. If a bronze screen is used as the carrier screen 90, then the watermark insert 92 will only be permeable through the perforation at those points at which a perforation of the insert 92 coincides with an open position in the screen 90, since the bronze screen itself is not part of the CO ₂ laser is perforated. He understands that this limitation can be taken into account and thus balanced when choosing the number, size and spacing of the perforations. Since the injected plastic shrinks much more when cooled than the Bronzesiebmaterial, the support screen is advantageously clamped during injection molding to avoid any blistering in the support 90.

If a plastic-metal mixed fabric or a pure plastic sieve fabric is used instead of a bronze sieve, both the watermark insert 92 and the support sieve 90 can be perforated by laser application under suitable laser parameters. In this case, a material is selected for the plastic of the mesh fabric, which has a higher melting point than the injection molding material. For example, as an injection molding material polyoxymethylene having a melting or glass transition temperature of 166 ° C and as a sieve polyetheretherketone having a melting or glass transition temperature of 335 ° C are used. The use of a plastic sieve or a plastic-metal mixed fabric also improves the warpage behavior during cooling, since the moduli of elasticity of the plastics used are substantially closer to one another than the moduli of elasticity of injection-molding material and bronze.

Even with the watermark inserts injected directly into the carrier screen, certain areas - as in Fig. 3 described - be designed so that they act as electric types. In the directly injected watermark insert, an area with a particularly high material thickness is provided for this purpose, which is not perforated. With the direct injection method, electrotypes can also be generated as a separate element. Another design option that can be used in all screen variants is to cut out the carrier screen 90 in the watermark area in such a way that it projects into the watermark insert 92 only in a defined edge area. On the one hand, such a design reduces any possible wire distortion due to different cooling behavior of the insert and screen material, and on the other hand offers the advantage that the watermark insert 92 can be perforated in the watermark area by means of laser radiation, without having to consider the properties of the carrier screen.

In all the designs described, the transition region between the watermark insert and the carrier screen in the finished paper will generally be visible. It therefore makes sense to include this transitional area in the design of the watermark. For example, as in Fig. 7 shown at a separate or one integrated into the support wire watermark insert 100 of the edge 102 and thus the transition region of Watermark insert and carrier screen artistically designed in the form of a motif or a pattern.

According to further aspects of the invention, the watermark inserts can be produced by deep drawing (thermoforming) or by hot stamping instead of by injection molding, as described below with reference to FIGS FIGS. 8 and 9 briefly explained.

In the production of inventive watermark inserts 110 by deep drawing, first, as in FIG Fig. 8 (a) shown, a plastic plate 112 of a suitable plastic material placed on a thermoforming mold 114. The plastic plate 112 is then, as in Fig. 8 (b) shown heated, for example, with a radiant heater 116, and the heated plastic plate is sucked by a negative pressure 118 in the deep-drawing mold 114, as in Fig. 8 (c) shown.

In a further method step, the deep-drawn plastic sheet is perforated as described above and connected to a support wire. Alternatively, an already perforated plastic plate 112 may be used for the deep drawing step. In this case, the perforated plastic plate is covered during deep drawing with a flexible, air-impermeable material in order to produce a suitable negative pressure can.

Although currently the described procedure is preferred, it is basically possible to bring a plastic plate already connected to the carrier screen by deep drawing into the desired shape of the watermark.

Regarding Fig. 9 In the production of inventive watermark inserts 120 by means of hot stamping, a suitable plastic material 122 is displaced and pressed in an embossing tool 124, 126. It is first, as in Fig. 9 (a) shown, the plastic material 122 placed in a hot stamping die consisting of a male mold 124 and a die 126.

In the embodiment shown, only the die 126 has a stamp shape, but it will be understood that the male die 124 may also have a shape. In particular, a watermark insert 120 having a uniform material thickness can be produced in this way.

Coming back to the presentation of the Fig. 9 (b) For example, the plastic material 122 is heated and embossed by the embossing tool 124, 126. In this case, the embossing tool 124, 126 itself should be heated. FIG. 9 (c) shows the embossed watermark insert 120 after final molding.

In a further method step, the hot embossed plastic material, as described above, perforated and connected to a support wire. Even when hot stamping, it is fundamentally possible to bring a plastic material already connected to a carrier screen into the desired shape.

Claims (13)

1. A dewatering screen for manufacturing paper having multi-level watermarks, having a carrier mold that, in a fractional region, exhibits a multi-level relief in the form of the watermark to be produced, characterized in that the multi-level relief is formed by an injection-molded, perforated watermark insert.
2. The dewatering screen according to claim 1, characterized in that the watermark insert is injected directly into the carrier mold.
3. The dewatering screen according to at least one of claims 1 to 2, characterized in that the watermark insert is formed from a hydrophobic plastic, such as from polyoxymethylene.
4. The dewatering screen according to at least one of claims 1 to 3, characterized in that the carrier mold exhibits a wire cloth having, in each case, at least one system of interwoven warp threads running lengthwise and weft threads running crosswise thereto, and that the wire cloth includes a pure plastic cloth.
5. A method for manufacturing a dewatering screen for manufacturing paper having multi-level watermarks, in which

   a) a carrier mold is provided,

   b) a separate watermark insert having a multi-level relief in the form of the watermark to be produced is manufactured in the injection molding method and perforated, and

   c) the watermark insert is welded or bonded to the carrier mold.
6. The method according to claim 5, characterized in that the watermark insert is provided with a plurality of perforations whose dimensions are so small that no fibers stick in them at paper manufacture, and that the perforations are produced by means of laser beam, preferably by means of infrared laser.
7. A method for manufacturing a dewatering screen for manufacturing paper having multi-level watermarks, in which

   a) a carrier mold is provided,

   b) a watermark insert having a multi-level relief in the form of the watermark to be produced is injected into the carrier mold in the injection molding method, and

   c) the watermark insert integrated in the carrier mold is perforated.
8. The method according to claim 7, characterized in that the watermark insert is provided with a plurality of perforations whose dimensions are so small that no fibers stick in them at paper manufacture, and that the perforations are produced by means of laser beam, preferably by means of infrared laser.
9. A dewatering screen for manufacturing paper having multi-level watermarks, having a carrier mold that, in a fractional region, exhibits a multi-level relief in the form of the watermark to be produced, characterized in that the multi-level relief is formed by a deep-drawn, perforated watermark insert.
10. A dewatering screen for manufacturing paper having multi-level watermarks, having a carrier mold that, in a fractional region, exhibits a multi-level relief in the form of the watermark to be produced, characterized in that the multi-level relief is formed by a hot-stamped, perforated watermark insert.
11. A watermark insert for a dewatering screen according to one of claims 1 to 4 or for a dewatering screen manufacturable according to one of claims 5 to 8, characterized in that the watermark insert constitutes an injection-molded, perforated plastic insert having a multi-level relief in the form of the watermark to be produced.
12. An injection mold for manufacturing a watermark insert for a dewatering screen according to one of claims 1 to 4 or for a dewatering screen manufacturable according to one of claims 5 to 8, that exhibits a multi-level relief in the form of the watermark to be produced.
13. A method for manufacturing a paper, especially a security paper, having a multi-level watermark, in which the paper accretion occurs on a dewatering screen according to one of claims 1 to 4, 9 or 10 or on a dewatering screen manufacturable according to one of claims 5 to 8.

Images