EP2886712B1 - Dewatering filter and method for producing the same - 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 WO 2008/071325 A1 For the production of multi-level watermarks, injection molding inserts for paper screens are disclosed. These inserts enable the production of particularly detailed and high-contrast watermarks. However, the transitions of the injection molding insert to paper screen in the finished watermark are clearly seen as an undesirable edge and thus disturb the actually desired optical impression.

According to prior art embodiments, the contours of the cut-out area and the watermark insert are parallel to each other with the contour of the cut-out area extending within the contour of the watermark insert. This means nothing else than that watermark insert and carrier wire always overlap in their edge regions with almost the same width. To ensure uniform dewatering in papermaking also in the area of the watermark insert, it is perforated. The perforation must also be sufficiently ensured in the overlapping area. Conventionally, the insert is perforated prior to introduction into the sieve, which, however, has the consequence that the gluing and welding in some perforations are closed again and also the sieve tissue perforation holes overlaps and thus makes impermeable. If the watermark insert is first injected and later perforated, this is not a problem outside of the overlap area. However, the laser radiation hits in the overlap area on a wire, no perforation can be done here and thus a dewatering in papermaking. This poorly perforated overlap area is later visible in the finished paper as a lighter, thicker and thus unwanted edge in the watermark.

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 have a stable bond between the watermark insert and the carrier screen, allow the production of paper with multi-level watermark high detail and at the same time reduce or avoid the unwanted edge formation.

This object is achieved by the dewatering screen having the features of the independent claims. A method for producing dewatering screens according to the invention, a method for producing a paper, a security paper and a value document with multistage watermarks 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 which is arranged in a cut-out region of the carrier screen and is connected to it only in its edge region, the contour of the watermark insert having the contour of the support screen overlaps at least partially and the overlap of watermark insert and cut-out area is different degrees.

A different degree of overlap means that the watermark insert and the carrier screen overlap with different widths in their edge regions.

The combination of watermark insert and carrier screen according to the invention permits the use of injection-molded multistage watermark inserts with extremely detailed relief representations with concurrent lamination of the hitherto undesired edges in the finished paper. At the same time, a stable bond between the watermark insert and the carrier screen is created, which allows a long and thus economical use of the screen in production.

The combination of watermark insert according to the invention with the carrier screen allows a significantly reduced overlap with the prior art while at the same time a solid bond between carrier screen and watermark insert. A lower overlap related to the area results in having to perforate a smaller area and thus achieving improved overall drainage in papermaking, particularly at the screen-watermark liner transition. Undesired edges in the paper are thus reduced or completely avoided.

In a preferred variant of the invention, the watermark insert is welded or glued to the carrier screen.

In an alternative, likewise advantageous variant of the invention, the watermark insert is injected directly into the carrier screen.

The contour of the cut-out area is linear, serrated, wavy, and / or step-shaped, preferably jagged.

The contour of the watermark insert is linear, serrated, wavy, and / or stepped, preferably linear.

The tines, undulations and / or steps preferably have a period of 0.01 mm to 5 mm, preferably 0.1 mm to 3 mm, particularly preferably 0.2 mm to 0.5 mm.

The tines, waves and / or steps preferably have an amplitude of 0.05 mm to 5 mm, preferably 0.1 mm to 3 mm, particularly preferably from 0.1 mm to 0.5 mm.

The contour of the cut-out region of the carrier screen preferably runs completely within the contour of the watermark insert, so that the carrier screen and watermark insert completely overlap in their edge regions.

Alternatively, the contour of the cut-out portion of the carrier wire is not partially within the contour of the watermark insert, so that the carrier screen and watermark insert partially overlap in their edge regions and partially the contour of the cut-out portion of the carrier screen is in shock or in abutment with the contour of the watermark insert or spaced therefrom.

The carrier screen and watermark insert overlap at the location of the least overlap, preferably less than 0.3 mm, particularly preferably less than 0.2 mm, very particularly preferably less than 0.1 mm.

The overlap of carrier wire and watermark insert is preferably at most up to 1 mm, particularly preferably at most 0.5 mm.

The period of the tines, waves and / or steps depends on the size and shape of the watermark insert and on the expected load on the finished carrier screen. The larger the watermark insert and the more irregular the shape of its outer border, the lower the period is chosen.

In order to further hide the transition from watermark insert to carrier screen in the finished paper or to include it in the motif design, the contours of the watermark insert and the carrier screen are preferably designed in the form of a motif or a pattern.

The usable materials that make up the watermark insert, as well as its perforations are in the WO 2008/071325 A1 are disclosed and incorporated in the disclosure of the present patent.

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. Within the meaning of the invention usable carrier screens are in the WO 2008/071325 A1 are disclosed and incorporated in the disclosure of the present patent. Preferably, the screen fabric contains a metal fabric, in particular a bronze fabric.

1. a) ein Trägersieb bereitgestellt wird, das einen ausgeschnittenen Bereich aufweist,
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 im ausgeschnittenen Bereich angeordnet und nur in seinem Randbereich mit diesem verbunden wird, insbesondere verschweißt oder verklebt, wird, dadurch gekennzeichnet, dass die Kontur des Wasserzeicheneinsatzes mit der Kontur des Trägersiebs zumindest teilweise überlappt und der Überlapp von Wasserzeicheneinsatz und ausgeschnittenem Bereich unterschiedlich stark ist.

The invention also includes a method for producing a multi-level watermark papermaking dewatering screen in which

1. a) providing a carrier screen which has a cut-out region,
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 arranged in the cut-out region and is connected, in particular welded or glued, only in its edge region, characterized in that the contour of the watermark insert overlaps at least partially with the contour of the carrier screen and the overlap of the watermark insert and the cut-out region differ strong.

1. a) ein Trägersieb bereitgestellt,
2. b) das Trägersieb im Bereich des Wasserzeichens ausgeschnitten,
3. c) ein Wasserzeicheneinsatz mit einem mehrstufigen Relief in Form des zu erzeugenden Wasserzeichens im Spritzgussverfahren in das Trägersieb so eingespritzt, dass die Kontur des Wasserzeicheneinsatzes mit der Kontur des Trägersiebs zumindest teilweise überlappt und der Überlapp von Wasserzeicheneinsatz und ausgeschnittenem Bereich unterschiedlich stark ist und
4. d) 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) cut out the carrier screen in the area of the watermark,
3. c) a watermark insert with a multi-level relief in the form of the watermark to be generated by injection molding in the carrier screen so injected that the contour of the watermark insert at least partially overlaps with the contour of the support screen and the overlap of watermark insert and cut-out area is different degrees and
4. d) perforated in the support screen integrated watermark insert.

When the watermark insert is injected into the carrier screen, the cut-out edge region of the screen fabric of the carrier screen is preferably squeezed and sealed in an injection molding tool, and the plastic is then injected into the sealed injection molding tool with the carrier screen.

Preferably, the hot runner technique is used as injection molding. The applicable injection molding technology is used in the WO 2008/071325 A1 and incorporated in the disclosure of the present application.

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 watermark inserts.

In particular, if the watermark is indeed very bright and rich in contrast, but the paper in the watermark area is very thin, it is advisable to use the security paper or the document of value in the area of the multi-level watermark with a transparent, preferably to provide 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 diffractive 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

das Trägersieb mit einem direkt eingespritzten Wasserzeicheneinsatz in Aufsicht,

Fig. 3

im Querschnitt: den mit dem Siebgewebe eines Trägersiebs verbundenen, perforierten Wasserzeicheneinsatz,

Fig. 4

einen Ausschnitt eines Siebgewebes mit Wasserzeicheneinsatz und Überlapp gleicher Breite gemäß Stand der Technik, und

Fig. 5a bis d

erfindungsgemäße Ausführungsform eines Siebgewebes mit Wasserzeicheneinsatz und unterschiedlich starkem Überlapp

Show it:

Fig. 1

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

Fig. 2

the support screen with a directly injected watermark insert in supervision,

Fig. 3

in cross-section: the perforated watermark insert connected to the mesh of a carrier screen,

Fig. 4

a section of a mesh with watermark insert and overlap the same width according to the prior art, and

Fig. 5a to d

Inventive embodiment of a mesh fabric with watermark insert and varying degrees of overlap

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 contains only suggested 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.

Fig. 2 shows a cut out in the watermark insert carrier screen with directly injected watermark insert in supervision. For direct injection into the carrier screen is a specially adapted injection mold, as in the WO 2008/071325 A1 described used, in which the mesh of the support wire 20 is squeezed and sealed for the injection process along a sealing edge. The liquid plastic can then not escape laterally during injection molding. According to the invention, the screen is cut out and the sealing edge is arranged so that the contour of the watermark insert overlaps at least partially with the contour of the carrier screen, and the overlap of the watermark insert and the cut-out area is different.

In this way, after the injection molding step, the in Fig. 2 in supervision and in Fig. 3 Cross-section shown carrier beam 20 with integrated watermark insert 22nd

The overlap 23 according to the prior art is shown schematically in FIG Fig. 4 shown. An inventive embodiment with varying degrees of overlap is in the Fig. 5a to 5c shown schematically.

In a further method step, the integrated watermark insert 22 is provided with dehydration perforations 40 by means of a laser beam, as described above.

Fig. 3 shows in cross-section the cut-out carrier screen 20 with injected watermark insert 22, which is already provided with perforations 40. The watermark insert and the carrier screen overlap (overlap 23).

Fig. 4 shows in plan view a section of a support screen with watermark insert according to the prior art. The (only partially shown) carrier screen 20 is cut out in a circle. The watermark insert 22 has been injected into this cut-out and has a circular contour, so that the circular cut-out region of the carrier screen and the watermark insert are arranged concentrically. In area 23 (overlap) overlap wire and watermark insert with substantially constant width D.

In the Fig. 5a to Fig. 5d an embodiment of a mesh according to the invention with watermark insert and varying degrees of overlap is shown.

Fig. 5a shows a plan view of a section of a support wire 20 with a cut-out area 24 in star shape. The contour of the cut-out area is jagged. The spikes are arranged here regularly. Of course, irregular arrangements are possible, both in terms of period and amplitude.

Fig. 5b shows in plan view a watermark insert 22 in a circular shape. The contour of the watermark insert is linear. This watermark insert is arranged in the region of the cut-out region of the carrier screen and connected thereto. Preferably, the insert is injected directly into the cut-out area by means of injection molding and then perforated.

Fig. 5c shows a section of the support according to the invention, the by the combination of the support wire 20 from Fig. 5a with the watermark insert 22 off Fig. 5b originated. The watermark insert completely overlaps the carrier screen in the edge regions, wherein the overlap 23 does not have a constant width but is of different strength.

Fig. 5d shows an enlargement of the screen 20 Fig. 5c with the focus on the region of the overlap 23. The jagged contour of the cut-out region 24 results in an overlap 23 of watermark insert 22 and cut-out region, which has different strengths. The maximum overlap has a width d2, the minimum overlap a width d1.

LIST OF REFERENCE NUMBERS

10

bill

12

watermark

20

support screen

22

Watermark use

23

overlap

24

Cut out area with jagged contour

40

perforations

Claims (13)

1. A dewatering screen for manufacturing paper having multi-level watermarks, with a carrier screen which has in a partial region a multi-level relief in the form of the watermark to be produced, the multi-level relief is formed by an injection-molded, perforated watermark insert which is disposed in a cut-out region of the carrier screen and is connected to this only in its edge area, wherein the contour of the watermark insert overlaps at least partly with the contour of the carrier screen, characterized in that watermark insert and cut-out region overlap to different extents.
2. The dewatering screen according to claim 1, characterized in that the contour of the cut-out region of the carrier screen extends completely within the contour of the watermark insert, so that carrier screen and watermark insert completely overlap in their edge areas.
3. The dewatering screen according to claim 1 or 2, characterized in that the contour of the cut-out region is line-shaped, toothed, wavy, and/or stepped, preferably toothed.
4. The dewatering screen according to at least one of claims 1 to 3, characterized in that the contour of the watermark insert is line-shaped, toothed, wavy, and/or stepped, preferably line-shaped.
5. The dewatering screen according to claim 3 or 4, characterized in that the teeth, waves and/or steps have a period of 0.01 mm to 5 mm, preferably 0.1 mm to 3 mm, particularly preferably from 0.2 mm to 0.5 mm.
6. The dewatering screen according to at least one of claims 1, 3 to 5, characterized in that the contour of the cut-out region of the carrier screen partly does not extend within the contour of the watermark insert, so that carrier screen and watermark insert partly overlap in their edge areas and the contour of the cut-out region of the carrier screen partly extends edge to edge with the contour of the watermark insert or is spaced apart therefrom.
7. The dewatering screen according to at least one of claims 1 to 6, characterized in that at the position of the smallest overlap carrier screen and watermark insert overlap less than 0.3 mm, preferably less than 0.2 mm, particularly preferably less than 0.1 mm.
8. The dewatering screen according to at least one of claims 1 to 7, characterized in that the watermark insert is welded or bonded to the carrier screen.
9. The dewatering screen according to at least one of claims 1 to 7, characterized in that the watermark insert is injected directly into the carrier screen.
10. The dewatering screen according to at least one of claims 1 to 9, characterized in that the screen fabric includes a metal fabric, in particular a bronze fabric.
11. A method for manufacturing a dewatering screen for papermaking with multi-level watermark, in which

    a) a carrier screen is provided, which has a cut-out region,

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

    c) the watermark insert is disposed in the cut-out region and only in its edge area is connected thereto, in particular welded or bonded, characterized in that the contour of the watermark insert overlaps at least partly with the contour of the carrier screen and watermark insert and cut-out region overlap to different extents.
12. A method for manufacturing a dewatering screen for papermaking with multi-level watermark, in which

    a) a carrier screen is provided,

    b) the carrier screen is cut out in the region of the watermark,

    c) a watermark insert with a multi-level relief in the form of the watermark to be produced is injected by injection-molding method into the carrier screen such that the contour of the watermark insert overlaps at least partly with the contour of the carrier screen and watermark insert and cut-out region of the carrier screen overlap to different extents and

    d) the watermark insert integrated in the carrier screen is perforated.
13. A method for manufacturing a paper, in particular a security paper, with a multi-level watermark, in which the paper deposit is effected on a dewatering screen of any of claims 1 to 10.

Images