EP3862191B1 - Drainage sieve for the production of security paper with a windowed security thread - Google Patents

Description

The invention relates to a drainage screen for the production of security paper with a window security thread.

Data carriers, such as banknotes, shares, bonds, certificates, vouchers, checks, high-quality admission tickets, but also other papers at risk of forgery, such as passports or other identification documents, are often provided with security elements for protection, which allow the authenticity of the value document to be checked and at the same time serve as protection against unauthorized reproduction. The security elements can be designed in the form of a security thread that is fully or partially embedded in the data carrier.

The incorporation of a security thread in banknote paper is, for example, in WO 2004/050991 A1 described. The security thread is unrolled from a driven roller during the paper manufacturing process and constant mechanical tension is ensured by monitoring the tensile force of the security thread. Window security threads are security threads that are neither applied to a surface of a data carrier substrate nor fully embedded in the substrate. Rather, they are partially embedded in the substrate in such a way that they are only visible in certain window areas on one or both opposite surfaces of the substrate.

In order to obtain data carriers with window security threads, bronze screen fabrics with brass embossing dies are usually molded into a form with several Webs brought to create contact surfaces for the security thread to be introduced during papermaking. From the designer's point of view, however, the possible designs are very limited and all known window thread variants have windows that are open over the entire width of the thread.

DE102013008082 shows a drainage screen for the production of security paper with a window security thread, in which the carrier screen is provided with an injection-molded insert that has a relief with motif elements that extend upwards from a base body and project beyond the surface of the carrier screen.

Proceeding from this, the object of the invention is to improve a drainage screen of the type mentioned above in such a way that the motif elements of the carrier screen correspond in their shape to the window areas in which the window security thread is visible.

This object is solved by the features of the independent claims. Developments of the invention are the subject matter of the dependent claims.

In a data carrier not according to the invention, it is provided that the window areas comprise microwindows produced by papermaking, which have an edge with characteristic irregularities produced during papermaking and whose width is transverse to the thread direction is less than 50% of the thread width and is between 0.2 mm and 4 mm.

In the context of the present description, the term window security thread is used not only for narrow security threads with a width of 4 mm or less, but also for wide security threads with a width of 4 mm to about 30 mm, which are sometimes also referred to as security tapes in the patent literature . The embedding of such broad security threads in papermaking is, for example, in the publication EP 0 625 431 A1 described.

In the context of the data carrier not according to the invention, all window areas of the data carrier can be designed in the form of microwindows or the data carrier can also have conventional window areas in addition to microwindows.

The length of the microwindows parallel to the longitudinal direction of the thread (sometimes also referred to as the height of the microwindows) is advantageously between 0.2 mm and 4 mm, preferably between 0.3 mm and 3 mm and particularly preferably between 0.5 mm and 1 mm. Alternatively or additionally, the width of the microwindows in the transverse direction of the thread is preferably between 0.3 mm and 3 mm, particularly preferably between 0.5 mm and 1 mm.

Provision can be made with particular advantage for the window regions to comprise a plurality of microwindows lying next to one another in the transverse direction of the thread. Advantageously, these microwindows are not exactly at the same height in the transverse direction of the thread, but rather are always offset from one another by a fraction of the window height. In other words, a straight line in the transverse direction of the thread intersects several of the microwindows mentioned, but at different points along the height extent of the microwindows.

The width of the microwindows can even be less than 40%, preferably less than 30%, of the width of the thread in the transverse direction of the thread.

The window areas of the data carrier not according to the invention preferably comprise microwindows whose outlines are patterns, characters or a code, in particular a sequence of letters or digits, such as a currency symbol or a value number. Particularly in the case of wide security threads, the microwindows can also be designed in the form of a face or portrait representation.

In advantageous configurations of the data carrier not according to the invention, the window areas include a plurality of microwindows, the spatial arrangement of which forms a motif. In this case, the individual microwindows are not necessarily designed in the form of a motif; the motif mentioned is rather formed by the arrangement of the entirety of the microwindows. Such a motif can in particular consist of letters, characters or figures which are composed of the micro-windows as small building blocks. The outlines of the microwindows can be the same or different. It is also possible that both the outlines of the microwindows and their spatial arrangement each represent a motif or information. These motifs or pieces of information can be related to one another or can be added together to form an overall piece of information. The micro-windows can also form rasterized, point-cloud-like or strip-shaped windows.

In a further development of the data carrier not according to the invention, the microwindows, as thin areas in the paper layer of the substrate, are part of a watermark projecting laterally beyond the window security thread. In this way, the micro-windows can be integrated into an overall design of the data carrier, so that the attention value and the security against imitation are further increased. In particular, the watermark can supplement, continue or repeat in the same or modified form a motif formed by the outline or the spatial arrangement of the microwindows.

According to another development of the data carrier, which is not according to the invention, is a motif formed by the outline or the arrangement of the microwindows continued through any other security feature beyond the window security thread. The other security feature can consist, for example, of a printed layer, a colored layer, a laser-cut area, a watermark, a film or a hologram. In such an embodiment, too, the other security feature can supplement, continue or repeat in the same or modified form a motif formed by the outline or the arrangement of the microwindows.

The window security thread can be provided with diffraction structures, liquid crystal layers, thin layer structures, gaps in opaque, in particular metallic, layers, fluorescent substances, magnetic, conductive and/or metallic layers.

The invention includes a drainage wire for the manufacture of security paper having a window security thread which emerges at certain window areas on a surface of the security paper and is embedded in intermediate areas in the interior of the security paper. The dewatering sieve comprises a carrier sieve which is provided in a partial area with an injection molded insert which has a relief with motif elements which extend upwards from a base body and project beyond the surface of the carrier sieve and which are designed in the form of the window areas of the window security thread. To create microwindows, the motif elements include micromotif elements which have a width transverse to the running direction of the thread to be embedded that is less than 50% of the thread width and is between 0.2 mm and 4 mm, and whose outlines are patterns, characters or a code, in particular represent a sequence of letters or numbers, and/or whose spatial arrangement forms a motif, in particular letters, characters or figures.

The invention further includes a dewatering screen of the type mentioned above, in which the dewatering screen comprises a carrier screen which, in a partial area has a screen embossing, which has a relief with motif elements projecting beyond the surface of the carrier screen, which are designed in the form of the window areas of the window security thread. To create microwindows, the motif elements include micromotif elements which have a width transverse to the running direction of the thread to be embedded that is less than 50% of the thread width and is between 0.2 mm and 4 mm, and whose outlines are patterns, characters or a code, in particular represent a sequence of letters or numbers, and/or their spatial arrangement forms a motif, in particular letters, characters or figures.

In advantageous variants of the invention, the injection molding insert or the screen embossing comprises a plurality of micromotif elements lying next to one another transversely to the direction of travel of the thread for the production of a plurality of microwindows lying next to one another in the transverse direction of the thread.

In both configurations of the drainage screen, the motif elements comprise micro-motif elements whose outlines represent patterns, characters or a code, in particular a sequence of letters or numbers. Alternatively or additionally, the motif elements include a plurality of micro-motif elements whose spatial arrangement forms a motif, in particular letters, characters or figures.

In an advantageous development of the invention, the injection molding insert or the screen embossing has a watermark relief in the form of a watermark to be produced in the security paper in addition to the motif elements for producing the window areas of the window security thread. In particular, the watermark relief can supplement, continue or repeat in the same or modified form a motif formed by the outline or the arrangement of the micromotif elements.

In the case of drainage screens with an injection-molded insert, this is expediently made of a hydrophobic plastic, for example polyoxymethylene. Wear-reducing additives can be added to the plastic to reduce wear during operation.

The injection-molded insert is preferably arranged in a cut-out area of the carrier screen and connected to it only in a preferably jagged edge area. For this purpose, for example, using a laser cutting device, a recess can be produced at the point of the screen fabric where the injection molded insert is provided, which is slightly smaller, for example 1/10 mm smaller than the desired shape of the injection molded insert. The edge area can in particular be designed in the form of a pattern, preferably in a jagged form. The injection-molded insert can be inserted or preferably injected into this cut-out partial area.

The carrier screen advantageously contains a screen fabric with at least one system of interwoven warp threads running in the longitudinal direction and weft threads running transversely thereto, the screen fabric advantageously being either a metal fabric, in particular a bronze fabric, a metal-plastic mixed fabric, in particular a bronze-plastic -Mixed fabric, or contains a pure synthetic fabric.

Furthermore, the injection molding insert preferably has a plurality of perforations that ensure drainage during papermaking. The dimensions of these dewatering perforations are chosen so small that no fibers stick to them during papermaking. Typical perforation diameters are between 100 μm and a few 100 μm, for example around 500 μm. Rejuvenate in advantageous configurations the perforations point towards the top design surface of the injection molded insert or the perforations are tapered.

To produce an injection molding insert with an injection molding relief of the type described above, an injection molding tool can be used which contains an injection molding cavity into which plastic can be injected to produce the injection molding insert and which is provided with a multi-stage tool relief in the form of the inverted injection molding relief. The injection molding tool including the injection molding cavity and the high-resolution, multi-stage tool relief can be formed by milling or by an additive manufacturing process as a layer sequence of a plurality of material layers that are firmly connected to one another.

To produce a screen embossing of the type described above, an embossing block can be used which is provided with a high-resolution, multi-stage relief in the form of the inverted screen embossing. The embossing block, including the high-resolution, multi-level relief, can be formed by milling or by an additive manufacturing process as a layer sequence of a plurality of material layers that are firmly connected to one another.

In particular, selective laser sintering, selective laser melting, electron beam melting, 3D printing with powder, melt coating, laser deposition welding, multi-jet modeling, a PolyJet process, stereolithography, laminated object modeling, film transfer imaging or digital light processing come into consideration as additive manufacturing processes.

Further details on the structure, properties and production of the injection molding tool or the embossing block can be found in the application DE 10 2014 008 752.2 be taken, the disclosure content of which is included in the present application.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, which are not shown to scale and proportions in order to improve clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem Sicherheitselement in Form eines Fenstersicherheitsfadens,

Fig. 2 und 3

jeweils eine Detaildarstellung von Fensterbereichen mit Mikrofenstern einer Banknote in Aufsicht,

Fig. 4 und 5

jeweils eine schematische Darstellung eines erfindungsgemäßen Entwässerungssiebs, das zur Erzeugung von Mikrofenstern eingesetzt wird,

Fig. 6

Aufsichten auf eine Banknote mit einer Mehrzahl von Mikrofenstern, die in Ensembles von Mikrofenstern in Form eines Eurosymbols angeordnet sind, wobei (a) ein einzelnes Ensemble von Mikrofenstern und (b) mehrere, in Fadenlängsrichtung beabstandet und in Fadenquerrichtung gegeneinander versetzt angeordnete Ensembles von Mikrofenstern zeigt, und

Fig. 7

eine Gestaltung, bei der das Design einer Reihe papiermacherisch hergestellter Mikrofenster außerhalb des Sicherheitsfadens von einem Druckmuster fortgesetzt wird.

Show it:

1

a schematic representation of a banknote with a security element in the form of a window security thread,

Figures 2 and 3

each a detailed representation of window areas with microwindows of a bank note in supervision,

Figures 4 and 5

each a schematic representation of a dewatering screen according to the invention, which is used to produce microwindows,

6

Top views of a banknote with a plurality of microwindows arranged in ensembles of microwindows in the shape of a euro symbol, showing (a) a single ensemble of microwindows and (b) multiple ensembles of microwindows spaced apart in the longitudinal direction and staggered in the transverse direction , and

7

a design in which the design of a series of paper-made microwindows outside the security thread is continued by a printed pattern.

Examples of window security threads for banknotes and other documents of value will now be discussed. 1 shows a schematic representation of a banknote 10 with a paper substrate 12, which is provided with a window security thread 14. The window security thread 14 emerges in window areas 16 on the surface of the banknote 10 while being embedded in the interior of the banknote 10 in the land areas 18 lying between them.

In the representation of 1 all window areas 16 of the window security thread 14 are shown schematically as rectangles. As in the detail of the 2 shown, the window areas 16 comprise microwindows 20 produced by papermaking, which in the exemplary embodiment are in the form of digits "1" and "5" lying next to one another in the transverse direction of the thread, which together form the sequence of digits "15". When viewed from above, the microwindows 20 reveal the window security thread 14 embedded in the paper, so that the security features arranged on the window security thread 14, for example a diffraction structure or a color-shifting layer, become visible there. In the web areas 18 between the window areas 16, the window security thread 14 is covered by the paper layer 12 and the security features arranged thereon are therefore not visible.

Since the microwindows 20, as described below, were produced during the manufacture of paper, they have an edge 22 with characteristic irregularities, which in this description is also often referred to as a deckle edge will. The irregular edge structure is created by an irregular accumulation of fibers in the edge area and by individual fibers protruding into the hole.

The width b _M of the microwindow 20 is significantly smaller than the thread width b _F , which is 4 mm, for example, and in the exemplary embodiment is only about 1 mm (25% of the thread width, digit "1") or 1.5 mm (37 .5% of the thread width, digit "5"). The height h _M of the microwindows 20, ie the extent in the longitudinal direction L of the thread, is approximately 2 mm and is therefore also significantly smaller than the window areas in conventional window threads. As usual, the direction parallel to the longitudinal extent of the security thread is referred to as the longitudinal direction L of the thread and the direction perpendicular thereto as the transverse direction Q of the thread.

A further special feature of the configurations described is that several microwindows 20 can lie next to one another in the transverse direction Q of the thread, in the exemplary embodiment in FIG 2 For example, the digits "1" and "5", which together form the sequence of digits "15".

3 shows another example in which the microwindows 20 in the form of small stars with an irregular deckle edge 22 and a diameter of approximately b _M =1.5 mm are offset from one another at a distance of approximately 2 mm. The micro-windows 20 provide a view of the window security thread 14 embedded in the paper, so that its security features can appear there. The size of the micro-windows b _M is significantly smaller than the thread width b _F (b _M =0.375 b _F ), and in some cases two micro-windows 20 are arranged next to one another in the thread transverse direction Q, but without being exactly at the same height.

It goes without saying that the banknote 10 can also have conventional window areas in addition to window areas with the described microwindows 20 . However, since these are known, they will not be discussed in more detail in the present application.

To designs like those related to the Figures 2 and 3 to produce the microwindow 20 described in the area of a window security thread 14, according to the invention in 4 Dewatering sieve 30 shown schematically in a section transverse to the direction of travel of the yarn is used.

The dewatering screen 30 comprises a carrier screen 32 with a screen fabric 34 which is cut out in a partial area 40 . The screen fabric 34 has at least one system of interwoven warp threads 36 running in the longitudinal direction and weft threads 38 running transversely thereto. Within the scope of the present invention, the screen fabric can contain, for example, a metal fabric, in particular a bronze fabric, a metal-plastic mixed fabric, in particular a bronze-plastic mixed fabric, or also a pure plastic fabric. The carrier screen 32 can contain both a single-layer and a multi-layer screen fabric, only a single-layer screen fabric being shown in the figure for the sake of simplicity.

A plastic injection-molded insert 50 is arranged in the cut-out partial area 40 of the screen fabric 34 and is connected to the screen fabric 34 at its edge. In principle, the connection can be made in a variety of ways, for example by a plastic encapsulation or rear injection molding, with the aid of a plurality of fastening knobs arranged along the edge, or also by welding or gluing. In the embodiment, a currently preferred variant is realized in which the injection-molded insert 50 is injected directly into the cut-out partial area 40 of the screen fabric 34 using a corresponding tool mold, thereby forming a particularly intimate connection with the screen fabric.

The injection-molded insert 50 has a relief 52 in the form of the window areas 16 of the window security thread 14 and contains a base body 54, starting from which motif elements in the form of the window areas 16 extend upwards and protrude beyond the screen surface. What is essential for the present invention is that the motif elements contain small micromotif elements 56 which are formed in the shape and size of the microwindows 20 and extend upwards with a sharp edge. In the exemplary embodiment, the relief 52 is produced using milling technology, so that the flanks 57 of the small micromotif elements 56 enclose an angle of approximately 15° with the surface normal.

During paper production in a cylinder mold paper machine, the security thread 14 to be embedded is fed as an endless element from a spool via a deflection roller to the drainage screen 30 with the injection molding insert 50 . During the immersion of the injection molded insert 50 into the paper pulp, the security thread 14 rests on the motif elements and in particular also on the micromotif elements 56 of the injection molded insert 50 .

Since there is a negative pressure inside the drainage screen 30, the water of the water-fiber dispersion of the pulp is sucked into the interior of the drainage screen. The fibers accumulate on the surface of the drainage screen 30 and the injection molding insert 50 and form the desired paper web. At the points where the security thread 14 rests on the motif elements or the micromotif elements 56, the security thread is sucked onto the dewatering sieve by the negative pressure, so that no fiber mass can accumulate there. Accordingly, the security thread 14 remains free of fiber mass in the areas of the motif elements or the micromotif elements 56, while paper fibers accumulate in the surrounding areas and embed the security thread 14 in the paper. The motif elements or the micromotif elements 56 therefore produce precisely the desired window areas or microwindows 20 in the paper layer that is being formed.

Because the microwindows 20 are produced by papermaking, the edge area 22 of the microwindows is not completely sharp, such as when holes are subsequently produced by means of punching or laser cutting. Instead, fibers accumulate in the edge area of the microwindow 20, which protrude slightly into the opening in an irregular manner and thereby produce the characteristic deckle edge.

The extent of the edge sharpness or edge blur of the microwindows 20 can be predetermined by the three-dimensional shape of the micromotif elements 56 . Micromotif elements, such as the micromotif elements 56 of FIG 4 , which have very steep flanks 57 and a small edge width, produce edge regions 22 with minor irregularities, while micromotif elements with flatter flanks and larger edge widths, such as those in figure 5 Micromotif elements 58, microwindows 20 shown with highly irregular edge regions 22 generate.

The edge width of a micromotif element is that width within which the height of a micromotif element falls from 90% of the maximum height to 10%. Micro-windows with only slightly irregular edge areas can be produced with micro-motif elements 56 with an edge width of 0.6 mm or less, 0.5 mm or less, or even 0.4 mm or less will. By contrast, micromotif elements 58 with an edge width of more than 0.6 mm, more than 1 mm or even more than 1.5 mm can produce microwindows with highly irregular edge regions 22 .

The injection molding insert 50 is also provided with a plurality of perforations 48 in order to ensure drainage during papermaking in the area of the injection molding insert. The diameter of the perforations 48 is selected to be so small that no fibers adhere to them during papermaking. Typical perforation diameters are between 100 μm and a few 100 μm, for example around 500 μm.

Figures 6 and 7 show further advantageous configurations of microwindows in banknotes or other data carriers. When designing the 6(a) the microwindows 20 are formed in the form of ovals measuring 0.4mm x 0.3mm. In each case, a plurality of oval microwindows 20 forms an ensemble 24, the microwindows 20 of which are spatially arranged in relation to one another in such a way that together they form the euro symbol “€” as a motif. As in 6(a) shown further, the ensemble 24 contains a plurality of microwindows 20 lying next to one another in the transverse direction of the thread, but these are never exactly at the same height in the transverse direction of the thread, but rather are always offset from one another by a fraction of the microwindow height.

As in the configurations described above, the microwindows 20 provide a view of the window security thread 14 embedded in the paper and allow the security features arranged thereon, for example formed by a printed layer, an ink layer or other functional layer, to become visible.

When designing the Fig.6(b) several ensembles 24 of micro-windows 20, each in the form of the euro symbol €, are spaced apart in the longitudinal direction L of the thread. The ensembles 24 as a whole are slightly offset from one another in the transverse direction Q in order to compensate for fluctuations when the security thread 14 is introduced into the paper, for example due to wobbling. If Δ denotes the maximum distance by which a security thread 14 can be inserted into the security paper 12 offset in the transverse direction Q due to wobbling, offsetting the euro symbol ensembles 24 by up to a distance Δ to the right and left can ensure that some complete symbol ensembles 24 always lie directly above the security thread 14 in the longitudinal direction and form the desired micro-windows in the form of the euro symbol.

The design of the microwindows does not have to be limited to the security thread 14, but can also continue laterally, for example in the form of a watermark or by another security feature. For illustration shows 7 a configuration in which a series of paper-made micro-windows 26 is placed over a window security thread 14 and reveals the security features of the embedded window security thread 14, as described above. The microwindows 26 in the form of circular disks have different sizes, but are all significantly smaller than the width of the thread, so that a plurality of microwindows 26 lie next to one another in the transverse direction Q of the thread.

The design formed by the microwindows 26 is continued outside of the security thread 14 by a print pattern 28 in the form of a printed point cloud and is thereby integrated into the overall design of the bank note 10 . This also significantly increases the counterfeit security of the banknote, since the security thread 14 does not have a security thread without a microwindow 26 can be replaced and since the security thread 14 must also be correctly aligned with the print pattern 28 in the longitudinal direction. Instead of a printed layer, a motif formed by the outline or the arrangement of the microwindows can also be continued by a watermark, for example. The microwindows, which in any case represent thin areas in the paper layer of a data carrier, are preferably part of a watermark that protrudes laterally beyond the window security thread.

Reference List

10

bank note

12

paper substrate

14

window security thread

16

panes

18

web areas

20

micro window

22

Edge with characteristic irregularities

24

Ensemble of microwindows

26

micro window

28

print pattern

30

dewatering screen

32

carrier screen

34

mesh

36

warp threads

38

weft threads

40

cut out section

48

perforations

50

watermark insert

52

relief

54

body

56, 58

micro motif elements

57

flanks

L

thread longitudinal direction

Q

yarn cross direction

Claims (6)

1. A dewatering screen (30) for manufacturing a security paper having a window security thread that, after its embedding, is visible on at least one surface of the security paper in predetermined window regions of the security paper, the dewatering screen (30) comprising a carrier mold (32) that is furnished in a sub-region (40) with an injection molded insert (50) that comprises a relief (52) having motif elements that extend upward from a base body (54) and overtop the surface of the carrier mold (32) and that are formed in the form of the predetermined window regions of the security paper in which the window security thread is to be visible, and the motif elements comprising, for producing microwindows, micromotif elements (56) that have, transverse to the running direction of the thread to be embedded, a width that is less than 50% of the thread width and is between 0.2 mm and 4 mm, and whose contours constitute patterns, characters or a code, especially a sequence of letters or numbers, and/ or whose spatial arrangement forms a motif, especially letters, characters or figures.
2. A dewatering screen (30) for manufacturing a security paper having a window security thread that, after its embedding, is visible on at least one surface of the security paper in predetermined window regions of the security paper, the dewatering screen (30) comprising a carrier mold (32) that comprises, in a sub-region, a mold embossing that comprises a relief having motif elements that overtop the surface of the carrier mold and that are formed in the form of the predetermined window regions of the security paper in which the window security thread is to be visible, and the motif elements comprising, for producing microwindows, micromotif elements that have, transverse to the running direction of the thread to be embedded, a width that is less than 50% of the thread width and is between 0.2 mm and 4 mm, and whose contours constitute patterns, characters or a code, especially a sequence of letters or numbers, and/or whose spatial arrangement forms a motif, especially letters, characters or figures.
3. The dewatering screen (30) according to claim 1 or 2, characterized in that the injection molded insert (50) or the mold embossing comprises multiple micromotif elements (56) that lie next to one another transverse to the thread running direction.
4. The dewatering screen (30) according to at least one of claims 1 to 3, characterized in that the injection molded insert (50) or the mold embossing comprises, besides the motif elements for producing the window regions of the window security thread, a watermark relief in the form of a watermark to be produced in the security paper.
5. The dewatering screen (30) according to at least one of claims 1, 3 or 4, characterized in that the injection molded insert (50) is arranged in a cut-out region (40) of the carrier mold (32) and is bonded therewith only in a preferably serrated edge region.
6. The dewatering screen (30) according to at least one of claims 1, 3 to 5, characterized in that the injection molded insert (50) comprises a plurality of perforations (48) whose dimensions are so small that no fibers stick in them at paper manufacture.

Images