WO2020078579A1 - Method and device for producing a security paper with window security threads - Google Patents

Abstract

The invention relates to a drum screen (12) of a drum-screen papermaking machine (10) for producing security paper (42A, 42B) with a partially embedded window security thread (22), the drum screen (12) drawing a paper mass in the form of a fibre-water suspension (14) from a vat (16) during the paper production process, and the drum screen (12) containing a production screen jacket (30) with a circumferential direction (U) and a transverse direction (Q) perpendicular thereto, which production screen jacket is provided in the circumferential direction (U) with a plurality of raised thread window elements (34), on which the window security thread (22) rests during the paper production process in order to locally prevent the accumulation of fibre-water suspension (14) for the generation of thread windows (40). According to the invention, the thread window elements (34) are arranged along the circumference with a periodic offset (36) in the transverse direction (Q), the drum screen circumference Ru being an integer multiple of the offset period P. The invention also relates to an associated method for producing a security paper.

Description

 Method and device for producing a security paper with

Window security thread

The invention relates to a method and an apparatus for producing a security paper with window security thread.

For security purposes, security papers or documents of value are often equipped with authenticity features, such as watermarks, embedded security threads and the like, which allow the authenticity of the security paper or security document to be checked and which at the same time serve as protection against unauthorized reproduction. In the past, authenticity features have proven themselves that can only be introduced into the security paper during manufacture, such as security threads fully or partially embedded in the security paper. Security threads that are neither completely applied to a surface of a security paper nor are completely embedded in the security paper are referred to as window security threads. Some of these are embedded in the security paper in such a way that they are visible on one or both opposite surfaces of the security paper only in certain window areas (hereinafter also called thread windows).

Such thread windows are conventionally produced in bronze screens by means of highly embossed webs. As a rule, the webs are rectangular embossments in the form of a plateau. The width of the plateau serves as a so-called wobble zone for the security thread, the width of which depends on the width of the thread. During the paper production, the thread is brought onto the circular sieve with the embossing and then onto it laid here, so that the laid threads later in the paper stack do not come to lie exactly one above the other, but a distribution of the threads is achieved on the sides. Such a so-called thread warp is indispensable to ensure that the sheets and stacks are sufficiently flat to be able to be cut on the cross cutter, when printing, when being used and when they can be processed on the cutpack.

If non-rectangular window shapes are used, however, the thread warping often leads to a worsened flatness and too much under different and not clearly defined window configurations. For a sensible addition, the wobble zone must also be taken into account in the design motif, which has great restrictions in finding the motif.

Based on this, the invention has for its object to avoid the disadvantages of the prior art and in particular to provide a method and an apparatus for producing security paper with window security thread, with which non-rectangular, in particular mo tive-shaped thread window can be used advantageously.

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

The invention provides a circular sieve of a circular sieve paper machine for the production of security paper with a partially embedded window security thread, the circular sieve scooping out a paper pulp in the form of a fiber-water suspension from a chest in papermaking. The circular screen contains a production screen jacket with a circumferential direction and a transverse direction perpendicular to it, which extends along the circumference is provided with a plurality of raised thread window elements on which the window security thread rests during paper production in order to locally suppress the deposition of fiber-water suspension for the production of thread windows. According to the invention it is provided that the thread window elements are arranged with a periodic offset along the circumference in the transverse direction, the circular screen circumference Ru being an integer multiple of the offset period P.

The circular screen size Ru is preferably equal to the displacement period P or twice the transfer period P. It is also possible in principle for the ratio of the circular screen size to the offset period Ru / P to be three or more, but correct thread guidance is technically more complex in large proportions, so that the smaller ratios of 1, 2 or 3 mentioned are currently preferred. The ratio is particularly advantageously 1, the circular screen size Ru is therefore equal to the displacement period P.

In an advantageous embodiment of the invention, at least one thread element is provided for each use provided on the production screen jacket. The thread window elements can also be combined with other screen elements, for example conventional watermark embossing, watermark inserts or E types.

At least some of these other sieve elements in advantageous Ge designs the same periodic offset as the thread window elements and are therefore always fitted with them on the security paper. Such an arrangement is particularly advantageous when the screen elements are arranged in the immediate vicinity of the thread window elements or the window security thread and / or with the thread window elements are in context and represent, for example, related information or additional information.

In further, likewise advantageous configurations, at least some of these other sieve elements are arranged without dislocation and are therefore fitted to the outer contour of the cut security paper. Such an arrangement is particularly advantageous when the screen elements are clearly, for example a few centimeters, spaced from the thread window elements and the window security thread and / or are not in context with the thread window elements.

The thread window elements can be at least partially formed by embossing in the production screen jacket. Alternatively or additionally, the thread window elements can be at least partially formed by watermark inserts, in particular injection molded watermark inserts. Such watermark inserts for producing high-resolution watermarks are described in more detail, for example, in the publications EP 2895310 A1 and EP 2899 312 A1, the disclosure of which is included in the present application.

The thread window elements are preferably non-rectangular, in particular motif-shaped.

In advantageous designs, the accumulation of fiber-water suspension is not completely suppressed in all areas, but is only partially suppressed in some areas. The thread window elements then produce watermarks during paper production, in which the security thread in some partial areas, namely the partial areas with complete suppression of the fiber attachment, on the surface of the paper. piers runs, while in other parts it runs inside the paper. Particularly advantageously, the thread window elements contain at least a partial area in which the accumulation of fiber-water suspension is completely suppressed and at least a partial area in which the accumulation of fiber-water suspension is only partially suppressed.

The thread window elements are advantageously arranged along the circumference with a sinusoidal or a triangular offset.

The invention also includes a method for the provision of a security paper for the production of security documents, such as banknotes, identity cards or the like, with a window security thread which is embedded in the security paper and is guided at least one opening in the security paper to at least one of the surfaces of the security paper , wherein a rotary screen of a rotary paper machine scoops a paper mass in the form of a fiber-water suspension from a chest, and wherein the rotary screen contains a production screen jacket with a circumferential direction and a transverse direction perpendicular thereto, which along the circumferential direction with a plurality of raised Fadenfensterele elements is provided, on which the security thread to be embedded rests during paper production in order to locally suppress the deposition of fiber-water suspension for the production of thread windows. It is provided according to the invention that the thread window elements are arranged with a periodic offset in the transverse direction along the circumference, the circular screen circumference Ru being an integral multiple of the offset period P.

The security thread to be embedded is advantageously moved back and forth synchronously with the rotation of the circular sieve in the transverse direction of the circular sieve. The security thread to be embedded is preferably moved back and forth n times in the transverse direction of the circular sieve per revolution of the circular sieve, n = Ru / P representing the integer ratio of the circular sieve circumference and the displacement period. As explained above, n is in particular 3, 2, or, particularly preferably, 1.

A circular sieve of the type described above is particularly preferably used in the method. Further exemplary embodiments and advantages of the invention are explained in the following with reference to the figures, in which the representation of scale and proportions has been omitted in order to increase the clarity. Show it:

1 shows schematically a circular screen paper machine according to an exemplary embodiment of the invention, FIG. 2 shows schematically part of the production screen jacket of the rotary screen of FIG. 1,

3 in (a) and (b) two security paper panels produced with the circular screen of FIGS. 1 and 2 with different horizontal positions of the thread window and correspondingly under different horizontal positions of the window security thread, Fig. 4 shows schematically the ver by the thread and window wobble flatness of several superimposed Papierbo gene, Fig. 5 is a security paper with oblique thread windows according to another embodiment of the invention, and

Fig. 6 is a security paper with a thread window in the form of a

 Watermark.

The invention will now be explained using the example of the production of security paper for banknotes with window security thread. 1 shows schematically a circular screen paper machine 10 with a circular screen 12 which is immersed in a fiber-water suspension 14 in a chest 16. During sheet formation, an endless security thread 22 is embedded in the paper web 20 as a window security thread. For this purpose, the security thread 22 runs before diving into the fiber-water suspension 14 on the hump 18 of the circular screen 12.

In the paper web 20 thus produced, the security thread 22 is basically in an inner plane of the paper, but no paper fibers from the fiber-water suspension 14 are deposited on the contact surfaces of the security thread 22 with the bumps 18, so that windows there arise at which the security thread 22 emerges on the surface of the paper.

In order to ensure that the threads laid later in the paper stack do not come to lie exactly one above the other, the security thread 22 to be embedded is used during the paper production in the cross-wire transverse direction 1 is perpendicular to the paper plane, moved back and forth.

As explained above, the security thread conventionally runs back and forth on rectangular bumps, so that the width of the bumps forms a so-called wobble zone for the thread.

However, in order to be able to use thread windows with more complex shapes, the bumps 18 are formed according to the invention by raised thread window elements 34, which are arranged along the circumference of the circular sieve 12 with a periodic offset in the transverse direction Q of the circular sieve.

The principle is explained with reference to FIG. 2, which schematically shows a part of the production screen jacket 30 of the circular screen 12 in the circumferential direction U and the transverse screen direction Q. The positions of the plurality of banknotes 32 are drawn with dashed lines. It is understood that a real production screen jacket 30 contains a substantially larger number of benefits in the circumferential direction and that the offset of the thread window elements 34 is in reality usually smaller than shown here for illustration.

A plurality of raised thread window elements 34, on which the security thread 22 rests during paper production, are now arranged along the circumferential direction U of the production screen jacket 30. The thread window elements 34 are arranged according to the invention with a periodic offset in the transverse direction Q along the circumference U, the circular screen circumference Ru being an integer multiple of the offset period P, that is Ru = n * P, with a natural number n, in particular n = l, 2 or 3. The particularly preferred case n = 1 and a sinusoidal displacement 36 are illustrated in the exemplary embodiment in FIG. 2, in which the displacement period P corresponds precisely to the circumference of the sieve Ru. The displacement amplitude A can be 15 mm, for example. In this way, the thread windows 40 (FIG. 3) are not generated at the same horizontal position within the panels 32, but their position wobbles back and forth with the displacement period P and the amplitude A. In papermaking, the movement of the thread linkage to generate the thread warp is now synchronized with the rotation of the circular sieve 12 and the point of use and the frequency are chosen such that the security thread 22 comes to lie exactly on the thread elements 34 during embedding. In the case shown here, n = 1, the security thread 22 is wobbled back and forth in the cross-wire transverse direction exactly once per revolution of the circular screen. It goes without saying that, in general, the security thread to be embedded is moved back and forth in the cross-wire cross direction per revolution of the circular screen, where n = Ru / P is the integer ratio of the screen size and the displacement period.

The effect produced by this synchronous thread and window warping is illustrated in FIG. 3, which in (a) and (b) shows two security paper panels 42A, 42B produced with the circular screen of FIGS. 1 and 2 with different horizontal positions F _A , F _{B of} the Thread window 40 and correspondingly under different horizontal position of the window security thread 22 shows. Since the thread wobble is synchronized with the displacement period P of the thread window elements 34, the window security thread 22 lies in the panels 42A, 42B at the same point within the thread window 40, even if the Position of the thread window 40 along with the thread 22 varies within the benefit.

For the viewer, the register-accurate alignment of thread window 40 and thread 22 is much more striking and important than the small differences in the relative position of the thread window 40 between different benefits 42A, 42B.

The security paper panels 42A, 42B of FIG. 3 have, in addition to the thread window 40, two further watermarks 44, 46 each with different orientations relative to the thread window 40 or the edges 48 of the panels. The watermarks 44, which are arranged in the immediate vicinity of the embedded security thread 22, have the same periodic displacement as the thread window elements 40. As a result, the relative position of thread window 40, security thread 22 and watermark 44 in the panels 42A, 42B remains the same in spite of the thread wobble and the appearance of the watermark 44 is not changed or impaired by the thread wobble. The watermarks 44 and the thread window 40 can also be in context and represent, for example, information which is complementary or related to one another, since their common appearance is the same in all the uses 42A, 42B.

On the other hand, the watermarks 46 are far away from the thread window 40 and the security thread 22 and are not affected by the thread wobble anyway. In addition, the position of the watermarks 46 relative to the nearby edges 48 of the panels 42A, 42B is much more noticeable to the viewer than the position relative to the security thread 22 and the thread window 40. The watermarks 46 are therefore unaltered in all security paper panels arranged in the same position with respect to the utility edges 48.

FIG. 4 schematically illustrates the flatness of a plurality of paper sheets 50 which are improved by the thread and window wobbling. For illustration, an embodiment is shown in which the circular screen circumference Ru is equal to the displacement period P and in which two sheets lie one behind the other in the circumferential direction of the circular screen. It goes without saying that, in practice, usually a larger number of sheets, for example 4, 5, 6, 8 or 10 sheets, lie one behind the other in the circumferential direction of a circular screen.

The sinusoidal displacements of the threads 22 and the associated windows 40 are shown schematically for two sheets of paper lying one above the other, for the first sheet of paper with a solid line (offset 52) and for the second sheet of paper with a dashed line (offset 54). The positions shown are repeated for other sheets of paper lying on top. The displacement amplitude A is also shown. It can be clearly seen how the thread 22 and the windows 40 lie side by side due to the wobble. A thickening when stacking the paper sheets results only in the intersection area 56, which can, however, be kept very short. Since, in the exemplary embodiment, two sheets lie one behind the other in the circumferential direction of the circular screen, the thread window 40 and the security threads 22 have just half a sinusoidal displacement period in each sheet. In practice, for example, if there are six sheets in a row in the circumferential direction of the circular screen, the thread windows and the security threads in each sheet show just one sixth of a sinusoidal displacement period. Positions of threads 22 and windows 40 lying one above the other then repeat only every six sheets. FIG. 5 shows a further exemplary embodiment in which a security paper 60 is provided with oblique thread windows 62. Conventionally, the window security thread 22 would assume an arbitrary position between the left window edge 64 and the right window edge 66 due to the wobble within position-fixed windows 62, and would therefore be too close to the upper and lower no. have edge 68.

The synchronization of the thread wobble and window wobble according to the invention, on the other hand, ensures that the thread 22 is always in the center of the window 62, regardless of its specific horizontal position on the security paper 60, and thus was at a sufficient distance from the note edges 68.

In the embodiment of FIG. 6, the thread window of the security paper 70 is in the form of a watermark 72, in which the embedded security thread 22 runs in some areas on the surface of the paper 70, while in other areas it is embedded inside the paper.

Conventionally, with such designs, it must be taken into account that the position of the security thread 22 fluctuates within a wobble zone W and therefore different and partially unusable combinations of thread position and watermark motif result. Inven tion according to the position of the watermark 72 is now changed as a thread window in the same way as the thread wobble, so that there is a synchronization of thread wobble and window wobble. This ensures that the security thread 22, regardless of its specific vertical position on the security paper 70, is always in the correct desired position relative to the motif of the watermark 72. Specifically, the security thread 22 of FIG. 6 always runs at the same height H through the sails of the ship motif 72 due to the synchronous thread and window warping.

It is understood that the window thread elements 34 described can have various shapes. The thread window elements 34 can in particular be formed both by embossing in the production screen jacket and by a watermark insert arranged in the screen jacket. The security thread 22 can be narrower, the same width or wider than that

Be window thread elements 34, in the latter case, the shape of the elements 34 can be reflected on the thread.

Reference list

10 rotary screen paper machine 12 rotary screen

 14 water-fiber suspension 16 chest

18 humps

20 paper web

22 Security thread

30 production sieve jackets 32 banknote benefits

34 thread window elements 36 dislocation

40 thread window

 42A, 42B security paper use 44 watermark

46 W ater marks

50 sheets of paper

52, 54 transfers

 56 intersection area

60 security paper

62 sloping thread windows

64, 66 window edge

68 note edges

 70 security paper

72 Thread window - watermark U circumferential direction

Q Circular wire cross direction FA, FB Position of the thread window

H height

Claims

Patent claims 1. Circular sieve of a circular sieve paper machine for the production of security paper with a partially embedded window security thread, wherein the circular sieve scoops a paper mass in the form of a fiber-water suspension from a chest in the paper production, and wherein the circular sieve a production sieve jacket with a Contains circumferential direction and a transverse direction perpendicular to it, which is provided along the circumferential direction with a plurality of raised thread window elements on which the window security thread rests during papermaking in order to locally suppress the deposition of fiber-water suspension for producing thread windows,  characterized in that the thread window elements are arranged with a periodic displacement along the circumference in the transverse direction, the circular sieve circumference Ru being an integral multiple of the displacement period P. 2. Circular sieve according to claim 1, characterized in that the circular sieve circumference Ru is equal to the displacement period P or twice the displacement period P. 3. Circular sieve according to claim 1 or 2, characterized in that at least one thread window element is provided for each use provided on the production sieve jacket. 4. Circular sieve according to at least one of claims 1 to 3, characterized in that the thread window elements are at least partially formed by embossing in the production sieve jacket. 5. Circular sieve according to at least one of claims 1 to 4, characterized in that the thread window elements are at least partially formed by watermark inserts, in particular injection molded watermark inserts. 6. Circular sieve according to at least one of claims 1 to 5, characterized in that the thread window elements are non-rectangular, in particular motif-shaped. 7. Circular sieve according to at least one of claims 1 to 6, characterized in that the thread window elements are arranged with a sinusoidal or a triangular offset along the circumference. 8. Circular sieve according to at least one of claims 1 to 7, characterized in that the thread window elements are combined with other sieve elements, in particular watermark embossing, watermark inserts or E types. 9. Circular sieve according to claim 8, characterized in that at least some of the other sieve elements mentioned are arranged with the same periodic offset in the transverse direction as the thread window elements on the production sieve jacket. 10. Circular sieve according to claim 8 or 9, characterized in that at least some of the other sieve elements mentioned are arranged without displacement in the transverse direction on the production sieve jacket. 11. Method for producing a security paper for the production of security documents, such as banknotes, identity cards or the like, with a window security thread which is embedded in the security paper and is guided at least one opening in the security paper to at least one of the surfaces of the security paper, a circular sieve of a circular sieve paper machine scoops a pulp in the form of a fiber-water suspension from a chest, and wherein the circular sieve contains a production sieve jacket with a circumferential direction and a direction perpendicular to it, which along the circumferential direction has a plurality of raised thread window elements is provided, on which the security thread to be embedded lies in the paper production in order to locally suppress the deposition of fiber-water suspension for the production of thread windows,  characterized in that the thread window elements are arranged with a periodic displacement along the circumference in the transverse direction, the circular sieve circumference Ru being an integral multiple of the displacement period P. 12. The method according to claim 11, characterized in that the encircling security thread is moved back and forth in the cross-wire transverse direction in synchronism with the rotation of the circular screen. 13. The method according to claim 12, characterized in that the encircling security thread is moved back and forth n times per revolution of the circular screen in the transverse wire direction, where n = Ru / P represents the integer ratio of the circular screen circumference and the displacement period. 14. The method according to any one of claims 11 to 13, characterized in that a circular sieve according to one of claims 1 to 10 is used.