EP2753754B2 - Method for producing a security paper and microlens thread - Google Patents

Description

The invention relates to a method for producing a security paper.

Documents of value, 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 document of value to be checked and at the same time serve as protection against unauthorized reproduction. The security elements can be designed, for example, in the form of a security thread that is fully or partially embedded in a banknote.

In recent years, security threads with microlenses have established themselves on the banknote market. These microlens filaments differ significantly from metallized filaments and offer attractive optical properties. The microlens threads are equipped with microlenses on the side facing the viewer, the focusing effect of which is created by refraction of light on an almost spherically curved surface. Microstructures are located in the focal plane of the microlenses, which are arranged in such a way that the interaction of the microlenses and the microstructures allows the viewer to display an enlarged image with special movement effects.

In order not to impair the focusing effect of the microlenses and thus the optical effect of the microlens thread, the lens side of the thread is not provided with adhesive before embedding it in a paper web, as is the case with conventional security threads such as hologram threads the case is. However, not using glue on the upper side of the thread (lens side) often leads to reduced durability of the banknotes produced and sometimes even to creases forming on the back of the banknote.

On this basis, the invention is based on the object of avoiding the disadvantages of the prior art and in particular of specifying a method for producing security paper that enables a microlens thread to be securely embedded in the paper and at the same time in the window areas in which the microlens thread is attached to the surface of the paper, ensuring an attractive visual appearance of the microlens thread.

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

• M) ein endloser Mikrolinsenfaden bereitgestellt wird, der eine Oberseite und eine gegenüberliegende Unterseite aufweist, wobei die Oberseite zumindest in Teilbereichen mit Mikrolinsen versehen ist,
• P) eine Papierbahn mit einem vorbestimmten Stegmuster erzeugt wird, welches Stegbereiche aufweist, in denen der Mikrolinsenfaden im Inneren der Papierbahn eingebettet ist, und das zwischen den Stegbereichen liegende Fensterbereiche aufweist, in denen der Mikrolinsenfaden an der Oberfläche der Papierbahn hervortritt, und
• E) der Mikrolinsenfaden in die Papierbahn eingebracht und dabei auf seiner Unterseite und in den Stegbereichen auch auf seiner Oberseite mit der Papierbahn verbunden wird, wobei die Papierbahn mit dem eingebrachten Mikrolinsenfaden das Sicherheitspapier bildet.

According to the invention, a generic method provides that

• M) an endless microlens thread is provided, which has an upper side and an opposite underside, the upper side being provided with microlenses at least in partial areas,
• P) a paper web is produced with a predetermined land pattern, which has land areas in which the microlens thread is embedded in the interior of the paper web and which has window areas lying between the land areas in which the microlens thread emerges at the surface of the paper web, and
• E) the microlens thread is inserted into the paper web and is connected to the paper web on its underside and in the web areas also on its upper side, the paper web with the inserted microlens thread forming the security paper.

• der Mikrolinsenfaden vor der Einbringung in die Papierbahn auf seiner Oberseite mit einer Klebstoffschicht in Gestalt des Stegmusters versehen wird, und
• der Mikrolinsenfaden in Schritt E) registriert in die Papierbahn eingebracht wird, so dass die mit Klebstoff beschichteten Bereiche des Mikrolinsenfadens mit den Stegbereichen der Papierbahn zusammenfallen.

According to the invention it is provided that

• the microlens thread is provided on its upper side with an adhesive layer in the shape of the ridge pattern before being introduced into the paper web, and
• the microlens thread is registered in step E) introduced into the paper web, so that the areas of the microlens thread coated with adhesive coincide with the land areas of the paper web.

A registered introduction of the microlens thread can, in particular, according to one of the documents WO 2004/050991 A1 described procedures. To this extent, the disclosure content of this publication is included in the present application.

In some configurations, the microlens thread may contain a motif with a motif jump. As in the pamphlet WO 2008/145333 A2 described in more detail, in the production of a microlens thread, an endless security element film is usually first produced as roll material, with the use of conventional production methods always causing breakage, in particular gaps or an offset in the appearance of the security elements. These fractures are due to the fact that Preliminary products for the embossing tools used in production are generally produced as flat plates that are mounted on a printing or embossing cylinder. At the seams, the mutually adjacent image patterns generally do not match and, after printing or embossing, result in a motif jump of the type mentioned in the appearance of the finished security elements. According to the invention, a microlens thread containing a motif with a motif jump is registered in the paper web introduced so that the motif jump comes to rest in one of the web areas of the paper web. The jump in motif then remains hidden from the viewer.

Motif jumps may also occur several times within an embossing cylinder. For example, if the patterns are assembled from small segments by means of recombination, seams with motif jumps result. In general, motif jumps occur due to the process, both in the grid of the microstructures and in the grid of the microlenses. Usually, an attempt is made to overlap the two seams during production, so that the viewer gets the impression of only one jump in the motif.

In a modification of the described method not according to the invention, the microlens thread is printed directly before it enters the paper web with an adhesive layer in the areas of its upper side that come to lie below web areas of the paper web during sheet formation.

• der Mikrolinsenfaden vor der Einbringung in die Papierbahn in einem Öffnungsbereich in Gestalt des Stegmusters mit einer Mehrzahl von Öffnungen versehen wird, und
• der Mikrolinsenfaden in Schritt E) registriert in die Papierbahn eingebracht wird, so dass die mit Öffnungen versehenen Bereiche des Mikrolinsenfadens mit den Stegbereichen der Papierbahn zusammenfallen.

In a variant of the method that is not according to the invention, it is provided that

• the microlens thread is provided with a plurality of openings in an opening area in the shape of the ridge pattern before being introduced into the paper web, and
• the microlens thread is registered in step E) introduced into the paper web, so that the areas of the microlens thread provided with openings coincide with the web areas of the paper web.

In this variant, too, the microlens thread can contain a motif with a motif jump and the microlens thread can be introduced in a registered manner, so that the motif jump comes to rest in one of the web areas of the paper web and is therefore hidden from the viewer.

According to a modification of the method not according to the invention, the microlens thread is provided with openings in the areas of its upper side directly before entering the paper web, which come to lie below web areas of the paper web during sheet formation.

The openings are advantageously produced by punching or laser cutting. If the openings are only produced immediately before the microlens thread enters the paper web, they are preferably produced by laser cutting.

In all configurations, the paper web is suitably formed with the predetermined land pattern in a paper machine and the continuous microlens thread enters the paper machine.

According to a further method variant not according to the invention, it is provided that in step M) a microlens thread is provided, the upper side of which has subareas with microlenses and microlens-free subareas, the microlens-free subareas being smaller than the width of the land areas of the land pattern in the paper web, and wherein the microlens-free portions are coated with adhesive prior to incorporation into the paper web. The microlens thread is introduced into the paper web in an unregistered manner, so that microlenses can be seen at least in certain areas in each window area and a part of the adhesive-coated subareas always comes to lie below the web areas of the paper web.

According to a further method variant not according to the invention, it is provided that in step M) a microlens thread is provided which, on the one hand, has partial areas with microlenses, which partial areas are coated with adhesive before being introduced into the paper web and which are smaller than the width of the land areas of the land pattern in the Are paper web, and on the other hand has partial areas with microlenses that are not coated with adhesive before being introduced into the paper web. The microlens thread is introduced into the paper web in an unregistered manner, so that in each window area at least some microlenses that do not have an adhesive coating can be seen and some of the adhesive-coated partial areas always come to lie below the web areas of the paper web.

In all of the method variants described, the microlens thread is advantageously provided with an adhesive layer over its entire surface before it is introduced into the paper web.

The disclosure also relates to a microlens thread for introduction into a paper web, in particular with the method just described. The microlens thread includes a top surface and an opposite bottom surface, with the top surface having microlens-bearing portions and microlens-free portions coated with adhesive.

The partial areas with microlenses and the microlens-free partial areas advantageously form alternating strips on the upper side of the thread, which each completely occupy the width of the microlens thread and which in the longitudinal direction of the microlens thread each have an extent of between 1 mm and 30 mm, preferably between 3 mm and 12 mm.

The partial areas with microlenses and the microlens-free partial areas can usually be in the form of rectangles. However, it would also be possible for the partial areas with microlenses and the partial areas without microlenses to be present in the form of diagonals. Diagonal paper webs can be produced, especially with wider threads.

The underside of the microlens thread is preferably coated with adhesive over its entire surface.

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 erfindungsgemäß hergestellten Banknote mit einem eingebetteten Mikrolinsenfaden,

Fig. 2

schematisch den Schichtaufbau eines Mikrolinsenfadens vor der Einbettung in das Sicherheitspapier,

Fig. 3

einen Querschnitt eines Sicherheitspapiers mit einem eingebetteten Mikrolinsenfaden nach Fig. 2,

Fig. 4

eine Aufsicht auf den Mikrolinsenfaden der Fig. 2,

Fig. 5

eine Aufsicht auf einen weiteren Mikrolinsenfaden vor der Einbettung in ein Sicherheitspapier,

Fig. 6

einen Querschnitt des Mikrolinsenfadens der Fig. 5,

Fig. 7

einen Querschnitt eines Sicherheitspapiers mit einem eingebetteten Mikrolinsenfaden nach den Figuren 5 und 6,

Fig. 8

einen Querschnitt des Mikrolinsenfadens; und

Fig. 9

einen Querschnitt eines Sicherheitspapiers mit einem eingebetteten Mikrolinsenfaden nach Fig. 8.

Show it:

1

a schematic representation of a banknote produced according to the invention with an embedded microlens thread,

2

Schematic of the layer structure of a microlens thread before embedding in the security paper,

3

a cross-section of a security paper with an embedded microlens thread 2 ,

4

a plan view of the microlens filament 2 ,

figure 5

a top view of another microlens thread before embedding in security paper,

6

a cross section of the microlens thread of FIG figure 5 ,

7

a cross section of a security paper with an embedded microlens thread according to Figures 5 and 6 ,

8

a cross section of the microlens thread; and

9

a cross-section of a security paper with an embedded microlens thread 8 .

The invention will now be explained using a bank note as an example. figure 1 shows a schematic representation of a bank note 10 produced according to the invention with a micro-optical window security thread 12, which is also referred to below as a micro-lens thread for short. The microlens thread 12 occurs in window areas 14 on the surface of the bank note 10 protrudes while being embedded in the intermediate land areas 16 inside the banknote 10 .

In a first embodiment of the invention, for the production of a security paper in the figures 2 and 4 illustrated microlens thread 12 is used. figure 3 shows a cross section of the security paper 50 with the microlens thread 12 already embedded. During the production of security paper, the microlens thread runs, for example, in endless form into a paper machine and is embedded there in a paper web forming on a cylinder mold. The paper web together with the embedded microlens thread is referred to as security paper in this description. A bank note 10 as in 1 shown.

figure 2 shows schematically the layer structure of the microlens thread 12 before embedding in the security paper, only the parts of the layer structure required for explaining the functional principle being shown. figure 4 shows a plan view of the microlens thread 12 of FIG 2 .

The microlens thread 12 contains a carrier 20 in the form of a transparent plastic film, for example a PET film approximately 20 μm thick. The upper side 30 of the microlens thread 12 has a grid-like arrangement of microlenses 22 which form a grid with a preselected symmetry on the surface of the carrier film. The spherically or aspherically designed microlenses 22 preferably have a diameter between 5 μm and 50 μm and in particular a diameter between only 10 μm and 35 μm and are therefore not visible to the naked eye. It goes without saying that larger or smaller dimensions are also possible in other configurations. The use of cylindrical lenses is also possible in the same way.

On the underside 32 of the microlens thread 12 there is a motif layer 26 which also contains a grid-like arrangement of micromotif elements 28 . The arrangement of the micromotif elements 28 also forms a lattice with a preselected symmetry, a desired magnification effect, characteristic movement effects and/or tilting effects being produced by matching the lattice of the microlenses 22 and the arrangement of the micromotif elements 28 . The micro motif elements cannot be seen with the naked eye. At this point, the WO 2009/000528 A1 referenced, which states that the microstructures can also consist of image fragments that are not arranged in a repeating manner. The microlens thread 12 typically contains other layers 24, such as protective, covering or other functional layers, which are not essential to the present invention and are therefore not described in detail.

Due to the production with embossing cylinders, the motif perceived by the viewer will usually have a motif jump, such as in the printed text WO 2008/145333 A2 described in more detail.

To produce security paper, a paper web 50 with a predetermined web pattern 18 ( 1 ) generated. The ridge pattern 18 has ridge areas 16 in which the microlens thread 12 is later embedded in the interior of the finished paper web 50 . Between the web areas 16 are window areas 14, in which the microlens thread 12 emerges on the surface of the finished paper web 50 .

As in the figures 2 and 4 shown schematically, the microlens thread 12 is provided with an adhesive layer 40 in the shape of the web pattern 18 on its upper side 30 before it is introduced into the paper web 50, so that the adhesive layer 40 forms an adhesive pattern 48 whose sequence of uncoated areas 44 and coated areas 46 of the Sequence of the window areas 14 and land areas 16 of the land pattern 18 corresponds. The underside 32 of the microlens thread 12 is provided with a full-surface adhesive layer 42 .

This microlens thread 12 coated with adhesive 40, 42 is now registered in the paper web 50, so that the areas 46 of the microlens thread coated with adhesive coincide with the web areas 16 of the paper web 50, as in FIG 3 shown.

Such a registered contribution can in particular according to one of the documents WO 2004/050991 A1 described procedures. For example, the microlens thread 12 can be introduced into the paper web under pretension by means of a coil. A first sensor detects the position of the coated areas 46 shortly before they are introduced into the paper web, and a second sensor detects the position of the webs 16 formed in the paper web immediately after the sheet is formed. The positions detected by the two sensors are evaluated and used to control the magnitude of the preload. When the prestress is increased, the microlens thread 12 is stretched to a greater extent, and when the prestress is lowered, the stretch is reduced. The microlens thread 12 can be used in this way with its coated and uncoated areas 44, 46 in register with the window and land areas 14, 16.

In the case of registered thread embedding, the procedure is preferably such that the thread carries a register mark which is recognized particularly well by a detection system. The embedding of the thread is then controlled by means of the tension on the thread in such a way that the register mark of the thread is in a fixed spatial relation to the register mark of the paper, usually a watermark mark. The areas in which the thread has adhesive on the upper side are then in a fixed, known local relationship to the register mark of the thread. In an analogous manner, the land areas in the paper are in a fixed spatial relationship to the register mark in the paper.

This procedure ensures that the web areas 16 of the paper web 50 are glued to the microlens thread 12, so that a secure embedding of the microlens thread 12 is guaranteed without wrinkling and without lifting or tearing of the paper webs during production. The stability of the paper webs against circulating stresses is also significantly improved. At the same time, the microlenses 22 of the uncoated areas 44 visible in the window areas 14 remain free of adhesive, so that the optical properties of the microlenses 22 are not impaired. The microlens thread 12 therefore exhibits the desired clear visual appearance in the window areas 14 after it has been embedded in the paper web 50 .

In advantageous configurations, the uncoated areas 44 and the coated areas 46 have the same size as the window areas 14 or the web areas 16. In some configurations, too It is envisaged that the coated areas 46 be smaller, e.g. no more than 10% or no more than 50% smaller than the land areas 16. How much the glue-coated part should be shorter compared to the paper lands of the thread also depends heavily the register tolerance for registered thread embedding. For example, with a register tolerance of ± 1 mm in the registered thread insertion, the areas of the thread that are free of adhesive should be 2 mm shorter than the paper webs. Even if in each case only part of the microlens thread 12 is glued to the web areas 16, the embedding is significantly improved compared to the prior art.

Configurations in which the uncoated areas 44 are somewhat smaller than the window areas 14 can also be considered. However, the focusing effect of adhesive-coated microlenses 22 in the window areas 14 is reduced or eliminated, so that the uncoated areas 44 are preferably no more than 10%, particularly preferably no more than 5% smaller than the window areas 14.

A further advantage of the registered insertion of the microlens thread 12 is that any motif cracks 34 in the motif image can be hidden under a paper web 16 of the security paper 50, as shown in 3 shown. This further increases the uniformity of the visual appearance of the microlens thread 12 .

In a modification of the process sequence described that is not according to the invention, the microlens thread 12 is not introduced into the paper web 50 in registration, but is printed with an adhesive pattern 48 immediately before it enters the paper machine in such a way that the coated areas 46 fit into the recessed sections of the cylinder mold in which the paper webs 16 form, come to rest. For this purpose, for example, a sensor can detect the position of the webs 16 formed in the paper web during sheet formation and the detected position can be used to control the printing positions for the adhesive pattern 48 . In this way, too, the uncoated and coated areas 44, 46 can be aligned with the window and web areas 14, 16 in register.

Another variant, but not according to the invention, will now be based on the Figures 5 to 7 explained. The show Figures 5 and 6 a top view or a cross section of the microlens thread 60 before embedding in the security paper and 7 shows a cross section of the security paper 50 with the embedded microlens thread 60.

In the variant of Figures 5 to 7 For example, the microlens thread 60 is not coated with adhesive on its upper side 30, but is provided with an opening pattern 68 in the form of the web pattern 18 before it is introduced into the paper web 50. The opening pattern 68 consists of a sequence of areas 66 with openings 62 and areas 64 without openings, which corresponds to the sequence of the land areas 16 and window areas 14 of the land pattern 18 . The underside 32 of the microlens thread 60 is preferably provided with a full-surface adhesive layer 42 .

The microlens thread 60 is now introduced into the paper web 50 in a registered manner, so that the areas 66 of the microlens thread 60 provided with openings coincide with the web areas 16 of the paper web 50, as already explained in principle in connection with FIGS Figures 2 to 4 described. In this case, the first sensor detects the position of the openings 62 shortly before the introduction of the microlens thread 12 into the paper web. In this way, the microlens thread 60 can have its opening pattern 68 are aligned with the window and web areas 14, 16 in register.

In this variant, the provision of the openings 62 ensures that during the formation of paper under the web areas 16, paper fibers or other components of the substrate 50 can penetrate through the openings 62 in order to establish a connection between the web areas 16 and the substrate material 52 under the microlens thread 60 ( 7 ). This also achieves an intimate connection between the paper web 50 and the microlens thread 60 and thus secure embedding without the formation of folds. Since the upper side 30 of the microlens thread 60 remains free of adhesive, the optical properties of the microlenses 22 are not impaired.

The openings 62 can, for example, be punched or produced by laser cutting. Each area 66 can contain one or more openings 62 . For illustration, show the figures 6 and 7 a design with only one opening 62 per region 66, while figure 5 a design with three openings 62 per region 66 is illustrated.

In a modification of the process sequence described, which is not according to the invention, the microlens thread 60 is not introduced into the paper web 50 in a registered manner, but is only provided with the opening pattern 68 by laser impingement immediately before it enters the paper machine in such a way that the areas 66 with openings 62 in the recessed sections of the cylinder mold, in which the paper webs 16 form, come to rest. For this purpose, for example, a sensor can detect the position of the webs 16 formed in the paper web and the detected position can be used to control the laser beam. Also in this way can the aperture pattern 68 is registered with the window and land areas 14,16.

In a further variant not according to the invention, which is illustrated in FIGS. 8 and 9, a microlens thread 70 is used which has a sequence of subregions 74 with microlenses 22 and microlens-free subregions 76 on its upper side 30 . The motif layer and any further layers of the microlens thread 70 are in FIGS Figures 8 and 9 not shown for the sake of clarity. The microlens-free partial areas 76 of the upper side 30 are coated with adhesive 40 and the underside of the microlens thread 70 is also coated with adhesive 42 over its entire surface.

The adhesive-coated, microlens-free partial areas 76 are smaller than the width of the window areas 14 of the ridge pattern 18 . This ensures that when the microlens thread 70 is introduced unregistered into a security paper 50, microlenses 22 can be seen at least in certain areas in each window area 14 ( 9 ).

In this way, on the one hand, a visually attractive appearance is obtained, and on the other hand, embedding that is improved compared to the prior art can be achieved even without a registered introduction of the microlens thread 70, since part of the adhesive-coated partial areas 76 always lie below web areas 16 of the paper web will come as in 9 illustrated.

According to a modification of the above, in the Figures 8 and 9 illustrated variant, not according to the invention, the areas coated with adhesive can certainly also have microlenses. These would optically ineffective due to the adhesive coating, but allow a uniform design of the thread with microlenses.

According to a further modification of the above, in the Figures 8 and 9 In the variant illustrated, which is not according to the invention, it is possible, particularly with wider threads, to arrange the microlens-free areas diagonally or in strips along the thread and thus optionally to provide areas over the entire length of the thread that can be coated with adhesive. The adhesive used in the present invention can be, for example, a heat seal lacquer. The adhesive can also have security features, such as dyes or color pigments and luminescent substances.

Reference List

10

bank note

12

microlens thread

14

panes

16

web areas

18

web pattern

20

carrier

22

microlenses

24

more layers

26

motif layer

28

micro motif elements

30

top

32

bottom

34

motif jump

40

Adhesive layer on top

42

Adhesive layer underneath

44

uncoated areas

46

coated areas

48

adhesive pattern

50

paper web

52

substrate material

60

microlens thread

62

openings

64

areas without openings

66

areas with openings

68

opening pattern

70

microlens thread

74

Sections with micro lenses

76

Microlens-free sections

Claims (3)

1. A method for manufacturing a security paper, in which

   M) an endless microlens thread is provided that exhibits a top and an opposing bottom, the top being provided with microlenses at least in fractional regions,

   P) a paper web is produced having a predetermined ridge pattern that exhibits ridge regions in which the microlens thread is embedded in the interior of the paper web, and that exhibits, lying between the ridge regions, window regions in which the microlens thread emerges at the surface of the paper web, and

   E) the microlens thread is introduced into the paper web and, at the same time, is joined on its bottom and, in the ridge regions, also on its top, with the paper web, the paper web with the introduced microlens thread forming the security paper, characterized in that

   the microlens thread includes a motif having a motif jump, the microlens thread being introduced in register, such that the motif jump comes to lie in one of the ridge regions of the paper web, wherein

   - before the introduction into the paper web, the microlens thread is provided on its top with an adhesive layer in the form of the ridge pattern and

   - in step E), the microlens thread is introduced into the paper web in register, such that the adhesive-coated regions of the microlens thread coincide with the ridge regions of the paper web.
2. The method according to claim 1, characterized in that the adhesive layer forms an adhesive pattern having a sequence of uncoated regions and adhesive-coated regions, the adhesive-coated regions each having an up to 50%, preferably up to 10%, smaller dimension than the ridge regions of the paper web.
3. The method according to one of claims 1 or 2, characterized in that the paper web having the predetermined ridge pattern is formed in a paper machine, and the endless microlens thread enters into the paper machine.

Images