EP1268935B1 - Antifalsification paper provided with applied coding consisting of luminescent mottled fibers and process for mechanical verification of this coding - Google Patents

Abstract

The invention relates to a security paper with at least two types of mottled fibers, which differ in terms of their luminescent characteristics and form a code. In each case one type of mottled fibers is present in a defined subarea of the security paper, and the code is represented by the defined geometric arrangement of the subareas on the security paper and/or by the presence or absence of mottled fibers of a specific type.

Description

The invention relates to a security paper with mottled fibers with luminescent. Properties and encoding, as well as a method of verifying this encoding.

The use of mottled fibers as a security feature for security documents has long been known. They are usually made of short plastic or cotton fibers, which are incorporated into security papers during papermaking. Mottling fibers have the advantage over other security features, such as planchettes or mica flakes, that mottled fibers are smaller and visually less noticeable and therefore exert less of a disruptive effect on the aesthetic overall impression of the security document.

DE 677 711 discloses under UV light fluorescent mottled fibers which are added to the paper pulp prior to sheet formation, so that the mottled fibers are then distributed arbitrarily in the volume of the finished security paper. It is also possible to use differently fluorescent mottled fibers, so that mixed fluorescence occurs under UV illumination.

DE 3122 470-C2 also discloses a security paper with luminescent mottled fibers incorporated therein. The mottled fibers here consist of cellulose acetate, which are dyed in the fiber volume with narrow-band emitting luminescent substances from the group of the lanthanide chelates. These luminescent substances can be introduced into the fiber material in concentrations up to 20 times higher than the previously known luminescent substances, and moreover have a relatively narrow-band emission spectrum. The mottled fibers can also become security threads twisted or interwoven. If different luminescent individual fibers are used for this purpose, it is also possible to produce a coding which is based on an evaluation of the presence or absence of certain luminescent substances. When viewed visually, such twisted or spun yarns are an excellent authenticating feature. However, despite the relatively high luminescence output of the proposed luminescent material, the intensity of the luminescence of the individual fibers is too low to be able to stir in a reliable machine authenticity test in practice.

The present invention is therefore based on the object to propose a security paper with luminescent mottled fibers, which represent an encoding, the encoding should be very easy to read by machine.

Furthermore, the invention has for its object to propose a method for checking the coding.

The object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

The invention is based on the finding that for a machine examination of the mottled fibers with a sufficient signal / noise ratio, the mottled fibers with different luminescent properties have to be arranged sufficiently spatially separated from one another. For this reason, non-overlapping partial areas are defined on the security paper according to the invention, in each of which a specific type of mottled fibers with specific luminescent properties is arranged. An encoding can be represented by a defined geometric arrangements of the subregions, and / or by the presence or absence of the mottled fibers.

The arrangement in limited subareas, the mottled fibers with the different properties can be easily located and measure the luminescent properties independently without mutual interference. Since only mottled fibers having a certain luminescent property are present in a subregion, the intensity of the measurement signal already increases compared with the known security documents due to the higher surface density of mottled fibers in the measuring region to be tested. The signal yield can additionally be increased if special luminescent substances with an intensity-intensive narrow-band luminescence emission are used, as described, for example, in US Pat. No. 5,448,582. These luminescent substances are multiphase systems which contain an optically "pumpable" light-emitting material, light-scattering centers and a transparent matrix material. These materials show laser-like effects with a spectrally extremely narrow-band emission. Another advantage of these materials is that the wavelength of the emission band can be adjusted in limited areas during manufacture.

The light-scattering centers consist of particulate, transparent materials with a preferably high optical refractive index. In the case of a flash excitation, the luminescent substance absorbs part of the flashlight and is thereby transferred in an excited, so-called "optically pumped" state. The luminescent light is formed by spontaneous emission from the excited state, wherein at least a portion of the emitted luminescent light does not leave the material directly, but is partially scattered several times at the light-scattering centers. This leads to a high amplification of the emitted light intensity as well as to particularly narrow emission bands.

The use of luminescent substances with narrow-band emission has the advantage that in the measurement of the luminescence light, the spectral sensitivity range of a detector can be tuned to a narrow spectral interval in which the emission band lies. This suppresses background light from adjacent spectral regions in the measurement and improves the signal-to-noise ratio.

However, other preferably narrow-band emitting luminescent substances can also be used since the measurement signal is not determined solely by the intensity of the emitted luminescence radiation of a pigment, but also by the concentration of luminescent substance that can be introduced into the mottling fiber and by the surface density of the mottling fibers on the paper.

When choosing the surface density, however, it should be noted that the mottled fibers visually attract attention with increasing surface density and lead to an increasing disturbance of the overall aesthetic impression of the security paper, which is often printed with an artistic representation. The areal density of mottled fibers should therefore be in the range 2 to 20 mottled fibers per square centimeter. The disturbance of the overall aesthetic impression, however, can also be reduced by suitable positioning of the subregions on the security paper. That is, the partial areas are preferably arranged so that the main motif of the artistic representation is not covered.

Since, as already mentioned, the mottled fibers should appear as little as possible when the security document is viewed visually, according to a preferred embodiment, the mottled fibers consist of transparent plastic fibers which are colored in the volume with luminescent substances which are also largely transparent in the visual spectral range.

If the luminescent substances have a certain intrinsic color, they can also be introduced into the mottling fiber in such low concentrations, given a corresponding luminescence light intensity, that the fiber itself still appears to be largely transparent.

Alternatively, however, the fibers can also be provided with the luminescent substance only superficially, for example in a dyebath

As fiber materials, other materials can be used, which can be processed into thin fibers, such as silk or cotton.

The partial regions in which the mottled fibers are arranged preferably have the form of strips which extend over the entire width of the security document. They preferably have a width in the range of 5 mm to 30 mm. However, the subregions may also have any other outline shapes, such as rectangular, round, oval, star-shaped, etc.

According to the invention, the mottled fibers are introduced in the production of the security paper so that the mottled fibers are at least partially crosslinked with the fiber web of the paper and therefore at least partially covered by paper fibers on the surface of the paper.

In the production of round-screen paper, for example, the so-called Wilcox process represents a suitable method for introducing mottling fibers into endless, strip-shaped subregions. The mottled fibers are slurried in an aqueous suspension and, during papermaking, through a tube whose end is a special outlet nozzle has applied to the rotating round screen near the point at which the sheet formation on the round screen just starts. By means of a negative pressure generated within the round screen, the layer of the mottled fibers thus applied is directly dewatered, whereby the mottled fibers, together with the first layer of the paper fibers accumulating on the round screen, lie firmly on the round screen.

In the manufacture of 4-ply papers, the fibers may be applied to the wire in a similar manner.

Depending on the type of coding, a plurality of application stations for mottled fibers with different luminescent properties are arranged parallel to one another in the paper machine. The feeding devices of the mottled fibers are controlled according to the applied coding. If the coding consists solely in the geometric arrangement of the subregions provided with different mottled fibers, then the feeders are positioned correspondingly on the paper machine at the beginning of the paper production. The Melierfaserzufuhr then takes place continuously.

If the coding consists exclusively or additionally in the presence or absence of one or more types of mottled fibers, the supply of mottled fibers must be stopped in accordance with the coding. If the coding does not change within the production of a paper web, it is sufficient to place the required feeding devices at the beginning of production.

The coding can represent any information, such as the denomination, issue date, issuing country or the like.

The finished security paper which, in addition to the coding according to the invention, of course further security elements, such as e.g. a security thread or the like, is then further processed in a conventional manner, in particular printed and cut into individual security documents, such as banknotes, stocks, checks or the like.

In the machine verification of the security documents according to claim 17, the coding is measured with corresponding sensors for the respective luminescent property of the mottled fibers to be evaluated and compared with a reference value. The luminescent property to be evaluated can be, for example, the luminescence wavelength or the decay time of the luminescence radiation.

Exemplary embodiments and further advantages of the invention are explained below with reference to the figures. It should be noted that the figures do not provide a true-to-scale representation of the invention, but are merely illustrative.

Fig. 1

eine Aufsicht auf ein Sicherheitsdokument, hier eine Banknote, mit drei streifenförmigen Teilbereichen, in die Melierfasern eingebracht sind;

Fig. 2a, b

eine Aufsicht auf zwei Sicherheitsdokumente mit je vier streifenförmigen Teilbereichen, die eine unterschiedliche Codierung darstellen;

Fig. 3

einen Ausschnitt aus dem Wellenlängen-Spektrum mit vier festgelegten Wellenlängen-Intervallen für ein Codiersystem aus vier verschiedenen lumineszierenden Stoffen;

Fig. 4

eine Anordnung zum Messen der lumineszierenden Eigenschaften von Melierfasern, die in verschiedenen Teilbereichen in ein Sicherheitsdokument eingebracht sind;

Fig. 5

den zeitlichen Verlauf der elektrischen Signale am Ausgang des Lichtdetektors aus der Anordnung von Fig. 4 bei der Überprüfung des Dokuments gemäß Fig. 2a.

Show it:

Fig. 1

a view of a security document, here a banknote, with three strip-shaped sections, are introduced into the mottled fibers;

Fig. 2a, b

a plan view of two security documents with four strip-shaped sections, which represent a different coding;

Fig. 3

a section of the wavelength spectrum with four fixed wavelength intervals for a coding system of four different luminescent substances;

Fig. 4

an arrangement for measuring the luminescent properties of mottled fibers, which are incorporated in various sub-areas in a security document;

Fig. 5

the time course of the electrical signals at the output of the light detector from the arrangement of Fig. 4 in the review of the document of FIG. 2a.

FIG. 1 shows a top view of a security document 1, here a banknote made of security paper 2. On the security document 1, the edge 3 of an image field is shown in dashed lines, wherein often an artistically designed pictorial representation 4 (not shown in the figure) is printed. On the security document 1 three strip-shaped control areas 8a, 8b, 8c are indicated by dotted lines. They indicate the areas in which the detector checks the properties of the luminescent mottled fibers. Their location on the security document 1 is therefore determined by the coding to be tested.

The distance between the control areas 8a and 8b is denoted by a and the distance between the control areas 8b, 8c to b, wherein the distances a, b are different in the embodiment shown. The ratio between the distances a, b can be, for example, an integer to get voted. Within the three strip-shaped control areas 8a, 8b, 8c are strip-shaped partial areas 5a, 5b, 5c in which mottled fibers are introduced into the security paper 2. The boundary lines of the strip-shaped portions 5a, 5b, 5c are shown in FIG. 1 by solid lines. However, the solid lines are for illustrative purposes only and are not present on a genuine security document.

In the embodiment shown in Figure 1, all strip-shaped portions 5a, 5b, 5c are provided with mottled fibers of the same type A, i. In all subregions 5a, 5b, 5c are mottled fibers with the same luminescent property. The coding is represented in this embodiment solely by the distances a, b of the partial regions 5a, 5b, 5c or the control regions 8a, 8b, 8c.

Figure 2 shows the example of two security documents 1a, 1b another possibility for a coding according to the invention. In this case, the distance a between the individual control areas 8a, 8b, 8c, 8d is constant and the coding is represented by the presence or absence of one or more partial areas with special mottling fibers within the control areas 8a, 8b, 8c, 8d. The mottled fibers arranged in the subregions differ here in the luminescent property to be tested. The document 1a, for example, has only within the control areas 8a, 8b subareas 7a, 7b in which there are mists of fibers A or B, whereas the document 1b only in the control areas 8a, 8d with mica fibers A, D having portions 7a, 7d is provided.

Thus, the coding system consists of four types of luminescent mottled fibers, A, B, C, D, which differ in one or more of their luminescent properties and whose presence or absence is checked in predetermined control ranges. If the presence of the correct luminescent property in the predetermined control region is assigned the logic state "1" and the absence of the corresponding substance is the state "0", then meaningful binary codes can be represented with the aid of the described coding system 2 ⁴ -1 = 15.

If the document 1a were checked within the measuring track 10 running along the document, a corresponding detector would detect the binary coding 1100 in this case. For the document 1b, the binary coding 1 0 0 1 results.

Of course, the number of control areas used as well as the number of different mottled fibers can be varied as desired. Thus, for example, the same mottling fibers with the same luminescent substance can also be used for all control areas. This has the advantage that the structure of the sensor can be made much simpler.

If, on the other hand, the coding is to be made even more complicated, then, in addition to the embodiment shown in FIG. 1, the distances of the control areas can additionally be varied.

When checking the document, any properties of the luminescent substances contained in the mottling fibers can be evaluated, such as eg the luminescence wavelength or the decay time of the luminescence radiation.

FIG. 3 shows, in the case of the wavelength-dependent evaluation, a possible spectral distribution of the emission wavelengths of the coding system described above from four types A, B, C, D of mottled fibers, which differ in the simplest case shown here, at least with respect to their emission wavelength. The luminescent substance A accordingly emits at shorter wavelengths than the luminescent substances B, C, D. As can be seen from FIG. 3, all substances A, B, C, D each have a very narrow-band luminescence emission which does not overlap with that of the other luminescent substances used, so that the luminescent substances A, B, C, D are very easy to distinguish from each other. The luminescence intensity of the substances is also sufficiently high so that the substances can be reliably detected and detected by machine.

FIG. 4 shows schematically a possible arrangement for detecting and evaluating a coding which is represented by means of the luminescent substances or mottled fibers having emission lines shown in FIG.

Usually, the checking of the bank note takes place in a bank note processing device, by means of which the bank notes are guided past the sensors with the aid of a transport system at high speeds. In FIG. 4, this transport of the banknote 2 according to the invention is indicated by the arrow 11. The banknote passes by an illumination source 12 whose radiation is focused onto the document with the aid of an optical system 13. The illumination source 12 is chosen so that it emits radiation of the excitation wavelength of the individual luminescent substances. Are the excitation wavelengths of the individual luminescent substances in different wavelength ranges, it may be useful to use as the illumination source a plurality of excitation sources, each of which emits light in the range of one of the excitation wavelengths. If a region of the document 2 according to the invention is illuminated in which, according to the invention, luminescent mottled fibers are present, they are excited to luminescence. The frequently diffuse luminescence radiation 14 is finally focused on a detector 16 via a further optical system 15. This detector 16 preferably includes a spectrometer with a diode array, each of the diodes being sensitive to one of the emission wavelengths 23a to 23d.

If, for example, the banknote 1a according to FIG. 2a is transported past the measuring device shown in FIG. 4 and the mottling fibers A, B show the emission lines 23a, 23b illustrated in FIG. 3, then the detector takes in the control areas 8a, 8b, 8c 8d associated measuring channels on the signals shown in Fig. 5.

In Fig. 5, the signals I of the individual Melierfaserarten A, B, C, D associated measuring channels over time t are plotted. The dashed time slots 30a, 30b, 30c, 30d correspond to the control areas 8a, 8b, 8c, 8d and denote the measurement windows, in each of which a signal is expected. If the note 1a passes under the sensor in the direction of the arrow 11, the control area 8d is first illuminated. Since there are no mottled fibers within this control range, the associated measuring channel does not detect any signal in the time window 30d. Since the mottling fibers of type C are not available, the associated measuring channel also receives no signal. Only when the partial region 7b or the control region 8b is transported past under the sensor arrangement does the sensor record the emission band 23b of the luminescent substance B in the time window 30b. analog applies to the subsequent subarea 7a or the signal 23a in the time window 30a. As already explained, if the presence of the luminescence emission 23a, 23b, 23c, 23d in the correct time window 30a, 30b, 30c, 30d means a binary "1" and the absence of a binary "0", then the signals in FIG the code 1 1 0 0 shown.

Claims (22)

1. A security paper (2) with mottling fibers (A, B, C, D) having a luminescent property for the purpose of a coding, characterized in that the security paper (2) has one or more separate partial areas (5a, 5b, 5c; 7a, 7b) in which only one type of mottling fibers (A, B, C, D) is present in each case and whose total surface area is smaller than the surface area of the security document (1; 1a; 1b), the mottling fibers (A, B, C, D) being distributed in the paper pulp solely in said partial areas (5a, 5b, 5c; 7a, 7b).
2. A security paper (2) with mottling fibers (A, B, C, D) having a luminescent property for the purpose of a coding, characterized in that the security paper (2) has at least two separate partial areas (5a, 5b, 5c; 7a, 7b) in which only one type of mottling fibers (A, B, C, D) is present in each case and whose total surface area is smaller than the surface area of the security document (1; 1a; 1b) and in which the mottling fibers (A, B, C, D) are solely present.
3. The security paper (2) according to claim 2, characterized in that the security paper (2) contains at least two types of mottling fibers (A, B, C, D) which differ with respect to their luminescent properties.
4. The security paper (2) according to claim 2, characterized in that the same mottling fibers (A, B, C, D) are present in both partial areas (5a, 5b, 5c; 7a, 7b).
5. The security paper (2) according to at least one of claims 1 to 4, characterized in that the mottling fibers (A, B, C, D) contain luminescent substances with characteristic luminescent properties.
6. The security paper (2) according to claim 5, characterized in that the luminescent substances have a spectrally narrow emission band (23a, 23b, 23c, 23d).
7. The security paper (2) according to claim 5 or 6, characterized in that the luminescent substances emit outside the visual spectral range.
8. The security paper (2) according to at least one of claims 5 to 7, characterized in that the luminescent substances are optical intensifying materials which have an optically pumpable, light-emitting material, light-scattering centers, and a transparent matrix material.
9. The security paper (2) according to at least one of claims 5 to 8, characterized in that the luminescent substances are present within the volume of the mottling fibers (A, B, C, D).
10. The security paper (2) according to at least one of claims 5 to 8, characterized in that the mottling fibers (A, B, C, D) are dyed with the luminescent substances.
11. The security paper (2) according to at least one of claims 1 to 10, characterized in that the mottling fibers (A, B, C, D) consist of a plastic material.
12. The security paper (2) according to at least one of claims 1 to 11, characterized in that the mottling fibers (A, B, C, D) are incorporated into the security paper (2) during papermaking.
13. The security paper (2) according to at least one of claims 1 to 12, characterized in that the mottling fibers (A, B, C, D) are incorporated into the security paper (2) by means of the Wilcox process.
14. The security paper (2) according to at least one of claims 1 to 13, characterized in that the partial areas (5a, 5b, 5c; 7a, 7b) have the form of strips.
15. The security paper (2) according to claim 14, characterized in that the width of the strips is in the range of from 5 mm to 30 mm.
16. The security paper (2) according to at least one of claims 1 to 15, characterized in that the mottling fiber density in the partial areas (5a, 5b, 5c; 7a, 7b) is in the range of from 2 to 20 mottling fibers (A, B, C, D) per square centimeter.
17. A method for machine testing of a coding in a security document (1; 1a; 1b) using a security paper (2) according to one of claims 1 to 16, comprising the steps of:

    a) measuring luminescent properties of the mottling fibers (A, B, C, D) contained in the partial areas (5a, 5b, 5c; 7a, 7b) of the security paper (2) by means of a sensor (12, 13, 15, 16),

    b) determining the coding of the security paper (2) from the sensor measuring values, and

    c) comparing the determined coding with a reference value.
18. The method according to claim 17, characterized in that in step a) emission spectra (23a, 23b, 23c, 23d) outside the visual spectral range are measured for measuring the luminescent properties of the mottling fibers (A, B, C, D).
19. The method according to claim 17 or 18, characterized in that in step a) the individual emission spectrum (23a, 23b, 23c, 23d) of a certain type of mottling fibers is measured for measuring the luminescent properties thereof.
20. The method according to claim 17, characterized in that in step a) it is tested whether different mottling fibers (A, B, C, D) are present in two different partial areas (5a, 5b, 5c; 7a, 7b).
21. The method according to any of claims 17 to 20, characterized in that in step a) strip-shaped partial areas (5a, 5b, 5c; 7a, 7b) are tested.
22. The method according to claim 21, characterized in that in step a) strips with a width of from 5 mm to 30 mm are tested.

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