EP3275685B2 - Security paper, security element and valuable document - Google Patents

Description

The invention relates to a security paper for the production of documents of value, such as banknotes, passports, identification documents or the like, and a document of value comprising the 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 present, for example, in the form of a security thread that is fully or partially embedded in a bank note, or in the form of a security strip or patch applied to the bank note.

In recent years, security elements, in particular security threads, with optically variable security features have become established on the banknote market. Optically variable security features give the viewer a different image impression from different viewing angles. The security features can be present in the form of optically diffractive micro- or nanostructures, such as in the case of conventional embossed holograms or other hologram-like diffraction structures (see, for example, the publications EP 0 330 733 A1 or EP 0 064 067 A1 ).

It is also known to use lens systems as security features. For example, in the pamphlet EP 0 238 043 A2 or in the DE 36 09 090 A1 describes a security thread made of a transparent material, on the surface of which a grid of several parallel cylindrical lenses is embossed. The thickness of the security thread is chosen so that it roughly corresponds to the focal length of the cylindrical lenses. A printed image is applied in register to the opposite surface, the printed image being designed taking into account the optical properties of the cylindrical lenses.

So-called moiré magnification arrangements have also been used as security features for some time. Such a moiré magnification arrangement is in the reference WO 2006/087138 A1 or in the DE 10 2005 028162 A1 disclosed. That in the WO 2006/087138 A1 disclosed anti-counterfeiting means has at least a first and a second security feature. In this case, the first authenticity feature comprises a first arrangement with a multiplicity of focusing elements which are present in a first grid, and a second arrangement with a multiplicity of microscopic structures which are present in a second grid. The first and second arrays are arranged relative to each other such that the microscopic structures of the second array can be seen in magnification when viewed through the focusing elements of the first array. Such a magnification effect is also called moiré magnification designated. Briefly, moiré magnification thereafter refers to a phenomenon that occurs when a grid of identical image objects is viewed through a lenticular array of approximately the same pitch. As with any pair of similar screens, a moire pattern results, in which case each of the moire fringes appears as an enlarged and rotated image of the repeated elements of the image screen.

It is also known to use optically variable security features based on periodic or aperiodic sawtooth gratings (see, for example, WO 2011/066991 A2 ).

Securities can be provided with a dirt-repellent protective layer to extend their service life and fitness for circulation. For example, in the reference EP 0 256 170 B2 proposed to provide printed banknotes with a protective layer containing mostly cellulose ester or cellulose ether and to a lesser extent micronized wax and which is applied over the entire surface of the banknotes. The micronized wax is thereby dispersed by dispersing or mixing with oil, a binder or a mixture thereof. The sheets freshly printed with the protective layer can be stacked without difficulty, without ink rubbing off from one sheet onto the sheet below. Another dirt-repellent layer, which is based on a UV coating, for example, is from the WO 2004/072378 A1 known.

Furthermore, it is known to equip documents of value with luminescent features. Black light tubes or LED UV lamps, for example, are used to check the authenticity of the value document. Due to the required chemical resistance, classic fluorescent paints are based on organic or inorganic pigments whose particle size is in the micrometer range. However, the particle size leads to optical scattering effects. If such fluorescent colors are printed on optically variable security elements, e.g. holograms or micromirror arrays, the scattering of the pigments causes a matting effect and thus a loss of brilliance in the area of the optically variable security element printed with the fluorescent color. In this way, the printed fluorescent color is easily recognizable to the observer without being stimulated by UV light and thus disrupts the appearance of the optically variable security feature.

The document DE 10 2004 053007 A1 discloses a security paper according to the preamble of claim 1.

Proceeding from this, the object of the invention is to avoid the disadvantages of the prior art and in particular to specify a security paper and an optically variable security element, with a chemically stable fluorescent feature being present in the area of the optically variable security feature.

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

Summary of the Invention

(First aspect of the invention) Security paper according to claim 1.

(Preferred embodiment) Security paper according to Claim 3. The structure developing the optically variable effect is a multi-layer thin-layer element, the color impression of which changes for the observer with the viewing angle. Such a thin-film element has, for example, a semi-transparent absorber layer, a dielectric spacer layer and a reflection layer. A large number of different color-shift effects can be designed by a suitable choice of material and thickness, in particular of the dielectric spacer layer. SiO2 or Al2O3, for example, are suitable as a dielectric spacer layer. The reflection layer of the thin-film element is preferably formed by an opaque or a semi-transparent metal layer, preferably by an opaque or a semi-transparent aluminum layer. In principle, however, other metals such as silver, nickel, copper, iron, chromium, gold or other highly reflective materials can also be considered. The semi-transparent absorber layer can be formed by a chromium layer, for example.

(Second aspect of the invention) A document of value according to claim 12.

Detailed Description of the Invention

According to a first variant, which is not part of the present invention, fluorescent nanopigments are used as fluorescent substances, the particle size of which is less than 1 μm, preferably less than 0.5 μm. Due to the small particle size, optical scattering effects are avoided. Since inorganic fluorescent pigments, also known as quantum dots, have a rather low light yield, fluorescent dyes are preferably used, which are dissolved in a suitable solvent and then applied to an inorganic carrier, the inorganic carrier being based on particles in the nanometer range (hereinafter also referred to as inorganic, nanoscale carrier). The inorganic, nanoscale carrier can in particular be calcium carbonate, a silicate, an aluminum silicate or aluminum hydroxide.

According to a further variant, which is not part of the present invention, fluorescent dyes are used as fluorescent substances, which are dissolved as completely as possible in the solvent of a printing ink.

In a variant according to the invention, thermally sublimable fluorescent dyes, eg Tinopal OB CO, are used as fluorescent substances from BASF, which are dispersed or dissolved in a paint. This color is applied, eg printed, to a transparent receiver layer. The sublimable fluorescent dye dispersed or dissolved in the printing ink is then caused to diffuse into the receiver layer and penetrate into the polymer of the receiver layer and be stored there by means of a brief, high temperature.

According to all three variants, a non-scattering, fluorescent printing feature can be provided above the optically variable security element.

In order to obtain the required chemical resistance, it is advisable to provide the fluorescent print layer with a suitable coating. In the case of an optically variable security element based on a film substrate, the coating should be present at least on the upper side of the security element. In the case of a paper substrate, the coating should preferably be both above and below the fluorescent print layer. In order to sufficiently protect the fluorescent print layer from lateral attack by chemicals, it is advantageous to design the protective coating in such a way that the coating overlaps the fluorescent print layer.

• Lackrezeptur A (mittels Flexo- oder Siebdruck verdruckbar, UV-trockend):
  • 64% kommerziell erhältlicher Stoff "SUO HH 8800 Polygon";
  • 36% sogenannter "Photoinitiator 1" (unten näher beschrieben).
  Die Viskosität kann entsprechend den Druckverfahren noch mit Monomeren wie HDDA (Hexan-1,6-diol-diacrylat) eingestellt werden.
• Lackrezeptur B (mittels Flexo- oder Siebdruck verdruckbar, UV-trockend):
  • 54% kommerziell erhältlicher Stoff "SUO HH 8800 Polygon";
  • 10% kommerziell erhältlicher Stoff "XDT-1018 Dymax";
  • 36% sogenannter "Photoinitiator 1" (unten näher beschrieben).

Preferred examples of transparent protective coatings that improve the chemical resistance of the fluorescent substance are the following coating formulations A and B:

• Coating recipe A (can be printed using flexo or screen printing, UV drying):
  • 64% commercial fabric "SUO HH 8800 Polygon";
  • 36% so-called "Photoinitiator 1" (described in more detail below).
  Depending on the printing process, the viscosity can also be adjusted with monomers such as HDDA (hexane-1,6-diol diacrylate).
• Varnish recipe B (can be printed using flexo or screen printing, UV drying):
  • 54% commercial fabric "SUO HH 8800 Polygon";
  • 10% commercial fabric "XDT-1018 Dymax";
  • 36% so-called "Photoinitiator 1" (described in more detail below).

Photoinitiator 1 :

• 10% kommerziell erhältlicher Stoff "Irgacure 819" der Firma BASF;
• 90% kommerziell erhältlicher Stoff "HDDA" der Firma Laromer.Der Photoinitiator 1 sollte vorsichtig mittels eines Dissolvers eingerührt werden.

Photoinitiator 1 is based on the following recipe:

• 10% commercially available material "Irgacure 819" from BASF;
• 90% commercially available substance "HDDA" from Laromer. Photoinitiator 1 should be stirred in carefully using a dissolver.

• "SUO HH 8800" der Firma Polygon;
• "Bomar BR 641D" der Firma Dymax.

A polybutadiene urethane acrylate forms the main component of the hydrophobic paint formulation:

• "SUO HH 8800" from Polygon;
• "Bomar BR 641D" from the Dymax company.

1. 1. Eine Schicht oberhalb des Papier-Substrats (auf Basis von Baumwollkämmlingen), basierend auf der obigen "Lackrezeptur A" (oder "Lackrezeptur B") mit einer Schichtdicke in einem Bereich von 4 bis 10 Mikrometer.
2. 2. Druck, basierend auf der Fluoreszenzfarbe "Rotoflex 012" mit 5% gelöstem "CD335" der Firma Honeywell. Die Schichtdicke (nass) beträgt etwa 5 bis 10 Mikrometer.
3. 3. Eine Schicht, basierend auf der obigen "Lackrezeptur A" (oder "Lackrezeptur B") mit einer Schichtdicke in einem Bereich von 4 bis 10 Mikrometer.

It is useful to make proofs with the following layer sequence 1-3:

1. 1. A layer over the paper substrate (cotton noil based) based on "varnish recipe A" (or "varnish recipe B") above with a layer thickness in a range of 4 to 10 microns.
2. 2nd print, based on the fluorescent ink "Rotoflex 012" with 5% dissolved "CD335" from Honeywell. The layer thickness (wet) is about 5 to 10 microns.
3. 3. A layer based on the above "Paint Formulation A" (or "Paint Formulation B") with a layer thickness in a range of 4 to 10 microns.

After a drying time of five days at room temperature, the above layer structure was experimentally tested in direct comparison with a sample that did not have a protective varnish with regard to resistance to ethyl alcohol, acetone, hydrochloric acid and sodium hydroxide and rated as extremely advantageous.

In a preferred embodiment, the fluorescer is a solvent-soluble luminescent, e.g., fluorescent or phosphorescent, dye.

According to a further preferred embodiment, the fluorescent substance is a dye that can be excited in the UV range and emits in the visible spectral range.

According to a further preferred embodiment, the fluorescent substance is a dye that can be excited in the visible spectral range and emits in the visible spectral range.

According to a further preferred embodiment, the fluorescent substance is a dye which emits in the IR range.

The fluorescent substance is preferably an organic substance or an organometallic complex.

Examples of suitable UV-excitable fluorescent dyes are organic fluorescent dyes or fluorescent metal complexes. Possible classes of dyes are, for example, cyanines, rhodamines, oxazines, phenoxazines, thiazines, phenothiazines, perylenes, terylenes, coumarins, benzoxazinones or benzothiazines and rare earth metal complexes, for example beta-diketonate complexes or dipicolinate complexes and their derivatives, preferably neutrally charged rare earth metal complexes. Other classes of organic dyes can also be used. Such fluorescent dyes are commercially available from Honeywell, for example, under the brand name Lumilux, for example Lumilux Red CD 335, Lumilux Yellow CD 397 or Lumilux Blue CD 312.

Examples of suitable substances that can be excited in the visible spectral range and emit in the visible spectral range are, for example, organic fluorescent dyes or fluorescent metal complexes. For example, fluorescent dyes from the classes of cyanines, rhodamines, oxazines, phenoxazines, thiazines, phenothiazines, perylenes, terylenes, coumarins, benzoxazinones or benzothiazines and rare earth metal complexes such as beta-diketonate complexes or dipicolinate complexes, preferably neutrally charged rare earth metal complexes. Perylene dyes are preferably used because of their high light stability. Perylene dyes are commercially available from companies such as BASF, e.g. under the brand name Lumogen, e.g. Lumogen F Orange 240.

Examples of suitable infrared-emitting fluorescent substances are, for example, organic fluorescent dyes or fluorescent metal complexes, for example IR-1048, Cy7 or Nd(TTA)3 (neodymium tristhenoyl trifluoroacetonate).

There are no particular limitations with respect to the security paper substrate. Banknote papers are typically made from fibers from annual plants, in particular cotton fibers or cellulose fibres, but papers which consist at least partly of plastic fibres, preferably of polyamide fibers or polyester fibres, can also be used. A cotton paper is particularly preferably used as the security paper substrate. The basis weight of the substrate varies depending on the application. Customary basis weights are in the range from 50 g/m 2 to 100 g/m 2 , preferably in the range from 60 g/m 2 to 90 g/m 2 , particularly preferably around 70 g/m 2 <2>. In the case of multi-layer substrates, the individual paper layers can consist of the same or different types of paper. For example, one layer of paper can be pure cotton paper, while another layer of paper has plastic fibers. Furthermore, multi-layer paper/foil composites can also be used as the security paper substrate, such as a paper/foil/paper composite or a foil/paper/foil composite.

There are also no special restrictions with regard to the type of production of the security paper substrate. The production preferably takes place by means of a cylinder mold machine.

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 eines Sicherheitspapiers in Querschnittansicht;
• Fig. 2 : eine schematische Darstellung des Sicherheitspapiers in Draufsicht;
• Fig. 3 : eine schematische Darstellung von Sicherheitselementen in Draufsicht, im Beispiel parallel angeordnete Sicherheitsstreifen in Form eines noch nicht geschnittenen Rollenmaterials;
• Fig. 4 : eine schematische Darstellung eines weiteren Sicherheitspapiers in Draufsicht;
• Fig. 5 : eine schematische Querschnittansicht eines Sicherheitselements mit einem Hologramm und einem optisch nicht streuenden, fluoreszierenden Druck-Merkmal und einem optisch streuenden, fluoreszierenden Druck-Merkmal;
• Fig. 6 : das Sicherheitselement der Figur 5 in Draufsicht;
• Fig. 7-8 : ein Beispiel für die Herstellung eines erfindungsgemäßen Sicherheitspapiers.

Show it:

• 1 : a schematic representation of a security paper in a cross-sectional view;
• 2 : a schematic representation of the security paper in plan view;
• 3 1: a schematic representation of security elements in plan view, in the example security strips arranged in parallel in the form of a roll material that has not yet been cut;
• 4 : a schematic representation of a further security paper in plan view;
• figure 5 1: a schematic cross-sectional view of a security element with a hologram and an optically non-scattering, fluorescent printing feature and an optically scattering, fluorescent printing feature;
• 6 : the security element of figure 5 in top view;
• Figures 7-8 : an example of the production of a security paper according to the invention.

1 shows a schematic representation of a security paper in a cross-sectional view. The security paper, in the present case a security paper for the production of banknotes, contains a paper substrate 1, a heat-sealing lacquer layer 2, a barrier lacquer layer 3, an embossing lacquer layer 4, e.g. a UV lacquer with an embossed surface relief, a metallization 5 (which can alternatively also be a metallic printing layer can be formed), a first, lower protective coating 6, a fluorescent printing layer 7 and a second, upper protective coating 8.

The second, upper protective coating 8 can additionally contain hydrophobic additives or oligomers in the formulation in order to avoid or reduce the wetting of test reagents or test chemicals.

In order to achieve better barrier properties, layers 6 and 8 can each consist of two or more individual layers. In this way, faults that can be traced back to defects (e.g. bubbles in the paint) within a single layer can be avoided.

The layer sequence 2 to 8 together forms an optically variable security element. The security element is applied to the paper substrate 1 by means of the adhesive layer 2 . It is alternatively possible for the second, upper protective coating 8 to be printed onto the fluorescent printed layer 7 as a separate layer after the application of the security element (with the layers 2 to 7).

The second, upper protective coating 8 can additionally contain a UV absorber which absorbs in part of the UV range, e.g. in the short-wave UV range.

The first, lower protective coating 6 can alternatively be applied below the metallization 5 or below the embossing lacquer layer 4 in order to also protect these layers from the influence of test chemicals.

2 shows a schematic representation of the security paper 1 in top view. The 2 makes it clear that the second, upper protective coating 8 advantageously completely envelops the fluorescent printed layer 7, so that a lateral attack, for example in the area of a cut edge, by the test chemical is also prevented.

• optional eine Kleberschicht;
• Foliensubstrat, z.B. Polyesterfolie;
• Prägelackschicht;
• Metallisierung;
• Bereiche aus einer fluoreszierenden Druckschicht;
• Schutzbeschichtung;
• optional eine Kleberschicht.

3 shows a schematic representation of security elements in plan view, in the example security strips 13, 14 and 15 arranged in parallel in the form of a roll of material that has not yet been cut. The roll material has the following layer structure:

• optionally an adhesive layer;
• film substrate, eg polyester film;
• embossing layer;
• metallization;
• areas of a fluorescent printing layer;
• protective coating;
• optionally an adhesive layer.

The reference number 9 designates a metallization. Areas 11 made of a fluorescent printed layer are present above the metallization 9 . The reference number 10 designates a protective coating placed over the metallization 9 and over the regions 11 of fluorescent printing layer. The dashed lines 12 indicate cutting lines for cutting the individual security strips or security threads 13, 14 and 15.

The 3 makes it clear that the protective coating 10 also protects the sensitive, fluorescent print 11 in the area of the cutting edges 12 produced by cutting the individual security strips 13, 14 and 15 to size.

In the present example, the individual security strips 13, 14 and 15 each have a film substrate, e.g. a polyester film. For this reason it is not absolutely necessary to provide a further protective coating below the areas 11 made of a fluorescent printed layer 11 .

4 shows a schematic representation of a further security paper 16, in the present case a bank note with the denomination "20", in top view. The reference numeral 17 designates a so-called window thread which is partially embedded in the paper substrate of the banknote 16, the areas 18 being visually recognizable to the viewer. The window thread 17 has a fluorescent printed layer on its surface. Banknote 16 was subsequently provided with a protective coating in area 19.

The areas of the bank note 16 adjoining the area 19 can optionally be provided with a special dirt-repellent coating. Of course, a full-surface dirt-repellent coating can also be produced over the entire bank note 16 afterwards.

The protective coating 19 itself can also have a dirt-repellent effect.

figure 5 shows a schematic cross-sectional view of a security element with a film substrate 20, an embossing lacquer layer 21, a metallization 22, an optically non-scattering, fluorescent printing feature 23 and an optically scattering, fluorescent printing feature 24. The embossing lacquer layer 21 and the metallization 22 together form one hologram layer.

The optically scattering, fluorescent print feature 24 is based on organic or inorganic pigments 25 with particle sizes in the micrometer range present in a binder. Optical scattering effects occur due to the large particle size, as is symbolized by the arrows 28 . As a result of the optically scattering fluorescent ink printed on the hologram layer (21, 22), matting effects occur in the area of the printing feature 24 and the hologram thus has a loss of brightness.

The optically non-scattering, fluorescent printing feature 23 is based, for example, on fluorescent nanopigments 26 present in a binder. Due to the small particle size, no visually visible, optical scattering effects whatsoever result. In the area of the print feature 23, the hologram layer (21, 22) therefore shows no matting effect and no loss of brightness.

6 Illustrates that the optically scattering, fluorescent print feature 24 is easily recognizable visually even without excitation by means of UV light and thus impairs the holographic information 22 or anticipates the information of the fluorescent print feature.

Figures 7 and 8 show an example for the production of a security paper according to the invention, namely the functioning of thermally sublimable luminescent substances in the cross section of a layer sequence.

The Indian figure 7 The layer structure shown contains a paper substrate 29, a lower protective coating 30, which can also act as a barrier layer for the sublimable fluorescent dye, a receiver layer 31 for receiving the sublimable fluorescent dye after heat mobilization, a fluorescent print layer 32, which contains a dissolved or dispersed sublimable fluorescent dye, and an upper protective coating 33 which can also act as a barrier layer for the sublimable fluorescent dye. The sublimable fluorescent dye contained in the fluorescent printing layer 32 is shown with black dots.

figure 8 shows the layer structure after thermal activation. The receiver layer is provided with the gaseous materials absorb and bind fluorescent substances after the temperature increase. This is possible, for example, with polymer fibers in the coating, eg nylon.

Claims (12)

1. (a) A security paper for manufacturing value documents,

   (b) comprising a security-paper substrate equipped with an optically variable security element (2-8),

   (c) wherein the optically variable security element contains a structure developing an optically variable effect (4, 5),

   (d) wherein the structure developing the optically variable effect is present in an emboss-lacquer layer (4) and is a relief structure,

   (e) and the structure developing the optically variable effect is printed with a fluorescent substance not impairing the optically variable effect (7),

   (f) and the optically variable security element has a transparent protective lacquer (6, 8) improving the chemical stability of the fluorescent substance, characterized in that

   (g) the fluorescent substance is supplied on side of the security paper of the structure facing the viewer,

   wherein the structure furnished with the fluorescent substance and developing an optically variable effect is a relief structure and is obtainable by furnishing the relief structure with a polymer-based transparent receiver layer, the receiver layer being printed with a thermally sublimable, fluorescent colorant containing printing ink and the thermally sublimable, fluorescent colorant contained in the printing ink penetrates into the receiver layer by means of a diffusion caused by a temperature elevation in order to be deposited there.
2. The security paper according to claim 1, wherein the structure developing the optically variable effect shows a diffractive structure, such as a hologram, a holographic grating image or a hologram-like diffractive structure or an achromatic structure, such as a matt structure, a micromirror arrangement, a blaze grating having a sawtooth-type groove profile or a Fresnel lens arrangement.
3. The security paper according to claim 1, wherein the structure developing the optically variable effect is a multilayer thin-film element whose color impression for the viewer changes with the viewing angle.
4. The security paper according to any of claims 1 to 3, wherein the transparent protective lacquer improving the chemical stability of the fluorescent substance is a UV lacquer.
5. The security paper according to claim 4, wherein the UV lacquer is a radically drying UV lacquer which is based preferably on a polybutadiene-urethane-acrylate-oligomer.
6. The security paper according to any of claims 1 to 5, wherein the transparent protective lacquer improving the chemical stability of the fluorescent substance additionally contains a hydrophobizing additive, which is chosen from the group consisting of waxes, fluorine silanes and silicones, so that the wettability of the protective lacquer with a test chemical is avoided and the test chemical is chosen from the group consisting of aqueous solutions, alcohols and chlorinated hydrocarbons.
7. The security paper according to any of claims 1 to 6, wherein the transparent protective lacquer improving the chemical stability of the fluorescent substance forms the uppermost layer of the optically variable security element.
8. The security paper according to any of claims 1 to 6, wherein the transparent protective lacquer improving the chemical stability of the fluorescent substance forms the second-uppermost layer of the optically variable security element and the uppermost layer of the optically variable security element is a dirt-repellent and/or scratch resistance-increasing, transparent protective layer.
9. The security paper according to claim 8, wherein the transparent protective lacquer improving the chemical stability of the fluorescent substance and/or the dirt-repellent and/or scratch resistance-increasing, transparent protective layer additionally contains a UV absorber which absorbs energy in a partial region of the UV spectrum, wherein the UV absorber preferably is a HALS which absorbs predominantly UV light in the short-wave UV region.
10. The security paper according to any of claims 1 to 9, wherein the transparent protective lacquer improving the chemical stability of the fluorescent substance is applied over the full area to the security-paper substrate equipped with the optically variable security element.
11. The security paper according to any of claims 1 to 10, wherein the fluorescent substance not impairing the optically variable effect is protected, in addition to the transparent protective lacquer improving the chemical stability of the fluorescent substance, by a further transparent protective lacquer improving the chemical stability of the fluorescent substance, so that the fluorescent substance is protected on both sides, i.e. above and below, by two separate protective lacquer layers.
12. A value document, comprising the security paper according to any of claims 1 to 11.

Images