METHOD FOR MANUFACTURING A VALUE DOCUMENT, VALUE DOCUMENT AND PRINTING DEVICE

Abstract

A method for manufacturing a value document includes: providing a value document substrate; printing the value document substrate with magnetically orientable effect pigments which are dispersed in a UV-curable lacquer; the step of exposing the lacquer containing the magnetically orientable effect pigments to a dynamic magnetic field; the step of irradiating the lacquer containing the effect pigments with UV radiation; and optionally the step of embossing the cured or at least partially cured UV lacquer.

Claims

1.-10. (canceled)

11. A method for manufacturing a value document, e.g. a bank note, comprising: a) providing a value document substrate; b) printing the value document substrate with magnetically orientable effect pigments which are dispersed in a UV-curable lacquer; c) the step c1) of exposing the lacquer containing the magnetically orientable effect pigments to a dynamic, in particular a rotating, magnetic field, so that the effect pigments in the lacquer arrange themselves parallel to the value document substrate and in particular edge to edge; the step c2) of irradiating the lacquer containing the effect pigments with UV radiation, wherein step c2) in particular is effected after step c1) or is effected simultaneously together with step c1).

12. The method according to claim 11, additionally comprising d) the step of embossing the cured or at least partially cured UV lacquer, which has the effect pigments which are arranged parallel to the value document substrate and in particular edge to edge, so that an embossed relief structure with effect pigments adapting to the relief is formed in the lacquer, conveying to the viewer an optically variable image.

13. The method according to claim 11, wherein the dynamic, in particular rotating, magnetic field in step c) is a continuously rotating magnetic field which preferably has a speed in the region of 50 revolutions per minute to 1500 revolutions per minute, more preferably a speed in the region of 100 revolutions to 1500 revolutions per minute and particularly preferably a speed in the region of 100 revolutions per minute to 500 revolutions per minute.

14. The method according to claim 11, wherein the step of embossing d) is effected by means of an intaglio printing plate.

15. The method according to claim 11, wherein the step b) of printing the value document substrate with magnetically orientable effect pigments which are dispersed in a UV-curable lacquer is effected in a selected region which is present in particular in the form of a pattern, in the form of characters or in the form of a coding.

16. The method according to claim 11, wherein the step c) has the following (sub)steps: c) the step c1a) of exposing the lacquer containing the magnetically orientable effect pigments to a dynamic, in particular a rotating, magnetic field, so that the effect pigments in the lacquer arrange themselves parallel to the value document substrate and in particular edge to edge, in order to arrange the effect pigments in this way in the form of a pre-orientation; the step c1b) in which a further orienting or aligning of the magnetically orientable effect pigments pre-oriented in the course of step c1a) is effected by applying a static magnetic field so that the effect pigments assume an orientation changed against the pre-orientation; the step c2) of irradiating the lacquer containing the effect pigments with UV radiation, wherein step c2) in particular is effected after steps c1a) and c1b).

17. The method according to claim 16, additionally comprising step d) of embossing the cured or at least partially cured UV lacquer, which has the pre-oriented effect pigments which first are arranged parallel to the value document substrate and in particular edge to edge and subsequently has effect pigments subjected to a changed orientation, so that an embossed relief structure with effect pigments adapting to the relief is formed in the lacquer, conveying to the viewer an optically variable image.

18. A value document, in particular a bank note, obtainable by the method according to claim 11.

19. A printing device for carrying out the method according to claim 11, comprising an apparatus for providing a value document substrate, an apparatus for printing the value document substrate with a UV-curable lacquer based on magnetically orientable effect pigments, an apparatus for providing a dynamic, in particular rotating, magnetic field which is suitable for aligning the effect pigments, an apparatus for curing the UV lacquer by means of UV radiation and an apparatus for embossing the cured or at least partially cured UV lacquer.

20. The printing device according to claim 19, wherein the apparatus for embossing is an intaglio printing plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The advantages of the invention will be explained hereinafter with reference to the strongly simplified Figures, in whose representation a rendition that is true to scale and to proportion has been dispensed with in order to increase clearness.

[0026] There are shown:

[0027] FIG. 1 the alignment of “leafing” pigments in a lacquer applied to a printing stock;

[0028] FIG. 2 the alignment of “non-leafing” pigments in a lacquer applied to a printing stock;

[0029] FIG. 3 the arrangement of pigments in a lacquer applied to a printing stock, before the embossing operation;

[0030] FIG. 4 the arrangement of pigments in a lacquer applied to a printing stock, after the embossing operation.

[0031] FIG. 5 the alignment of OVMI® pigments dispersed in a UV-curable lacquer, which are exposed to a rotating magnetic field, when viewed in cross-sectional view;

[0032] FIG. 6 the orientation of OVMI® pigments dispersed in a UV-curable lacquer, which are exposed to a rotating magnetic field, when viewed in plan view; and

[0033] FIGS. 7 and 8 the arrangement of OVMI pigments, which are exposed to a rotating magnetic field, in a UV-curable lacquer applied to a printing stock, respectively before and after the embossing operation.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0034] The method according to the invention preferably includes the embossing of a dispersion solution which contains thin-film pigments. It is known in the prior art that the alignment of the pigments of an optically variable ink (OVI® pigments) in the dispersion medium is based on the complex interaction of various factors such as the viscosity of the medium and shrinkage during drying. If the manufacturing parameters are chosen correctly, it is possible that the pigments align themselves approximately parallel to the boundary area of the dispersion medium. A distinction is made between “leafing” pigments and “non-leafing” pigments: “Leafing” pigments move towards the surface of the dispersion medium after the application to a printing stock (see FIG. 1; reference number 1 refers to the value document substrate, in the example a paper substrate; reference number 2 refers to “leafing” pigments; reference number 3 refers to the dispersion medium, e.g. a UV-curable lacquer), whereas “non-leafing” pigments 4 (see FIG. 2) spread randomly and at different heights within the dispersion medium.

[0035] “Leafing” pigments can arrange themselves at the boundary layer “substrate—lacquer” as well as at the boundary layer “lacquer—air”.

[0036] Advantageously, the dispersion medium meets the following requirements:

1) embossability of the cured or at least partially cured UV lacquer;
2) controlled curability by UV radiation.

[0037] In the following, the combination of dispersion medium (UV-curing lacquer) and OVI® pigments is referred to as “OVI embossing lacquer”.

[0038] It is preferred to apply the OVI embossing lacquer uniformly onto the value document substrate to be printed.

[0039] For embossing the OVI embossing lacquer, a suitable embossing tool 5 must be used (see FIG. 3). The lower limit for the dimensions of the embossing structure is given in particular by the size of the pigments 2 (in the example “leafing” pigments), e.g. in a region from 2 μm to 100 μm. According to one variant, the pigments which are present in a relatively large dimension (i.e. in a dimension larger than the dimensions of the embossing structure) can be broken up into smaller fragments during embossing.

[0040] If the OVI embossing lacquer is now embossed, the local layer height of the lacquer changes: in some places the OVI embossing lacquer is strongly pressed in by the embossing structure of the embossing tool and the layer height is reduced. In other words, a transfer of the OVI embossing lacquer takes place, which leads to a local fluid dynamic of the embossing lacquer: a buoyancy gradient arises, i.e. at embossed depressions the buoyancy which acts on the pigments is less strong than at elevations. Therefore, the pigments at the places where the embossing lacquer is strongly pressed in move downwards, whereas the pigments at the places where the embossing structure has an elevation move upwards (or the pigments move less strongly downwards). The movement can also be different along a pigment, which results in an inclination of the pigment. Thus, the pigments are aligned along the orientation of the embossing structure located immediately above (see FIG. 4). The pigments follow the embossing structure of the lacquer.

[0041] Still during the embossing operation, or even before the embossing operation, the OVI embossing lacquer can be completely cured by UV radiation. In this way, the pigments are immobilized and fixed with regard to their final alignment.

[0042] Since the embossing structure of the embossing tool can be manufactured with a high degree of freedom of design, e.g. by milling, 3D printing, lithography or the like, the method makes possible a high level of detail.

[0043] In particular, embossing structures can easily be manufactured such that neighboring flanks have slopes that differ greatly from one another.

[0044] Hereinafter, a method for manufacturing a value document, e.g. a bank note, is described, comprising

a) providing a value document substrate;
b) printing the value document substrate with magnetically orientable effect pigments or OVMI® pigments which are dispersed in a UV-curable lacquer;
c) the step c1) of exposing the lacquer containing the magnetically orientable effect pigments to a dynamic, in particular rotating, magnetic field, so that the effect pigments in the lacquer arrange themselves parallel to the value document substrate and in particular edge to edge; the step c2) of irradiating the lacquer containing the effect pigments with UV radiation, wherein c2) in particular is effected after step c1) or is effected simultaneously together with step c1); optionally d) the step of embossing the cured or at least partially cured UV lacquer, which has the effect pigments which are arranged parallel to the value document substrate and in particular edge to edge, so that an embossed relief structure with effect pigments adapting to the relief is formed in the lacquer, conveying to the viewer an optically variable image.

[0045] The combination of dispersion medium (UV-curing lacquer) and OVMI® pigments herein is also referred to as “OVMI embossing lacquer”.

[0046] FIG. 5 illustrates the alignment of OVMI® pigments 6 dispersed in a UV-curable lacquer 3, which are exposed to a rotating magnetic field, when viewed in a cross-sectional view. Reference number 1 refers to the value document substrate, in the example a paper substrate. The UV-curable lacquer 3, which comprises the OVMI® pigments 6, was applied to the paper substrate 1 by screen printing. The rotating magnetic field is produced by means of a magnetic stirrer (not shown in FIG. 5) arranged underneath the paper substrate 1 and in the example is a continuously rotating magnetic field with a speed of 150 revolutions per minute. Due to the rotating magnetic field, the OVMI® pigments 6 form a substantially homogeneous, mirroring area. The arrangement of the individual OVMI® pigments is effected so to speak “edge to edge”.

[0047] FIG. 6 shows a detail of the “edge-to-edge” alignment of OVMI® pigments 6 dispersed in a UV-curable lacquer, which alignment can be recognized under the microscope, which pigments are exposed to a rotating magnetic field, when viewed in plan view.

[0048] According to FIGS. 7 and 8, besides the step c1) of exposing the UV-curable lacquer 3 containing the magnetically orientable effect pigments 6 to a rotating magnetic field so that the effect pigments 6 in the lacquer 3 arrange themselves edge to edge along the area of the value document substrate 1, there is simultaneously effected the step c2) of irradiating the lacquer 3 containing the effect pigments 6 with UV radiation. Depending on the duration or dose of the UV treatment, the UV irradiation leads to a cured or at least partially cured UV lacquer 3 which has the effect pigments 6 which are arranged edge to edge along the area of the value document substrate 1. In the step of embossing by means of an embossing tool 5, e.g. an intaglio printing plate, an embossed relief structure 7 with effect pigments 8 adapting to the relief is formed in the lacquer 3, conveying to the viewer an optically variable image.

[0049] The method according to the invention, because of the interaction of the four measures 1) OVMI® pigments, 2) dynamic, in particular rotating, magnetic field, 3) UV irradiation and 4) embossing, makes possible an extremely advantageous control of the pigment alignments, so that in particular homogeneously lustrous, structured surfaces can be imitated. A granular, noisy texture, which is known in the prior art, can also be produced.

[0050] According to a preferred variant, the method according to the invention includes the following steps:

a) providing a value document substrate;
b) printing the value document substrate with magnetically orientable effect pigments which are dispersed in a UV-curable lacquer;
c) the step c1a) of exposing the lacquer containing the magnetically orientable effect pigments to a dynamic, in particular a rotating, magnetic field, so that the effect pigments in the lacquer arrange themselves parallel to the value document substrate and in particular edge to edge, in order to arrange the effect pigments in this way in the form of a pre-orientation; the step c1b) in which a further orienting or aligning of the magnetically orientable effect pigments pre-oriented in the course of step c1a) is effected by applying a static magnetic field so that the effect pigments assume an orientation changed against the pre-orientation; the step c2) of irradiating the lacquer containing the effect pigments with UV radiation, wherein step c2) in particular is effected after steps c1a) and c1b);
optionally, d) the step of embossing the cured or at least partially cured UV lacquer, which has the pre-oriented effect pigments which first are arranged parallel to the value document substrate and in particular edge to edge and subsequently has effect pigments subjected to a changed orientation, so that an embossed relief structure with effect pigments adapting to the relief is formed in the lacquer, conveying to the viewer an optically variable image.

[0051] The preferred variant achieves a particular attractiveness and brilliance of the ink layer having the effect pigments. The effects obtained are due to the fact that the effect pigments in the alternating field change not only their alignment (i.e. the tilt angle) but also their arrangement (i.e. the position in the lacquer). In the case of a rotating bar magnet, the effect pigments appear to accumulate in one plane and arrange themselves “edge to edge”. The effect pigments thus form a layer that is as closed as possible, which leads to an increased utilizable reflecting area and thus to increased brilliance. In this way, further, the quantity of effect pigments to be employed can be reduced.