HK1134271B - A security element comprising an oriented image on a transparent substrate, and preparation an use of the same, as well as security documents - Google Patents

Description

Security element with an oriented image coating on a transparent substrate, method for the production thereof, use thereof and security document

Technical Field

The invention relates to a security element for securities and identity documents. More particularly, it relates to angle-dependent images on transparent substrates that preferably exhibit a three-dimensional effect of positive or negative relief, if viewed from the front or back, respectively.

Background

Various types of optically variable (optically variable) devices are used as effective copy protection means on security and security documents. Among these, particularly important optically variable transfer protecting means are optically variable inks (A), (B), (C), and (C)(ii) a EP-A-0227423). Optically variable ink (A)) Are used for printing surfaces and/or markings which display viewing-angle-dependent colors (═ color shifts).

The anti-copy ink contains Optically Variable Pigments (OVP)^TM) (ii) a Preferred types are flake-shaped thin film optical interference pigments of the type described in U.S. patents 4,705,300, 4,705,356, 4,721,271 and related publications.

The magnetic optically variable pigments in the printing inks or paints can be used to create magnetically induced images, designs and/or patterns by applying corresponding magnetic fields to cause orientation of the magnetic optically variable pigments in the coating and then by drying/curing the coating. The result is a fixed magnetically induced image, design or pattern of the optically variable ink. Depending on their design, the images, patterns or designs are seen to have a three-dimensional or relief-like appearance, although the printing itself is still geometrically planar.

The magnetic optically variable printing inks disclosed in co-pending european patent application EP06113891.3 of the same applicant, the content of which is incorporated herein by reference, are particularly suitable for producing magnetically induced images.

Materials and techniques for orientation of magnetic particles in coating compositions, and corresponding printing processes, have been disclosed in US 2,418,479, US 2,570,856, US3,791,864, US3,676,273, US 5,364,689, US 6,103,361, US 2004/0051297, US 2004/0009309, US 2002/0160194, WO 02/09002, US 2005/0106367, WO 04/007095, WO 2005/058608 and WO 2005/002866, the respective contents of which are incorporated herein by reference.

Thus, the prior art documents provide various methods and apparatus for producing magnetic image coatings on substrates. In all cases, the magnetic image coating is provided in such a way that it can only be viewed from a single side of the substrate (notably from the printed side). The use of magnetically oriented coatings for the front-back side has not been disclosed.

Description of the invention

The problem of the invention is to provide a security element which allows items such as banknotes to be easily authenticated and which can be handled by the naked eye of the average person.

According to the invention, the problem is solved by a security element as defined in claim 1. More particularly, the present invention relates to security elements comprising a transparent substrate and a magnetically oriented image coating on said substrate.

It has surprisingly been found that optically variable security elements comprising a transparent substrate which can allow the coating thereon to be viewed from the front and back, said coating carrying a design of a particular visual appearance, preferably a three-dimensional appearance, produced by the orientation of pigment flakes, for example by the application of a magnetic field, are very valuable security elements for the rapid visual (overt) authentication of documents, in particular transparent articles or articles comprising transparent regions. In fact, the particularly preferred magnetic force produces a pronounced three-dimensional relief that flips due to the transition of the viewing surface; therefore, flipping the document and observing the flipping of the magnetically induced image is sufficient to perform a quick authentication of the document.

The magnetic orientation of the image coating produces a visual effect that can vary depending on the viewing angle from which the image coating is viewed. The effect is preferably a three-dimensional effect which is reversed when the image is viewed from above or below (obverse or reverse). However, other visual effects are possible, such as a switching optical effect or a scroll bar type image.

For example, if a design is viewed as a circular bend, line or point of maximum reflection exhibited on the design; the lines or points move with viewing angle, either in the same sense (convex appearance) or in the opposite sense (concave appearance) depending on the viewing plane.

The security element of the present invention is thus an angle-dependent image on a transparent substrate, preferably arranged so as to exhibit, for example, a three-dimensional effect which appears as a positive or negative relief, respectively, when viewed from the front or back, as shown in fig. 1, which will be explained in detail later. Depending on the viewing plane, the three-dimensional image appears to be out of plane or into plane.

Examples of suitable three-dimensional designs are cylinders, hemispheres, pyramids, cones, crowns (roof), etc. Several geometric forms may also be combined. Their simple appearance can be easily recognized as coming out of or into the plane of the image. More complex designs, such as numbers, letters, graphics, or icons, may also be produced. The security element of the present invention is preferably combined with a colour shifting element such as the "switching optical effect" and the "rolling bar type image" disclosed in WO 04/007095.

The security element of the present invention can be easily identified by the naked eye simply by flipping the document or article and viewing the angle-dependent image on either side. It is therefore very suitable for use by the average person, providing its simple means to check, for example, the authenticity of a banknote.

It is also possible to laminate a transparent foil on top of the security element of the invention, thereby increasing the resistance and lifetime of the security element.

The transparent substrate may be any plastic or polymeric material that is transparent at least in part of the visible spectrum (i.e., in the wavelength range of 400nm to 700 nm). In fact, it is sufficient for the visual authentication of the disclosed security element if the viewer can see through the substrate at least in part in the visible spectral region. Preferably, the transparent substrate is selected from the group consisting of polyethylene terephthalate, polycarbonate, polyvinyl chloride, polyacrylate, polyacrylonitrile, polystyrene, polypropylene, polynaphthalene terephthalate (polynaphthalene-terephthalate), and mixtures or copolymers thereof.

The transparent substrate may be fully or partially colored, provided that it is transparent in at least part of the visible spectrum, so that a viewer can see through, for example, the transparent substrate and the laminate, and can view the magnetically induced image from both the front and back sides of the laminate product.

"transparent" in the context of the present invention means: "providing optical transparency at least in part of the visible spectrum (wavelengths 400nm-700 nm)".

The angle-dependent image on the transparent substrate is produced by applying, orienting and drying/curing a magnetically oriented coating on the transparent substrate, for example according to co-pending application EP06113891.3 filed by the same applicant, the content of which is incorporated herein by reference.

Thus, a method of producing the magnetically induced image coating on a transparent substrate comprises the steps of: a) applying a coating composition comprising magnetically oriented pigments to a surface of a transparent substrate; b) orienting the magnetic pigment particles in the coating composition applied in step a) by applying a magnetic field so as to produce a special visual effect which varies according to the viewing angle from which the image coating is viewed, for example if the three-dimensional effect of the coating exhibiting a positive or negative relief is viewed from the front or back; and c) curing/drying the oriented coating composition of step b) to fix the oriented particles.

In detail, for producing the magnetically induced image coating, a printing ink or coating composition comprising magnetic orientation pigments, preferably magnetic optically variable interference pigments, is applied to the transparent substrate by a printing process, such as copperplate gravure, flexographic printing, gravure printing, screen printing or roller coating, and the magnetic pigments are oriented, for example according to WO 2005/002866; finally, the coating is dried/cured as known to the skilled person.

Suitable printing inks or coating compositions are disclosed in co-pending european patent application EP06113891.3, wherein magnetic optically variable printing inks or coating compositions are described in detail, which have the required properties of magnetic orientation of the pigment particles for forming the pattern, image or design of the coating.

The pigment comprised in the magnetic optically variable printing ink or coating composition is preferably a magnetic optically variable interference pigment selected from the group consisting of vacuum deposited magnetic thin film interference pigments, interference coated metallic pigments, interference coated non-metallic pigments, magnetic liquid crystal pigments and mixtures thereof. The magnetic optically variable pigments of WO02/073520, US 4,838,648, EP-A688675, WO 02/73250, WO 03/00801 or US 6,838,166 are preferably used according to the invention. The vacuum deposited magnetic thin film interference pigments may be selected from the five-layer and seven-layer vacuum deposited magnetic thin film interference pigments of US 4,838,648 and WO 02/73250.

The magnetic pigments in the coating are oriented by applying a suitable magnetic field, preferably so as to exhibit a three-dimensional effect. The orientation step b) may be carried out simultaneously with the coating step a) or after the coating step a). The magnetic orientation of magnetic particles has been described in the art. References in the relevant art in the prior art documents are cited in the introductory part of the present application.

The curing/drying step c) may be performed by physical evaporation of volatile compounds, uv curing, oxidative reticulation, chemical crosslinking, electron beam curing, or by any combination thereof.

The method of producing the security element may further comprise the step of laminating a transparent foil over the magnetically induced image coating, thereby improving the resistance and lifetime of the security element. The transparent foil may be selected from the group consisting of polyethylene terephthalate, polycarbonate, polyvinyl chloride, polyacrylate, polyacrylonitrile, polystyrene, polypropylene, polynaphthalene terephthalate, and mixtures or copolymers thereof. Thus, for the selection of the transparent overlaminate foil, the same criteria as for the transparent substrate are used. In a specific embodiment, the magnetically induced image coating is arranged between two plastic foils of the same type.

The security element according to the invention may also comprise other marking means, such as infrared marks, luminescent marks, such as fluorescent or phosphorescent marks, uv marks, magnetic marks, forensic marks or mixtures thereof, as well as other security elements (holograms etc.), physically embossed reliefs or marks.

A characteristic of the security element of the invention is that when it is backlit, for example on a light table or held against a luminous background such as a lamp or the sky, the colour, appearance relief and colour shift characteristics are cancelled out.

This additional effect further increases the value of the security element of the invention, since it allows its rapid authentication by front-light versus back-light viewing. In fact, the perception of the angle-dependent positive-negative three-dimensional relief features of the security element of the present invention is dependent on the front light conditions.

Furthermore, the perception of translucency of the security element of the present invention also depends on the local coloration of the transparent substrate and the local coloration of the overlaminate foil. This allows the skilled person to implement other valuable embodiments.

The security element of the invention may be used in security documents or security articles, such as banknotes, credit cards, access cards, security badges, securities, rights or identity documents, transportation tickets, lottery tickets, contest tickets, tax banderols, security threads, labels, foils, tear tapes or product security applications, as protection against counterfeit or illegal copying.

Generally, the security document or security article needs to have a transparent region to which the security element of the present invention is applied. This can be achieved by integrating transparent areas such as windows, lines etc. into the document, e.g. punched holes covered with a transparent foil, or the document is made entirely of such a transparent substrate, providing transparent areas (i.e. areas without ink or paint). Some currencies made of polymeric substrates provide such transparent regions and can therefore carry the security element of the invention.

The invention will be further elucidated herein by means of non-limiting examples and figures.

Figure 1 shows a computer generated image of text relief inverted viewed from the front and back, respectively.

Figure 2 shows the results of a copier scan of a magnetically induced image comprising the magnetic optically variable interference pigment of the present invention. Both the front and back sides were scanned and replicated.

Fig. 3 schematically shows a cross-sectional view of how a relief or three-dimensional appearance is created in a geometrically planar coating by a suitable orientation of the particles.

As shown in fig. 1, the angle-dependent images (designs, patterns) of the present invention should be readily observable as relief out of or into the image plane when viewed from one side or the other.

In fig. 2, no particular difference between the three-dimensional effects of the front and back is seen. However, on the original, "20" on the front side (a) appears as a positive relief on the concave surface, and "20" on the reverse side (b) appears as a negative relief on the convex surface. This shows that the security element of the invention cannot be copied or scanned.

Fig. 3 schematically shows a cross-sectional view of how a relief or three-dimensional appearance is created in a geometrically planar coating by a suitable orientation of the particles. The pigment flakes (1) in the coating (2) are oriented in the same way as if they would be present on the surface of the hemisphere (3), but projected down into the plane of the coating. In the frontal view a), the flakes fixed in their position provide very the same appearance as if they were present on a convex hemisphere. In the reverse observation b), the pigment flakes appear as if they were present on concave hemispheres.

This relief in figure 3 cannot be confused with a physically embossed three-dimensional relief structure, which is a different security element. In fact, the security element of the invention may be combined independently with such an embossed relief.

Claims (22)

1. A security element comprising a transparent substrate and a magnetically oriented image coating on the substrate.

2. The security element of claim 1, wherein the image coating is arranged to exhibit a three-dimensional effect which appears as a positive or negative relief, respectively, if viewed from the front or back, respectively.

3. The security element according to claim 1, wherein the transparent substrate is selected from the group consisting of polyethylene terephthalate, polycarbonate, polyvinyl chloride, polyacrylate, polyacrylonitrile, polystyrene, polypropylene, polynaphthalene terephthalate and mixtures or copolymers thereof.

4. The security element of claim 1 wherein a transparent foil is laminated over the magnetically oriented image coating.

5. The security element according to claim 4, wherein the transparent foil is selected from the group consisting of polyethylene terephthalate, polycarbonate, polyvinyl chloride, polyacrylate, polyacrylonitrile, polystyrene, polypropylene, polynaphthalene terephthalate and mixtures or copolymers thereof.

6. The security element of claim 1, wherein said magnetically oriented image coating comprises magnetic optically variable interference pigments.

7. The security element according to claim 6, wherein said magnetic optically variable interference pigments are selected from the group consisting of vacuum deposited magnetic thin film interference pigments, interference coated metallic pigments, interference coated non-metallic pigments, magnetic liquid crystal pigments and mixtures thereof.

8. The security element according to claim 7, wherein the pigment is selected from the group consisting of five-layer and seven-layer vacuum deposited magnetic thin film interference pigments.

9. The security element according to claim 1, further comprising a marking means selected from the group consisting of infrared markers, fluorescent markers, ultraviolet markers, phosphorescent markers, magnetic markers, forensic markers and mixtures thereof.

10. The security element of claim 1, further comprising other security elements selected from holograms, embossed reliefs, indicia or combinations thereof.

11. The security element of claim 1, further comprising a color shifting element.

12. The security element of claim 11, said color shifting element being a switching optical effect or a rolling bar type image.

13. A method of making a security element according to any one of claims 1 to 12, said method comprising the steps of:

a) applying a coating composition comprising magnetically oriented pigments to a surface of a transparent substrate;

b) orienting the magnetic pigment particles in the applied coating composition of step a) by applying a magnetic field; and

c) curing/drying the oriented coating composition of step b) to fix the particles in the oriented position to obtain a magnetically oriented image coating.

14. The method of claim 13, further comprising the step of laminating a transparent foil over the magnetically oriented image coating.

15. The method of claim 13, wherein said orienting step b) is performed simultaneously with said coating step a).

16. The method of claim 13, wherein said orienting step b) is performed after said coating step a).

17. The method of claim 13, wherein the curing/drying step c) is performed by a method selected from the group consisting of physical evaporation, uv curing, oxidative reticulation, chemical crosslinking, electron beam curing, or any combination thereof.

18. The method of claim 13, wherein said step a) is performed by a printing method selected from the group consisting of copperplate gravure, flexographic, gravure, screen printing, or roll coating.

19. Use of a security element according to any one of claims 1 to 12 for security documents.

20. The use according to claim 19, wherein the security document is a banknote, a credit card, an access card, a security badge, a security, an entitlement or identity document, a transportation ticket, a lottery ticket, a competition ticket, a tax banderole, a security thread, a label, a foil or a strip.

21. A document, wherein the document comprises at least one security element according to any one of claims 1 to 12.

22. The document of claim 21, wherein the document is a banknote, credit card, access card, security badge, security, rights or identity document, transportation ticket, lottery ticket, contest ticket, tax banderole, security thread, label, foil or tear strip.