EP1592561B1 - Method for printing a security element and security element - Google Patents

Abstract

The process involves printing a semi-transparent security unit (2) with variable optical ink on a base (1) of a substrate. The security unit is printed to cover the base. The semi-transparent security unit is printed by a serigraphy process. A sifter utilized in the serigraphy process comprises 180 to 230 lines per inch according to X and Y directions of the sifter. An independent claim is also included for a value-paper.

Description

The present invention relates to a method of printing a security element for securities, such as banknotes, checks, credit cards, passports or identity documents and other similar documents.

The present invention also relates to a security element for securities, such as bank notes, passports, identity documents and the like.

In the field of securities, especially banknotes, there is a growing need for security features as protection against counterfeiting. In recent years, computers, scanners and photocopiers have undergone significant technical improvements and it is possible to purchase high-performance devices at reasonable prices. As these devices have become very efficient, it has become necessary to develop new security elements, themselves also more efficient, for securities, such as banknotes, checks, credit cards, passports or documents. identity documents and other similar documents to protect these documents against counterfeiting and prevent them from being copied by current computers, scanners and photocopiers.

Such security elements use, for example, specific inks such as optically variable inks ("OVI" ®) and other inks having iridescent properties, these inks being used to print particular patterns or geometric shapes on the substrate of the invention. paper-value, optically variable elements ("OVD" ®) in the form of metallized patches (called "foils") or holograms, and also moirés and other similar patterns, all being, on the one hand, very difficult or impossible to copy with current devices but, on the other hand, very easy to control visually or with the naked eye.

Other security elements are formed by combinations of lines and / or patterns with colors, which are only visible under certain conditions, for example UV light or transparency. Again, the interest of such security features is that they are easy to print or place on the document to be protected and they can be controlled by simple devices, even with the naked eye, but they are impossible to reproduce with current printers, scanners and copiers.

For example, the patent US 6,050,606 , incorporated by reference in the present application, describes a security element for securities, for example for banknotes. This security element is formed by a bottom having at least two juxtaposed regions, each region having clean geometric patterns, said regions having a different color density. The security element further comprises a pattern corresponding to the region of the lowest color density superimposed on said region in a color selected to compensate for the difference in color density between said two regions. Thus, the security element appears uniform and without a pattern to the naked eye, but the pattern is clear in a photocopy of said element.

The patent US 5,443,579 , incorporated by reference in the present application, discloses another method of printing a latent image on a substrate. According to this patent, the printing of raised lines is combined with lines without relief. Thus, a latent color image is created which can not be reproduced with a photocopier or other photomechanical processes.

Licences US 5,853,197 and US5,487,567 , incorporated by reference in the present application; show security features that are not easily visible to the naked eye, but which, on the other hand, become clearly apparent when copying or scanning the item.

Another specific technique uses watermarks in which the substrate, for example paper, is marked with lines or a pattern that are visible only in transparency. One development of this technique concerns pseudo-watermarks formed by the creation of a window in the substrate, a technique used in particular with paper substrates which themselves are not normally transparent, said window being transparent.

The patent US 6,082,778 , the contents of which are incorporated by reference in the present application, discloses an identity card protected against unauthorized copying by photocopiers. In this patent, the idea is to create a security element by combining the protective effect provided by a thin metal film with the physical properties, in particular optical properties, of an additional layer whose combination of effects prevents reproduction. from the menu. Under a transparent cover layer, there is a layer of metal over a layer having specific optical properties. In a first embodiment, the metal layer is demetallized locally exposing the layer with specific optical properties, that is to say making it visible in the demetallized zone. The difference in contrast between the layers makes the marks formed by demetallization easy to recognize with the naked eye. In a particular embodiment, the layer having specific optical properties has a dark color, for example black. The combination of the direct reflection of the metallized zone and a layer having a strong absorption (black layer) prevents the detection of the contrast difference so that the information formed by the demetallization disappears completely on a copy of this element of security.

According to other techniques known in the state of the art, a laser is used either to mark the substrate directly, or to mark a layer applied to said substrate and thus create security elements impossible to reproduce by photocopying or scanning.

An object of the invention is to define an improved printing method for a security element used in particular on securities.

Another object of the invention is to create a security element for securities improving elements already known and requiring a simple process and easy to implement.

Another object of the invention is to provide a security element very difficult to copy and counterfeit with modern standard scanners and photocopiers and other equivalent devices but which can be easily printed with the current printing means.

For this purpose, the method according to the invention is defined by the steps of claims 1 to 8, the security element according to the invention is defined by the features of claims 9 to 11 and the paper value is defined by the characteristics of claim 12.

• La figure 1 montre un schéma-bloc du procédé d'impression formant un élément de sécurité selon l'invention.
• La figure 2 montre un premier mode d'exécution d'un élément de sécurité selon l'invention.
• La figure 3 montre un deuxième mode d'exécution d'un élément de sécurité selon l'invention.
• La figure 4 montre un papier-valeur comportant un élément de sécurité selon l'invention.

The description of several embodiments and related figures will better understand the invention.

• The figure 1 shows a block diagram of the printing process forming a security element according to the invention.
• The figure 2 shows a first embodiment of a security element according to the invention.
• The figure 3 shows a second embodiment of a security element according to the invention.
• The figure 4 shows a paper-value comprising a security element according to the invention.

In the figure 1 an embodiment of the method according to the invention is shown in block diagram form. In the first step, a background is first printed on the substrate, for example using an offset method known in the state of the art. The background may be monochrome or polychrome, such printing being possible by the methods known from the state of the art. According to this method, the pattern to be printed is transferred from an offset plate cylinder inked by inking rollers to a blanket cylinder which in turn transfers the pattern onto the substrate, for example paper. The patent application FR 2,222,214 discloses an offset printing process and an offset printing machine. As another example, the patent US 6,101,939 discloses another printing machine using the offset method. This background can extend to the entire surface of the paper-value or be limited to a particular area thereof.

On top of printing said background, a semitransparent pattern is then printed by means of an appropriate printing process using an optically variable ink. Such inks which have iridescent properties, contain metal particles and are generally applied as an opaque pattern on the security papers, said pattern forming a security element. Indeed, because of the presence of metal particles, these optically variable ink-shaped patterns change color depending on the angle at which they are viewed, the colors depending both on the color of the ink same and metal particles. Such inks are particularly powerful for forming security elements because it is not possible to reproduce the iridescence effect with color photocopiers or scanners: during the copying, the optically variable ink pattern loses in particular its iridescence properties so that a copy is easy to identify with the naked eye.

Preferably, the semi-transparent pattern in optically variable ink is printed by a screen printing process. Such a printing method is known in itself in the state of the art. According to this method, the pattern to be printed is formed by a screen-through which the ink is applied to the substrate, for example the value paper. For positive printing, the sieve holes are closed out of the pattern, so that the ink passes through the sieve to form the pattern itself on the substrate, while for negative printing, the holes corresponding to the pattern. are closed and the ink marks the outline of the pattern, the pattern itself being created by absence of ink on the substrate. For example, patents US 6,109,172 and US 5,671,671 describing silk screen printing machines are cited.

In the context of the present invention, a specific printing process, for example a screen printing method as described above and in the US patents mentioned, is combined with optically variable ink but the fineness of the sieve for screen printing. that is to say, the size of the holes of the sieve, is chosen so that the pattern created in screen printing with optically variable ink is semi-transparent. Thus, on the one hand, the background printed on the substrate is seen through the semi-transparent pattern in optically variable ink, nevertheless, on the other hand, since said pattern is formed in optically variable ink, it retains iridescent properties. due to the optically variable ink. Two special optical effects are thus combined that are very difficult to reproduce satisfactorily: on the one hand semi-transparency and on the other hand the iridescence of the optically variable ink. In addition, a combination of at least three superimposed colors (the background color and the two colors of the optically variable ink) is obtained which varies according to the angel of view of the pattern, the whole then forming a particularly secure element. performance.

In the case of a screen printing process, the fineness of the screen is of the order of 70 to 90 lines per cm (180 to 230 lines per inch), in each X and Y direction of the screen. Preferably, a fineness of the order of 90 lines per cm (230 lines per inch) is chosen. Of course, it is possible to adapt the fineness of the sieve according to the optically variable ink used and in particular the size of the metal particles contained in said ink, the aim being to obtain a semi-transparent printing with the optically variable ink. The optimization of these parameters can of course be done by simple printing tests to adjust the size of the holes and consequently the amount of ink deposited during printing to obtain the desired effect.

Other printing processes allowing the deposition of a semi-transparent pattern in optically variable ink are of course possible, especially a gravure printing process or a flexographic method, and the present invention is not limited to screen printing, the aim, as indicated above, is to obtain a semitransparent pattern with an optically variable ink. These methods are known in the state of the art, for example publication DE 35 35 993 for flexography.

In the case of a photogravure process, a printer form having a fineness of about 60 to 120 lines per centimeter, the screen angle of which can vary from 0 ° to 75 °, is preferably used. the depth of the etched cells is between 10 microns and 50 microns. These parameters can of course be adapted according to the type of optically variable ink used and the degree of transparency that one wants to obtain. The adjustment of these parameters can in particular be done by comparative tests.

In the case of a flexographic printing process is used anylox cylinder having a lineation of the order of 100 to 120 lines per centimeter, the depth of the cells is between 30 microns and 50 microns. The parameters can be adapted according to the type of optically variable ink used and the degree of transparency that one wants to obtain.

In the third step of the method which is optional, a dry embossing step of the security element is then carried out. This step allows to form an additional pattern and embossed in the security element created by the superimposition of the background and the semi-transparent printing pattern embossed that it is of course also impossible to reproduce by photocopying or scanning . For embossing, a conventional intaglio process can be used in the field of printing, omitting the use of ink for dry embossing. This pattern is also only visible according to a particular viewing angle of the security element, which, in such an embodiment, combines effects of color, iridescence and a tactile effect by the relief pattern.

A security element according to the invention is described with reference to Figures 2 to 4 .

The figure 2 shows a security element according to the invention with a background 1, printed for example in offset, and which comprises alphanumeric characters "2000" placed next to each other. On top of this background, a semi-transparent pattern 2 was printed with an optically variable ink. Although optically variable ink is used for pattern 2, which is normally opaque due to optically variable ink, pattern 2 printing process is such that said pattern is semi-transparent, so that the bottom 1 is visible through the pattern 2. As indicated above, a method that can be used to create the semi-transparent pattern with optically variable ink is a screen printing process in which the sieve has a fineness particular, namely from 180 to 230 lines per inch.

Thus, a pattern having both the properties of a printed pattern with optically variable ink and having a semi-transparent effect to see the background on which it is printed.

In the figure 3 the various components of the security element according to the invention have been highlighted in a particular embodiment. There is always the background 1 with the characters "2000" repeated regularly, then we distinguish the semi-transparent pattern 2 in optically variable ink through which we can see the characters of the background thanks to the effect of semi -transparency. There is also a relief pattern 3, in this case a face, which has been formed, for example, by dry embossing of the security element.

A degree of security in the element is thus added, in that not only is it semi-transparent, it has the characteristics of an optically variable ink security element, but in addition a dry embossing relief is added, all these different properties are very difficult, if not impossible, to reproduce with a photocopier or a modern scanner.

In the figure 4 a paper-value 4 is shown by way of example with a security element according to the invention. This paper-value 4, in this case a schematic banknote, has in its lower corner a security element with a bottom 1, a semi-transparent pattern 2 in optically variable ink and dry embossing 3 as shown with reference to FIG. figure 3 of this application. It should be noted that the bottom 1 can extend over the entire surface of the value paper.

In addition, other printing techniques can be used to print the background 1 and the pattern 2, within the limits of the protection conferred by the claims, the important thing for the reason 2 being to present both the characteristics of the an optically variable ink pattern and a semi-transparency effect.

Claims (12)

1. A method for printing a security element for paper securities such as banknotes and other similar documents onto a substrate, characterized by the following steps:

   - printing a background onto the substrate;

   - printing a pattern at least partially covering said background using opaque optically variable ink, said pattern being printed using a screen printing method by means of a screen, the screen fineness of which is chosen so that the printed pattern created using the optically variable ink is semi-transparent and so that said background can be seen through said pattern printed in optically variable ink.
2. The method as claimed in claim 1, wherein the screen used in the screen printing method comprises about 70 to 90 lines per centimeter (180 to 230 lines per inch) in the X and Y directions of said screen.
3. A method for printing a security element for paper securities such as banknotes and other similar documents onto a substrate, characterized by the following steps:

   - printing a background onto the substrate;

   - printing a pattern at least partially covering said background using opaque optically variable ink, said pattern being printed using a flexographic method by means of an anylox cylinder, the screen ruling of which is chosen so that the printed pattern created using the optically variable ink is semi-transparent and so that said background can be seen through said pattern printed in optically variable ink.
4. The method as claimed in claim 3, wherein the anylox cylinder used in the flexographic method has a screen ruling of about 100 to 120 lines per centimeter and the depth of the cells of which is between 30 and 50 microns.
5. A method for printing a security element for paper securities such as banknotes and other similar documents onto a substrate, characterized by the following steps:

   - printing a background onto the substrate;

   - printing a pattern at least partially covering said background using opaque optically variable ink, said pattern being printed using photogravure by means of a printing forme, the screen fineness of which is chosen so that the printed pattern created using the optically variable ink is semi-transparent and so that said background can be seen through said pattern printed in optically variable ink.
6. The method as claimed in claim 5, wherein the printing forme used in the photogravure method has a screen fineness of the order of 60 to 120 lines per centimeter, the screen angle of which can vary from 0 to 75° and the depth of the engraved cavities of which is between 10 and 50 microns.
7. The method as claimed in one of claims 1 to 6, wherein the background is printed using a monochrome or polychrome offset method.
8. The method as claimed in one of the preceding claims, and which comprises a step of dry embossing the security element.
9. A security element for paper securities such as banknotes and other similar documents, placed on a substrate, the essential features of said security element being: a printed background (1) on the substrate; a pattern (2) at least partially covering said background, said pattern being semitransparent and formed using opaque optically variable ink according to the method as defined in one of claims 1 to 6 so as to leave said background (1) visible through said pattern printed in optically variable ink.
10. The security element as claimed in claim 9, wherein the background (1) is in offset printing.
11. The security element as claimed in claim 9 or 10, and which further comprises dry embossing (3).
12. A paper security (4), particularly a banknote or other similar document, and which comprises a security element as claimed in one of claims 9 to 11.

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