EP0882599B1 - Security patterns for security papers - Google Patents

Abstract

The background (10) of a valued paper such as a banknote is divided into two regions with straight and curved lines. The two regions have different colour densities and the region of lower colour density forms a motif. The motif (20) is also overprinted over the lower density region forming the motif on the background. The overprinting is made in a colour chosen to compensate the lower colour density of the background motif so that the latter is invisible to the naked eye but may be seen very clearly on a photocopy including those taken using the most recent photocopier designs.

Description

The present invention relates to a safety design for securities, in particular banknotes, a security paper with such a security drawing and a method of printing such a security drawing on a security paper.

One of the main problems that currently arises in the manufacture of securities, and in particular of banknotes, is to create security elements which, on the one hand, are easy to transfer to banknotes by techniques conventional printing, and which, on the other hand, are very difficult, even impossible to reproduce, in especially with the new generations of color photocopiers. Their technology having made big progress, it becomes essential to achieve security features such that it is possible to very easily distinguish a color copy, i.e. counterfeit money, real security or Bank note.

The use of security drawings to prevent falsification of securities by photocopying color is known in the state of the art, see for example EP-A-0 551 205. The EP 0 384 897, in the name of the same applicant, describes a compound security drawing mainly of three superimposed drawings, each drawing being of a different color and comprising parallel lines oriented angularly, the whole lines of each drawing being shifted laterally so that when juxtaposing the drawings, the lines do not overlap but give the impression of a uniform background. Each safety drawing has further areas in which the segments of lines have a different orientation than that of lines parallel, so that these are discontinuous. These areas actually correspond exactly to letters that become almost invisible to the naked eye when the drawings are superimposed but which, in however, stand out clearly when performing a photocopy of the safety drawing. It is so possible to see immediately and in a very simple if a given security is an original or a photocopy, where this includes such a drawing of security.

The object of the present invention is to improve the known security drawings, and more particularly of make a safety drawing with a pattern in latent color invisible or almost invisible to the naked eye on real value paper, this latent color pattern clearly revealed on a color photocopy of the said value paper, also on photocopies made using photocopiers from the last generation.

This goal is achieved by a safety drawing according to the claim 1.

The principle of the invention is based on the fact that, on the one hand, the background of the drawing is composed of two regions with straight lines and curved lines, both regions with different color density and the lowest color density region forming a pattern. The safety drawing also includes a overprint corresponding to the pattern and which is printed overlay on said density region lower in color to a selected color of so as to compensate for the difference in color density between the two regions, thus forming a pattern in latent color or a latent color image, of so that the safety pattern appears as uniform and without pattern with the naked eye, but that the pattern stands out clearly and in a different color than that of the highest color density region in a photocopy of the safety drawing.

Indeed, during a photocopy, this combination of different densities and shades of colors creates interference with the copier's scanner. The contrast between the background of the safety drawing and the pattern will be greatly amplified and the latter will appear clearly on the copy and in a color other than the rest of the security drawing making such tampering evident with the naked eye and allowing easily distinguish a photocopy from an original.

Dependent claims 2 to 11 define specific modes of execution of the safety drawing according to the invention.

The latent pattern or design is preferably a letter or sign, such as "X", or still a set of letters forming a word such as "VOID" or "COPY". It can also include one or multiple digits, or even any pattern.

Independent claim 12 defines a security with a safety drawing according to the present invention. The use of such drawings of security is of course not limited to only securities and banknotes. Indeed, this safety drawing can also be used on cards, such as credit cards or other, checks or stamps. In fact, we may use this design on any printed medium of which we wish to avoid falsification by such means than the photocopy.

Independent claim 13 defines a method of production of a security paper with a drawing of security according to the present invention.

Dependent claims 14 and 15 define particular printing processes used for the production of a security paper with a drawing of security according to the present invention.

The invention will be better understood using the description of an embodiment of the invention and related figures which illustrate the principle of the invention.

Figure 1 shows a known safety drawing according to the prior art.

FIG. 2 represents an example according to the invention, in black and white, from the bottom of a security drawing and a latent motif or design in the form of a cross, the background and latent drawing being shown separately.

Figure 3 shows an enlargement of different geometric patterns of the background.

Figure 4 shows a color photograph of a safety design with an "X" pattern according to the invention.

Figure 5 shows a color photocopy of the photograph of figure 4.

Colored figures representing the present invention are filed with the present application in as in Figures 4 and 5, the principle of the invention being indeed very difficult to demonstrate and to reproduce with black and white photocopies.

In Figure 1, an art security element according to patent application EP 0 384 897 is represented. The three designs of three colors have already been stacked into a set 1 of parallel and dense lines giving an impression of uniform background. Safety drawing has areas 2, 3, 4 in which the parallel lines are oriented in a direction other than the direction general of the bottom lines, these areas having the form of letters, the letters making up the word "VOID". The figure being an enlargement of the safety drawing and already a copy of it, the words are easily recognizable on it. If we consider the actual size of such safety drawings, then these words are much more difficult to discern on a original drawing. On the other hand, all the lines are straight lines or line segments.

In FIG. 2, the bottom 10 of a safety drawing according to the invention is shown with separate next to it, an overprint 20 in the shape of a cross, this overprint 20 being intended to be printed on the background 10. The color nuances are obviously difficult to render with photocopies, but this example is given by way of illustration.

The background 10 of the security drawing is divided into regions having triangular geometric areas 11 placed next to each other, alternately. There is in this example has 3 types of areas with different line configurations. The first type of zones 11 has only parallel lines. Among this type of areas with this first configuration, there are zones 11a with lines oriented angularly according to a first direction, zones 11b with oriented straight lines angularly in a second direction and zones 11c with straight lines oriented angularly according to a third direction. The bottom also includes a second type of zones 12 having lines spiral curves and a third type of zones 13 comprising a mixture of line segments angularly oriented parallels and segments of spiral lines. Printing lines and spirals is made so that they form a pattern corresponding to the overprint 20 intended for be printed as an overlay, in the example described a "X".

The overprint 20 of this embodiment has the form an "X" also comprising parallel lines oriented in a given angular direction, by example 45 °. When printing this overprint 20 on the bottom, an overlay of straight lines and curves will therefore occur actually as well as a color overlay compensating for differences in color density.

The angles of orientation of the parallel lines of the background and overprint can have any value, the important thing being that the background has at least lines oriented in two different directions, and the overlay of lines oriented in one direction different from the other two. Preferably, the lines parallels from the bottom are oriented at about 22.5 ° and 67.5 ° and those of the overlay are oriented about 45 °. If the background has more lines oriented in a third direction, the angle chosen is preferably about 112.5 °. These values have a approximate tolerance of +/- 20%.

The width of the lines printed in parallel, spiral lines and lines of the overlay is also variable. It can vary between around 15 µm and 100 µm. Preferably, the lines printed in have a width of approximately 82.55 µm and the curved lines a width of about 41.275 µm. Of moreover, the lines of the overlay have preferably a width of about 41.275 µm. These values have an approximate tolerance of +/- 20%.

The distance between each printed line, measured between the center of two adjacent lines, which we calls the pitch, can vary between around 100 µm and 800 µm. The value chosen depends on the uniformity that we want to get for the background and for the overprint. Preferably, this distance is worth around 349.25 µm for the parallel bottom lines, approximately 247.65 µm for overprint and approximately 250 µm for curved lines. These values have a approximate tolerance of +/- 20%.

The color density of the overlay intended for to be printed as an overlay is worth approximately 0.010 to 0.300.

The background areas containing the lines can have any geometric shape, for example a triangular, hexagonal, rectangular shape, circular etc.

In Figure 3, an enlargement of the drawings in zones 11 and 12 east given. There are segments of parallel lines and oriented in three different directions corresponding to those of zones 11a, 11b, 11c, and spiral curved straight lines corresponding to those of zones 12.

Figure 4 shows a color photograph of a safety drawing according to the invention with the motif in "X" shape printed on top of a background. The bottom of this safety drawing corresponds to bottom 10 of embodiment described with reference to FIG. 2, with alternating triangular areas whose lines are oriented in three different directions and the pattern corresponds to the overprint 20 described in reference to figure 2. In this photograph, the latent color pattern is difficult to distinguish from background, which has a uniform appearance At first glance.

In Figure 5, a color photocopy of the drawing of Figure 4 security is shown. On this photocopy, the latent color pattern stands out clearly in the safety drawing and so unequivocal, contrast and color difference between the bottom and the latter being clearly marked.

Safety drawings according to the invention are produced by conventional printing methods such as: Offset dry or wet, intaglio or a combination of these. In the case of a process Offset, at least two plates are required, one for the background and the other for the overprint. These plates may of course contain other patterns in addition and they are mounted on a plate cylinder Offset. The drawings are then transferred to a blanket cylinder which then transfers them on the paper itself. Such printing processes Multi-color offset are described in EP B 0 092 887 and EP B 0 132 858, for example.

In the case of a combination of printing processes different, we can for example use the process intaglio for the background and the offset process for the overprint.

• impression avec une première plaque d'impression d'un fond composé d'au moins une première région et une deuxième région juxtaposées, lesdites régions comportant des dessins géométriques propres à chaque région, de manière que la première région ait une densité de couleur plus forte que celle de la deuxième région, la deuxième région formant un motif,
• impression avec une deuxième plaque d'impression d'une surimpression correspondant au motif formé par la deuxième région en superposition sur ladite deuxième région en une couleur choisie de manière à compenser la différence de densité entre les deux régions, de sorte que le dessin de sécurité apparaít comme uniforme et sans motif à l'oeil nu, mais que ledit motif ressort clairement et dans une autre couleur que la première région lors d'une photocopie du dessin de sécurité.

The method of printing a security design according to the invention on a security paper or bank note comprises at least the following two steps:

• printing with a first printing plate of a background composed of at least a first region and a second region juxtaposed, said regions comprising geometric drawings specific to each region, so that the first region has a higher color density than that of the second region, the second region forming a pattern,
• printing with a second printing plate of an overprint corresponding to the pattern formed by the second region superimposed on said second region in a color chosen so as to compensate for the difference in density between the two regions, so that the security design appears uniform and without pattern to the naked eye, but that said pattern appears clearly and in a color other than the first region when a photocopy of the security drawing.

It is possible to increase the number of colors used in the safety drawing. For example, geometric designs of the background can be colored different and the overlay made up of several colors. In this case, the number of plates printing should also be increased by result.

The invention is not limited to the embodiment described, but other variants are possible in the protection claimed.

For example, you can print the lines in a spiral in the overlay, and only leave on the bottom parallel lines oriented in directions different. The same effect of alternating lines lines and curves is thus repeated and the principle of the invention reproduced.

Other forms of geometric zones are possible, for example a hexagonal, circular shape or a any other form.

Instead of spirals, we can use, as curved lines, concentric circles, or ellipses, or ripples, or other equivalents.

Claims (15)

1. Safety drawing for securities, for example bank notes, having a background (10) composed of at least a first region and a second region juxtaposed, characterised in that said regions each comprise their own geometrical drawings so that the first region has a colour density stronger than that of the second region, said second region forming a pattern, and in that on said second region an overprint (20) corresponding to said pattern is superposed, said overprint (20) comprising geometrical drawings different than that of said second region and in a colour chosen in order to compensate the difference in colour density between said regions, so that the safety drawing appears uniform and with no pattern to the naked eye, but said pattern is clearly brought out and in another colour than that of said first region on a photocopy of the safety drawing.
2. Safety drawing according to claim 1, characterised in that the region of stronger colour density comprises groups of lines (11a,11b) printed in parallel and angularly oriented according to two different directions, and the other region comprises curved lines (12) or straight lines, and in that the overprint (20) comprises straight or curved lines such that the lines of the overprint cross the lines of said region of weaker colour density when the superposition is carried out.
3. Safety drawing according to claim 2, characterised in that said groups of lines and said straight and curved lines are arranged in closed geometrical zones (11).
4. Safety drawing according to claim 2 or 3, characterised in that the curved lines of the region of weaker colour density are spirals and the lines of the overprint (20) are straight lines.
5. Safety drawing according to one of claims 2 to 4, characterised in that the angle of the lines (11a,11b) oriented according to a first direction is about 22,5°, according to a second direction is about 67,5° and the angle of the lines of the overprint (20) is about 45°, these values having a margin of ± 20%.
6. Safety drawing according to one of claims 2 to 5, characterised in that the drawing comprises zones (11c) with parallel lines oriented according to a third direction and in that the angle according to the third direction is about 112,5°, with a margin of ± 20%.
7. Safety drawing according to one of claims 2 to 6, characterised in that the width of the straight lines is about 90 µm and the distance between the different lines of a same zone taken between the centre of each line is about 350 µm, with a margin of ± 20%.
8. Safety drawing according to one of claims 2 to 7, characterised in that the width of the curved lines is about 41 µm and the distance between each curved line taken between the centre of each line is about 250 µm, with a margin of ± 20%.
9. Safety drawing according to one of claims 1 to 8, characterised in that the colour density of the overprint (20) is about 0,010 to 0,300.
10. Safety drawing according to one of claims 3 to 9, characterised in that said zones (11) have a triangular shape, or rectangular, or hexagonal, or circular or other.
11. Safety drawing according to one of claims 1 to 10, characterised in that said geometrical drawings are of different colours and said overprint (20) is composed of several colours.
12. Note of value characterised in that it comprises on at least one of its sides a safety drawing according to claims 1 to 11.
13. Process for printing a safety drawing on securities, notably bank notes, characterised by the following steps:

    impression with a first printing plate of a background composed of at least a first region and a second region juxtaposed, each of said regions comprising their own geometrical drawing, in such a way that the first region has a colour density which is stronger than that of the second region, the second region forming a pattern,

    impression with a second printing plate of an overprint superposed over said second region in a colour chosen to compensate the difference of colour density between both regions, so that the safety drawing appears uniform and with no pattern to the naked eye, but said pattern is clearly brought out and in another colour than the first region on a photocopy of the safety drawing.
14. Process according to claim 13, characterised in that one uses as many printing plates as they are different colours.
15. Process according to claim 14, characterised in that the printing process used is an offset process or an intaglio process.

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