DE69804113T2 - SECURITY DOCUMENT WITH SECURITY PRINT - Google Patents

Description

The present invention relates to a security document or an equivalent document of the type comprising a support on which security prints are provided.

The term "security document" refers to all documents such as banknotes, cheques, Eurocheque cards that are used to transfer a sum of money. The term "equivalent document" refers to all documents issued by a state authority to confirm the identity or driving license, etc. of a person. Without claiming to be exhaustive, this includes identity cards, passports, driving licenses, etc. This term also refers to any document that serves to prove the authenticity of a valuable object. It could, for example, be a label that is attached to a luxury item of clothing.

What all these documents have in common is that they contain security features or at least security prints which are very difficult to reproduce and which allow their authenticity to be guaranteed.

Ultraviolet radiation detectors are known which make it possible to distinguish genuine from counterfeit notes, in particular by making prints with fluorescent inks visible and/or by the absence of reflections from the paper backing.

Attempts are regularly made to improve security devices, especially as a result of the fact that experienced forgers, with the help of very powerful copying machines, are able to reproduce security documents in such quality that their authenticity is not even doubted by most people.

In the patent specification US-A-5 005 873 (WEST) an article is described which is equipped with means which make it possible to provide authenticity protection in a visible manner. The article is a laminate which consists of a base layer and two fluorescent layers placed on top of it. The materials used are, for example, plastics, such as polyvinyl chloride. Fluorescent materials are dispersed in the plastic materials of the two layers. It is stated in more detail that the first and second fluorescent materials are selected so that they have different excitation and emission spectra, so that they emit different colors in the visible and infrared (IR) regions of the spectrum.

The object can be an adhesive label which can be attached to a video cassette, for example.

Such a technique from the field of laminated materials is difficult to implement on security documents such as banknotes.

The patent specification GB-A-2 300 596 (PORTALS) relates to a fluorescent security element for cheques and banknotes, which is visible to the naked eye but cannot be reproduced by photocopy or scanner. This element comprises a transparent or translucent base formed by a plastic film or paper which partially absorbs ultraviolet rays. A first and second fluorescent coating are applied to this base. These two coatings consist of a filler material in which a pigment or color solution is dispersed. The two coatings are chosen to emit fluorescence at different wavelengths. Therefore, the security element takes on the color of one or the other of the two coatings depending on the type of light under which it is viewed.

Finally, patent EP-A-595 583 (CANON) relates to a means which is not visible to the naked eye and which makes it possible to verify the authenticity of the document on which it is applied. The invention also relates to a technique for verifying whether the document is authentic or not. It comprises equipment which makes it possible to read information contained in said means and to check whether the document is a copy or an original.

The means, which is not visible to the naked eye, is a label made from an ink containing a plurality of fluorescent dye materials, each having a fluorescence wavelength close to the IR. In addition, these materials have an absorption spectrum with maximum absorption wavelengths that do not overlap.

Until now, the techniques described above have required radiation of different wavelengths to ensure the authenticity of a document.

The present invention aims to provide additional security for security documents by adding to them an additional means of guaranteeing their authenticity, without this security being reproducible, in particular by photocopying, and by using a simple technique commonly used in the field of security documents.

Thus, the present invention proposes a security document or equivalent document, such as a banknote, passport, identity card or Eurocheque card, which comprises a support on which security prints are provided, said security prints comprising:

- a first print made in an ink of a first colour which is invisible to the naked eye but fluoresces or phosphoresces,

- a second print covering the first and made in an ink of a second colour which is visible or invisible to the naked eye but which fluoresces or phosphoresces,

the second print is made in such a way that it creates a visual disturbance of the first print, such that under illumination with neutral or ultraviolet light only this second print is visible, whereas the first print is only visible under illumination with ultraviolet light and through a filter of the same color as that of the first print.

So if it is a banknote with a second print with visible ink, it is visible to the naked eye. Under ultraviolet (UV) lighting, only the second print remains visible, while under UV lighting and through a filter, the first print can be seen.

If the second print is made with invisible ink, it is only visible under UV light.

This provides additional security, which can only be seen under UV lighting and through a filter, which allows the authenticity of a document to be guaranteed.

In addition, prints made with invisible fluorescent or phosphorescent inks cannot be reproduced using a photocopier, which limits the risk of counterfeiting.

The invention, which makes use of printing with certain inks, is always compatible with the usual technology for producing security documents.

According to other advantageous features without claiming to be exhaustive:

- the said first print consists of information in the form of letters and/or digits and/or other characters,

- the said second print consists of guilloches,

- said first and second prints are produced using inks in complementary colours,

- the said first print is made in red ink, which is invisible but fluoresces or phosphoresces,

- said second print is made in green ink, which is visible or invisible but fluorescent or phosphorescent,

- the second print occupies a surface above that of the first print.

Other features and advantages of the invention will become apparent upon reading the following detailed description of a preferred embodiment. This description refers to the accompanying drawings in which:

- Figure 1 is a schematic plan view of a security document covered with two prints according to the invention.

- Figures 2A and 2B are diagrams intended to illustrate what an observer sees when the document of Figure 1 is illuminated by UV radiation.

- Figures 3A and 3B are diagrams intended to illustrate what an observer sees when the document of Figure 1 is illuminated by UV radiation and the observer looks through a filter.

Document 1, which is shown schematically in Fig. 1, is for example a banknote. The symbols, patterns, values and other inscriptions that a banknote usually bears are not shown here for the sake of clarity.

According to the invention, this note is covered with a first print 3, in this case the initials "ABC", made with an ink C1, invisible to the naked eye but fluorescent or phosphorescent. This ink is, for example, red.

This first print 3 cannot be seen with the naked eye and under white light (daylight/artificial light).

The print can be made as a uniform print or as a multitude of lines. This is how it is shown in Fig. 1. However, in other designs it can be intertwined lines or any other form of writing.

This first print can take the form of information in letters, as shown in Fig. 1. However, such information can also include numbers and/or other characters. It can have a completely arbitrary character or, on the contrary, a meaning for the reader.

The document 1 carries a second print 4 which covers the first print. In a very advantageous manner, this print occupies a surface above that of the first print.

The print 4 is made using an ink that is visible to the naked eye or invisible. In any case, it is an ink of a colour C₂ which is different from C₁. Preferably, a colour C₂ which is complementary to C₁ is used in order to obtain a good contrast. In this case, C₂ is green.

According to the invention, the second print is made so as to form a visual disturbance of the first print, so that only the second print 4 is visible when, under the illumination with neutral light, the ink C2 is a visible ink or, under UV illumination, the ink C2 is an ink invisible to the naked eye. This is illustrated in Figures 2A and 2B, where the reference point O represents the eye of an observer, while the oblique arrow represents UV radiation.

Particularly preferably, the second print is made in the form of guilloches, i.e. an arrangement of intertwined lines directed in any direction, so that the distribution of these lines and their density due to the closed surface are such that they obscure the view of the first print.

This second print represents a first level of security for the document.

It is clear that the second print is visible directly on the document if C2 is an ink visible to the naked eye.

On the other hand, if C2 is an invisible fluorescent or phosphorescent ink, it is necessary to have a conventional UV source to make the second print visible.

Ideally, the carrier 2 of the document, which is made of paper if it is a banknote, will not contain any optical brightener, so that under UV radiation no light is reflected by it. Otherwise this additional reflected light would make it much more difficult to read the second print (lack of contrast).

It is unnecessary to recall that what is being done here is what is called additive color mixing. This means that it is the emission of colors from the fluorescent pigments excited by UV light that is perceived by the eye.

Figures 3A and 3B show the situation in which the observer in addition to UV light looks at the document through a filter, for example made of plastic, whose color is the same as that of the first print 3.

Here too, we are dealing with additive color mixing; the little light that is possibly reflected by the carrier 2 is filtered out by the filter 5 and the carrier looks black to the observer.

The same applies to the light reflected by the second print 4 in color C₂, which does not pass through the filter of color C₁.

In contrast, the first print 3 can be recognized through the filter 5, which allows the corresponding radiation to pass through. This is how the abbreviation "ABC" becomes recognizable.

Reading the abbreviation is made even easier (strong contrast) if the colors C₁₁ and C₂₀ are complementary.

So we are dealing with a second security level, which can be made visible by simple and well-known means, namely a UV lamp and a filter.

C₁ is preferably red, while C₂ is preferably green. However, all other preferably complementary color pairs can be used.

It should be noted that the security prints according to the invention cannot be reproduced using a photocopier, since at least C1 is an ink that is invisible to the naked eye.

Claims (7)

1. Security document or the like (1) such as banknote, passport, identity card, check card, which comprises a carrier (2) on which security prints (3, 4) are provided, said security prints having - a first print (3) made in an ink of a first color (C₁) which is invisible to the naked eye but fluoresces or phosphoresces, - a second print (4) covering the first and which is made in an ink of a second colour (C2) which is not visible or invisible to the naked eye but which fluoresces or phosphoresces, the second print (4) being made to form a visual disturbance of the first print, such that under illumination with neutral or ultraviolet light only this second print (4) is visible, whereas the first print (3) is only visible under illumination with ultraviolet light and through a filter of the same colour (C1) as that of the said first print (3). 2. Document according to claim 1, characterized in that the said first print (3) consists of information in the form of letters and/or numbers and/or other characters. 3. Document according to claim 1 or 2, characterized in that said second print (4) consists of guilloches. 4. Document according to one of claims 1 to 3, characterized in that said first and second prints (3, 4) consist of inks in complementary colors (C₁, C₂). 5. Document according to one of claims 1 to 4, characterized in that the said first print (3) is made in red ink which is invisible but fluorescent or phosphorescent. 6. Document according to one of claims 1 to 5, characterized in that the said second print (4) is made in green ink which is visible or invisible but fluorescent or phosphorescent. 7. Document according to one of claims 1 to 6, characterized in that the second print (4) occupies a surface above that of the first print (3).