THE IMPLEMENTATION THEREOF

The object of the invention is optical security of paper and printed matter by using NIR (near infrared) fluorescent dyes and/or pigments in the production of paper with security features and in printing printed matter with security features, and a method for the implementation thereof.

Paper and printed matter of the present invention are used particularly for the production of documents, banknotes, identity cards and similar documents which are protected against counterfeiting and/or altering to the best possible extent.

The present invention belongs to the field of paper and graphic industry, namely to paper-making and printing; it particularly relates to manufacturing of documents, banknotes and similar documents which are protected against counterfeiting and altering to the best possible extent.

The technical problem which is successfully solved by the present invention is a new possibility of optical security of paper and printed matter by using NIR fluorescent dyes and/or pigments in paper and printed matter. Paper and printed matter with security features need to be constantly improved in the field of adding and/or changing security elements since counterfeiters have access to more and more equipment and materials, with which counterfeits can be produced, and this makes them more and more successful. Many optical security elements are known worldwide. They contain watermarks in paper, fibres that fluoresce when exposed to UV light, UV fluorescent planchettes, UV fluorescent security threads, use of optically variable dyes, etc.

Protective dyes used for security features in paper are visible and/or invisible dyes which fluoresce in the visible spectrum if illuminated by UV light which makes them visible.

Optical security features in paper are known, for instance those described in patent document ES2432189, where security fibres are printed from a plurality of various colours which glow when illuminated by UV light. The fibres are added to paper pulp.

Patent document WO2007/144657 discloses fluorescent planchettes for inclusion in paper. The planchettes have shapes that are complex, the colour is visible only when illuminated by UV light.

A security thread incorporated in paper during paper making can offer various optical security features disclosed in patent documents US 0,964,014; US 4,652,015; US 5,068,008; US 5,324,079; WO 90/08367; WO 92/1 1 142; WO 96/04143; WO 96/39685; WO 98/19866; EP 0 021 350; EP

0 185 396; EP 0 303 725; EP 0 319 157 EP 0 518 740; EP 0 608 078; in EP

1 498 545. The thread can be metallic, may contain a hologram it can be printed with UV fluorescent dyes or optically variable dyes.

All mentioned documents describe use of various optical security features in paper or printing, but use of NIR fluorescent dyes and/or pigments in the production of paper and printed matter with security features is not foreseen in any of them. NIR fluorescent dyes have been unknown in the world of paper and printed matter with security features. Dyes and pigments are not yet prepared for colouring paper, security fibres and for printing security threads and planchettes. This is why the present invention also solves a problem of counterfeiting which has become easier for counterfeiters due to the availability of dies and materials.

In the hitherto known solutions UV fluorescent dyes need to be illuminated by UV light, wherein they fluoresce in the visible spectrum. NIR fluorescent dyes, on the other hand, can be illuminated by visible light or by UV light and a fluorescent response is obtained in the NIR spectrum. A majority of fluorescent materials absorb energy at higher energy (lower wavelengths in the spectrum) and emit low energy (at higher wavelength). This phenomenon is called down-conversion. Such printing inks are typically based on UV fluorescent materials that glow in the visible spectrum if illuminated by UV light. NIR fluorescent materials on the other hand convert visible light to NIR light, which means that fluorescence is obtained in the NIR light region.

The invention refers to optical security of paper and printed matter by using NIR fluorescent dyes and/or pigments in printing printed matter having security features, to use of NIR dyes and/or pigments in colouring security fibres, paper pulp and in printing security threads, planchettes or other additional elements which can be added to paper pulp and convey efficient security of paper in a final product. The invention further refers to use of NIR dyes in printing.

The invention will now be described in more detail with reference to the accompanying drawings and by way of embodiments of use and implementation of optical security features by NIR fluorescent dyes and/or pigments in the production of paper and printed matter of the invention, where the drawings show:

Figure 1A NIR fluorescent pigments added to entire paper pulp (left) and NIR fluorescent pigments added to a water-based print coating (right). The images have been recorded in the visible spectrum;

Figure 1 B Paper (left in the figure) and print coating with NIR fluorescent pigments in the NIR region;

Figure 2 security fibres coloured with NIR pigments in the visible region (left) and the NIR region (right);

Figure 3 invisible security fibres coloured with NIR pigments in the visible region (left) and the same fibres visible in the NIR region (right);

Figure 4 invisible security planchettes in paper in the visible region

(left) and the same visible security planchettes in the NIR region (right); Figure 5 incorporated security thread with a coating of NIR pigments in paper in the visible region (left) and the NIR region (right).

As visible from Figure 1A and Figure 1 B, NIR fluorescent pigments were added during the process of making a paper with optical security to the entire paper pulp and the print coating. NIR fluorescent pigments are visible only in the NIR region. The paper with added NIR fluorescent pigments is made by a known method, while the pigments were mixed to the print coating homogenously as the coating in the NIR region is uniformly visible.

Figure 2 and Figure 3 show coloured security fibres with NIR fluorescent pigments with a fixing agent, where the fibres were added in a certain portion to the paper pulp during the production of paper or printed matter having optical security.

Figure 4 shows production and functioning of invisible security planchettes, where a certain paper is printed with a coating containing a NIR fluorescent pigment. The planchettes coloured by a NIR fluorescent pigment and/or dye are added to the entire paper pulp in a certain portion during the process of producing paper or printed matter having optical security.

In optical security of paper and printed matter by using NIR fluorescent dyes and/or pigments, the pigments and/or dyes for colouring paper are added to the paper pulp during the paper making phase. The dyes and/or pigments can be visible, which means that the paper is coloured, or invisible, which means they have no influence on paper colour. NIR fluorescent dyes and/or pigments can also be used to colour security fibres. Security fibres are viscose, polymer/synthetic or cellulose fibres. The fibres are coloured by using NIR fluorescent dyes and/or pigments which are added to the paper pulp. The paper is made from a paper pulp containing cellulose fibres and/or also added polymer fibres to enhance certain physical and chemical properties of the paper. The coloured security fibres are also added to this pulp. The dyes and/or pigments can be visible, which means that the fibres are coloured, or invisible in the visible spectrum.

NIR fluorescent dyes and/or pigments can be printed on foils (from polyester, polypropylene or other types), from which a security thread to be incorporated into paper is cut according to a known cutting method, usually to a width 0.8 to 6 mm. A security thread is a ribbon of thermoplastic polymer material, or of any other substance, which can be metallised, which is embedded into paper as an additional security element during the method of production. There are several types of security threads from polymer threads to threads having a metallic coating, from colour threads and threads containing a micro text in a protected sheet to high-tech machine- readable threads, such as magnetic or holographic personalized security threads. A security thread can be fully embedded into a substrate or intermittently visible on the surface.

The invention further foresees a method for implementing the above- described optical security features in the production of paper and printed matter by using NIR fluorescent dyes and/or pigments, where: - When the entire paper pulp is coloured with NIR fluorescent pigments and/or dyes, the latter are added during the technological process for producing optically secured paper to the entire paper pulp;

- When a paper having optical security features is produced by a method of printing with a coating containing NIR fluorescent pigments and/or dyes, the NIR fluorescent pigments and/or dyes are added to the coloured or uncoloured coating and the paper can be printed with conventional printing techniques. The coating may be water-based, solvent-based or UV-curable.

- When security fibres are coloured with NIR fluorescent pigments that are added to a paper having optical security features, the fibres can be coloured by an added fixing agent. If the fibres are coloured with NIR fluorescent dyes, a known method of fibre colouring is used.

- When a security thread to be embedded into a paper is coloured, the security thread is printed with a coloured or uncoloured coating (with varnish or dye), to which NIR fluorescent pigments and/or dyes are added. The thread is then cut and embedded into a paper by a known method. A coating containing NIR fluorescent pigments and/or dyes can be printed by known printing techniques. The coating may be water-based, solvent-based or UV- curable.

- When planchettes are coloured, a paper suitable for the production of planchettes is printed by a coating (with varnish or dye), to which NIR fluorescent pigments and/or dyes are added. The planchettes are then punched and embedded into a paper by a known method. The coating containing NIR fluorescent pigments and/or dyes can be printed by known printing techniques. The coating may be water-based, solvent-based or UV- curable.

A security thread printed with a coating containing NIR fluorescent pigments as visible intermittently in a paper or printed matter having optical security features is shown in Figure 5.