WO2024042213A1

WO2024042213A1 - Method for authenticating and/or identifying a security document

Info

Publication number: WO2024042213A1
Application number: PCT/EP2023/073369
Authority: WO
Inventors: Henri Rosset
Original assignee: Oberthur Fiduciaire Sas
Priority date: 2022-08-25
Filing date: 2023-08-25
Publication date: 2024-02-29
Also published as: FR3139029A1

Abstract

The invention relates to a method for identifying and/or authenticating a security document comprising a paper substrate, wherein the substrate is analysed to detect the presence of one or more markers representative of the presence, in the substrate, of one or more compounds extracted from hardwood(s), and information relating to the identity and/or authenticity of the document is generated according to the nature and/or the proportion in the substrate of the one or more markers.

Description

Title of the invention: Method of authentication or identification of a security document

Technical area

[0001] The present invention relates to security documents and the identification or authentication thereof.

[0002] By “security document”, we mean a document of value, such as a means of payment, for example a bank note, a check, a bank card or a restaurant receipt, an identity document, such as such as an identity card, a visa, a passport or a driving license, a lottery ticket, a transport ticket or even an entry ticket to cultural or sporting events.

Prior art

[0003] To secure a document, it is common to use security elements which are added to the paper during the manufacture of the document.

[0004] It is thus known to use mineral pigments to authenticate or identify a paper, by giving it a specific signature. These mineral pigments are introduced during wet part papermaking. They can be made up of mixtures of rare earths, as described in the publications EP0975460, WO9938702, W09938700, WO9939051, WO9938703, WO2004111951, WO2005035261, WO2005035271, WO2005035272,

W02005036470, W02005036477, W02005036478 and W02005036479.

[0005] The use of such pigments poses several problems. On the one hand, their mineral nature contributes to the increase in the mineral load of the paper and therefore increases the ash rate of the paper. In addition, an overload of mineral pigments tends to degrade the mechanical strength of the paper. On the other hand, as for other mineral opacification fillers (for example titanium dioxide), their retention during draining is imperfect and their loss in the water under the canvas can be significant and, with regard to markers which are sometimes very expensive, this can have a significant economic impact. In certain cases, moreover, due to the toxicity inherent to their chemical nature, their use can pose environmental problems. Finally, their detection often requires the use of specific, high-tech electromagnetic detectors, which complicates the authentication of the document.

[0006] Furthermore, it is known to use microscopic observation techniques to identify and quantify specific synthetic or natural fibers of a paper substrate. Publications W02015/200575, W02015/200577 and W02015/200572 describe such methods. In certain situations, and particularly in the case of mixing with other fibers such as cotton fibers, paper refining operations can make the identification of these “special” fibers very difficult and require analysis by a particularly experienced operator. The similarity in fibrous nature of a particular species with the other fibrous components of paper, which have a thin and elongated shape, contributes to this difficulty.

[0007] There is a need to further increase the security of documents, in particular by simplifying their authentication and/or their identification.

Summary of the invention

[0008] The invention aims to meet this need and it achieves this, according to one of its aspects, thanks to a method of identification and/or authentication of a security document comprising a paper substrate, in in which the substrate is analyzed to detect the presence of one or more markers representative of the existence in the substrate of one or more compounds extracted from hardwood(s) and information concerning the identity and/or authenticity of the document is generated depending on the nature and/or the proportion in the substrate of said marker(s).

[0009] A “compound extracted from hardwood(s)” comprises cellulose and hemicellulose fibers as well as vessels. The vessels and fibers differ in size. The fibers are generally longer and thinner than the vessels. The compound may be a solid compound. The compound can be introduced in the form of a paste. Hardwood fibers are generally short and not very thick. The fibers and vessels include cellulose or hemicellulose.

[0010] By “deciduous” we must understand a tree producing well-developed leaves, as opposed to conifers or conifers. Deciduous trees can cyclically lose their leaves, particularly in autumn, in which case we speak of deciduous trees. The leaves of deciduous trees are generally broad.

Unlike deciduous trees, conifers have leaves in the form of needles which are renewed over time, we then speak of evergreen foliage. Softwoods always have the same appearance. Softwoods can also be called conifers. The following trees are examples of deciduous trees: birch, hornbeam, chestnut, oak, eucalyptus, beech, sweetgum, nyssa, poplar, American tulip tree.

[0011] The advantage of using a compound extracted from hardwood in a paper substrate is twofold. On the one hand, the compound extracted from hardwood, due to its fibrous cellulosic nature, is well suited to the manufacture of a paper substrate. The paper substrate obtained thus has good mechanical resistance. On the other hand, the markers representative of the existence in the substrate of one or more compounds extracted from hardwood(s) are easily identifiable markers. Identification and/or authentication can be done without difficulty, particularly by visual observation at low magnification. [0012] Furthermore, the process according to the invention has the advantage of being harmless to health and the environment, compared to the use of certain mineral pigments. It therefore does not require the detection of an unnatural marker which could be toxic and/or harmful to the environment.

The process according to the invention is economical since it only requires the use of a compound extracted from hardwood(s). However, deciduous trees are widespread trees.

[0014] The paper substrate may include cellulosic fibers other than hardwood fibers. In particular, the substrate may include cotton fibers, particularly when the production of banknotes is aimed at.

[0015] It is possible to vary the nature and/or the proportion of one or more compounds extracted from hardwood(s) in the composition of the substrate in order to produce security documents with a unique signature. For example, we can mix compounds extracted from two different hardwoods to make the paper substrate and distinguish this substrate from another substrate comprising, for example, the same compounds in different proportions or other compounds extracted from hardwood(s).

The analysis of the substrate can be carried out with and/or without magnification, in particular with the naked eye, for example after having carried out a specific coloring. Analysis of the substrate with magnification is preferably done with a microscope. The analysis of the substrate is preferably carried out without a particular electromagnetic detector, for example under white light.

[0017] The method according to the invention thus has the advantage of being simple to implement. It does not require devices other than an optical microscope to detect the marker(s). It is therefore economical and quick to implement.

The marker(s) representative of the existence in the substrate of one or more compounds extracted from hardwood(s) can also be detected without magnification. The security document can thus be authenticated and/or identified by an uninformed observer (“the man in the street”).

The hardwood or hardwoods whose presence is sought in the paper are preferably made up of at least one of the following species: birch, hornbeam, chestnut, oak, eucalyptus, beech, styraciferous sweetgum, nyssa, poplar, tulip tree 'America.

The hardwood tree(s) preferably belong to the eucalyptus family. They consist in particular of at least one of the following varieties of eucalyptus: eucalyptus globulus, eucalyptus camaldulensis, eucalyptus rostrata, eucalyptus citriodora, eucalyptus cordata, eucalyptus deglupta, eucalyptus gundal, eucalyptus gunnii, eucalyptus pauciflora, eucalyptus radiata, eucalyptus regnans, eucalyptus sideroxylon.

[0021] Eucalyptus trees have the advantage of being fast-growing trees that can grow easily in various regions of the world. They therefore constitute an easily accessible resource for the manufacture of a paper substrate. Preferably, at least one of the markers consists of hardwood vessels. In particular, at least one of the markers consists of eucalyptus vessels.

[0023] The vessels of hardwood(s) have the advantage of having an easily identifiable morphology, which makes it possible to distinguish the fibers of compounds extracted from hardwood(s) from cotton fibers, during the analysis of the substrate.

[0024] Furthermore, their morphology also has the advantage of offering them a significant specific surface area which contributes to their retention, in particular without loss, during the manufacture of the paper substrate. The vessels of compounds extracted from hardwood(s) can therefore contribute to the mechanical reinforcement of the paper substrate, in the same way as hardwood(s) and cotton fibers.

[0025] Due to their organic and cellulose composition, these vessels do not contribute significantly to the generation of ash.

[0026] During the method according to the invention, the shape of the vessels is preferably analyzed. Information regarding the identity and/or authenticity of the document can be generated at least on the basis of the result of this analysis.

[0027] When analyzing the shape of the vessels, we preferably calculate at least one ratio between the length of the vessels and their width.

It is preferably determined during the analysis whether said ratio is between 0.7 and 4.5, better between 0.8 and 4 (in particular for eucalyptus), even better between 0.9 and 3 .5, better between 1 and 3, better between 1.1 and 2.5, better between 1.2 and 2, for example around 1.8.

[0029] The length of a vessel, in particular a eucalyptus vessel, is preferably between 100 and 550 pm, better between 120 and 500 pm, better between 150 and 450 pm, better between 200 and 350 pm, for example around 290pm.

[0030] The width of a vessel, in particular a eucalyptus vessel, is preferably between 50 and 400 pm, better between 75 and 350 pm, better between 100 and 300 pm, better between 100 and 250 pm, for example around 160pm.

[0031] When implementing the method according to the invention, the vessels having a substantially rectangular shape in cross section are preferably counted.

[0032] The hardwood vessels, in particular the eucalyptus vessels, have a substantially rectangular, or even square, shape in cross section. They are also quite thick and quite short. They therefore differ greatly from usual cotton fibers which are elongated and fine. Their enumeration during the analysis of the substrate is thus facilitated.

To carry out the analysis, the substrate can be brought into contact with a substance suitable for selectively coloring at least one of said markers. This selective staining can take place before vessel counting. The substance can in particular be chosen to color the vessels and fibers, particularly cotton, differently. This selective coloring makes it easier to identify the markers, in particular the identification of the vessels. The identification after coloring can thus be done with or without magnification.

The substance suitable for selectively coloring at least one of said markers is preferably a solution of Herzberg reagent.

[0036] The use of Herzberg reagent (or zinc chloroiodide) on a substrate mainly composed of cotton fibers and one or more compounds extracted from hardwood(s) makes it possible to color the compound(s) extracted from hardwoods of a first color, for example blue, and cotton fibers in a second color, distinct from the first, for example red.

The elements having the first color can be visible without magnification, which makes it possible to detect the presence of one or more compounds extracted from hardwood(s). The specific coloring therefore allows a first authentication and/or identification that can be achieved with the naked eye.

[0038] A more precise analysis with magnification, for example under a microscope, can then be carried out. We then seek to analyze the morphology of the markers, for example of the vessels, to help determine the hardwood species used. Due to their very characteristic morphology, eucalyptus vessels are particularly easy to spot.

[0039] During the analysis, the colored markers are preferably counted.

Preferably, the markers are counted on a given surface of the substrate analyzed and the proportion of compounds extracted from hardwood(s) in the substrate manufacturing paste is deduced.

The marker(s) preferably appear in isolation. They can be directly identifiable on the surface of the paper substrate, with or without magnification. It is then not necessary to crush and/or disintegrate the security document to carry out its analysis.

The analysis of the substrate is thus carried out, preferably, without destruction of the document. For example, we do not take a deduction from the document. The analyzed marker(s) may be present on the document during this analysis. In the case of a banknote, it is for example examined under a microscope to determine the presence and/or content of markers.

[0043] At least one of the markers used for implementing the identification and/or authentication method according to the invention may be present in a proportion in low number compared to the other constituents extracted from the hardwood and present in the paper. For example, in the case where the marker is made up of vessels, there may be 10 times fewer vessels than fibers in the compound extracted from hardwood which is integrated into the paper during its manufacture, better still 50 times fewer vessels than fibers, better 100 times fewer vessels than fibers, or even 1000 times fewer vessels than fibers.

Security element [0044] It is also possible to check the presence on the document of one or more additional conventional security elements.

[0045] Among these additional security elements, some are detectable by eye, in daylight or artificial light, without the use of a particular device. These security elements include, for example, colored fibers or planks, totally or partially printed or metallized security threads, a secure knitted structure, a security film, a watermark, an optically variable element (called “OVD”), in particular a hologram. These security elements are called first level.

Other types of additional security elements are detectable only using a relatively simple device, such as a lamp emitting in ultraviolet (UV) or infrared (IR). These security elements include, for example, fibers, planks, strips, threads or particles. These security elements may or may not be visible to the naked eye, for example being luminescent under illumination from a Wood lamp emitting in a wavelength of 365 nm. These security elements are called second level.

[0047] Other types of additional security elements require a more sophisticated detection device for their detection. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more sources of external excitation. Automatic signal detection allows the document to be authenticated, if necessary. These security elements include, for example, tracers in the form of active materials, particles or fibers, capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are called third level.

The additional security element(s) present within the paper according to the invention or the secure document according to the invention may have first, second or third level security characteristics.

The analysis of the substrate is preferably carried out by automatic image analysis, for example via a computer, in particular a computer connected to the optical microscope used for the analysis.

Security document

[0050] The invention also relates, independently or in combination with the above, to a security document comprising a paper substrate comprising cellulosic fibers and one or more compounds extracted from hardwood(s).

[0051] The addition of compounds extracted from hardwood(s) in the composition of the paper substrate of the security document makes it possible to increase the mechanical resistance of the paper. The fibrous and cellulose nature of the compounds extracted from hardwood contributes to the development of the mechanical resistance of the paper substrate. The internal cohesion and dry and wet tensile strength of the security document according to the invention are improved by the presence of compounds extracted from hardwoods. THE The level of durability of the paper is thus increased, which makes it possible to increase the circulation life of the security document, particularly in the case of a bank note.

[0052] Hardwood fibers, in particular eucalyptus fibers, have the advantage of being short and not very thick. In addition, they have a high specific surface area, in particular compared to cotton fibers which are traditionally used in the manufacture of paper substrates.

[0053] The substrate preferably comprises between 2 and 50%, by mass relative to the mass of the substrate, of one or more compounds extracted from hardwood(s), better between 3 and 40%, better still between 5 and 30% . Weighing of the substrate is preferably done at a relative humidity level of 50% at room temperature (20°C).

[0054] The substrate may in particular comprise between 0.1 and 1% vessel of hardwood(s), in particular eucalyptus, per surface unit.

[0055] The substrate may comprise at least 50% by mass of cotton fibers, relative to the total mass of the substrate.

[0056] The hardwood tree(s) preferably belong to the eucalyptus family, and may in particular be chosen from the following eucalyptus species: eucalyptus globulus, eucalyptus camaldulensis, eucalyptus rostrata, eucalyptus citriodora, eucalyptus cordata, eucalyptus deglupta, eucalyptus gundal, eucalyptus gunnii, eucalyptus pauciflora, eucalyptus radiata, eucalyptus regnans, eucalyptus sideroxylon.

[0057] The compounds extracted from eucalyptus have the advantage of containing hemicelluloses which allow, due to the reactivity of their carboxylic groups, active collaboration with the resins, in particular with a polyamide-polyamine-epichlorohydrin resin (PAAE resin). , which improves the development of the wet strength of the paper substrate.

[0058] The substrate can thus advantageously contain both compounds extracted from eucalyptus, in particular eucalyptus fibers and vessels, and a resin conferring wet strength to the paper, preferably a PAAE resin.

[0059] One or more security elements can be integrated or attached to the substrate, this or these security elements being of first, second and/or third level, as detailed above, being chosen for example from: a security wire , a board, a security film, a watermark, an optically variable element (called “OVD”), in particular a hologram, a tracer in the form of a material capable of generating a specific signal when subjected to electrical excitation , magnetic or electromagnetic, in particular optical, for example a luminescent agent under UV or IR, an intaglio print, or an optically variable ink.

[0060] In exemplary embodiments, the substrate comprises compounds extracted from at least two different hardwood species, in particular eucalyptus and on the other hand a hardwood chosen from: birch, hornbeam, chestnut, oak, beech, styraciferous liquidambar, nyssa, poplar, American tulip tree.

Brief description of the drawings

[0061] The invention can be better understood on reading the description which follows, non-limiting examples of its implementation, and on examining the appended drawings, in which:

[0062] [Fig 1] Figure 1 is a schematic view of an example of a security document according to the invention,

[0063] [Fig 2] Figure 2 is a block diagram of steps of an example of an identification and/or authentication method,

[0064] [Fig 3] Figure 3 is a microscope view of a substrate comprising a compound extracted from hardwoods after selective coloring,

[0065] [Fig 4] Figure 4 is a view similar to Figure 3 with greater magnification,

[0066] [Fig 5] Figure 5 is a photograph of four substrates comprising a compound extracted from hardwood in increasing proportions after selective colorization of the vessels and surroundings for counting.

detailed description

1 shows a security document 10 which comprises a substrate 11 in which a security element 12 is integrated or on which is attached.

This substrate 11 is fibrous. It may include fibers and adjuvants conventionally used in the papermaking field, in particular cellulose fibers. The substrate may comprise a mixture of long and short cellulosic fibers. This substrate 11 comprises one or more compounds extracted from hardwoods, namely hardwood fibers and vessels.

The substrate may comprise a single fibrous layer or several fibrous layers (also called jets) assembled after formation, particularly in the wet phase.

[0070] The substrate may comprise one or more security structures obtained during manufacturing, and the substrate may in particular comprise a fibrous layer carrying a watermark.

[0071] The fibrous layer(s) of the substrate can be produced on a flat table or round-shaped paper machine, and the watermark(s) can be produced in the wet part according to conventional processes known to those skilled in the art.

[0072] At least one fibrous layer of the substrate, or even the substrate itself, may have a weight (according to ISO 536 standard) of between 60 and 120 g/m ² , preferably between 70 and 90 g/m ² . [0073] At least one fibrous layer of the substrate, or even the substrate itself, may have a thickness (according to ISO 534) of between 60 and 120 pm, preferably between 70 and 110 pm, for example around 110 pm .

[0074] Steps of an example of an identification and/or authentication method according to the invention are shown in the block diagram of Figure 2.

[0075] First of all, in order to analyze the security document, during a first step El, the document is dipped in a Herzberg reagent solution. This first step El makes it possible to selectively color the desired markers.

[0076] Then, during a second step E2, the document is left to dry. Once the document is dry, it can be observed using an optical microscope (step E3).

[0077] We look for the presence of a compound extracted from hardwood in the substrate of the document.

[0078] Studying the morphology of the detected markers makes it possible to determine the nature of the hardwood used in the composition of the substrate. We can thus carry out a first identification of the document.

[0079] We then count, using the microscope, the number of colored markers on a given surface of the document (step E4). From this count, we can deduce an estimate of the mass percentage of compound extracted from hardwood in the composition of the document substrate. This estimate makes it possible to identify the document.

[0080] Following the analysis, and in particular following the count, information can be generated concerning the identity and/or authenticity of the document (step E5).

[0081] In the example of Figures 3 to 5, the markers representative of the existence in the paper substrate of one or more compounds extracted from hardwood(s) are eucalyptus vessels.

The substrates shown in Figures 3 to 5 were selectively colored by dipping in a Herzberg reagent solution. The compounds extracted from hardwoods, that is to say the vessels and fibers, then turn blue and can be distinguished from the other elements of the substrate.

[0083] As can be seen in Figure 3, the eucalyptus vessels 1 differ from the eucalyptus fibers 2 by their wider and shorter shape.

[0084] The length L and the width / of a eucalyptus vessel are visible in Figure 4. The length L is for example of the order of 290 pm. The width / is for example of around 160 pm.

[0085] Figure 5 shows four substrates comprising an increasing mass proportion, from left to right, of compounds extracted from eucalyptus. The substrate SI comprises 5% by mass of eucalyptus paste, the substrate S2 comprises 10% by mass of eucalyptus paste, the substrate S3 comprises 20% by mass of eucalyptus paste, the substrate S4 comprises 30% by mass eucalyptus paste. The vessels of eucalyptus 1 were selectively stained with Herzberg's reagent. We see in this photograph that the greater the mass proportion of compounds extracted from eucalyptus in the substrate, the greater the number of vessels. This correlation is also established in the following Examples 2 and 3.

Examples

[0087] Example 1

[0088] The effect of the introduction of 5, 10, 20 and 30% by mass of eucalyptus pulp is evaluated relative to the total mass of pulp in replacement of part of the cotton pulp (cotton 1 , cotton 2) on the mechanical properties of the paper substrate.

The substrates obtained undergo surfacing in a size press.

As a control, a substrate comprising only cotton fibers and no compounds extracted from eucalyptus is used.

[0091] The Zeta Potential is measured with a “System Zeta Potential” device, model Mütek SZP-06 from the company BTG.

[0092] In order to evaluate the tensile strength in the dry state, in particular the breaking length in the dry state (or “dry breaking length”), we can measure the length at which the sheets break under the effect of their own weight according to the ISO 1924-2 standard.

[0093] In order to evaluate the tensile strength in the wet state, in particular the breaking length in the wet state (or “wet breaking length”), we can measure the length at which the sheets break under the effect of their own weight according to the ISO 3781 standard.

[0094] The strength in the wet state (REH) is defined as the ratio between the breaking length in the wet state and the breaking length in the dry state according to the following formula:

[0095] [Math 1]

Breaking length at 1 wet state

RE H — - ; - - - 777 -

[0096] Breaking length at 1 dry state

[0097] The internal cohesion (or resistance to delamination) is measured using a SCOTT device, model B, No. ESO33, according to the Tappi 569 om-09 standard.

[0098] The results of the evaluations are presented in the table below. The percentages of cotton 1, cotton 2 and eucalyptus pulps are mass percentages relative to the total mass of pulp. [Table 1]

[0099] In the table above: “MD” means “travel direction”, “CD” means “cross direction” and “Avg. » means “average”.

[0100] It is noted that the internal cohesion, the dry tensile strength and the wet tensile strength of the substrates comprising eucalyptus are improved compared to the control substrate which only comprises cotton fibers.

[0101] The Zeta Potential (PZ) of the substrates is also measured. We see that it gradually evolves from 2.2 mv to -3.2 mv, -5.3 mv and -10.5 mv for eucalyptus rates going respectively from 5% to 10%, to 20% and to 30% in mass. This reflects the increasing presence of associated hemicelluloses from eucalyptus, thus increasing the fixing potential of the PAAE resin. [0102] By comparing the substrate comprising 20% by mass of compound extracted from eucalyptus to the control substrate comprising no compound extracted from eucalyptus, it is found that with the substrate comprising eucalyptus, the internal cohesion is improved by 33.2%, stiffness is improved by 23.1%, dry traction is improved by 5%, and wet traction is improved by 14.5%.

[0103] The introduction of compounds extracted from eucalyptus into the substrate therefore makes it possible to improve the mechanical resistance of this substrate.

[0104] Furthermore, the above results show that the presence of eucalyptus fibers does not unduly alter the color of the paper used for the security document.

[0105] Example 2

[0106] In this example, we seek to count eucalyptus vessels on paper substrates containing different mass proportions of compounds extracted from eucalyptus by direct observation of the substrate, that is to say without the use of a microscope. The substrate analyzed comprises a cotton pulp comprising cotton fibers of two different references mixed in equal mass proportions. The substrate also contains a portion of eucalyptus paste. The compositions of the different paper substrates used are indicated in the following table. The percentages indicated are mass percentages.

[Table 2]

[0107] Each substrate is soaked for at least 30 seconds in a Herzberg reagent solution. We see that areas of the substrate corresponding to the eucalyptus vessels turn blue-violet. The substrate is then allowed to air dry.

[0108] The eucalyptus vessels which are then colored can be counted easily. The results of the counts carried out for each of the substrates are indicated in the table below. [Table 3]

[0109] A correlation is noted between the number of eucalyptus vessels counted and the proportion of compounds extracted from eucalyptus in the substrate. The greater the proportion of compounds extracted from eucalyptus in the substrate, the greater the quantity of vessels counted.

[0110] Example 3

[OR I] In this example, we seek to count eucalyptus vessels on paper substrates containing different mass proportions of compounds extracted from eucalyptus. The substrate analyzed comprises a cotton pulp comprising cotton fibers of two different references mixed in equal mass proportions. The substrate also includes a portion of eucalyptus paste. The compositions of the different paper substrates used are indicated in the following table. The percentages indicated are mass percentages. [Table 4]

[0112] We begin by preparing dispersions of the substrates in the following manner:

[0113] 1 - A 4 x 4 cm square is cut out and weighed from each substrate. Then we cut the square into pieces of approximately 1 x 1 cm. Then we transfer them to the bowl of a mixer.

[0114] 2 - 50 ml of demineralized water are added and ground for 3 minutes at maximum speed.

[0115] 3 - The bowl and the lid of the mixer are rinsed with demineralized water and the fibrous suspension obtained is transferred to a beaker. Then dilute with approximately 200 mL of rinsing water.

[0116] 4 - Filtered through a sieve with a square mesh of 53 μm. Then rinse and transfer to a beaker and dilute with approximately 50 mL of rinsing water. This makes it possible to eliminate charges, in particular titanium dioxide (TiO2).

[0117] 5 - The beakers are placed in an oven at 105°C to evaporate the water and to obtain a slightly moist paste.

[0118] The blades are then prepared to count the vessels:

[0119] 1 - A few drops of Herzberg reagent are placed on a microscope slide (26 x 76 mm). Using two curved dissecting needles, we take a little paste and disperse it in the reagent until we obtain a homogeneous distribution without agglomerates of fibers, also called sticks. Cover with coverslip (24x32 cm). We prepare around ten blades in this way.

[0120] 2 - Place the slide on the stage of the optical microscope (Olympus / transmitted light / 5X objective)

[0121] 3 - Using the cross movement of the plate, the blade is moved in order to cover it completely without superimposing the fields of observation.

[0122] 4 - The eucalyptus vessels are counted in each circular field.

[0123] The results of the count are presented in the following table:

[Table 5]

[0124] A correlation is noted between the number of eucalyptus vessels counted and the proportion of compounds extracted from eucalyptus in the substrate. The greater the proportion of compounds extracted from eucalyptus in the substrate, the greater the quantity of vessels counted. Counting the number of eucalyptus vessels therefore makes it possible to estimate the mass proportion of eucalyptus in the composition of the substrate. It is thus possible to identify and/or authenticate a security document made from a substrate containing a portion of eucalyptus.

[0125] The substrate will for example be authenticated when a proportion by mass of eucalyptus corresponding to that expected for an authentic substrate is counted.

[0126] The substrate can be identified for example according to the nature of the hardwood used, if several documents exist with different varieties of hardwood.

Claims

1. Method for identifying and/or authenticating a security document comprising a paper substrate, in which the substrate is analyzed to detect the presence of one or more markers representative of the existence in the substrate of a or several compounds extracted from hardwood(s), and information concerning the identity and/or authenticity of the document is generated depending on the nature and/or the proportion in the substrate of said marker(s).

2. Method according to the preceding claim, the analysis of the substrate being carried out with and/or without magnification, in particular with the naked eye.

3. Method according to one of the preceding claims, in which the hardwood or hardwoods consist of at least one of the following species: birch, hornbeam, chestnut, oak, eucalyptus, beech, sweetgum, nyssa, poplar, tulip tree America, preferably eucalyptus.

4. Method according to any one of the preceding claims, in which the hardwood tree(s) belong to the eucalyptus family, being in particular constituted by at least one of the following eucalyptus varieties: eucalyptus globulus, eucalyptus camaldulensis, eucalyptus rostrata, eucalyptus citriodora, eucalyptus cordata, eucalyptus deglupta, eucalyptus gundal, eucalyptus gunnii, eucalyptus pauciflora, eucalyptus radiata, eucalyptus regnans, eucalyptus sideroxylon.

5. Method according to claim any one of the preceding claims, at least one of the markers consisting of hardwood vessels.

6. Method according to the preceding claim, in which the shape of the vessels is analyzed and said information is generated at least on the basis of the result of this analysis.

7. Method according to the preceding claim, in which during the analysis of the shape at least one ratio is calculated between the length of the vessels and their width.

8. Method according to the preceding claim, in which it is determined during the analysis whether said ratio is between 0.7 and 4.5, better between 0.8 and 4, even better between 0.9 and 3.5 , better between 1 and 3, better between 1.1 and 2.5, better between 1.2 and 2, for example around 1.8. Method according to any one of the three immediately preceding claims, in which the vessels having a substantially rectangular shape in cross section are counted. Method according to any one of the preceding claims, in which to carry out the analysis the substrate is placed in contact with a substance suitable for selectively coloring at least one of said markers. Method according to the preceding claim, wherein said substance is a solution of Herzberg reagent. Method according to one of the two immediately preceding claims, in which during the analysis the colored markers are counted. Method according to any one of the preceding claims, the analysis of the substrate being carried out without destruction of the document. Method according to any one of the preceding claims, in which the presence on the document of one or more security elements is also checked, the security element(s) being chosen in particular from: a security thread, a board, a structure secure knitted fabric, a security film, a watermark, an optically variable element (called “OVD”), in particular a hologram, a tracer in the form of a material capable of generating a specific signal when subjected to electrical excitation, magnetic or electromagnetic, in particular optical. Method according to any one of the preceding claims, the analysis of the substrate being carried out by automatic image analysis. Method according to any one of the preceding claims, the substrate analyzed comprising between 2 and 50%, by mass relative to the mass of the substrate, of one or more compounds, preferably vessels, extracted from hardwood, in particular from eucalyptus, better between 3 and 40%, better between 5 and 30%. Safety document comprising a paper substrate comprising between 2 and 50%, by mass relative to the mass of the substrate, of one or more compounds, preferably vessels, extracted from hardwood, in particular eucalyptus, better between 3 and 40 %, better between 5 and 30%, the security document comprising one or more security elements integrated or attached to the substrate. Security document according to the preceding claim, the security element(s) being chosen from: a security thread, a board, a secure knitted structure, a security film, a watermark, an optically variable element (called “OVD”), in particular a hologram, a tracer in the form of a material capable of generating a specific signal when subjected to electrical, magnetic or electromagnetic, in particular optical, excitation. Security document according to one of the two preceding claims, the eucalyptus being chosen from the following eucalyptus species: eucalyptus globulus, eucalyptus camaldulensis, eucalyptus rostrata, eucalyptus citriodora, eucalyptus cordata, eucalyptus deglupta, eucalyptus gundal, eucalyptus gunnii, eucalyptus pauciflora, eucalyptus radiata, eucalyptus regnans, eucalyptus sideroxylon. Security document according to any one of claims 17 to 19, the security document being chosen from: a bank note, a check, a bank card or a restaurant ticket, an identity document, such as a travel card identity, a visa, a passport or a driving license, a lottery ticket, a transport ticket or even an entry ticket to cultural or sporting events. Security document according to any one of claims 17 to 20, the substrate comprising compounds extracted from at least two different hardwood species, in particular eucalyptus on the one hand and a hardwood tree on the other hand chosen from: birch, hornbeam, chestnut, oak, beech, sweetgum, nyssa, poplar, American tulip tree.