EP2407314A1 - Method for producing a pattern on a substrate using security ink - Google Patents

Abstract

The method involves marking a layer that is sensitive to laser radiation, with a laser beam by ablation of the sensitive layer at beam impact points on the sensitive layer for forming a predefined thickness profile such that the profile generates a luminous intensity modulation reproducing a pattern (24) observable through a safety ink layer at a predefined wavelength. The safety layer is formed from a material comprising a liquid crystal ink e.g. OASIS(RTM: complete line of water based ink), optical variable ink(RTM: anti-counterfeiting ink), or iridescent ink. An independent claim is also included for a safety document comprising a support.

Description

The present invention relates to the technical field of security documents, identification documents and / or securities documents.

More generally, the invention relates to documents which, because of their nature or rights they may confer, must be protected from counterfeiting or falsification.

It applies more particularly but not specifically to documents including a carrier carrying secure data, including personal data, such as an identity card, a driver's license, or a passport, this enumeration is not exhaustive. For example, the medium is in the form of a page of a booklet (passport, etc.) or a general form of card (identity card, etc.).

These documents generally comprise on the one hand invariable printed data, also designated by fixed mentions, and on the other hand variable printed data, also designated by variable mentions, related for example to the identity of its bearer (the portrait, the names, first names of the bearer) which therefore differ from one holder to another.

To fight against attempts to counterfeit or fraudulent forgery of these documents, the manufacture and personalization of the latter implement increasingly complex and expensive techniques.

For this purpose, the documents generally comprise a combination of security elements that make their reproduction or falsification very complex.

A security element may consist for example of an insert (security thread, electronic chip) incorporated in the support, but also in a pattern (text, portrait, logo, etc.) printed on the support, etc. Such a security element can be controllable without requiring equipment for example by simple observation with the naked eye (first-level security) but may also require an external device for its control (second-level security) or even very sharp analyzes only feasible in specific laboratories (third-level security).

In particular, it is known to form a security motif by printing on the support with a security ink. For the purposes of the present invention, the term "security ink" means an ink which produces a special effect, for example a variable optical effect as a function of an observation angle, a thermochromic effect, a metallic effect, etc.

Iridescent inks, also known as "pearlescent" inks, ultraviolet luminescence inks, photochromic inks, phosphorescent inks, etc., may be especially mentioned as security ink. Generally, to produce such special effects, these security inks comprise a matrix that incorporates substances that have specific physical properties (optical, thermal, etc.), for example liquid crystals.

However, the particular characteristics of these substances (dimensions, method of incorporation into the matrix, etc.) sometimes make their use difficult to reconcile with printing equipment dedicated to the personalization of documents (for example inkjet printer, printer thermal, laser printing) allowing the printing of variable mentions for the personalization of documents.

To customize a document with security inks, it is then necessary to use specific printing equipment compatible with a security ink but which generally allows only serial printing of fixed mentions on the documents. The use of such printing equipment for personalization with security ink is particularly expensive and difficult to implement.

The object of the invention is to propose a method for producing a security motif on a medium that overcomes this drawback.

For this purpose, the subject of the invention is in particular a method for producing a pattern with a security ink on a support, characterized in that the support comprising at least one layer sensitive to laser radiation and a layer of security ink arranged above the sensitive layer so that the sensitive layer is observable through the security layer at least a predefined wavelength, the method comprises a step of marking the sensitive layer with a laser beam by ablation of this layer at a plurality of beam impact points on the layer to form a predefined thickness profile of this layer. layer so that this thickness profile generates a modulation of light intensity reproducing the pattern, observable through the security layer at the predefined wavelength.

The layer of security ink thus acts as a protective layer preventing tampering (indeed, the ink layer can not be easily removed without creating irreversible damage to the support easily identifiable) while allowing to reveal the pattern.

Indeed, the pattern, marked in the sensitive layer by the laser beam through the layer of security ink, is in the form of a profile of varying thickness with strong ablation zones and zones. lower ablation thus creating a light intensity modulation observable through the ink layer. The desired pattern can thus be reproduced in grayscale.

The thickness variation of the sensitive layer produces a modulation of the light intensity perceptible by an observer through the security layer.

With the laser marking, it is possible to form a pattern with great detail and good contrast which allows for the realization of fine structures, difficult to reproduce by counterfeiters.

Preferably, the security layer is deposited in flat form, that is to say a layer of substantially uniform thickness. In addition, in a preferred embodiment, the security layer defines itself another pattern, said external pattern as opposed to the observable pattern through this layer, said internal pattern. Both motifs are for example in locating with respect to one another to compose together an observable image at least at the predefined wavelength.

Preferably, since the security layer is insensitive to radiation, the laser beam is directed on the support, once the security layer has been deposited, and the sensitive layer is marked through the security layer on one of the faces of the security layer. the sensitive layer opposite the security layer.

Thus, the ablation zone is located opposite the ink layer which makes it possible to make the pattern directly visible in reflective observation.

However, in another embodiment, a hollow surface profile, and thus ablation by the laser beam of the sensitive layer, can be made from the opposite side of the face opposite the security layer. In this case, the pattern may be revealed in observation by translucency of at least the sensitive layer.

Preferably, the laser beam being emitted by a source of pulses of adjustable intensity and duration, to form the pattern according to the predefined depth profile, the intensity, the number and / or the duration of the pulses of the source of the laser beam to vary the ablation depth.

Preferably, the pattern being decomposed into a matrix of pixels, each pixel being associated with a gray level of a predefined gray scale, to vary the gray level from one pixel to another, the number of impact points per pixel of the laser beam on the sensitive layer and / or the ablation depth of each of the impact points of the pixel is varied.

In one embodiment of the invention, the security layer is applied to the support by screen printing, flexography, offset, intaglio, letterpress, pad printing, thermal transfer and / or gravure printing.

Preferably, the sensitive layer is also an ink layer which incorporates security tracers, such as fluorescent particles, reaction-type particles at a predefined wavelength, photochromic particles, and / or thermochromic particles. . Of course, this list is not exhaustive.

In the example described, the sensitive layer has optical properties that differ in a vertical direction of the support. For example, the sensitive layer comprises at least two sublayers superimposed on each other and made of materials having distinct optical properties.

The security layer is made of a material comprising an ink with a variable optical effect of the liquid crystal type, for example the ink of the OASIS® brand sold by SICPA, a variable optical effect ink, such as, for example, OVI® ink, sold by SICPA, or an iridescent ink, etc.

For example, the support comprises at least one other layer, called the carrier layer, forming a substrate of the support and being flexible or rigid.

In one embodiment of the invention, the support incorporating at least one security element, at least partially reveals this element by ablation of the sensitive layer to the right of the element.

The invention also relates to a security document comprising a support and a security element carried by the support, characterized in that the support comprises at least one layer sensitive to laser radiation and at least one layer of security ink, said security layer, the security element comprising a pattern made according to a method according to the invention. The pattern can in particular be reproduced in gray level.

Preferably, the document is selected from a bank note, a passport and a microcircuit card.

• la figure 1 illustre un document de sécurité selon un premier mode de réalisation de l'invention comprenant un motif réalisé au moyen d'un procédé selon l'invention ;
• la figure 2 est une vue en coupe selon la ligne 2-2 de la figure 1 ;
• la figure 3 illustre un document de sécurité selon un deuxième mode de réalisation de l'invention ;
• la figure 4 est une vue en coupe selon la ligne 4-4 de la figure 3 ;
• la figure 5 illustre un document de sécurité selon un troisième mode de réalisation ;
• la figure 6 est une vue en coupe selon la ligne VI-VI de la figure 5;
• la figure 7 illustre un document de sécurité selon un quatrième mode de réalisation de l'invention ;
• la figure 8 est une vue en coupe selon la ligne VIII-VIII de la figure 7;
• les figures 9 et 10 illustrent des étapes du procédé d'impression du motif du document de la figure 1.

Other characteristics and advantages of the invention will become apparent in the light of the description which follows, made with reference to the appended drawings in which:

• the figure 1 illustrates a security document according to a first embodiment of the invention comprising a pattern produced by means of a method according to the invention;
• the figure 2 is a sectional view along line 2-2 of the figure 1 ;
• the figure 3 illustrates a security document according to a second embodiment of the invention;
• the figure 4 is a sectional view along line 4-4 of the figure 3 ;
• the figure 5 illustrates a security document according to a third embodiment;
• the figure 6 is a sectional view along the line VI-VI of the figure 5 ;
• the figure 7 illustrates a security document according to a fourth embodiment of the invention;
• the figure 8 is a sectional view along line VIII-VIII of the figure 7 ;
• the Figures 9 and 10 illustrate steps of the process of printing the motif of the document of the figure 1 .

There is shown in the Figures 1 and 2 a security document according to a first embodiment of the invention. The security document is designated by the general reference 10.

In this embodiment of the invention, the security document 10 is an identity document, such as an identity card. In non-illustrated variants of the invention, the security document 10 may be for example a document-value such as a bank note, a bank card or an identity document such as a passport, etc.

As illustrated on the Figures 1 and 2 The document 10 includes a support 12. In the example illustrated in the figures, the support 12 form a body 14 of the card 10 and defines a first 12A and second 12B opposite faces, one of the faces 12A carrying data. For example, the card 10 is an identity card in standardized format ID-2, that is to say of dimensions 105 x 74 mm or in ID-1 format, that is to say of dimensions 85.6 x 53.98 mm. Alternatively, in the case of the passport, the document may be a page of this passport format standardized ID-3, that is to say, dimensions 125 x 88 mm.

The identity document 10 comprises, for example, variable data related to the bearer of the document such as a portrait 16 representing the wearer, personal data such as the date of birth, the address, the surname and given names of the wearer, etc. . In addition, these variable data may also consist of an identification number of the document 10, here the number "123456789".

In order to allow an effective control of the authenticity of the document 10, the document also comprises at least one security element 22. Preferably, the document 10 comprises several security elements 22. For example, the document 10 comprises security elements 22 embedded in the support 12 such as a near-field communication circuit including an antenna and a microcircuit connected to the antenna (not shown), a safety wire, a hologram (not shown), etc.

According to the invention, one of the security elements 22 comprises a pattern 24 made on the support 12 with a security ink. In this example, the pattern 24 comprises for example a variable datum such as the photograph 16 of the wearer. However, in a variant, the pattern 24 may represent other data of the document 10.

For this purpose, the support 12 comprises a sensitive layer 26 to laser radiation. For example, the laser radiation comes from an Nd: YAG laser source (yttrium garnet laser and doped with neodymium). Such a source emits radiation in the near infrared spectrum, generally around the wavelength of 1 micron (accurately at 1064 nm).

A sensitive layer 26 made of a material substantially opaque to visible light will preferably be chosen. In the example described, the sensitive layer 26 is made with a white ink (for example, the Phoenix 940 ® ink sold by the company INX or the ink referenced 94911 sold by the company SIEGWERK). Preferably, the sensitive layer 26 is deposited in gravure printing. However, other printing techniques may be suitable, such as screen printing, flexography, etc.

In addition, the sensitive layer 26 preferably incorporates security tracers, such as fluorescent particles, photochromic particles and / or thermochromic particles, this to further increase the reproduction complexity and therefore the level of security.

Furthermore, the support 12 comprises a layer of security ink, called the security layer 28. Preferably, this security layer 28 is deposited in the form of a solid surface on the support 12, for example in a predefined area of the support 12. For the purposes of the present invention, the term "solid area" is intended to mean a layer having a substantially uniform overlap on the support 12. This security layer 28 may optionally comprise at least two distinct color zones.

In the example illustrated, the security layer 28 uniformly covers a limited area of the support 12. In a variant illustrated for example by the figure 4 , the security layer 28 may extend over the entire surface of the support 12.

According to the invention, the security layer 28 and the sensitive layer 26 are arranged on the support 12 so that the sensitive layer 26 is observable at least one predefined wavelength of observation through the insensitive layer 28. This observation is preferably also carried out under a predefined observation angle. Thus, for example, depending on the viewing angle of the sensitive layer 28, a shiny appearance appears.

Preferably, the predefined wavelength is a wavelength of the visible spectrum. As a variant, the security layer 28 may possibly allow only wavelengths outside the visible spectrum to pass, the observation of the sensitive layer 26 through the security layer 28 then being made possible in this case than by means of an external optical device.

The security layer 28 is deposited on the support 12 for example by screen printing, flexography, offset, pad printing, intaglio printing, typography and / or gravure printing. This list is of course not limiting.

Preferably, as illustrated on the Figures 1 and 2 , the security layer 28 is deposited directly on the sensitive layer 26. However, in a not shown embodiment, a transparent layer at the predefined wavelength can be inserted between the sensitive layer 26 and the security layer 28.

According to the invention, the pattern 24 is marked by means of a laser beam 30 in the sensitive layer 26 by ablation of the latter at a plurality of impact points of the beam 30 on the layer 26 to form a profile. predefined thickness 27 a sectional view is shown on the figure 2 . More particularly, the thickness profile 27 is formed in order to generate a light intensity modulation reproducing the pattern 24, this modulation being observable through the security layer 28 at the predefined wavelength. The ablation of the sensitive layer 26 is carried out for example by total or partial vaporization of this layer 26 at the point of impact.

The hue observed through the security layer 28 thus depends on the amount of vaporized material of the sensitive layer 26 and / or the density of the impact points. In the example described, the greater the amount of vaporized material, the darker the hue observed.

The pattern 24 is then formed by means of a laser beam by modulation of the thickness of the sensitive layer 26, this modulation producing a light intensity modulation observable through the security layer 28.

Preferably, the pattern 24 is decomposed into a matrix 31 of pixels 33, that is to say the pattern 24 is sampled, which makes it possible to choose the fineness of printing as a function of the number of sampling pixels of the pattern 24. Preferably, each pixel of the matrix is associated with a gray level of a predefined gray scale.

To vary the gray level from one pixel to another, the number of points of impact per pixel of the laser beam on the sensitive layer 26 is varied and / or the ablation depth of each of the pixel impact points. This sampling is illustrated schematically for example on the figure 9 .

In this first embodiment, the support 12 also comprises a carrier layer 32, forming a substrate of the support 32, distinct from the other two layers 26 and 28. For example, the substrate 32 is made of a plastic material chosen from polycarbonate, polypropylene, polyester and PVC, or a mixture of these products.

Substrate 32 may further comprise, for example, several layers laminated together in which security elements 22 are incorporated.

As a variant, the carrier layer 32 can be made of paper (especially for banknotes) based on natural and / or synthetic fibers or in any other material suitable for forming a document substrate.

In this example described, the substrate 32 is substantially rigid. However, and particularly in the case of the passport, the substrate 32 may be relatively flexible to facilitate its insertion into a booklet. In another embodiment of the invention, the sensitive layer 26 can also form the carrier layer of the support 12.

Preferably, the security ink forming the layer 28 is a liquid crystal ink, for example of semi-transparent nematic or cholesteric type. Such a security ink has the advantage of changing color depending on the angle of observation and to change color by observation by means of a polarizing filter. By way of example, mention may be made of liquid crystal ink of the OASIS® brand marketed by SICPA or the Securalic LC® brand marketed by MERCK.

Preferably, in the first embodiment, the security layer 28 and the carrier layer 32 are insensitive to laser radiation.

For the purposes of the present invention, the term "laser-insensitive" means a layer through which a laser beam passes substantially without damage, as opposed to "sensitive to laser radiation", which means that the crossing of the layer causes a marking the layer as ablation, carbonization, etc.

Since the security layer 28 is insensitive to the radiation of the laser beam, the marking of the sensitive layer 26 is performed through the security layer 28 to form a hollow surface profile on the face 26A of the layer 26 located opposite of the security layer 28. This has the advantage of producing a well-marked modulation of light intensity.

In the embodiment illustrated on the Figures 5 and 6 the security layer 28 is also sensitive to laser radiation and the carrier layer 32, on the other hand, is insensitive. In this case, the laser marking is then carried out through the carrier layer 32.

However, it is furthermore preferable that the sensitive layer 26 is at least translucent at the predefined wavelength of observation so that the variable depth profile of the sensitive layer 26 is observable by translucency through this layer. 26 and the security layer 28.

We have shown on the figure 3 a security document according to a second embodiment of the invention. In this second mode, the sensitive layer 26 has optical properties that differ in a vertical direction of the support 12.

For example, the sensitive layer 26 comprises at least two sub-layers 40A, 40B superimposed on each other and made of materials having distinct optical properties. Thus, depending on the depth of ablation of the sensitive layer 26 by the laser beam, different optical effects appear.

For example, the first sublayer 40A is formed by a first ink layer producing a first variable optical effect and the second sublayer 40B is formed by a second ink layer producing a second variable optical effect.

According to the ablation depth of the layer 26, the first or second optical effect appears. This is for example illustrated in this figure by the pattern 42 in the form of sun. The sun 42 thus comprises a core 44 and spokes 46, the core 44 having concentric rings having a second optical effect bonded to the second sublayer 40B and the spokes 46 have a first optical effect related to the first sublayer 40A . In this example, the core 44 has a tonal gradient corresponding to a variable depth profile of the sublayer 40B.

For example, the first upper sublayer 40A is formed by depositing a layer of a first ink sensitive to iridescent laser radiation or to a variable optical effect, or else to a metallic effect (effect silver, gold or copper). The presence of this upper sub-layer makes it possible to accentuate the intensity modulation obtained. This upper sublayer is deposited by any desired printing technique, chosen for example from screen printing, pad printing, flexography, offset, intaglio, letterpress and / or gravure printing. The lower sublayer 40B is formed by a substantially opaque white ink layer.

There is shown in the Figures 7 and 8 a security document according to a third embodiment. In this third mode, the support 12 incorporates a security element 22 embedded in the support 12 and which is revealed by ablation of the sensitive layer 26 to the right of this security element 22.

For example, the security element 22 embedded in the support comprises an impression 48 on a face 32A of the carrier layer 32 facing the sensitive layer 26.

The printed element 48 comprises, for example, a discovery portion visible in reflected light and possibly a portion hidden by the non-vaporized sensitive layer 26, possibly visible in transmitted light (if the sensitive layer 26 is substantially translucent at the predefined wavelength) . Thus, it is possible to form transvision optical effects in transmission and / or in reflection. The hidden portion 50 and the uncovered portion 52 of the printed element 48 may for example complement each other in transmitted light to reveal information, etc. In this case, to allow this observation in transmitted light, the carrier layer 32 is preferably translucent.

The main aspects of an embodiment according to the invention will now be described with reference to Figures 9 and 10 for producing a security document according to the first embodiment described with reference to Figures 1 and 2 .

In a first step in this example, a location of a substrate in the format of the desired document is predefined in a larger support, for example in a sheet of a plastics material essentially based on a polyolefin. Then, in a second step, we depositing the sensitive layer 26 in the form of an opaque white ink layer. This sensitive layer 26 is preferably deposited by gravure printing.

During a third step, after drying of the opaque white ink layer 26, the security ink layer 28 is deposited, preferably on a surface of the support in the form of a solid surface, this surface delimiting a predefined zone. to customize.

During a fourth step, the substrate is cut for example according to the predefined location. At the end of this step, the substrate is ready for the customization step.

To personalize, the desired pattern 24, for example photograph 16, is sampled to form a matrix of pixels ( figure 9 ). At each point of the matrix, a gray level is associated, this level of gray being itself associated with a depth of ablation of the layer 26 or density of points.

Then, by means of the laser beam, the predefined area of the support is scanned to mark the sensitive layer 26 by ablation ( figure 10 ). Preferably, the laser beam 30 is directed on the area and passes through the security layer 28 by the transparency of this layer 28 to the laser radiation to reach and mark the sensitive layer 26.

Preferably, the power, number, and duration of pulses of the beam-emitting laser source 30 are adjusted to form a predefined thickness profile, each desired gray level corresponding to a depth of ablation or dot density. For example, the number of points of impact per pixel of the laser beam on the sensitive layer 26 is varied and / or the ablation depth of each of the points of impact of the pixel is varied.

In the example described, the sensitive layer 26 is marked only from a face 26A. However, it is possible to alternatively form a predefined thickness profile by marking the layer 26 from the two faces 26A and 26B, but in this case it is desirable to choose a substantially translucent sensitive layer 26 with a small thickness. Moreover, in this case and preferably, the support 32 is chosen not sensitive to laser radiation.

Once the marking is completed, the pattern 24 is observable through the security layer 28. Thus, the resulting variable thickness profile produces a modulation of the observable light intensity in reflection on the sensitive layer 26, or even in transmission, when the sensitive layer 26 is translucent.

Thanks to the invention, it is possible to form a pattern 24 with a relatively great fineness of detail, such as a photograph, providing an additional level of security of the document against forgery. Indeed, to falsify such a document, it is necessary to remove the layer of security ink which is difficult or impossible to operate without creating irreversible damage to the document.

It is understood that the embodiments which have just been described are not limiting and they can receive any desirable modification without departing from the scope of the invention.

Claims (14)

Process for producing a pattern (24) with a security ink on a support (12), characterized in that the support (12) comprising at least one sensitive layer (26) with a laser radiation and a layer (28) ) of security ink arranged above the sensitive layer so that the sensitive layer (26) is observable through the security layer at least at a predefined wavelength, the method comprises a marking step of the sensitive layer (26) with a laser beam (30) by ablation of this layer (26) at a plurality of impact points of the beam (30) on the layer (26) to form a predefined thickness profile of this layer (26) so that this thickness profile generates a light intensity modulation reproducing the pattern, observable through the security layer at the predefined wavelength. Method according to the preceding claim, wherein, the security layer (28) being insensitive to radiation, the laser beam (30) is directed on the support (12), once the security layer (28) has been deposited, and it is realized marking the sensitive layer (26) through the security layer (28). A method as claimed in any one of the preceding claims, wherein the laser beam (30) is emitted by a pulse source of adjustable intensity and duration to form the pattern (24) according to the thickness profile. predefined, the intensity, the number and / or the duration of the pulses of the source of the laser beam are changed. A method according to any one of the preceding claims, wherein, the pattern (24) is decomposed into a pixel matrix, each pixel being associated with a gray level of a predefined gray scale, to vary the gray level from one pixel to another, the number of points of impact per pixel of the laser beam on the sensitive layer (26) is varied and / or the ablation depth of each of the impact points of the pixel. A method according to any one of the preceding claims, wherein the security layer (28) is deposited on the support (12) under as a solid, for example by screen printing, flexography, offset, intaglio printing, pad printing, typography and / or gravure printing. A method according to any one of the preceding claims, wherein the sensitive layer (26) is formed by an ink layer which incorporates security tracers, such as fluorescent particles, reaction type particles at a length of predefined wave and / or thermochromic particles. A method according to any one of the preceding claims, wherein the sensitive layer (26) has optical properties which differ in a vertical direction of the support (12). Method according to the preceding claim, wherein the sensitive layer (26) comprises at least two sublayers (26A, 26B) superimposed on one another and made of materials having distinct optical properties. A method as claimed in any one of the preceding claims, wherein the security layer (28) is made of a material comprising a liquid crystal type variable optical effect ink. A method according to any one of the preceding claims, wherein the support (12) comprises at least one other layer, said carrier layer, forming a substrate of the support (12) and being flexible or rigid. Method according to the preceding claim, wherein the support (12) incorporating at least one security element (22) at least partially reveals this element by ablation of the sensitive layer (26) to the right of the element (22). . Security document (10) comprising a support (12) and a security element (22) carried by the support (12), characterized in that the support (12) comprises at least one sensitive layer (26) for laser radiation and at least one layer (28) of security ink, said security layer, the security element (22) comprising a pattern (24) made according to a method according to any one of the preceding claims. Document (10) according to the preceding claim, the pattern (24) being reproduced in gray level. The document (10) of claim 12 or claim 13 being selected from a bank note, a passport and a microcircuit card.

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