EP2539154B9 - Method for the colored marking of value or security documents - Google Patents

Description

The invention relates to a method for multicolor marking value or security documents, which are designed for a permanent colored marking a value or security document by means of laser light.

Security documents are those documents and objects that are protected by at least one security feature or security element against corruption and / or unauthorized copying. Security documents that embody a value are also referred to as value documents. Security documents include, for example, identity documents, driver's licenses or motor vehicle papers and documents of value, with value documents, for example banknotes, postage stamps or checks.

At least in some of the security documents or value documents, it is advantageous to be able to mark these permanently, preferably individually. Different methods are known from the prior art, with which value and / or security documents can be marked individually. Historically, most value and security documents have been paper-based and, in particular, have been customized by means of printing techniques, modern security documents and value documents are often at least partially made from plastic materials. Modern identity cards and driver's licenses are joined together, for example, as lamination bodies comprising a plurality of plastic layers and optionally one or more paper layers.

For the permanent individual marking of plastics so-called laser marking methods have been developed in the prior art. For this purpose, individual plastic layers, which are to be marked later with a laser, special pigment substances added. These do not affect transparency in the visible optical range or are not or barely perceptible to a user. If such a layer is irradiated with laser light of sufficient intensity, an increased absorption of the laser light occurs at the pigments. This makes it possible to use energy in the otherwise couple transparent plastic, which then leads to the localized inking over the amount of energy deposited here, for example via a heating and a partial carbonization of the plastic material. Depending on the amount of energy applied, a degree of blackening of the plastic can be set in a targeted manner. From individual local pixels, patterns, in particular grayscale images, lettering and other characters, can be permanently marked in the value or security document.

For a long time, however, the goal has been pursued to highlight the value or security document in color, preferably multi-colored. Ideally, a full-color marking should be possible, which can represent colors from a gamut, which is spanned by preferably three primary colors, such as red, blue and green.

From the DE 100 11 486 A1 a card-shaped data carrier is known, consisting of at least one layer in which visually readable information in the form of a change in optical properties due to an irreversibly caused by a laser beam material change are introduced, the absorption capacity of this layer for at least one wavelength due to the laser radiation at least partially is reduced. In this process, original colored or opaque layers are "bleached" in terms of absorption.

From the DE 30 48 733 A1 For example, an identification card and a method for producing such an identification card with information applied are known in the form of patterns, for example letters, numbers and / or images. The identification card has layer areas of different colors arranged one above the other on at least one surface, which are at least partially interrupted by visually recognizable personalization data. It is envisaged that the information is displayed by the action of a controlled laser beam on one or more layers of paint applied to one another on a plastic carrier. As a result of the laser irradiation, the color can be changed locally.

From the DE 696 05 788 T2 For example, there is known a method of producing an article having a colored mark by irradiating the surface of the article with laser light in the form of the mark, the article being made of a plastic composition at least in that region where the mark is applied contains three color-forming components that lose their color-forming ability under the influence of laser light selected and present in a concentration such that at each wavelength between 400 and 700 nm at least a portion of the amount of incident light is absorbed for the character one or more colors are selected, the wavelength of the laser light in the sequence is set to a value depending on the selected color, and then the surface of the object is irradiated with the laser light.

From the WO 01/28778 A2 is a method for applying colored characters on a data carrier, preferably made of plastic, known by means of a laser system, wherein in at least one surface layer and / or near-surface layer of the data carrier introduced latent pigments, which takes place by energetic excitation, a change in the absorption behavior of the for the character provided areas of the disk by laser irradiation, which is in the IR and / or visible range, energetically excited such that the same pigments color change takes place and that after the color change of the laser-irradiated latent pigments, not excited by laser irradiation latent pigments be energetically excited in such a way by irradiation with light waves in the UV wavelength range, that in the so-irradiated pigments colorlessness is brought about.

From the DE 100 53 264 A1 a method for writing data, in particular personalization data, on and / or in a data carrier by means of electromagnetic radiation is known, wherein the method any data carrier is provided on and / or in which at least one colorant is provided at least locally, and this colorant is irradiated by means of the electromagnetic radiation of at least one wavelength range, so that there is a change in the color of the colorant by bleaching in the region of the irradiation, wherein the color change can be determined by machine and / or by a human eye. This results in an increased security against counterfeiting and manipulation for the data carrier.

From the DE 199 55 383 A1 a method for applying colored information to an object is known, wherein the article has at least in a near-surface layer at least two different coloring particles that change the color of this layer under the influence of laser radiation, wherein the laser radiation is used with at least two different wavelengths, around the color of this layer to change, the application of laser radiation to the object in the vector and / or raster method via a two-coordinate beam deflection device and a focusing device for focusing the laser radiation is applied to the layer of the object. At least one beam guiding means is provided for guiding a first laser beam having the wavelength λ ₁ and at least one further laser beam having a wavelength λ ₂ different from the wavelength of the first laser beam via the two-coordinate beam deflecting means and the focusing means to the layer of the object , For the Zweikoordinatenstrahlablenkeinrichtung an arrangement of two mutually perpendicular axes rotatably mounted deflecting mirror is proposed. A focusing is done by a fixed plan field optics. Since the light does not pass through the planar field optics on the optical axis, chromatic aberration effects occur in the focusing device. In particular, if differently colored laser light is used for marking, this requires a complex compensation.

From the DE 10 2006 014 367 A1 For example, a data carrier and a method for its production are known. The data carrier comprises a visually or machine recognizable marking in the form of a pattern of letters, numbers or pictures. In the method of manufacture, a data carrier with a data carrier substrate is provided and a marking layer is applied to the data carrier substrate. The marking is introduced into the marking layer by means of short laser pulses.

From the US 2010/0040836 A1 For example, a method of introducing high contrast markers into the interior of transparent polymeric material using femtosecond, picosecond, or nanosecond fiber laser pulses is known. Further, an apparatus for forming such marks is described.

From the JP 2007-261114 A For example, a method is known for writing invisible information into an ID card comprising an optical waveguide by means of laser pulses having a pulse duration of less than one picosecond. The optical waveguide is modified here.

In a group of the prior art methods which allow a colored marking, different colorants are incorporated in the value or security document, which together have an additive or subtractive color mixture in a cause a color impression to human observers. In the unmarked state, a uniform color impression is produced over the entire surface. By locally targeted change of individual colorants, the color mixture changes, so that locally creates a desired color impression. The practical problem of the prior art methods is to achieve high-contrast intense hues.

From the US 2005/0001419 A1 For example, a color laser engraving system is known that engraves a surface layer and / or multiple sublayers. The sublayers have different colors and arrangements of ink. A laser creates openings in the surface layer to expose the colored ink in the lower layers and to produce a colored image and / or a colored text.

The invention has for its object to provide an improved method for permanent color marking of value or security documents that eliminate or reduce the disadvantages of the prior art.

The object is achieved by a method with the features of claim 1. Advantageous embodiments of the invention will become apparent from the dependent claims.

Basic idea of the invention

The basic idea of the invention is to carry out the marking of the value and / or security document with laser light, which is generated by a short-pulse laser source. This means that the individual laser light pulses used for marking have a pulse duration of less than 100 picoseconds, preferably less than 10 picoseconds. This makes it possible to make the interaction with the material of the document body or the colorants contained therein so that a change of the material and / or the colorant wholly or largely takes place without a thermal interaction. Since the coupling of the energy occurs in a short time window and the process caused by the interaction proceeds so quickly that no or only a very small dissipation of the energy takes place in the form of heat away from the interaction site, the change is well localized. Adjacent to the interaction site, there is no change in the material of the security or security document or the colorants contained therein. This possibility of selectively performing local marking for the purpose of local color change at closely adjacent locations, i. With high areal resolution, without affecting the colourfulness of the neighboring locations, it is possible to create high contrast and / or intense color impressions for a pattern marked in a document body.

definitions

A security element is a structural unit comprising at least one security feature. A security element can be an independent structural unit which can be connected, for example glued, to a security document, which can also be a value document. It can also be an integral part of a security document. An example of the former is a so-called holopatch (a hologram-containing patch for example, a hologram film section) or a visa stickable to a security document. An example of the latter is a diffractive surface relief embossed in an identity document.

A security feature is a structure that is only producible or reproducible with (compared to simple copying) increased effort or not at all unauthorized, or makes forgery and / or falsification visually and / or mechanically recognizable.

By way of example, security documents may include identity cards, passports, ID cards, access control cards, visas, tax stamps, tickets, driver's licenses, motor vehicle papers and documents of value including, in particular, banknotes, checks, postage stamps and credit cards, and any smart cards and adhesive labels (for example for product security). Security documents, which also embody a value, are also referred to as value documents. A sharp distinction between these two terms is often not possible. A credit card, for example, represents a security document protected by security features and security elements against counterfeiting and falsification, which does not directly represent a value beyond the pure material value of the card, but makes it possible to dispose of large assets.

A pulsed laser is a laser that, in contrast to a continuous wave or CW laser that continuously emits laser light, emits laser light in temporally limited portions called pulses. As a short pulse laser is understood here a laser that generates light pulses whose pulse duration is less than 100 picoseconds. The literature also speaks in part of ultrashort laser pulses, with no uniform definition for this. Ultrashort pulses are pulses whose pulse duration is less than 10 picoseconds.

An optical fiber is a fiber made of a transparent material, at the interface of which total reflection can cause conduction of light in the interior of the fiber.

A fiber laser is a laser whose active medium in which light-induced emission of electromagnetic radiation occurs is an optical fiber.

A pattern typically consists of a multiplicity of juxtaposed pattern units or pixel dots. The pattern units or pixels of a pattern are associated with one another and arranged laterally in a defined manner, typically in one or two spatial dimensions, and overall give a representation, for example a picture, a symbol, a logo, a lettering (letters, numbers, alphanumeric characters) or a code (eg a barcode). An individualization pattern is a pattern that is used for individualization. In a colored pattern, a pixel may include a plurality of sub-pixels, each of which is monochrome and determine a coloration of the pixel as a whole via a color addition or color subtraction.

Individualizing is a pattern when it is unique to a person or an object or a group of persons or objects from a largest set of persons or objects. For example, a code individualizing a group of persons within the total population of a country is the city of residence. An individualizing for a person code, for example, the number of the identity card or passport photo. A code individualizing a group of bills within the total amount of bills is the value. Individualizing for a banknote is the serial number. Non-individualizing is a pattern that is identical for all elements of an entity. For bills this is for example a coat of arms, which is printed on all banknotes.

A basic pattern is an array of monochromatic areas or sub-areas thereof, which, with appropriate modification of the colors of the areas or sub-areas thereabove, permits marking of a multicolor pattern.

Colored is an entity that causes a color impression when viewed by a human. Multicolor is an entity that produces at least two distinguishable color impressions. Monochrome, on the other hand, is an entity when it produces a single color impression.

Colorants are all entities responsible for causing a color impression via emission or absorption of light in the visible wavelength range.

The light of a Planckian radiator, which produces a continuous spectrum in the visible wavelength range, is regarded here as white light. Natural sunlight is an example of white light.

Preferred embodiments

• Bereitstellen eines Dokumentkörpers, der Bereiche unterschiedlicher Farbigkeit umfasst, wobei die einzelnen Bereiche jeweils einfarbig sind;
• Bereitstellen einer Markierungsvorrichtung, welche mindestens eine Laserlichtquelle zum Erzeugen von Laserlicht und
• eine Lichtführungsvorrichtung umfasst, die mit der Laserlichtquelle gekoppelt ist, so dass ein Fokus des Laserlichts der Laserlichtquelle auf oder in dem Dokumentkörper des Wert- oder Sicherheitsdokuments gesteuert positionierbar ist;
• iteratives gezieltes Positionieren des Fokus auf oder in dem Dokumentkörper und Einstrahlen des Laserlichts, um gezielt lokal die Farbe eines oder mehrere der Bereiche zu verändern, so dass der Dokumentkörper anschließend einen mehrfarbigen Farbeindruck bei einer Bestrahlung mit weißem Licht für einen menschlichen Betrachter hervorruft,
• wobei das zu Markierung verwendete Laserlicht mittels kurzer oder ultrakurzer Laserpulse eingestrahlt wird, die eine Plusdauer von weniger als 100 ps oder weniger als 10 ps aufweisen.

In particular, there is provided a method of multicolor marking value or security documents comprising the steps of:

• Providing a document body comprising areas of different colors, each area being monochromatic;
• Providing a marking device, which at least one laser light source for generating laser light and
• a light guide device coupled to the laser light source such that a focus of the laser light of the laser light source is positionally controllable on or within the document body of the value or security document;
• iteratively selectively positioning the focus on or in the document body and irradiating the laser light to selectively locally change the color of one or more of the areas such that the document body subsequently produces a multicolor color impression upon irradiation of white light to a human observer;
• wherein the laser light used for marking is irradiated by means of short or ultrashort laser pulses having a plus duration of less than 100 ps or less than 10 ps.

• mindestens eine Laserlichtquelle und
• eine Lichtführungsvorrichtung, die mit der Laserlichtquelle gekoppelt ist, so dass Laserlicht der Laserlichtquelle auf einem Wert- oder Sicherheitsdokument gesteuert positionierbar ist,
• wobei die Laserlichtquelle eine Kurzpulslaserquelle oder Ultrakurzpulslaserquelle ist, die Laserpulse mit einer Pulsdauer von weniger als 100 ps oder weniger als 10 ps erzeugt. Neben der rein optischen Fokussierung ist die bei Verfahren nach dem Stand der Technik eine erreichbare Auflösung hinsichtlich der hergestellten Markierung in der Regel dadurch begrenzt, dass die Wechselwirkung zwischen dem Laserlicht und dem Wert- oder Sicherheitsdokument auf thermischen Effekten beruht. Dieses lässt sich durch die Verwendung von Laserlicht von Kurzpluslasern vermeiden.

A marking device for multi-colored marking of value or security documents thus comprises:

• at least one laser light source and
• a light guide device coupled to the laser light source so that laser light of the laser light source can be positioned controlled on a value or security document,
• wherein the laser light source is a short pulse laser source or ultrashort pulse laser source that generates laser pulses having a pulse duration of less than 100 ps or less than 10 ps. In addition to purely optical focusing, the achievable resolution in the method according to the prior art with respect to the marking produced is usually limited by the fact that the interaction between the laser light and the value or Security document based on thermal effects. This can be avoided by using laser light from short-circuit lasers.

Iterative targeted positioning of the focus on or in the document body and irradiation of the laser light comprises repeatedly irradiating light several times successively at the same focus position relative to the document body as well as repeatedly irradiating light, the position of the focus being relative to the material to the surface of the document body and / or perpendicular to the surface of the document body is varied. A variation of the focus position perpendicular to the document surface alters a selection of a plane parallel to the surface of the document body in which the focus is positioned.

One advantage of using short-pulse laser light is that intensity densities can be achieved with this laser light, so that non-linear optical interactions can also be triggered. This makes it possible, for example, to produce markings with a higher resolution, since thermal interaction processes, which are always associated with a dissipation of the heat into surrounding areas and cause a resolution limitation over it, can be avoided.

An embodiment of the invention thus provides that the local change in the color of a region is made via a non-linear interaction with the irradiated laser light.

In order to create a multicolored color impression, for example to mark a full-color colored passport image in a security document, in one embodiment at least three regions of different colors are provided with each other in a basic pattern of nested sub-regions or arranged in the basic pattern when provided. The at least three areas can thus be divided into many, usually regularly arranged sub-areas. As belonging to a region, the subregions having the same color are considered. The subregions may be two-dimensional area or three-dimensional volumes. For example, such a basic pattern can be printed by printing using different inks on a substrate layer. Likewise, it is also possible in a further embodiment, the sub-areas on different substrate layers so imprint that the sub-areas of the various substrate layers from which the document body by stacking the substrate layers and subsequent assembly, for example in a lamination process, each other, with respect to a viewing direction parallel to the lamination direction, not or substantially not overlap.

In order to produce a desired color impression, an exact positioning of the laser light on or in the document body is necessary to selectively correct the individual subregions with regard to their color. As a result, a falsification or marking with not provided hardware is made much more difficult.

Particularly preferably, the document body comprises at least three areas of different color, each having a base color of a color system, which spans a multicolor gamut. Thus, with a suitable choice of the primary colors in the document information can be encoded, which can use almost the entire human-perceivable color space.

In a preferred embodiment, the subregions that are not or at least not completely overlapping with respect to a normal of a surface of the document body are arranged such that they represent a Bayerpattern prior to marking. This makes it possible to mark a pattern composed of regularly arranged pixels which, with regard to the usable colors, can use almost the entire perceptible color space. With regard to their assignment to the at least three regions and the arrangement relative to one another, the subregions are optimally adapted to the sensitivity of the human eye, so that over a maximum of four markings of subregions, one image pixel each can be generated which produces any color impression from the gamut spanned by the primary colors causes.

In order to be able to store the color information in a plane of the value or security document via the markings, in one embodiment the Bayerpattern is or is printed on a substrate layer surface. This is or is preferably formed as an inner substrate layer surface, so that a manipulation is difficult.

According to a further embodiment, the colored areas in the form of layers which overlap one another in a planar manner are introduced into the document body or are thus introduced during the provision.

In one embodiment, the markings are made by removing material. Here, cavities are introduced into the document body from the surface. A depth of the cavities in the document body determines which color impression is produced on the document body at the location of the cavity. By using short pulse laser light or ultrashort pulsed laser light, the cavities can be formed so close to each other that the remaining material does not cause color degradation of the entire marked pattern as in the prior art. Because the edge surfaces of the cavities can be formed smoothly and perpendicularly to the surface of the document body (with perpendicular irradiation of the laser light), web widths of the document body remaining between adjacent cavities can be minimized. As a result, intense color patterns can be generated which are not impaired by the color of the web areas.

In order to achieve a high localization of the individual markings, the focusing of the laser light is performed in one embodiment such that a diameter of an interaction region of the non-linear interaction of a laser pulse in an image plane perceived by the human user in the order of magnitude of less than 100μm, more preferably less than 20μm , most preferably on the order of 5 to 15 microns.

The local change in the color of a region can be made by changing the colorant causing the colorant by means of the non-linear interaction.

Particularly advantageous short laser pulses with pulse durations in the range less than 100 picoseconds, preferably in the range of 100 femtoseconds to 10 picoseconds, with a fiber laser can be generated. Compared with other solid state lasers fiber lasers have the advantage that they can be constructed very compact and have a high electro-optical efficiency. In addition, fiber lasers are much more modest in terms of adjustment and handling than most known solid state lasers.

An advantage of using short laser pulses with pulse durations of less than 100 picoseconds, preferably less than 10 picoseconds, is that a very precise spatial confinement of the interaction zone between the laser light and the material of the security or security document can be achieved non-linear optical interaction effects can be used to form the label. A preferred embodiment of the method therefore provides that the marking is triggered via a non-linear optical effect in the value or security document.

In an embodiment, it is provided that the light-guiding device comprises a relative to the value and / or security document movably mounted optical fiber, which is coupled to at least one drive means so that the laser light via a movement of an exit surface of the optical fiber in a positioning plane relative to the value - And / or security document can be positioned laterally on the value or security document. The laser light of the laser light source is thus guided by means of an optical fiber, and a positioning of the laser light on the value or security document to be marked takes place by moving the exit surface of the optical fiber relative to the value or security document. Compared to the prior art, there is the advantage that the laser light used for marking with a suitable orientation of the positioning plane relative to a surface of the security or valuable document, preferably parallel thereto, respectively at the same angle, preferably perpendicular, to the value and / or security document incident and beyond a path length of the traveled light path is the same regardless of the illuminated lateral position on the security and / or security document. This makes it possible to focus the laser light used stronger and yet to use an identical focus extension at the marking at all lateral positions of the value or security document. Problems that are known due to a slightly different direction of irradiation in the guide devices of the prior art, can thus be avoided.

To achieve a high resolution in the marking, a good focus is advantageous. For this purpose, a focusing optics can be used. Preferably, a focusing optics, if used, with the respective exit surface of the Pairing optical fiber. This means that the focusing optics is moved by means of the drive device together with the exit surface of the optical fiber. The advantage is that the light path through the focusing optics is the same in each case, regardless of the position on or in the value or security document that is being marked.

Different implementations are possible in order to specifically set a focus position in the value or security document.

In one embodiment, the focusing takes place by means of the Kerr effect. In this case, the focal length of the material of the focusing lens changes due to the non-linear interaction of the electromagnetic radiation with the material of the lens. The focal length of the lens is inversely proportional to the intensity of the electromagnetic radiation in a Gaussian radiation profile.

In an embodiment in which the light guide is performed by means of an optical fiber, it is provided that in addition to the movement in the positioning plane, which is usually oriented parallel to a surface of a plane security document, a movement of the exit surface of the optical fiber is possible to vary a light path between the exit surface and a surface of the document. This can be used to vary a focus position within the value or security document. Such a change in direction can be achieved, for example, in one embodiment in that the exit surface, from which the laser light is rectilinearly guided on the document surface, in addition to the movement in the positioning plane, which is parallel to the surface of the value or security document, perpendicular to the Positioning level or the surface of the value or security document is movable.

In other embodiments, for example, where the exit surface is moved in the positioning plane together with an imaging and / or focusing optic to position the exiting laser light laterally on the surface of the asset or security document, a change in the light path may occur, for example, in some embodiments be achieved that the exit surface of the optical waveguide in addition to the elements of the imaging and / or focusing optics, such as a deflection mirror, in the positioning plane is relatively movable. Thus, on the one hand, a positioning laterally on the document via a movement of the exit surface together with the imaging and / or focusing optics is possible and additionally by a relative movement of the exit surface relative to the imaging and / or focusing optics in the positioning plane a change in the focus position perpendicular to Surface of the value or security document possible.

In a further embodiment, the focusing optics consists of a piezoelectric material. By applying tension, the material can be deformed and thus the focal length of the material can be adjusted.

In a preferred embodiment, the laser light source is integrated in the optical fiber. As a result, any coupling losses are reduced in the coupling into the fiber. Thus, a compact and simple construction is possible. Compared with solid-state lasers, for example Ti: sapphire lasers, fiber laser systems do not require expensive cooling and achieve a high electro-optical efficiency. Furthermore, laser light of different wavelengths can be generated by parametric tuning with the same hardware. This is effective with fiber lasers.

In order to enable a faster marking of the value or security document, it is provided in a further development of the invention that the light guiding device comprises at least one further movable, preferably even more, further movably mounted optical fibers. This makes it possible, at the same time at several points or at the same time with different wavelengths of light to attach a mark on the security or security document or bring in the value or security document. If different wavelengths of light are used, then each optical fiber can be provided with a focusing optics adapted to the corresponding wavelength of light. It should be noted that with pulse durations of more than 10 ps it is still possible to speak of a defined wavelength. At pulse lengths shorter than 10 ps, the spread due to the Heisenberg uncertainty principle is significant. For example, the blur at a pulse of 10 ps is about 0.41 meV, which corresponds to about 0.12 nm at a wavelength of 620 nm (2 eV). At pulse durations of 10 fs, the blur is about 0.41 eV, which means at a wavelength of 620 nm (2 eV) that the bandwidth is at least 125 nm.

In a preferred embodiment of the invention, the exit surface of the at least one optical fiber is positionable relative to the at least one further optical fiber or optionally relative to the plurality of exit surfaces of the plurality of optical fibers in the positioning plane. Particularly preferably, the plurality of optical fibers or their exit surfaces are individually driven in the positioning plane and can be positioned relative to one another. It goes without saying for the person skilled in the art that there are mechanical residual actions since the optical fibers can not penetrate one another and thus can not be arranged at one and the same position at the same time.

If a plurality of optical fibers are present, then the focus position within the value or security document along a normal to the surface of the security document can be set individually for them in one embodiment. This can be targeted markings in different levels or layers, from which the value or security document is joined, are introduced. Preferably, this is controlled possible.

The features of the method according to the invention have the same advantages as the corresponding features of the marking device according to the invention.

Fig. 1

eine schematische Darstellung einer Markierungsvorrichtung für Wert- oder Sicherheitsdokumente;

Fig. 2

eine schematische Darstellung eines Dokumentkörpers zum Einbringen einer farbigen Markierung;

Fig. 3

eine schematische Darstellung eines markierten Dokumentkörpers;

Fig. 4

eine schematische Darstellung eines Strahlprofils im Fokus;

Fig. 5

eine schematische Darstellung eines Grundmusters; und

Fig. 6

eine weitere Ausführungsform einer Markierungsvorrichtung.

The invention will be explained in more detail with reference to preferred embodiments with reference to a drawing. Hereby show:

Fig. 1

a schematic representation of a marking device for value or security documents;

Fig. 2

a schematic representation of a document body for introducing a colored marking;

Fig. 3

a schematic representation of a marked document body;

Fig. 4

a schematic representation of a beam profile in focus;

Fig. 5

a schematic representation of a basic pattern; and

Fig. 6

another embodiment of a marking device.

In Fig. 1 schematically a marking device 1 for permanently marking a value or security document 2 is shown. The value document 2 is arranged on a holder 3. This can be supplied to the value or security document 2 by means of a transport device 4 and / or removed from it. In some embodiments, it is possible that the transport device 4 forms the holder 3. The person skilled in various devices for transporting value or security documents are known. In general, the marking of the value or security document 2 is carried out after this is completed except for the mark still to be attached. However, it is also possible to make the marking before the value or security document 2 is completely finished, for example, before it is separated from a sheet or a strip.

The marking device 1 comprises a laser light source 5. The laser light source 5 is designed to generate laser light 6. The laser light source 5 is a pulsed light source. For example, it may be a solid-state laser, eg a Ti: sapphire laser. In order to mark the value or security document 2, the laser light 6 has to be positioned in a targeted manner on the value or security document 2, ie on its surface 7 or in the interior of the value or security document 2. For this purpose, a light guide device 8 is provided. In the embodiment described here, the light-guiding device 8 comprises an optical fiber 9, into which the laser light 6 is coupled. An exit surface 10 of the optical fiber 9 is moved in a positioning plane 11. The positioning plane 11 is formed parallel to the surface 7 of the value or security document 2 in a preferred embodiment. In order to be able to move or position the exit surface 10 in the positioning plane 11, the optical fiber 9 is coupled to a drive device 12. The drive device 12 comprises in the illustrated embodiment an X-axis actuator 13, a Y-axis actuator 14 and a Z-axis actuator 15. These are connected and aligned so that the X-axis actuator movement of the exit surface 10 of the optical fiber 9 parallel to a X-axis 16, the Y-axis actuator 14 parallel to a Y-axis 17 and the Z-axis actuator 15 parallel to a Z-axis 18 causes. It should be noted that a movement parallel to the Z-axis causes a change of the positioning plane 11. Via the drive device 12, it is thus possible, a position of a focal point 19 of the exit from the exit surface 10 laser light 6 'along a normal to the surface. 7 of the value or security document 2. By contrast, a movement of the exit surface 10 in the positioning plane 11 effects a lateral alignment and positioning of the laser light 6 'emerging from the exit surface 10 or the focal point 19 formed thereof. It should be noted that other embodiments may have and use differently configured light guiding devices.

In some embodiments, it is provided that an imaging and / or focusing optics 20 is coupled to the exit surface 10 of the optical fiber 9. This is moved with the exit surface 10 of the optical fiber. In some embodiments, the exit surface 10 of the optical fiber is configured so that the exiting laser light 6 'is focused and no or supplemental focusing optics are necessary.

About the introduced at the respective position in the value or security document amount of energy, which can be varied for example via a pulse intensity or a number of introduced at the same position light pulses, the color of the mark or its color impression caused regulated. Via the drive device 12 it is possible to make a marking vectorially (but broken down into individual pixels (marking points)) or in a grid.

A distance 27 of the positioning plane 11 from the surface 7 or the value or security document 2 need not be varied in some applications in the marking. Then, a positioning device 8 which comprises only one X-axis actuator 13 and one Y-axis actuator 14 is sufficient. It is understood by those skilled in the art that for the positioning of the exit surface 10 of the optical fiber 9 in the positioning plane 11, a set of actuators can be used, which cause no movements parallel to the coordinate axes, but in cooperation are able, the exit surface 10th in the positioning plane 11 laterally flat at different locations to position.

It goes without saying for the person skilled in the art that the light exit surface 10 in the positioning plane 11 need not be positionable in all embodiments so that all points on the surface of the document can be illuminated with the exiting laser light 6 '. The laser light only needs to be positionable at those positions on the asset or security document at which markings are to be made. Is only a limited range of value or Security document provided for a mark, as well as an adapted to this area positioning range 26, in which the exit surface 10 of the optical fiber 9 is positioned.

In Fig. 2 For example, an exemplary embodiment of a document body 40 of a value or security document 2 suitable for introducing a colored mark is shown. The document body 40 is formed as a lamination body. During production, a carrier foil 41, a black foil 42, a blue foil 43, a green foil 44, a red foil 45 and a clear, ie transparent cover foil 46 are stacked on top of one another. These are then subsequently joined together in a lamination process using heat and pressure to the monolithic document body 40. Preferably, the films 41-46 are all made of the same thermoplastic material, such as polycarbonate or polyvinyl chloride. Additional security elements may be inserted between the foils 41 to 46. In addition, individual or all foils may be printed.

The black film 42, the blue film 43, the green film 44, and the red film 45 each represent monochrome areas each having a different color from the others. Blue, red, green represent the basic colors of an RGB color system. The gamut of the RGB color system makes it possible to display full-color objects. In order to be able to represent black in a simple manner, a black foil is additionally provided.

For example, using a cyan yellow magenta (black) color system (CYM (K) color system) one would use a cyan film instead of the blue film 43, a yellow film instead of the green film 44 and a yellow film instead of the red film 45 use magenta foil.

The order of the slides can also be chosen differently. Preferably, the films 41-45 are opaque. As a result, a color space comparable to the normal printing systems is clamped, since only the uppermost color layer is always visible. As a result, standard systems can be used to optimize the color space. In a transparent embodiment of the films 41-45 a corresponding adjustment of the colors is necessary, since in this case all remaining color layers characterize the color impression. As a result, the generation but also the falsification or adjustment is much more difficult.

Based on Fig. 3 The introduction of a colored marking will now be explained by way of example. Schematically, a document body 40 is similar to that of FIG Fig. 2 shown. The same technical features are identified by the same reference numerals throughout the application. The document body 40 contains a barrier film 47 instead of the cover film 46 over the red film 45. This is, for example, opaque and white. Over the barrier film 47, a protective film 48 is arranged, which is laminated, for example, after the colored marking.

Before introducing a mark, the document body 40 appears white when viewed under natural daylight (white light). Cavities 51-54 are introduced into the different foils 47, 45, 44, 43 by means of short or ultrashort laser light pulses. A depth of the cavities 51-54 determines which color impression a surface 7 has locally at the location / position of the respective cavity 51-54. The cavities 51 and 54 in each case extend completely through the white barrier film and into the red film 45. Thus, a red color impression is imparted locally. In the cavity 52 and the red film 45 is completely penetrated. The cavity 52 ends in the green foil, so that locally a green color impression is mediated. The cavity 53 terminates in the blue film 43. All overlying films are completely pierced. It is generated locally a blue color impression.

The depth of the cavity can be selectively varied via a choice of the energy deposited via one or more short or ultrashort laser pulses, a choice of the depth of focus, an adaptation of the wavelength of the laser pulse or pulses to the color of the respective film 43-45, 47 to be removed ,

A cross-sectional shape of the cavities can be controlled by a choice of beam profile as well as a sidewall shape of the cavities. Factors influencing this are the depth of focus and the defocusing of the laser beam and optionally a Kerr effect present in the document material, which can lead to additional focusing or defocusing of the beam.

Due to the short pulse duration and the high light intensities achievable in this case, nonlinear interactions can be exploited, so that no thermal effects occur in the document body 40 which lead to a dissipation of energy in the document body and thus to less precisely defined cavity cross-sectional shapes. In particular, the possibility of producing cavities with side walls 55 oriented almost perpendicular to the surface 7 of the value or security document 2 or of the document body 40 allows cavities to be introduced into the document body 40 in a targeted manner at small distances 56, 57. Remaining webs 58 between the cavities 52-54 are thus viewed from the surface 7 of area small, so that a high density of points and thus resolution of the information shown on the marks is possible. In addition, the remaining lands affect a color intensity less than in the prior art. It is understood that the color addition or color subtraction of the local color impressions caused by the individual cavities 51-54 are responsible for a macroscopic areal color impression of a viewer.

The subsequently applied protective film 48 protects the cavities 51-54 during use of the document body 40 as a value or security document 2. Also introducing further cavities to falsify the value or security document 2 is at least made more difficult since this also damages the protective film 48 would effect.

If non-linear interactions are exploited, the shape of the beam profile can be used to achieve a focus which is smaller than the focusing of the laser light. This is below based on Fig. 4 explained.

The individual components of the marking device are controlled by a controller 22, so that the marking is carried out automatically. The controller 22 is only supplied with data containing the pattern for the mark, so that the corresponding areas of the value or security document 2 are irradiated with a corresponding laser light intensity to effect the corresponding marking in the value or security document 2.

The embodiment according to Fig. 1 is characterized in that the laser light 6 as a pulsed laser light with short pulse durations of less than 100 ps, preferably of less than 10 ps is generated. As a result, an exploitation of non-linear optical effects for introducing the markings on or in the value or security document is possible.

By using the optical fiber 9 for guiding the laser light 6 'onto or into the value or security document 2, a path length 27 between the light guiding device 8 and the value or security document 2 can be kept small. This can be selected in the range from contact to a few cm, preferably 0.2 to 10 mm. This makes it possible to form the beam guide strongly divergent and to focus sharply. Thus, a very narrow focusing can be achieved both transversely to the beam direction (propagation direction) and along the beam direction.

With a suitably chosen intensity and suitably selected beam profile, a non-linear interaction is achieved only in a "core region" of the beam of the laser light in focus. As a result, an even closer to the geometric light focusing light focusing is achieved. As a result, an improved resolution during marking can be achieved both laterally (transversely to the direction of irradiation of the laser light 6 'and also longitudinally, that is to say in the direction of propagation of the laser light 6'.) For example, micro writing with a character size in the range of a few micrometers can be realized.

In Fig. 4 a so-called beam profile 61 in focus is shown schematically. A light intensity I is plotted against the position r transversely to the propagation direction (z direction in FIG Fig. 1 ). (r, for example, becomes parallel to the x-axis according to Fig. 1 chosen.) It is assumed here that a beam profile 61 of the laser light 6 '(acc Fig. 1 ) in focus 19 (after Fig. 1 ) has a Gaussian profile. Since nonlinear interactions depend on the square I ² 62 of the intensity I of the laser light, that is to say a so-called I ² dependence, with suitably chosen pulse intensity, the nonlinear interaction takes place only in the core region 63 of the steel profile, in which the square I ² 62 the intensity I of the beam profile 61 exceeds a threshold value 64. As a result, the focal extent of the marking is determined by an extension 65 of the core region 63 and not by the extent 66 of the focus 19 of the laser light 6 ', which corresponds to the extent of the beam profile 61.

In another embodiment, the regions having different colors are introduced into the document body in the form of subregions. The subregions are arranged so that these subregions form a predetermined pattern when viewed on a surface of the document body. As a predetermined pattern, for example, a Bayer pattern 81 can be used, which is exemplarily sections in Fig. 5 is shown. For each colored pixel 82 of the information to be marked, four subregions 83 are provided in each case. A sub-area 83-r is red and a sub-area 83-b is blue, two sub-areas 83-g1, 83-g2 are green.

The individual subregions 83 are preferably arranged in a plane of the document body parallel to a surface of the document body. For example, the subregions 83 may be printed on a surface. Likewise, it is possible for the subregions 83 to be printed on different surfaces of foils which are gathered and assembled so that the individual subregions are arranged in register and give the predetermined pattern.

Colored marking is accomplished by modifying the subregions 83 for their color by means of short or ultrashort laser pulses of less than 100 ps or less than 10 ps, preferably 100 fs-10 ps. The sizes and the distances of the individual subregions 83 can be selected such that they are smaller than the focus size of the laser light pulses. Targeted modification of the color, for example by removing the ink causing the color or by "destroying" the pigments causing the color in the corresponding subregion, can be achieved by utilizing nonlinear interactions. By means of a suitable choice of the beam profile, it is thus possible to obtain and utilize a focusing of the interaction region which is improved compared to the optical focusing of the laser light.

Thus, for example, information in the form of micro-writing can be color-coded into a value or security document for individualizing it.

It will be understood by those skilled in the art that alternative patterns to a Bayer pattern may also be used, allowing for color addition or color subtraction appropriate modification of the subregions can achieve a variety of different color impressions.

In Fig. 6 a further embodiment of a marking device 1 is shown schematically. Technically equivalent features are provided with identical reference numerals. The illustrated embodiment differs from that according to Fig. 1 in that the light-guiding device 8 in this embodiment comprises two optical fibers 9, 9 '. These are correspondingly respectively coupled to a drive device 8 or 8 ', which analogously to the drive device 8 according to Fig. 1 are formed. This embodiment offers the advantage that the value or security document 2 can be marked simultaneously or quasi simultaneously at several locations.

The laser light source 5 is shown schematically in this embodiment as a fiber laser 23 with a seed laser 24 and an amplifier ring 25. It will be understood by those skilled in the art that another laser light source may be used with this embodiment. Likewise, a fiber laser 23 as a laser light source 5 in the embodiment according to Fig. 1 be used.

LIST OF REFERENCE NUMBERS

1

marking

2

Value or security document

3

bracket

4

transport device

5

Laser light source

6, 6 '

laser light

7

surface

8, 8 '

Lighting device

9, 9 '

optical fiber

10, 10 '

exit area

11

positioning level

12, 12 '

driving means

13, 13 '

X-Achsenaktor

14, 14 '

Y Achsenaktor

15, 15 '

Z-Achsenaktor

16

X axis

17

Y-axis

18

Z-axis

19

focus point

20

Imaging and / or focusing optics

22

control

23

fiber laser

24

Seed laser

25

amplifier ring

26

positioning

27

distance

40

document body

41

support film

42

black foil

43

blue foil

44

green foil

45

red foil

46

cover sheet

47

barrier film

48

protector

51-54

wells

55

Side wall

56.57

distances

58

Stege

61

beam profile

62

Square of intensity (I ² )

63

core area

64

threshold

65

Extension of the core area

66

Extent of focus

81

Bayer pattern

82

Pixel (of information)

83

subfield

83-r

Subsection (red)

83-b

Subsection (blue)

83-g1, 83-g2

Subsection (green)

Claims (8)

1. Method for the multi-coloured marking of value documents or security documents (2), comprising the steps:

   preparing a document body (40), which comprises regions of different colouration, wherein the individual regions are in each case of one colour; providing a marking device, which comprises at least one laser light source (5) for the generating of laser light (6) and a light guide device (8, 8'), which is coupled to at least one laser light source (5) in such a way that a focus (19) of the laser light (6) from the laser light source (5) can be positioned in a controlled manner on or in the document body (40) of the value document or security document (2); the iterated deliberate positioning of the focus (19) on or in the document body (40) and irradiating of the laser light (6'), in order to deliberately change the colour locally of one or more regions, such that the document body (40) subsequently conveys a multicoloured colour effect under irradiation with white light for a human observer, characterised in that the laser light (6) is irradiated by means of short or ultra-short laser pulses, which comprise a pulse duration of less than 100 ps or less than 10 ps.
2. Method according to claim 1, characterised in that the coloured regions are introduced in the form of layers, which are superimposed flat-surface on one another into the document body (40) or are introduced at the time of preparation.
3. Method according to claim 1 or 2, characterised in that the document body (40) comprises at least three regions of different colouration which in each case comprise a basic colour of a colour system which comprises a multicoloured gamut.
4. Method according to claim 3, characterised in that the at least three regions of different colouration are prepared with one another in a pattern of nested sub-regions, or are arranged at the time of preparation.
5. Method according to claim 4, characterised in that the pattern is or becomes formed as a Bayer pattern (81).
6. Method according to any one of claims 1 to 5, characterised in that local change of colouration of a region is carried out by a non-linear interaction with the irradiated laser light (6').
7. Method according to any one of claims 1 to 6, characterised in that the local change of the colour of a region is carried out by means of a change of the colouring agent causing the colour, by means of the non-linear interaction.
8. Method according to any one of claims 1 to 7, characterised in that the focusing of the laser light is carried out in such a way that a diameter of a interaction region of the non-linear interaction of a laser pulse in an image plane perceivable by the human user lies in the order of size range of less than 100µm, preferably less than 20µm.

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