EP3475099B1 - Method for producing a security or valuable product with a diffractive security element - Google Patents

Description

The invention relates to a method for producing a security or valuable product with a carrier substrate made of paper and a diffractive security element which is connected directly to the carrier substrate via an adhesive layer. The invention also relates to a security product or product of value produced by the method.

Technological background

Security or value products, such as personal documents, access control cards, vehicle documents, banknotes, postage stamps, tax codes, VISA, tickets or bank cards, usually have defined security features that are intended to make counterfeiting difficult or even impossible. The security features that can be recognized by humans can be subdivided into optical, haptic and acoustic security features. The security or value documents relevant in connection with the present invention have an optical security feature. In particular, the security or value documents carry diffractive security elements.

Diffractive security elements have optically diffractive microstructures (also referred to as DOVID = Diffractive Optically Variable Image Devices). The microstructures include grids, mostly in the form of surface reliefs, which change incident light through diffraction. This creates various effects such as two or three-dimensional images, kinematic effects or color changes. The different types of DOVID differ in their image resolution, brightness and animation properties. Examples include holograms and kinegrams.

At present, in the manufacture of the security or valuable products mentioned, to increase the security against forgery (mostly metallized) diffractive security elements such as holograms, kinegrams and alphagrams are used, which are glued to a paper carrier substrate with a hot melt adhesive. It is known that forgeries occur time and again with these security features, in which, for example, kinegrams are completely detached by heating the hot melt adhesive or the use of solvents and are used for forgeries can be reused. In order to avoid manipulation or at least to make it more difficult, an indicator can be incorporated into the adhesive (e.g. rhodamine), which triggers a color reaction when manipulated with solvents such as ethanol and acetone. This chemical reaction creates a colored reaction product that penetrates the carrier substrate, usually paper, and / or discolors the security element. However, rhodamines are classified as potentially carcinogenic, mutagenic and ecotoxic.

DE 10 2008 052 572 A1 describes a security or value document with a core layer which contains electronic components or diffractive security elements embedded in a polymer matrix. Polymer layers are applied by lamination to the top and bottom of the security or value document. To avoid damage to the functional elements of the core layer during lamination, a protective layer made of a polymeric material is provided between the polymer layers and the core layer. The core layer, the protective layers and the outer polymer layers are bonded to one another as a composite, a latently reactive adhesive being used, which enables a material bond between the respective polymeric materials of the layers.

From the DE 10 2009 031 877 A1 A security element for bonding to a substrate such as a value document is known, the security element having at least one bonding surface coated with at least one adhesive layer and the adhesive containing at least one powdery antiblocking agent as a component, the antiblocking agent being exposed to heat and / or radiation and / or mechanical action can be activated and, after activation, is able to enter into a chemical reaction with a component of the adhesive and / or with itself.

From the WO 2009/062602 A1 an identification document is known which has two thermoplastic layers and one layer made of a storage-stable and latently reactive adhesive.

From the EP 2 455 228 A1 a method for producing a security document is known in which at least one electromechanical transducer is applied to a thermoplastic plastic film, on the side of the thermoplastic plastic film on which the electromechanical transducer or transducers are located, a further thermoplastic plastic film is placed on or one or more further thermoplastic plastic films are placed under the film stack and the film stack is then laminated.

the WO 2010/072339 A2 teaches a method for producing a security element and a transfer film, in particular a hot stamping film, for transferring one or more multilayer bodies onto a target substrate.

the DE 10 2010 035 889 A1 relates to a method for producing a security element, in which a stack of foils is laminated to a laminate by means of pressure and heat and the security document is separated from the laminate, the third foil having no printing layer and at least one security thread over before the foils are brought together to form a stack of foils a Holtmelt adhesive is applied to the third film.

However, there is a continuing need for at least alternative measures that prevent manipulation of security or valuable products with a carrier substrate made of paper and a diffractive security element that is directly connected to the carrier substrate via an adhesive layer.

Summary of the invention

1. (i) Auftragen eines Schmelzklebstoffs und eines latent-reaktiven Klebstoffs a) auf einem Bereich des Substrats, der für das Sicherheitselement vorgesehen ist, und/oder b) auf dem Sicherheitselement, wobei entweder ein Gemisch aus Schmelzklebstoff und latent-reaktivem Klebstoff oder der Schmelzklebstoff und der latent-reaktive Klebstoff abschnittsweise voneinander getrennt aufgetragen werden und wobei eine Applikationstemperatur T_a1 des Schmelzklebstoffs niedriger ist als eine Applikationstemperatur T_a2 des latent-reaktiven Klebstoffs und für eine Temperatur T₁ während des Auftragens gilt T_a1 ≤ T₁ < T_a2;
2. (ii) Aufbringen des Sicherheitselements auf dem Substrat; und
3. (iii) Erwärmen auf eine Temperatur T₂, wobei T₂ ≥ T_a2 ist.

At least some of the limitations of the prior art can be remedied with the aid of the method according to the invention for producing a security or valuable product, in particular a security or valuable document, with a substrate, preferably made of paper, and a diffractive security element that is directly connected to the by means of an adhesive layer Substrate is connected, fix or at least reduce. The procedure comprises the following steps:

1. (i) Application of a hot-melt adhesive and a latent-reactive adhesive a) on an area of the substrate which is intended for the security element, and / or b) on the security element, either a mixture of hot-melt adhesive and latent-reactive adhesive or the hot-melt adhesive and the latent-reactive adhesive are applied separately from one another in sections and an application _{temperature T a1 of} the hot-melt adhesive is lower than an application _{temperature T a2 of} the latent-reactive adhesive and for a temperature T ₁ during the application, T _a1 T ₁ <T _a2 applies;
2. (ii) applying the security element to the substrate; and
3. (iii) heating to a temperature T ₂ , where T ₂ ≥ T _a2 .

The invention is based on the knowledge that a connection of the security element and substrate by means of a latently reactive adhesive can prevent manipulation by detaching the security element. The latently reactive adhesive is introduced into the hot melt adhesive matrix or is present separately in sections. The latently reactive adhesive is activated during the application process and creates a permanent chemical bond between the substrate and the security element. A full-surface detachment is made more difficult or completely prevented because manipulation of the security element causes cohesive destruction of the paper and security element, which makes reconstruction of the security feature almost impossible.

The process sequence according to the invention is basically designed in such a way that the joining process is subject to a differentiated temperature regime, in which temperatures prevail in a first phase which only enable the hot melt adhesive to be processed for a specific purpose. Only when the security element is fixed in the intended area of the substrate with the aid of the hot melt adhesive is the temperature increased in a second phase in such a way that the latently reactive adhesive is activated and the desired (additional) chemical bond takes place. The temperature in the second phase must always be specified so that the hot melt adhesive used in the application is not thermally damaged.

In the present case, the application temperature is understood to mean the processing temperature of the adhesive recommended by the manufacturer. If the manufacturer specifies a temperature range, the lower limit is decisive. If different temperature specifications from one manufacturer are known for one and the same adhesive, the most recent specification from this manufacturer is decisive. In the event that different manufacturers specify different processing temperatures for exactly the same adhesive composition, the application temperature is the lowest temperature specification. If there is no information about the processing temperatures of the hot melt adhesives, the application temperature for hot melt adhesives is the glass transition temperature of the base polymer. Anything is missing Information on the processing temperatures of the latent-reactive adhesives, the application temperature for latent-reactive adhesives is the temperature at which at least 90% of the functionalities required to cure the adhesive are consumed within a time window of 15 minutes. In the case of a latently reactive adhesive based on a surface-deactivated di- or polyisocyanate and at least one isocyanate-reactive polymer, for example, the degradation of isocyanate functionality over time would be decisive.

According to a preferred variant of the method, the application _{temperature T a1 of} the hot melt adhesive is in the range from 45 to 245 ° C, in particular in the range from 55 to 145 ° C, and the application temperature T _{a2 of} the latent reactive adhesive is in the range from 50 to 250 ° C , especially in the range from 60 to 150 ° C. If the application temperatures T _a1 and T _{a2 are} in the range mentioned, it is ensured that neither the substrate material nor the diffractive security element are thermally damaged during the joining step. Independently or in combination thereof, it is preferred if the application _{temperature T a2 of} the latent-reactive adhesive is at least 5 ° C. above the application temperature T _{a1 of} the hot-melt adhesive. In particular, the application _{temperature T a2 of} the latently reactive adhesive is 5 ° C. to 40 ° C., particularly preferably 10 ° C. to 20 ° C., above the application temperature T _{a1 of} the hot melt adhesive. This ensures that a material connection between the carrier substrate and the security element by the latent-reactive adhesive does not take place until after it has been placed and that the adhesive properties of the latent-reactive adhesive do not hinder the processing beforehand.

Latent-reactive adhesives for the purposes of the invention are adhesive compositions which can be stored at room temperature and which cure by themselves at higher temperatures through the formation of covalent bonds. In the present case, an adhesive composition based on a combination of a surface-deactivated di- or polyisocyanate and at least one isocyanate-reactive polymer is preferably used as the latently reactive adhesive. It can also be a latently reactive hot melt adhesive, in particular if a mixture with the (non-latently reactive) hot melt adhesive is used.

Examples of latently reactive adhesives suitable for the purposes of the invention can be found EP 2 712 879 A1 remove. The latently reactive hot melt adhesive composition described there comprises a mixture of polymers which are in the melting temperature and the number of functionalities present that can in principle react with an isocyanate group. The composition also contains a surface-deactivated di- or polyisocyanate.

EP 0 598 973 B1 describes a process for the production of reactive enamel masses. These consist of a polymer that is solid at room temperature but meltable with isocyanate-reactive groups and a premix of a solid isocyanate and a deactivating agent. The melt is applied in layers to carrier materials so that the deactivated isocyanate and polymer layers are not mixed. Above 40 ° C, these layers can be liquefied and reshaped. They harden between 100 ° C and 120 ° C.

EP 1 231 232 B1 describes a reactive one-component hot-melt adhesive which is solid at room temperature and which comprises an isocyanate which is liquid or solid at room temperature, an isocyanate-reactive polymer which is solid at room temperature and a polymer which is inert towards isocyanate groups. This adhesive is non-adhesive at room temperature and only becomes adhesive when heated to temperatures between 60 ° C and 160 ° C.

Another example of a suitable latent-reactive adhesive can be EP 0 922 720 A1 remove. The use of an aqueous dispersion which contains at least one surface-deactivated polyisocyanate and at least one isocyanate-reactive polymer for the production of storage-stable, latently reactive layers or powders is described.

Hotmelts, also known as hotmelts, are solvent-free and more or less solid products at room temperature that are applied to the adhesive surface when they are hot and create a firm bond when they cool down. Hotmelt adhesives are purely physically setting adhesives, i.e. the already finished adhesive is introduced into the adhesive joint, which has been converted into a workable form by heating and solidifies again when it cools. This group of adhesives is based on various basic chemicals. The preferred hot melt adhesive is an adhesive composition with a base polymer selected from the group comprising polyamides (PA), polyethylene (PE), amorphous polyalphaolefins (APAO), ethylene vinyl acetate copolymers (EVAC), polyester elastomers (TPE-E), polyurethane elastomers ( TPE-U), copolyamide elastomers (TPE-A) and vinylpyrrolidone / vinyl acetate copolymers are used, especially when a mixture with the latently reactive adhesive is used.

If a mixture of hot melt adhesive and latently reactive adhesive is used, preferably 100 parts by weight of the hot melt adhesive are mixed with 5 to 50 parts by weight of the latently reactive adhesive.

According to a preferred variant of the method, the hot melt adhesive and the latently reactive adhesive are present separately from one another in sections and sections with the latent reactive adhesive are applied before sections with the hot melt adhesive. Since the application temperature of the hot-melt adhesive is lower than the application temperature of the latent-reactive adhesive, the subsequent application of the hot-melt adhesive does not activate the adhesion of the latent-reactive adhesive. As a result, more functionalities are available for the later covalent attachment to the substrate and the security element. The ratio of the total area of all sections of the hot-melt adhesive to the total area of all sections of the latent-reactive adhesive is preferably 20: 1 to 2: 1. The latent-reactive adhesive is preferably applied by means of screen printing.

A further aspect of the invention lies in the provision of a security or valuable product, in particular a security or valuable document, with a substrate, preferably made of paper, and a diffractive security element that is connected directly to the carrier substrate by means of an adhesive layer, the security or product of value is produced by the process described above. Accordingly, the latently reactive adhesive is cured and covalently bonded to the substrate and security element.

Valuable and / or security products in the sense of the invention include, for example, passports, identity cards, driver's licenses, access control cards or other ID cards, vehicle registration documents, vehicle documents, visas, checks, means of payment, in particular banknotes, company IDs, credentials, membership cards, gift or shopping vouchers, waybills, Tax stamps, postage stamps, tickets, (game) chips, certificates or adhesive labels (e.g. for product security).

Further preferred embodiments of the invention can be found in the following description or in the subclaims.

Brief description of the figures

Figur 1

eine schematische Schnittdarstellung durch ein Sicherheits- oder Wertprodukt gemäß einer ersten Ausführungsform der Erfindung; und

Figur 2

eine schematische Schnittdarstellung durch ein Sicherheits- oder Wertprodukt gemäß einer zweiten Ausführungsform der Erfindung.

The invention is explained in more detail below on the basis of exemplary embodiments and the associated drawings. Show it:

Figure 1

a schematic sectional view through a security or valuable product according to a first embodiment of the invention; and

Figure 2

a schematic sectional view through a security or valuable product according to a second embodiment of the invention.

Detailed description of the invention Embodiment 1

1. a) 100 Gewichtsteile eines Schmelzklebers mit einer Applikationstemperatur von etwa 60°C; und
2. b) 20 Gewichtsteile eines latent-reaktiven Klebstoffs mit einer Applikationstemperatur von etwa 80°C.

Figure 1 represents - in a highly schematic manner - a sectional view through a security or valuable product 100 according to the invention, for example a bank note, according to a first variant. The security or valuable product 100 comprises a carrier substrate 10 made of paper. A diffractive security element 20, for example a kinegram, is applied to the carrier substrate 10 by means of an adhesive layer 30. The security or valuable product 100 can be produced as follows:
A mixture of the following components is applied to a carrier substrate 10 made of paper:

1. a) 100 parts by weight of a hot melt adhesive with an application temperature of about 60 ° C; and
2. b) 20 parts by weight of a latently reactive adhesive with an application temperature of about 80 ° C.

The mixture is applied at a temperature that corresponds to the application temperature of the hot melt adhesive. The hot glue mixture in the glue joint is quickly applied to the back of aluminum foil applied kinegram and then increased the temperature to the application temperature of the latent-reactive adhesive.

Embodiment 2

Figure 2 represents a sectional view through a further variant of the security or valuable product 100 according to the invention - likewise in a highly schematic manner. The security or valuable product 100 can be produced as follows:
In a first partial step, first sections 34 of the joining area are coated on a carrier substrate 10 made of paper by means of screen printing with a latent-reactive adhesive with an application temperature of about 80 ° C. Approx. 15% of the total area of the adhesive joint is coated.

In a second sub-step, the remaining second sections 32 are filled with a hot-melt adhesive with an application temperature of approximately 60 ° C., the temperature corresponding to the processing temperature recommended by the manufacturer.

A kinegram is then quickly applied to the back of the aluminum foil and the temperature is increased to the application temperature of the latent-reactive adhesive.

List of reference symbols

10

Substrate

20th

diffractive security element

30th

Adhesive layer

32

Sections with hot melt glue

34

Sections with latent reactive adhesive

100

Security or value product

Claims (8)

1. A method of fabricating a security product or product of value (100) including a substrate (10) made of paper and a diffractive security element (20) which is directly connected to the substrate (10) by means of an adhesive layer (30), the method comprising the steps of:

   (i) applying a hot-melt adhesive and a latent-reactive adhesive a) onto a region of the substrate (10) which region is provided for the security element (10) and/or b) onto said security element (20), wherein either a mixture of the hot-melt adhesive and the latent-reactive adhesive is applied or the hot-melt adhesive and the latent-reactive adhesive are applied separately from each other section by section and wherein the application temperature T_a1 of the hot-melt adhesive is lower than the application temperature T_a2 of the latent-reactive adhesive and a temperature T₁ is selected such that during the application process T_a1 ≤ T₁ < T_a2;

   (ii) placing the security element (20) onto the substrate (10); and

   (iii) heating thereof to a temperature T₂, where T₂ ≥ T_a2.
2. The method as claimed in claim 1, wherein the application temperature T_a1 of the hot-melt adhesive is in the range of between 45 °C and 245 °C and wherein the application temperature T_a2 of the latent-reactive adhesive is in the range of between 50 °C and 250 °C.
3. The method as claimed in claim 1 or 2, wherein the application temperature T_a2 of the latent-reactive adhesive is at least 5 °C above the application temperature T_a1 of the hot-melt adhesive.
4. The method as claimed in any of the preceding claims, wherein an adhesive composition based on a combination of a surface-deactivated di-isocyanate or polyisocyanate and a polymer reactive with at least one isocyanate is used as a latent-reactive adhesive.
5. The method as claimed in any of the preceding claims, wherein an adhesive composition including a base polymer selected from the group comprising polyamide (PA), polyethylene (PE), amorphous polyalphaolefins (APAO), ethylene vinyl acetate copolymers (EVAC), polyester elastomers (TPE-E), polyurethane elastomers (TPE-U), copolyamide elastomers (TPE-A), and copolymers of vinyl pyrrolidone and vinyl acetate is used as a hot-melt adhesive.
6. The method as claimed in any of the preceding claims, wherein the hot-melt adhesive and the latent-reactive adhesive are provided separate from each other section by section and wherein sections (34) with the latent-reactive adhesive are applied prior to sections (32) with the hot-melt adhesive.
7. The method as claimed in claim 6, wherein the latent-reactive adhesive is applied via screen printing.
8. A security product or product of value (100) including a substrate (10) made of paper and a diffractive security element (20) which is directly connected to the substrate (10) by means of an adhesive layer (30), said product being fabricated in accordance with a method as claimed in claim 1.

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