SAFE ELEMENT WITH A CARD-SHAPED BODY MADE OF MULTIPLE LAYERS AND METHOD FOR ITS MANUFACTURING

Description

[0001] The invention relates to a safety element with a card-shaped body made of several layers arranged one above the other and produced by coextrusion, and to a method for its manufacture.

[0002] Secure, card-shaped cards are commonly known as chip cards. These are used, for example, as ID cards, access cards, or bank cards (debit cards, credit cards, payment cards, etc.), usually in conjunction with other designs, typically in one or more colors and featuring a motif. Various types of color design are possible: cards with a colored core, cards with a colored border, cards with colored overlays, transparent and translucent cards, and so on. Depending on the design, a specific aesthetic impression is intended. Such cards can be manufactured using sheet lamination or by co-extrusion of films.

[0003] US patent 2003 / 0203177 A1 discloses a process for producing a plastic film by co-extrusion through the mixing of different color batches, resulting in a pattern with a random distribution of several colors when viewed from above. In this process, two or more material streams exiting from respective extruders are introduced into a cavity of a housing until the mixed material streams are extruded at the other end of the cavity.

[0004] US patent 2017 / 0182697 A1 discloses the production of multicolored plastic films based on the random mixing of different color components. These plastic films are used, for example, to manufacture a kayak, in which two films are thermoformed into a predetermined shape and then welded together.

[0005] DE 4118624 C1 describes a process for producing a plastic film with a colored structure by extrusion. Before extrusion, a heterogeneous mixture of two or more plastic materials is prepared and mixed with a blowing agent. The plastic materials differ, for example, in their color. The heterogeneous mixture is heated above its softening temperature, thereby activating the blowing agent. The heated heterogeneous mixture is then extruded and subsequently thermoformed. After thermoforming, a colored structure is created that, for example, resembles a wood grain.

[0006] From DE 102017115380 A1, the production of a food-safe film with a randomized color gradient is known, which is suitable for articles produced by thermoforming such as trays, cups or blister packs.

[0007] The film has a decorative layer comprising a matrix of a first polymeric material and streaks of a second polymeric material embedded within the matrix. Visually, the film appears as numerous strip-like streaks running parallel to the machine direction, with irregularly varying widths and blurred edges. The decorative effect is achieved by extruding poorly miscible polymeric materials that preferably differ in their mass flow rates.

[0008] DE 10 2009 058803 A1 discloses a card body, in particular for the production of a chip and / or magnetic stripe card, the structure of which comprises at least one co-extruded film which has at least one surface area with a first material property and at least one second surface area with a second material property.

[0009] The object of the invention is to provide a safe element with a card-shaped body made of several produced layers, which is colored in volume and features various randomly distributed color tones.

[0010] This problem is solved by a safe element according to the features of claim 1 and a method for manufacturing the safe element according to the features of claim 10. Advantageous embodiments are set forth in the dependent claims.

[0011] A safe element with a card-shaped body is proposed, consisting of several superimposed layers produced by coextrusion. The safe element comprises a first layer as a base layer made of a first material. This first material comprises a base polymer. A first color, the body's base color, is homogeneously distributed within this first layer. The safe element also includes at least one second layer as a color layer made of a second material. This second material comprises a carrier polymer. Within each second layer, one or more color areas in a second color, different from the first color, are unevenly distributed in random shapes. The base polymer and the carrier polymer have different material properties, preventing homogeneous mixing and resulting in a randomized (randomly distributed) multicolor appearance visible in both top and cross-sectional views.

[0012] The randomly distributed color areas create a unique characteristic for each individual secure element and can be captured and processed electronically, e.g., using a camera or scanner, as a unique identification feature.

[0013] The number of superimposed layers is, in principle, arbitrary. In its simplest form, the secure element can consist of two layers: a base layer in which the primary color is homogeneously distributed, and a second layer with unevenly distributed color patches. In another embodiment, multiple second layers, each with one or more color patches in their respective secondary colors, can be provided. It is understood that, in the case of multiple second layers, the one or more color patches in each secondary layer are unevenly distributed, with the secondary colors of several secondary layers preferably being different from each other and from the primary color.

[0014] The randomly distributed multicoloration of the card-shaped body, both in top view and in cross-section, requires that the colors of the first layer and the at least one second layer do not mix homogeneously. This is achieved by ensuring that the base polymer and the respective carrier polymers of the at least one second layer have deliberately different material properties.

[0015] In a first variant, the base polymer and the support polymer are polymers with different melt viscosities. For example, one polymer can be a long-chain polycarbonate (PC) with a high molecular weight, and the other a short-chain polycarbonate (PC). Preferably, the other polymer is made from a recycled material, e.g., so-called Ocean Plastic, which is based on marine plastic waste. Such recycled material is inherently short-chain. After processing and chain extension, it can then be used, for example, as the base polymer for the base layer.

[0016] It is advantageous if the melt volume flow rate of one polymer is approximately 5 cm³ / 10 min and the melt volume flow rate of the other polymer is approximately 35 cm³ / 10 min at a temperature of 300°C and a mass of 1.2 kg. The melt volume flow rate is also known as the melt volume-flow rate (MVR).

[0017] Alternatively or additionally, the base polymer and the support polymer can be polymers with different melt temperatures. The material parameters melt viscosity and melt temperature are partially interrelated. Melt viscosity is also temperature-dependent, meaning it can be adjusted within certain limits via temperature control. In this configuration, one polymer can be polylactic acid (PLA) and the other polycarbonate (PC). For example, the polylactic acid (PLA) polymer can have a melt temperature of 200°C, and the other polymer can be polyester with a melt temperature of 260°C.

[0018] In another alternative or additional embodiment, the base polymer and the support polymer are polymers with different polar and nonpolar properties. These can be, for example, polyesters and polar or nonpolar polyolefins. In particular, one polymer can be PETG (a glycol-modified polyethylene terephthalate (PET)) and the other polyethylene.

[0019] It is not necessary to add a blowing agent to the carrier polymer or the base polymer. A safe element produced according to the invention therefore has no blowing agent-induced pores or inclusions.

[0020] A further method for manufacturing a safe element is proposed, designed according to one or more of the foregoing descriptions. The method comprises the following steps: a) Providing a first material stream of a first material with a base polymer in which a first color is distributed as the base color of the body; b) Providing a second material stream of a second material with a carrier polymer in which a second color, different from the first color, is unevenly distributed in one or more color accumulations, wherein the carrier polymer of the second material stream and the base polymer have different material properties so that the materials cannot mix homogeneously; c) Combining the first and the second material streams in an extrusion device to form a layered structure with a base layer comprising the first material with its coloration and at least one color layer comprising the second material with one or more unevenly distributed color areas.

[0021] The method according to the invention has the advantage that commercially available extrusion devices can be used, and in particular the use of expensive multi-channel nozzles can be avoided.

[0022] In a suitable embodiment, the first material stream from a first extruder and the second material stream from at least a second extruder are fed to the extrusion device.

[0023] The first and second material streams are subjected to a melt pressure between 10 bar and 100 bar in the extrusion device, in particular a compression device and / or a conveying block and / or a die of the extrusion device. Preferably, the melt pressure is between 10 bar and 60 bar. Most preferably, the melt pressure is between 20 bar and 50 bar.

[0024] The invention is described in more detail below with reference to exemplary embodiments shown in the drawing. The drawing shows: Fig. 1 a cross-sectional view of a safe element according to the invention, which is produced from three layers; Fig. 2 a top view of a section of a card-shaped body; Fig. 3 a cross-section through a card-shaped body; Fig. 4 a block diagram of an extrusion device for producing the safe element according to the invention; and Fig. 5 a photographic representation of a top view of a safe element according to the invention, which is produced according to the method according to the invention.

[0025] Fig. 1 Figure 1 shows a schematic cross-sectional view of a card-shaped body 10 of a safety element according to a first embodiment. By way of example, the body 10 of the safety element has a layered structure consisting of three superimposed u-layers produced by coextrusion. The layered structure has at least one visible surface 12, which exhibits a randomized multicolor pattern that is clearly visible when looking down at the safety element. Advantageously, a randomized multicolor pattern is also visible when viewed from the underside opposite the top surface.

[0026] The secure element can be designed as a chip card in a known manner. Such a chip card is used, for example, as an identification card, access card, or bank card (debit card, credit card, payment card, etc.), with a chip module integrated inside the card body. Such a chip module, comprising a (semiconductor) chip and a contactless and / or contact interface, is not shown in any of the figures. The design of a chip card is familiar to those skilled in the art, so a detailed description is omitted here.

[0027] The card-shaped body 10 of the safe element exhibits in the example of the Fig. 1 a three-layer structure with a first layer 11 as a base layer and two second layers 21, 22, each forming color layers. In the Fig.1 In the illustrated configuration, the second layer 21 lies directly on a (e.g., upper) main side of the first layer 11, which is also referred to as the base layer in the following. The second layer 22 is arranged on the side of the second layer 21 facing away from the first layer 11.

[0028] The first layer 11, as the base layer, consists of a first material comprising a base polymer. Often, the base layer 11 is a transparent material. Alternatively, the base polymer of the first layer 11 can be mixed with color particles, so that the first layer 11 has a first color 11F. The first color 11F, as the base color, can be, for example, white or gray; in principle, any color can be chosen.

[0029] Each of the second layers 21, 22 consists of a second material, each comprising a carrier polymer. Advantageously, the carrier polymers of the two second layers 21, 22 are different from each other and also from the material of the base layer 11. Preferably, the carrier polymers differ in their viscosity. Furthermore, the two second layers 21, 22 are provided with color particles in different colors, giving each layer its own base color. For example, the base color of the second layer 21 can be green and the base color of the second layer 22 blue. In a particular embodiment, one of the two layers 21, 22 can also be transparent.In order to enable mixing and transitions through superimposition, layers 21, 22 are expediently not completely opaque but slightly translucent, so that when two second layers 21, 22 are superimposed, the lower one is perceptible through the one above it, resulting in a color mixing effect.

[0030] To achieve a randomly distributed multicolor appearance of the card-shaped body 10 of the safety element in both plan view and cross-section, the base polymer of the first material of the first layer 11 and the support polymers of the respective second materials of the second layers 21, 22 exhibit different material properties. Preferably, the polymers used for the base layer 11 and the second layers 21, 22 have different melt viscosities and / or different melt temperatures or different polar / nonpolar properties.

[0031] Sufficient differentiation between the polymers of the base layer 11 and the carrier polymers of the second layers 21, 22 ensures that the polymers of the different layers, and thus the color particles (color masterbatches) contained therein, do not mix homogeneously during extrusion. The color particles themselves, or the colors or dyes used, are not crucial in this process.

[0032] Melting viscosity and melting temperature influence each other. Within certain limits, the melting viscosity can be adjusted via temperature control.

[0033] A material combination with different viscosities is created, for example, by combining a long-chain polycarbonate (PC) with a high molar mass and a short-chain polycarbonate. Either can be used for the base layer or as a support polymer.

[0034] A material combination whose materials differ in melting temperatures consists, for example, of polylactic acid (PLA) and polycarbonate. Here, too, it is selectable which of the two polymers is used for the base polymer or the support polymer.

[0035] Polyesters and polyolefins (which can be either polar or non-polar) are a material combination with different polar properties.

[0036] Reused materials, such as so-called Ocean Plastic, which is based on marine plastic waste, are particularly suitable for providing such material combinations. Recycled or reusable materials are inherently short-chain and can be used, for example, as base materials or carrier materials in combination with processed recycled materials that have extended chains.

[0037] For combinations with different melt viscosities, polymers with differing melt volume flow rates (MVR) can be selected. For example, the melt volume flow rate of one polymer might be 5 cm³ / 10 min, while the MVR of another could be 35 cm³ / 10 min. These melt volume flow rates are valid at a temperature of 300°C and a mass of 1.2 kg.

[0038] If polymers with different melting temperatures are used, for example polylactic acid (PLA) with a melting temperature of 200°C can be chosen as one polymer and polyester with a melting temperature of 260°C as another polymer.

[0039] If polymers with different polar or non-polar properties are chosen, PETG can be selected as one polymer and polyethylene as the other.

[0040] The different material properties mean that during extrusion, the base polymer of the first layer 11 and the carrier polymers of the second layers 21, 22 do not mix homogeneously. Instead, random color areas 23 form in the extruded film, in each of which the polymer of one layer, and thus the color added to that polymer, dominates by having a higher volume fraction than the other. If, for example, two polymers with different viscosities are used, a film is produced with color areas in which the higher-viscosity polymer dominates and color areas in which the polymer with the lower viscosity dominates.

[0041] The colored areas have random sizes and random border contours. To a user, their boundaries may appear to blend seamlessly into one another, or they may be nearly sharp. The colored areas may also differ in surface quality. For example, areas dominated by a low-viscosity material may have an uneven surface, while areas dominated by a high-viscosity material appear comparatively smooth and uniformly flat. Such differences in surface quality may be desirable to enhance the impression of color distribution. Alternatively, it may be possible to smooth out such differences in surface quality and layer thickness through a pressing process. From a top view, this results in a randomized multicolor appearance.

[0042] Due to their differing material properties, the carrier polymers of the second layers 21, 22 mix well but not homogeneously. The different carrier polymers primarily mix into each other. Furthermore, as a result of the differing material properties and specific extruder parameter settings, the combination of the carrier polymers of the second layers 21, 22 in the extrusion device 50 leads to – intentional – irregularities in the material flow, which cause or contribute to an uneven distribution of the carrier polymers of the second layers 21, 22.

[0043] Due to these mixing impairments, the carrier polymers in the surface stream practically never arrange themselves in a homogeneous distribution on top of each other. Instead, areas are formed where only one of the carrier polymers is present, areas where a thin layer of the first carrier polymer is superimposed on a comparatively thicker layer of the second carrier polymer, areas where both carrier polymers are mixed, and areas that are essentially formed by the base layer. Fig. 1 schematically illustrates superimposition possibilities.

[0044] Fig. 1 Figure 1 shows a cross-section through a card-shaped body 10 composed of a base layer 11 and two secondary layers 21 and 22. The body 10 has a constant overall thickness. Within this constant overall thickness, the thickness distributions of the three layers 11, 21, and 22 vary vertically with respect to the visible surface 12. They are not uniformly arranged on top of each other, but rather varying, random thickness distributions are formed relative to the visible surface 12. Only the base layer 11 is formed as a continuous support layer and, although also with varying thickness, is present over the entire surface of the body 10.

[0045] In the example, the first second layer 21 has a slightly translucent color 21F, the second second layer 22 has a significantly more translucent color 22F, and the base layer 11 has a highly translucent color 11F.

[0046] For an observer, the different local distribution of layers 11, 21, 22 results in the following: Fig. 1 The randomly arranged situation, from left to right, represents a color impression of a sequence of color area regions 23. In the first color area region 23A, hereinafter referred to simply as region, layer 22 is thicker than layer 21 and its color dominates the color impression. In the adjacent region 23B, the first layer 21 is missing, and the color impression is dominated by color 22F of the second layer 22. In the adjacent region 23C, only layer 22 is present in a thin layer, so the color impression is determined by a mixture of the clearly translucent color 22F of the second layer 22 and the highly translucent color 11F of the base layer 11. In the adjacent region 23D, only the base layer 11 is present, and the color impression is determined by its color 11F.In area 23E, the two second layers 21 and 22 are present in equal thickness, so their colors 21F and 22F mix, with the less translucent color 21F of the first second layer 21 showing through the more translucent color 22F. In the adjacent areas 23F and 23G, only layer 21 is present, albeit in varying thicknesses. The perceived color is thus determined more strongly in one area and less strongly in the other by color 21F of layer 21. In area 23H, layer 22 determines the perceived color, while in area 23I, the colors 21F and 22F of layers 21 and 22 mix, with color 21F predominating in the perceived color.

[0047] If the first color 21F is blue, for example, the second color 22F is green, and the base layer 11 is white, then for an observer the following results: Fig. 1 The random situation depicted, for example, is a sequence of color impressions from left to right as follows: area 23A appears greenish-turquoise, area 23B distinctly green, area 23C slightly green, area 23H translucent white, area 23E turquoise, area 23F light blue, area 23G blue, area 23H green, and area 23I blue-turquoise.

[0048] The number and distribution of the respective color area areas 21F, 22F, 11F of the respective second layers 21, 22 and the base layer 11 is random and independent of each other.

[0049] Fig. 2 Figure 12 shows a section of a card-shaped body 10 of a security element with a base layer 11 and two second layers 21, 22, which were joined together to form a random distribution of different randomly shaped color area areas 23 corresponding to the respective colors of the layers 21, 22.

[0050] Areas form in an uneven distribution where the first of the second layers 21, 22, and thus its color, dominate; areas where the second of the second layers 21, 22, and thus its color, dominate; and areas where the base layer 11, and thus its color, dominates. If one of the second layers 21, 22 is transparent, this leads to a significant lightening and reduction in the opacity of the color of the other second layer 21, 22 in the areas dominated by this second layer. For example, an intense blue becomes a milky light blue. If the base layer is also transparent, the effect is intensified.

[0051] Fig. 3 schematically illustrated by a cross-section through the Fig. 2 The distribution shown along line A-A illustrates the formation of different color areas. In a first area, viewed from top to bottom in Fig. 2 The second layer 21 dominates in one area, the base layer 11 dominates in an intermediate area, the second layer 22 dominates in a subsequent area, and the second layer 21 again dominates in a following area. It is indicated in each case that in the areas dominated by a second layer 21, 22, or the base layer 11, the materials of the other layers are generally also present, but in significantly lower concentrations. The surfaces of the adjacent layer areas must, as in Fig. 3 The surface should be indicated, not flat. Depending on the varying layer thicknesses, this can create – desired – random color gradients within an area.

[0052] The in Fig. 1 The schematically shown structure is arranged symmetrically, and the card-shaped body 10 is built up from five layers, with two second layers 21, 22 being applied symmetrically to each side of the base layer 11. In this way, a random distribution of color areas 23 is created on both sides of the first layer 11, as described previously. The number and distribution of the color areas 23 of the respective second layers 21, 22 are independent of each other. In further variations, more than two second layers 21, 22 can be applied to each side of the base layer 11; it is also conceivable to apply different numbers of second layers 21, 22 to the sides of a base layer 11. Furthermore, the base layer 11 can also consist of several layers.

[0053] In the manufacturing process, which is described below with reference to Fig. 4 As explained in more detail, a material flow can be divided for the second layers 21, 22.

[0054] Fig. 4 Figure 50 shows an extrusion device 50, which is used to produce the card-shaped body 10 according to the embodiments shown in the figures. Fig. 1 and 4 for a safe element. The extrusion device 50 comprises a first extruder 110 for supplying a first material stream 11MS consisting of the first material containing the base polymer. Furthermore, two second extruders 210, 220 are provided for supplying a second material stream 21MS, 22MS, respectively, containing a carrier polymer. The first material stream 11MS and the two second material streams 21MS, 22MS are fed to a feed block 300.

[0055] The starting material for extruders 110, 210, and 220 is polymer in granular form. The starting material is preferably pre-dried at approximately 60°C to 80°C. No blowing agents are added.

[0056] In conveying block 300, the material streams are combined into a single material stream, which is discharged as a surface stream via a nozzle 310 (the so-called "die"). The surface stream has, for example, a layered structure as is generally found in Fig. 1 is shown.

[0057] In an optional subsequent compression unit 320, the surface flow and thus the layer structure are solidified into a film. The film contains the subsequent card-shaped bodies 10.

[0058] The melt pressure in the nozzle 310 is expediently between 10 bar and 100 bar. Preferably, the melt pressure is between 10 bar and 60 bar or 20 bar and 50 bar.

[0059] Fig. 5The black and white illustration depicts a realistic pictorial view of a card-shaped body 10 constructed as described above, where the random distribution of color area regions 23 consisting of three colors (black - gray - white, corresponding, for example, to black - blue - green) is recognizable. This gives the card-shaped body 10 a unique optical feature that can be optically detected and evaluated.

[0060] All structural elements described above can, in principle, be freely combined with one another in ways other than those described in the exemplary embodiments; the exemplary embodiments are not to be understood as a restriction to specific combinations of elements.

Claims

1. Secure element having a cardlike body (10) with a visible surface composed of a plurality of layers (11, 21, 22) arranged one atop another and generated by coextrusion, comprising: - a first layer (11) as base layer composed of a first material which comprises a base polymer, - at least one second layer (21, 22) as color layer composed of a second material which comprises a carrier polymer, the at least one second layer (21, 22) possessing a color, - the at least one second layer (21, 22) and the first layer (11) are arranged one atop another in varying thickness distributions vertically with respect to the visible surface (12) of the body (10) in such a way that in nonuniform distribution, color surface regions (23) are formed in which the at least one second layer (21, 22) and therefore its color (21F, 22F) dominates, and also color surface regions (23) in which a different layer (11, 21, 22) of the cardlike body (10) and therefore its color dominates, - wherein the base polymer and the carrier polymer have different physical properties, so that they do not mix homogeneously, as a result of which, in plan view onto a cardlike body (10), a randomized polychromatism is apparent.

2. Secure element according to Claim 1, characterized in that the layers (11, 21, 22) arranged one atop another are free from blowing agent-induced pores or inclusions.

3. Secure element according to Claim 1, characterized in that the first layer (11) is transparent or in the first layer (11) a first color (11F) as base color of the cardlike body (10) is distributed.

4. Secure element according to any of the preceding claims, characterized in that the base polymer and the carrier polymer are polymers having different melt viscosities or having different melting temperatures.

5. Secure element according to any of the preceding claims, characterized in that one polymer comprises long-chain polycarbonate (PC) of high molar mass and the other polymer comprises short-chain polycarbonate, more particularly composed of recycled materials.

6. Secure element according to any of the preceding claims, characterized in that a melt volume flow rate of the one polymer is about 5 cm3 / 10 min and the melt volume flow rate of the other polymer is about 35 cm3 / 10 min at a temperature of 300°C with a mass of 1.2 kg.

7. Secure element according to any of the preceding claims, characterized in that one polymer comprises polylactic acid (PLA) and the other polymer comprises polycarbonate (PC).

8. Secure element according to any of the preceding claims, characterized in that the one polymer is polylactic acid (PLA) having a melting temperature of 200°C and the other polymer is polyester having a melting temperature of 260°C.

9. Secure element according to any of the preceding claims, characterized in that the base polymer and the carrier polymer are polymers having different polar or nonpolar properties.

10. Secure element according to any of the preceding claims, characterized in that the one polymer is PETG and the other polymer is polyethylene.

11. Secure element according to any of the preceding claims, characterized in that the carrier polymer is translucent, and so a further second layer (21) arranged under the second layer (22) containing the carrier polymer is perceptible through the carrier polymer.

12. Method for producing a secure element according to any of the preceding claims, with the steps of: a) providing a first material stream (11MS) of a first material with a base polymer which possesses a first color (11F) as base color of the body (10); b) providing at least one second material stream (21MS, 22MS) of a second material with a carrier polymer which possesses a second color (21F, 22F), which is different to the first color (11F), wherein the carrier polymer of the second material stream and the base polymer have different physical properties, so that they do not mix homogeneously; c) uniting the first and the at least one second material streams (11MS, 21MS, 22MS) in an extrusion device (50) to give a layer structure with a base layer (11) which comprises the first material and with at least one color layer (21, 22) which comprises the second material, wherein the layers (11, 21, 22) lie one atop another in varying thickness distributions vertically with respect to the visible surface (12) of the body (10) and form nonuniformly distributed color surface regions (23), as a result of which, in plan view onto the body (10), a randomized polychromatism is apparent.

13. Method according to Claim 12, in which the extrusion device (50) is supplied with the first material stream (11MS) from a first extruder (110) and with the second material stream (21MS, 22MS) from at least one second extruder (210, 220).

14. Method according to either of Claims 12 and 13, in which the first material stream (11MS) and the second material stream (21MS, 22MS) in the extrusion device (50), more particularly a compression facility (320) and / or a feed block (300) and / or a die (310) of the extrusion device (50), are exposed to a melt pressure of between 10 and 100 bar, preferably 10 and 60 bar, and most preferably 20 to 50 bar.

15. Method according to any of Claims 12 to 14, characterized in that in the uniting of the material streams (11MS, 21MS, 22MS), material flow irregularities of the material streams (21MS, 22MS) of the second material are permitted which bring about nonuniform distribution of the carrier polymers of the second layers (21, 22).