Laminated card comprising a thermochromic pattern and method for manufacturing such a card

Abstract

The invention relates to a laminated card and a method for manufacturing such a card. The card comprises, in order: a thermoplastics backing layer (100); an adhesive layer (101); a primer layer (102); a thermochromic pattern (103) which is printed using a thermochromic ink; and a plastics protective layer (104). The primer layer is suitable for the thermochromic ink, enabling good adhesion of the thermochromic pattern to the lower layers, i.e. to the backing layer via the adhesive layer. The adhesive layer (101) and the primer layer (102) are both water-based or both polymerised under UV radiation. The thermochromic ink comprises a liquid crystal compound.

Description

[0001] Description

[0002] Title of the invention: Laminated card comprising a thermochromic pattern and method of manufacturing such a card

[0003] Technical field of the invention

[0004] The present invention relates to a laminated card and a method of manufacturing such a card.

[0005] The invention particularly relates to a card adapted to contain information. Such a card may be a means of identification, for example an identity card, or a means of payment, such as a payment card.

[0006] State of the art

[0007] A common problem with this type of card intended to contain information, particularly personal information, is ensuring a high level of security.

[0008] In this context, document EP 3045321 discloses a card and a method of manufacturing it. The card comprises a plurality of laminated layers. At least one thermochromic pattern is printed on one of the layers, said thermochromic pattern having a thermochromic ink composition comprising leuco dye.

[0009] Such a thermochromic ink exhibits a first color when its temperature is within a given temperature range, and becomes transparent when its temperature is outside said given temperature range.

[0010] It is thus possible to print a pattern using thermochromic ink that one wishes to make visible or invisible depending on the temperature and in particular visible when the card has a temperature within the given temperature range. This pattern can be, for example, a security code, such as a cryptogram or CW code (card validation code) of a payment card. The pattern becomes visible by changing color when its temperature is outside the temperature range. To do this, the pattern is for example heated.

[0011] Thermochromic inks containing leuco dye have the disadvantage of having a slow activation time, i.e. the time required to change from their single color to transparency. In addition, this type of thermochromic ink only allows a change in opacity of a single color.

[0012] Statement of the invention

[0013] The present invention aims to provide a laminated card and a method of manufacturing said card comprising at least one thermochromic pattern having a rapid activation time.

[0014] To this end, it offers, according to a first aspect, a laminated card comprising in order:

[0015] - a thermoplastic support layer;

[0016] - a layer of adhesive;

[0017] - a bonding layer;

[0018] - a thermochromic pattern printed using a thermochromic ink; and

[0019] - a plastic protective layer, the adhesive layer and the bonding layer both being water-based or polymerizing under ultraviolet radiation, said thermochromic ink comprising a liquid crystal compound.

[0020] Preferably, the thermochromic ink does not comprise a leuco-dye.

[0021] The primer layer is adapted to the thermochromic ink. It is thus configured to allow good adhesion of the thermochromic pattern (ink) to the lower layers, therefore to the support layer via the adhesive layer.

[0022] Thanks to its particular structure, the resulting card has very good mechanical properties while incorporating a thermochromic pattern with a rapid activation time (of the order of one or two seconds). In addition, a multiple color change is obtained depending on the temperature thanks to liquid crystal technology, unlike a card comprising a thermochromic pattern with leuco-dye which only allows the change of a single color towards transparency.

[0023] The thermochromic pattern can be used to mask information, for example security data on a payment card. This information only becomes visible if the thermochromic pattern is heated to a certain temperature, called the activation temperature.

[0024] The thermochromic pattern may cover the entire surface of the card. Alternatively, the thermochromic pattern may cover a continuous or discontinuous portion of the card surface. The thermochromic pattern may be a design, one or more characters, a colored area, etc. The surface of the card corresponds to the surface of the support layer.

[0025] The stacking and choice of the different layers allows good adhesion between the layers, in particular improved mechanical strength of the thermochromic pattern on the thermoplastic support layer, including resistance to tearing or degradation of the protective layer. Several adhesion interfaces are in fact formed for this. A first adhesion interface is formed by the adhesive layer and the support layer. Conventional adhesives (water-based or UV-based) offering effective adhesion can be used. A second adhesion interface is formed between the adhesive layer and the thermochromic pattern, thanks to the adhesion layer. The adhesion layer is adapted to the thermochromic ink to allow good adhesion of the thermochromic pattern.The invention provides for the use of an adhesive layer and a bonding layer of the same type (of the same base) in order to guarantee compatibility between the layers as well as high adhesion between the two layers, and consequently between the thermochromic pattern and the support layer.

[0026] The peel force between the different layers of the card is preferably at least 3.5 N. This peel force can be measured by tests and following known standards, in particular ISO 10373-1, ISO24-78962, or ISO 3225-19.

[0027] Finally, the different layers, particularly the adhesive layer and the bonding layer, are chosen so as not to damage the liquid crystals and thus preserve the thermochromic pattern.

[0028] According to one characteristic, liquid crystals are chiral nematic liquid crystals.

[0029] According to one characteristic, the liquid crystals are contained in microcapsules, said microcapsules having a diameter of less than 50 microns, preferably between 5 and 15 microns.

[0030] The thermochromic pattern can thus dry quickly.

[0031] Liquid crystal microcapsules consist of about 80% oleic liquid crystal mixture inside the microcapsules and about 20% dry microcapsule wall material.

[0032] According to one feature, the primer layer and the thermochromic ink comprise the same compound. This presence of a common compound ensures that the primer layer is suitable for the thermochromic ink. The compound is notably other than water, acrylic resin and liquid crystal microcapsules, which traditionally form thermochromic ink.

[0033] Preferably, each of the primer layer and the thermochromic ink comprises at least 10% of said same compound.

[0034] According to one feature, the liquid crystal compound constitutes between 10 and 30% by weight of the thermochromic ink (used to form the thermochromic pattern), preferably 20% by weight of the thermochromic ink.

[0035] According to one characteristic, the thermochromic ink and the bonding layer are acrylic matrix.

[0036] The choice of the same matrix, in particular the acrylic matrix, respectively for the thermochromic ink and the bonding layer, allows for good compatibility and good adhesion between the layers. According to one characteristic, the card further comprises a non-thermochromic pattern printed using a water-based ink or an ink curing under ultraviolet radiation, the non-thermochromic pattern being printed on the support layer before the adhesive layer.

[0037] Printing the non-thermochromic pattern onto the backing layer before printing the adhesive layer prevents the ink from migrating from the non-thermochromic pattern to the liquid crystals and thus degrading them. The adhesive layer and the primer layer form an effective double barrier between the thermochromic pattern carrying the liquid crystals and the non-thermochromic pattern.

[0038] Furthermore, liquid crystals are transparent when their temperature is not within a predefined temperature range, and in particular when it is below or above the activation temperature. Liquid crystals can therefore advantageously be printed on a light-colored non-thermochromic pattern without requiring the non-thermochromic pattern to be delimited by a resist or knockout.

[0039] The laminated card may be a smart card. It preferably conforms to the ID-1 format, with or without a chip.

[0040] The invention proposes, according to a second aspect, a method of manufacturing a laminated card comprising the following steps:

[0041] - Provide a thermoplastic support layer;

[0042] - Apply a layer of adhesive to the support layer;

[0043] - Apply a primer layer to the dried adhesive layer, the adhesive layer and the primer layer preferably both being water-based or both polymerizing under ultraviolet radiation;

[0044] - Printing a thermochromic pattern on the dried primer layer using a thermochromic ink, said thermochromic ink comprising a liquid crystal compound;

[0045] - Place a protective layer of plastic on the dried thermochromic pattern; and

[0046] - Laminating the assembly. According to one feature, the method comprises, after the step of providing the support layer and before the step of depositing the adhesive layer, a step of printing a non-thermochromic pattern on the support layer using a water-based ink or an ink polymerizing under ultraviolet radiation.

[0047] According to one feature, the step of laminating comprises the substeps:

[0048] - hot rolling at a temperature between 120°C and 160°C, preferably 125°C, and a pressure between 30 N / cm 2 and 200 N / cm 2 , preferably 120 N / cm 2 ; Then

[0049] - cold rolling at a temperature between 10°C and 20°C, preferably at 15°C, and a pressure between 50 N / cm 2 and 300 N / cm 2 , preferably 100 N / cm 2 .

[0050] According to one feature, to manufacture a laminated card having a thermochromic pattern having an activation temperature Ti, said thermochromic printing ink before hot lamination has an activation temperature To = Ti + 8, where 8 is between 2 and 5 degrees Celsius (for example 3 or 4 °C).

[0051] It is thus possible to choose and adapt the thermochromic ink before lamination according to the desired activation temperature Ti after lamination. The inventors have in fact noted that the difference 8 between the activation temperature To before lamination and the temperature Ti after lamination is due to the high pressure and temperature to which the thermochromic pattern is subjected during the lamination step.

[0052] Brief description of the figures

[0053] Other features and advantages of the invention will become apparent in the description below with reference to the appended drawings, given as non-limiting examples:

[0054] - Figure 1 is a schematic representation of the front of a laminated card; - Figure 2 is a schematic representation of the back of the laminated card of Figure 1;

[0055] - Figure 3 is a schematic view, in section, of a laminated card according to one embodiment of the invention; and

[0056] - Figure 4 is a schematic view, in section, of a laminated card according to another embodiment of the invention.

[0057] Detailed description

[0058] Figures 1 and 2 schematically represent a card, in particular a payment card 1 .

[0059] Card 1 here has a typical ID-1 format, corresponding to the format of payment cards.

[0060] The payment card 1 comprises a front face 10, shown in figure 1, and a back face 11 shown in figure 2.

[0061] The payment card 1 conventionally includes several printed pieces of information. The front side 10 of the payment card includes, for example, the card number referenced 12, the name of the cardholder referenced 13, and the expiry date of the card referenced 14. The back side 11 of the payment card includes other types of information, for example a cryptogram or security code enabling the holder to be identified.

[0062] Board 1 may include a chip in the form of a flush contact chip module (not shown).

[0063] Figure 3 represents a schematic section of the payment card 1 according to one embodiment of the invention.

[0064] Payment card 1 comprises several stacked layers. Payment card 1 is laminated. In other words, the layers of payment card 1 undergo lamination, i.e., heat and pressure treatment of the different layers to permanently assemble them to form an object (here the payment card).

[0065] The payment card 1 comprises a support. The support comprises at least one layer, called the support layer 100. The support here comprises two PVC support layers 100 attached, by gluing, to an inlay layer or substrate. A first support layer 100 serves as a base for the front 10 of the payment card 1. A second support layer 100 serves as a base for the back 11 of the payment card 1.

[0066] The support is made of thermoplastic material, or in other words the support layers 100 are made of thermoplastic material.

[0067] The thermoplastic material is preferably polyvinyl chloride (PVC). The carrier is, for example, polyvinyl chloride (PVC). The thermoplastic material can alternatively be selected from the following group of materials: Acrylonitrile butadiene styrene (ABS), Polyvinyl chloride (PVC), Polycarbonate (PC), Polyethylene terephthalate (PET), Polyetheretherketone (PEEK), Polyethylene naphthalate (PEN), PLA (polylactic acid), PBS (polybutylene succinate), PA (polyamide). Other examples are possible.

[0068] The support is preferably dark in color, for example black.

[0069] The front 10 and the back 11 of the payment card 1 have substantially the same structure here. The description of the layers constituting the front 10 of the payment card 1 therefore also applies to the back 11 of the payment card 1.

[0070] The front of the payment card 1 comprises an adhesive layer 101 and a bonding layer or primer layer 102.

[0071] The adhesive layer 101 extends over the backing layer 100.

[0072] The adhesive layer 101 may cover all or part of one face of the support layer 100.

[0073] The bonding layer 102 extends over the adhesive layer 101. The bonding layer 102 may cover all or part of one face of the first adhesive layer 101.

[0074] The adhesive layer 101 and the bonding layer 102 are different.

[0075] The adhesive layer 101 and the bonding layer 102 are both preferably water-based or polymerized under ultraviolet radiation. The adhesive layer 101 and the bonding layer 102 thus have the same base, which ensures good compatibility and good adhesion between these layers.

[0076] The water-based adhesive for adhesive layer 101 has the advantage of liquefying slightly when laminated, thus allowing good adhesion between the layers between which the adhesive is applied.

[0077] The adhesive layer 101 and the bonding layer 102 are, for example, made of an acrylic matrix.

[0078] The front 10 of the payment card also includes a thermochromic pattern 103. A thermochromic pattern is a pattern whose color changes depending on its temperature.

[0079] The thermochromic pattern 103 here extends over the entire surface of the card. By varying from this flatness, the thermochromic pattern 103 can be partial. The thermochromic pattern 103 can thus constitute a local pattern such as an inscription and / or a shape. In such an embodiment, the adhesive layer 101 and the bonding layer 102 are preferably local, extending so as to cover at least the same area as the thermochromic pattern 103.

[0080] The thermochromic pattern 103 is printed on the primer layer 102. The thermochromic pattern 103 is printed using a thermochromic ink. The primer layer 102 is adapted to the thermochromic ink used, in order to ensure good adhesion of this ink (and therefore of the thermochromic pattern 103 formed) on the lower layer 101.

[0081] The thermochromic ink is preferably an acrylic ink. The thermochromic ink is thus compatible with the adhesive layer 101 and the bonding layer 102.

[0082] The thermochromic ink used is preferably water-based, as solvent-based inks are likely to damage the microcapsules.

[0083] The thermochromic ink uses a liquid crystal type active ingredient. In other words, the thermochromic ink comprises liquid crystal compounds, in particular in the form of liquid crystal microcapsules. The thermochromic ink is typically an aqueous solution which comprises, in addition to water, liquid crystals, acrylic resin and possible pigments. The bonding layer 102 is adapted to the thermochromic ink in that they comprise the same compound distinct from those above, in a proportion of at least 10% by weight, preferably between 10 and 30% by weight, typically 20%.

[0084] Liquid crystal phases constitute an intermediate state existing between the crystalline solid and the fully disordered liquid phase.

[0085] The liquid crystals here are chiral nematic liquid crystals, or cholesteric liquid crystals.

[0086] Liquid crystals are microencapsulated in ink. Specifically, a mixture containing liquid crystals is microencapsulated in ink. Typical liquid crystal mixtures contain several chemicals and are optically active oil-based mixtures. During the microencapsulation process, droplets of oil-based liquid crystal mixtures are surrounded by a polymer coating to form microcapsules with diameters between 5 and 15 microns. The process then involves combining the microcapsules with polymers or resins and water to make the ink.

[0087] Thermochromic ink thus contains microcapsules enclosing the liquid crystals in an acrylic matrix, namely an aqueous base integrating an acrylic resin and possible pigments. Liquid crystal microcapsules consist of approximately 80% of an oleic liquid crystal mixture inside the microcapsules and approximately 20% of dry material from the microcapsule walls.

[0088] Documents FR2322914, FR2361456, US 4149413 and FR2386594 describe examples of liquid crystal type mixtures that can be used. Document US 3697297 describes an example of micro-encapsulated liquid crystals that can be used.

[0089] Liquid crystal ink selectively reflects incident light. Liquid crystals change color when a certain temperature, called the activation temperature, is reached and continues to change with increasing temperature. Liquid crystals are transparent when their temperature is outside a predefined temperature range, the lower limit of which is the activation temperature, and the upper limit is a temperature called the deactivation temperature. Liquid crystals are thus transparent when their temperature is below the activation temperature or above the deactivation temperature. Liquid crystals take on different colors of the visible spectrum when their temperature is within the predefined temperature range. Within the predefined temperature range, liquid crystals change, in particular, from red to blue as the temperature increases.

[0090] Thanks to the liquid crystals in the thermochromic ink, the thermochromic pattern 103 changes color depending on its temperature.

[0091] The color change of thermochromic ink is reversible. In other words, the color change is observed in the opposite direction when the temperature decreases.

[0092] The color change of the thermochromic ink is repeatable as desired. Further heating beyond the activation temperature will cause the color of the thermochromic pattern 103 to change again.

[0093] The dark, preferably black, layer of the support layers 100 ensures good visibility of the colors reflected by the liquid crystal ink.

[0094] The bonding layer 102 ensures good adhesion of the thermochromic pattern 103 to the support layer 100.

[0095] The bonding layer 102 extending between the adhesive layer 101 and the thermochromic pattern 103, furthermore makes it possible to create a protective barrier for the thermochromic pattern 103. In other words, the bonding layer 102 makes it possible to protect the thermochromic pattern 103 from the compounds of the adhesive layer 101.

[0096] In another exemplary embodiment, a second bonding layer 102 could also be deposited between the thermochromic pattern 103 and the protective layer 104.

[0097] The front 10 of the payment card 1 also includes a protective layer 104, also called an overlay. The protective layer 104 covers the thermochromic pattern 103.

[0098] The protective layer 104 has the same dimensions and shape as the support.

[0099] The protective layer 104 is for example a film.

[0100] The protective layer 104 is made of thermoplastic material.

[0101] The protective layer 104 is preferably a plastic film. The protective layer 104 may be, for example, made of polyvinyl chloride (PVC), polycarbonate (PC) or polyethylene terephthalate glycol (PETG).

[0102] The protective layer 104 is coated to enable its adhesion to the rest of the payment card. The protective layer 104 is in particular coated with a water-based adhesive.

[0103] The protective layer 104 is configured to protect the payment card from wear. The protective layer 104 also protects the thermochromic pattern.

[0104] The protective layer 104 may be UV-treated or include UV absorbers to protect the liquid crystals of the thermochromic pattern from alteration by UV radiation.

[0105] The back 11 of the payment card 1 here has the same structure as the front 10 with one difference. The back 11 of the payment card 1 further comprises a non-thermochromic pattern 105. A non-thermochromic pattern is understood to mean a pattern printed using a non-thermochromic ink.

[0106] In one variant, the back 11 of the payment card 1 may contain no thermochromic or non-thermochromic printing, or only one of the two.

[0107] Non-thermochromic ink can be water-based ink or UV-curable ink.

[0108] The non-thermochromic pattern 105 is here printed on the second support layer 100.

[0109] Before lamination, the adhesive layer 101, the bonding layer 102 and the thermochromic pattern 103 of the unlaminated card 1 have, for example, a thickness of each between 4 and 10 microns. In particular, the thermochromic pattern 103 has a maximum thickness of 10 microns, preferably between 5 and 10.

[0110] The thickness of the protective layer 104 can vary between 40 and 100 microns. The thickness of the support layer 100 can be up to 350 microns.

[0111] After lamination, payment card 1 loses a total of approximately 5% of its thickness.

[0112] In another exemplary embodiment illustrated in Figure 4, the smart card comprises three support layers 100. A third support layer 100, extending between the first support layer 100 and the second support layer 100, may comprise an RF antenna. This is the case in particular for a dual interface or contactless card, the RF antenna being for example connected to a chip module.

[0113] The manufacturing process of the card, here a payment card 1, is as follows, applicable to one or two sides of the support. This process aims to manufacture a card having a thermochromic pattern whose activation temperature is Ti and the deactivation temperature is Ti'.

[0114] The assembly of the front 10 or back 11 of the payment card 1 is carried out as follows.

[0115] A first step of the method consists of providing one of the support layers 100.

[0116] The adhesive layer 101 is deposited on the support layer 100.

[0117] A first drying step then takes place in which the adhesive layer 101 is dried.

[0118] The bonding layer 102 is deposited on the dry adhesive layer 101.

[0119] A second drying step then takes place in which the bonding layer 102 is dried.

[0120] The thermochromic pattern 103 is then printed on the dry bonding layer 102.

[0121] The adhesive layer 101, the bonding layer 102 and the thermochromic pattern 103 are for example deposited or printed by screen printing, in a coating machine, in flexography, in lithography, in gravure printing or in typography.

[0122] The thermochromic ink used here has an activation temperature To = Ti + 8 and a deactivation temperature is To' = Ti' + 8. 8 is between 2 and 5 degrees Celsius, typically 3°C.

[0123] A third drying step takes place in which the thermochromic pattern 103 is dried.

[0124] The protective plastic layer 104 is then deposited on the thermochromic pattern 103.

[0125] The protective layer 104 also makes it possible to protect the thermochromic pattern 103 in order to prevent it from deteriorating during friction that it may be subjected to, for example to increase its temperature.

[0126] For the back 11 of the payment card 1, two intermediate steps take place after the step of providing the second support layer 100. First, the non-thermochromic pattern 105 is printed on the second support layer 100. A step of drying the non-thermochromic pattern 105 then takes place.

[0127] The non-thermochromic pattern 105 printed at this stage allows it to be separated from the thermochromic pattern 103 by two layers (the adhesive layer 101 and the bonding layer 102). The two layers thus act as a barrier to prevent the non-thermochromic pattern 105 from damaging the liquid crystals.

[0128] The drying stages each last at least 8 hours, preferably 24 hours.

[0129] The drying temperature is chosen according to the thermochromic ink. A minimum temperature is set to ensure the drying function and a maximum temperature is set to avoid degrading the support layer. For example, the drying steps are each carried out between 60°C and 70°C, preferably at 65°C.

[0130] The assembly formed by these layers and patterns, and forming the front 10 or the back 11 of the payment card 1 is finally laminated.

[0131] Lamination is carried out under pressure, first hot and then cold. The lamination parameters, in particular temperature and pressure, are chosen so as not to damage the liquid crystals.

[0132] Hot lamination is carried out at a pressure between 30N / cm 2 and 200 N / cm 2 preferably 120 N / cm 2 .

[0133] Hot lamination is carried out at a temperature between 120°C and 160°C, preferably at 125°C.

[0134] Cold lamination is carried out at a pressure between 50N / cm 2 and 300N / cm 2 , preferably 100 N / cm 2

[0135] Cold lamination is carried out at a temperature between 10°C and 20°C, preferably at 15°C.

[0136] Lamination is carried out over a total period of between 15 and 40 minutes, for example 30 minutes.

[0137] The lamination step lowers the activation temperatures of the thermochromic ink by 8 degrees. Also, the thermochromic pattern obtained after lamination has an activation temperature of approximately Ti and a deactivation temperature of approximately Ti'.

[0138] The steps previously described, except for lamination, are repeated here twice to obtain the front and back of payment card 1.

[0139] When the payment card 1 comprises three support layers 100, the manufacturing method comprises a step of providing the third support layer 100. The third support layer 100 may for example be arranged between the first support layer 100 and the second support layer 100 after stacking the layers of the front 10 and before stacking the layers of the back 11.

[0140] All the steps of printing, layer assembly and lamination are carried out, for example, for large layers or sheets which are cut after lamination into several cards in the desired format, in this case in the ID-1 format. This results in several 1 cards.

[0141] When the card is a smart card, the manufacturing process includes a final step consisting of placing the chip. The chip is placed separately for each card. A cavity is formed in the card, for example using a milling cutter. The cavity is formed over only a few microns. The cavity is formed until it reaches, in particular, the antenna of the third support layer 100. The chip is then placed and glued in the cavity. The contact between the chip and the antenna creates the contact.

[0142] The sequence of payment card manufacturing steps and the parameters at each step were chosen to obtain a card comprising at least one thermochromic pattern 103 and having good resistance. Thanks to these choices, the liquid crystals are not damaged despite the various manufacturing constraints (use of various adhesives which could penetrate the microcapsules, lamination under pressure and at high temperature which could break the liquid crystals) and the payment card has the required resistance properties.

[0143] The obtained payment card 1 can be used in the following ways.

[0144] The thermochromic pattern 103 may be an inscription of security data, for example a security element such as a figure, a symbol, a sequence of characters or a cryptogram. The thermochromic pattern 103 is transparent and not visible when its temperature is outside the predefined temperature range. When the thermochromic pattern 103 is heated or cooled so that its temperature is within the predefined temperature range and in particular reaches the activation temperature, the thermochromic pattern 103 changes color and the security data becomes visible.

[0145] In this way, the security data, for example the cryptogram, are invisible to the naked eye when the temperature is outside the predefined temperature range. The security data are in particular invisible to the naked eye when the temperature is below the activation temperature. A malicious person observing the payment card could not fraudulently obtain the security data since the activation temperature is not reached. If the security data in the form of a thermochromic pattern constitutes personal data, also called variable data because it is specific to each cardholder, such as a payment card verification cryptogram, when the user wishes to know the security data, he simply heats (for example, rubbing) the thermochromic pattern 103 in order to reach the activation temperature.

[0146] If the security data in the form of a thermochromic pattern 103 is an invariable security element, the thermochromic pattern 103 can be revealed at a given temperature so as to verify the authenticity of the payment card 1. The method according to the invention is thus all the more applicable on a large scale, because it does not integrate any individual personalization, the pattern being for example specific to the establishment and / or to the batch of cards, in particular by serial number ranges. Similarly, this embodiment finds an interesting application in the field of identity cards by integrating such thermochromic security data, for example in the form of a design specific to the country. The activation temperature can in this case be chosen to ensure the transparency of the thermochromic pattern 103 under normal conditions of use of the payment card 1. For example, the activation temperature is at least 40°C.The security data printed on the card only becomes visible after exceeding this activation temperature.

[0147] In the various use cases, the security of the payment card is improved in particular because the addition of such a thermochromic pattern considerably limits servile copying and / or the security data is not permanently visible.

[0148] Since thermochromic ink is reversible, the process of revealing or hiding security data can be repeated endlessly, throughout the lifetime of the payment card, depending on the cardholder's usage needs.

[0149] In another exemplary embodiment, the thermochromic pattern 103 can be used to mask security data, whether variable or not, while still allowing large-scale application of the method according to the invention. Thus, for example, in order to mask security data, such as a cryptogram, specific to the cardholder, this security data being printed using a non-thermochromic ink on the card only during a personalization step subsequent to the lamination step, the thermochromic pattern 103 can constitute an area under the security data to be printed in personalization. The support and the security data are preferably of the same color so that the security data are not visible outside the predefined temperature range of the thermochromic pattern 103.The choice of the black color makes it possible in particular to improve the contrast when the thermochromic ink is within the predefined temperature range. The security data is then printed superimposed on the thermochromic pattern 103 so as to make the security data invisible, outside the predefined temperature range, which are then printed in the same color as the support, the inactive thermochromic pattern 103 being transparent, and so as to reveal the printed security data when the temperature makes the thermochromic pattern 103 active by making it change color. The thermochromic pattern 103 is transparent when its temperature is outside the predefined temperature range and “under-masks” the security data. The thermochromic pattern 103 is colored and reveals the security data when its temperature is within the predefined temperature range.In order to make the thermochromic pattern transparent and conceal the security data, the thermochromic pattern 103 is cooled so that its temperature is lower than the activation temperature or heated so that its temperature is higher than the deactivation temperature. Similarly, this embodiment finds an interesting application in particular for identity cards.

[0150] The predefined temperature range can in this case be chosen to correspond to a normal temperature range for using the payment card, by adjusting the properties of the thermochromic ink. Cholesteric phase liquid crystals have a helical structure. The transition temperature depends in particular on the pitch of the helix. Changing the helix pitch of the liquid crystals thus makes it possible to change the activation temperature of the thermochromic pattern 103.

[0151] The normal temperature range of the payment card is understood to mean, for example, a temperature range between 0 and 40° Celsius, which corresponds to the possible ambient temperature range in which the payment card 1 is used. The security data printed on the card then only become visible outside this normal temperature range of the card.

[0152] The heating of the thermochromic pattern 103 can be carried out in various ways, for example by rubbing the thermochromic pattern 103 with a finger or by placing the payment card 1 or at least the area of ​​the thermochromic pattern 103 in a warm environment. The cooling of the first pattern can be carried out by stopping the heating, for example by stopping the rubbing with the finger. The cooling of the thermochromic pattern 103 can also be carried out by placing the payment card 1 in a cold environment.

[0153] The invention provides a card with improved security, while allowing easy and convenient use, particularly thanks to the rapid activation of the thermochromic pattern. The smart card also has the advantage of having good mechanical properties.

[0154] Other variations not shown are mentioned below.

[0155] The chip card can be of a type other than a payment card, for example an identity card, a badge, or a transport ticket, etc.

[0156] The substrate may comprise a single support layer common to both the front and back of the card. In other words, a single substrate may be used without an additional support layer, said substrate then acting as a support layer for the deposition and printing of other layers.

[0157] The described smart card includes a thermochromic pattern on each of the front and back. The card may include a different number of thermochromic patterns. For example, the card may include one or more thermochromic patterns on only the front or back. The front and back of the smart card may have the same layer and pattern structure.

[0158] The smart card may include other elements, including personalization, figures or information made on the protective layer. These elements can be printed on the protective layer after lamination.

[0159] The smart card may further comprise an ultraviolet filter configured to protect the thermochromic pattern from ultraviolet radiation. The ultraviolet filter is, for example, integrated into the protective layer. The protective layer may comprise, for example, an ultraviolet absorber. Alternatively, the ultraviolet filter may be a separate layer from the protective layer. The smart card may comprise an ultraviolet filter between the protective layer and the thermochromic pattern.

Claims

DEMANDS 1. Laminated card containing, in order: - a thermoplastic support layer (100); - a layer of adhesive (101); - a bonding layer (102); - a thermochromic pattern (103) printed using thermochromic ink; and - a protective layer (104) of plastic, the adhesive layer (101) and the tack layer (102) both being water-based or both being cured under ultraviolet radiation, said thermochromic ink comprising a liquid crystal compound.

2. Map according to claim 1, wherein the liquid crystals are chiral nematic liquid crystals.

3. Card according to claim 2, wherein the liquid crystals are contained in microcapsules, said microcapsules having a diameter of less than 50 microns, preferably between 5 and 15 microns.

4. Card according to any one of claims 1 to 3, wherein the tack layer (102) and the thermochromic ink comprise the same compound.

5. Card according to claim 4, wherein the liquid crystal compound constitutes between 10 and 30% by weight of the thermochromic ink, preferably 20% by weight of the thermochromic ink.

6. Card according to any one of claims 1 to 5, wherein the thermochromic ink and the tack layer (102) are acrylic matrix.

7. Card according to any one of claims 1 to 6, wherein the card is a smart card.

8. Process for manufacturing a laminated card comprising the following steps: - Provide a thermoplastic support layer (100); - Apply a layer of adhesive (101) to the support layer (100); - Deposit a tack coat (102) on the dried adhesive layer (101), the adhesive layer (101) and the tack coat (102) both being water-based and / or both being cured under ultraviolet radiation; - Print a thermochromic pattern (103) on the dried tack layer (102) using a thermochromic ink, said thermochromic ink comprising a liquid crystal compound; - Apply a protective layer (104) of plastic to the dried thermochromic pattern (103); and - Laminate the whole thing.

9. A method according to claim 8, wherein the rolling step comprises the following substeps: - hot rolling at a temperature between 120°C and 160°C, preferably at 125°C, and a pressure between 30 N / cm 2 and 200 N / cm 2 , preferably 120 N / cm 2 ; Then - cold rolling at a temperature between 10°C and 20°C, preferably at 15°C, and a pressure between 50 N / cm 2 and 300 N / cm 2 , preferably 100 N / cm 2 .

10. A method according to claim 8 or claim 9 for manufacturing a laminated card (1) having a thermochromic pattern (103) with an activation temperature Ti, wherein said thermochromic printing ink prior to hot lamination has a activation temperature To = Ti + 8, where 8 is between 2 and 5 degrees Celsius.

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