Laminated cards containing thermochromic patterns and methods for making such cards
The laminated card with a thermoplastic support, adhesive, and tie layers using liquid crystal compounds addresses slow activation and limited color change issues, offering fast and reversible color changes for enhanced security and mechanical strength.
Patent Information
- Application Number
- JP2024573581
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-09-02
- Publication Date
- 2025-09-09
AI Technical Summary
Existing laminated cards with thermochromic patterns using leuco dyes suffer from slow activation times and limited color change, posing security risks due to the visibility of sensitive information outside the intended temperature range.
A laminated card structure comprising a thermoplastic support layer, adhesive and tie layers, and a thermochromic pattern using liquid crystal compounds, which allows for fast activation and multiple color changes based on temperature, with improved adhesion and mechanical strength through compatible adhesive and tie layers.
The solution provides a laminated card with a thermochromic pattern that activates quickly and changes color reversibly, enhancing security by ensuring sensitive information remains hidden outside the predefined temperature range, while maintaining mechanical integrity.
Smart Images
Figure 2025529618000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to laminated cards and processes for making such cards.
[0002] The invention is particularly directed to cards suitable for containing information, such cards may be identification means, for example identity cards or payment means such as payment cards. [Background technology]
[0003] A common challenge with this type of card, which is intended to contain information, especially personal information, is ensuring a high level of security.
[0004] In this regard, document EP 3045321 discloses a card and a manufacturing process thereof, the card comprising a plurality of laminate layers, at least one thermochromic pattern being printed on one of the layers, said thermochromic pattern comprising a thermochromic ink composition containing a leuco dye.
[0005] Such thermochromic ink exhibits a first color when its temperature is within a predetermined temperature range and is clear when its temperature is outside the predetermined temperature range.
[0006] In this way, thermochromic inks can be used to print patterns that are desired to become visible or invisible depending on the temperature, in particular to become visible when the temperature of the card is within a certain temperature range. This pattern can be, for example, a security code such as a payment card code or CVV (card verification code) code. The pattern becomes visible by changing color as soon as its temperature falls outside the temperature range. For this purpose, the pattern can be, for example, heated.
[0007] Thermochromic inks containing leuco dyes have the disadvantage of slow activation times, i.e., the time required to change from their single color to transparent. Furthermore, this type of thermochromic ink can only change the opacity of one color. Summary of the Invention [Problem to be solved by the invention]
[0008] The present invention is directed to providing a laminated card containing at least one thermochromic pattern with a fast activation time and a process for producing said card. [Means for solving the problem]
[0009] To this end, the present invention provides, according to a first aspect, a laminated card comprising, in order: a thermoplastic support layer; an adhesive layer; a binding layer; - a thermochromic pattern printed by thermochromic ink; - With protective plastic layer wherein the adhesive layer and the tie layer are both water-based or both polymerizable under ultraviolet radiation, and the thermochromic ink comprises a liquid crystal compound.
[0010] Preferably, the thermochromic ink is leuco dye-free.
[0011] The tie layer is suitable for thermochromic inks and is therefore configured to allow good adhesion of the thermochromic pattern (ink) to the underlying layer, and therefore the support layer, via the adhesive layer.
[0012] The resulting card, due to its particular structure, exhibits very good mechanical properties while incorporating a thermochromic pattern with a fast activation time (on the order of 1 or 2 seconds).
[0013] Additionally, unlike cards containing thermochromic patterns that use leuco dyes, which only allow for a change from a single color to a transparent color, the liquid crystal technology allows for multiple color changes depending on the temperature.
[0014] Thermochromic patterns can be used to mask information, such as security data on a payment card, that becomes visible only when the thermochromic pattern is heated to a specific temperature, called the activation temperature.
[0015] The thermochromic pattern may completely cover the surface of the card. Alternatively, the thermochromic pattern may cover a continuous or discontinuous portion of the surface of the card. The thermochromic pattern may be a design, one or more letters, a colored area, etc. The surface of the card corresponds to the surface of the support layer.
[0016] The stacking and selection of the various layers allows for good adhesion between the layers, improving the mechanical strength of the thermochromic pattern on the thermoplastic support layer, and in particular the resistance to tearing or deterioration of the protective layer, since several adhesive interfaces are formed for this purpose. The first adhesive interface is formed by the adhesive layer and the support layer.
[0017] Conventional adhesives (water-based or UV-based) that provide effective adhesion can also be used. A second adhesive interface is formed between the adhesive layer and the thermochromic pattern by a tie layer. The tie layer is compatible with thermochromic inks to allow good adhesion of the thermochromic pattern.
[0018] The present invention provides for the use of adhesive and tie layers of the same type (same base) to ensure compatibility between the layers and high adhesion between the two layers and consequently between the thermochromic pattern and the support layer.
[0019] The peel strength between the various layers of the card is preferably at least 3.5 N. This peel strength can be measured according to known standards, in particular according to the tests of standards ISO 10373-1, ISO 24-78962 or ISO 3225-19 and beyond.
[0020] Finally, the various layers, particularly the adhesive and tie layers, are selected so as not to damage the liquid crystal and thus protect the thermochromic pattern.
[0021] According to one feature, the liquid crystal is a chiral nematic liquid crystal.
[0022] According to one feature, the liquid crystal is contained in microcapsules, said microcapsules having a diameter of less than 50 microns, preferably between 5 and 15 microns.
[0023] Therefore, the thermochromic pattern dries quickly.
[0024] The liquid crystal microcapsules consisted of approximately 80% oleic acid liquid crystal mixture inside the microcapsules and approximately 20% dry microcapsule wall material.
[0025] According to one feature, the tie layer and the thermochromic ink contain the same compound. The presence of such a common compound ensures that the tie layer is compatible with the thermochromic ink. The compound is, in particular, other than the water, acrylic resin, and liquid crystal microcapsules that conventionally form thermochromic inks.
[0026] Preferably, the tie layer and the thermochromic ink each contain at least 10% of said same compound.
[0027] According to one feature, the liquid crystal compound constitutes 10% to 30% by weight of the thermochromic ink (used to form the thermochromic pattern), preferably 20% by weight of the thermochromic ink.
[0028] According to one feature, the thermochromic ink and tie layer have an acrylic matrix.
[0029] By choosing the same matrix, especially an acrylic matrix, for the thermochromic ink and the tie layer respectively, it is possible to have good compatibility and good adhesion between the layers.
[0030] According to one feature, the card additionally comprises a non-thermochromic pattern printed with a water-based ink or an ink that is polymerizable under ultraviolet radiation, the non-thermochromic pattern being printed on the support layer before the adhesive layer.
[0031] Printing the non-thermochromic pattern onto the support layer before printing the adhesive layer prevents ink migration from the non-thermochromic pattern to the liquid crystal, and therefore prevents degradation of the liquid crystal, because the adhesive and tie layers effectively form a double barrier between the thermochromic pattern bearing the liquid crystal and the non-thermochromic pattern.
[0032] Additionally, the liquid crystal is transparent when its temperature is not within a predefined temperature range, particularly below or above the activation temperature, and therefore the liquid crystal can be advantageously printed onto a light-colored, non-thermochromic pattern without the need to separate the non-thermochromic pattern with a resist or knockout.
[0033] The laminated card may be a smart card, preferably according to the ID-1 format, with or without a chip.
[0034] According to a second aspect, the present invention provides a process for producing a laminated card, comprising: - providing a thermoplastic support layer; - depositing an adhesive layer on a support layer; - depositing a tie layer on the dried adhesive layer, the adhesive layer and the tie layer being preferentially both water-based or both polymerizable under ultraviolet radiation; - printing a thermochromic pattern on the dried tie layer with a thermochromic ink, the thermochromic ink comprising a liquid crystal compound; - depositing a protective plastic layer on the dried thermochromic pattern; - laminating the assembly; The present invention provides a process including:
[0035] According to one feature, the process comprises, after the step comprising providing a support layer and before the step comprising depositing an adhesive layer, a step comprising printing a non-thermochromic pattern on the support layer by means of a water-based ink or an ink polymerizable under ultraviolet radiation.
[0036] According to one feature, the step comprising laminating comprises: - 120°C to 160°C, preferably 125°C, and 30 N / cm 2 ~200N / cm 2 , preferably 120N / cm 2 A partial process of hot laminating under pressure, then - 10°C to 20°C, preferably 15°C, and 50 N / cm 2 ~300N / cm 2 , preferably 100N / cm 2 Partial process of cold laminating under pressure Includes.
[0037] According to one feature, to produce a laminated card, the thermochromic pattern of which exhibits an activation temperature T1, the thermochromic printing ink exhibits an activation temperature T0=T1+δ before hot lamination, where δ is between 2°C and 5°C (e.g., 3°C or 4°C).
[0038] This allows the pre-lamination thermochromic ink to be selected and adapted depending on the desired activation temperature T1 after lamination, since the inventors have recognized that the difference δ between the pre-lamination activation temperature T0 and the post-lamination temperature T1 is due to the high pressure and high temperature experienced by the thermochromic pattern during the lamination process.
[0039] Other characteristic features and advantages of the invention will become more apparent from the following description, given by way of non-limiting example with reference to the accompanying drawings, in which: [Brief explanation of the drawings]
[0040] [Figure 1] FIG. 1 is a schematic diagram of the front of a laminated card. [Figure 2] FIG. 2 is a schematic diagram of the back of the laminated card of FIG. 1. [Figure 3] 1 is a schematic cross-sectional view of a laminated card according to one embodiment of the present invention; [Figure 4] 1 is a schematic cross-sectional view of a laminated card according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0041] 1 and 2 schematically represent a card, in particular a payment card 1. FIG.
[0042] Card 1 presents in this example a typical ID-1 format corresponding to the format of a payment card.
[0043] The payment card 1 includes a front side 10 shown in FIG. 1 and a back side 11 shown in FIG.
[0044] A payment card 1 conventionally includes several printed items of information. The front side 10 of the payment card includes, for example, the card number, indicated at 12, the cardholder's name, indicated at 13, and the card's expiration date, indicated at 14. The back side 11 of the payment card includes other types of information to enable the holder to be identified, such as a cryptogram or security code.
[0045] The card 1 may include a chip in the form of a flat contact chip module (not shown).
[0046] FIG. 3 shows a schematic cross-sectional view of a payment card 1 according to one embodiment of the present invention.
[0047] Payment card 1 includes several stacked layers. Payment card 1 is laminated. In other words, the layers of payment card 1 undergo lamination, a heat treatment under pressure of the various layers, to permanently assemble them and form an object (in this example, the payment card).
[0048] The payment card 1 includes a support. The support includes at least one layer called support layer 100. The support includes, in this example, a two-layer PVC support 100 adhesively bonded to an inlay or substrate layer. The first support layer 100 serves as the base for the front side 10 of the payment card 1. The second support layer 100 serves as the base for the back side 11 of the payment card 1.
[0049] The support is made of a thermoplastic material, or in other words the support layer 100 is made of a thermoplastic material.
[0050] The thermoplastic material is preferably polyvinyl chloride (PVC). The support is, for example, made of polyvinyl chloride (PVC). Alternatively, the thermoplastic material may be selected from the group consisting of the following materials: acrylonitrile-butadiene-styrene (ABS), polyvinyl chloride (PVC), polycarbonate (PC), polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyethylene naphthalate (PEN), PLA (polylactic acid), PBS (polybutylene succinate) and PA (polyamide). Other examples are also possible.
[0051] The support is preferably dark in colour, for example black.
[0052] The front 10 and back 11 of payment card 1 in this example exhibit substantially the same structure, and therefore the description of the layers making up front 10 of payment card 1 also applies to back 11 of payment card 1.
[0053] The front surface of the payment card 1 comprises an adhesive layer 101 and a tie or primer layer 102 .
[0054] An adhesive layer 101 extends over the support layer 100 .
[0055] The adhesive layer 101 can cover all or part of the surface of the support layer 100 .
[0056] The bonding layer 102 extends over the adhesive layer 101. The bonding layer 102 can cover all or part of the surface of the first adhesive layer 101.
[0057] The adhesive layer 101 and the bonding layer 102 are different.
[0058] The adhesive layer 101 and the tie layer 102 are preferentially both water-based or polymerizable under ultraviolet radiation.
[0059] Therefore, the adhesive layer 101 and the bonding layer 102 have the same base, which makes it possible to ensure good compatibility and good adhesion between these layers.
[0060] The water-based adhesive of adhesive layer 101 offers the advantage that it liquefies slightly when laminated, thereby enabling good adhesion between the layers to which it is applied.
[0061] The adhesive layer 101 and the bonding layer 102 have, for example, an acrylic matrix.
[0062] The front face 10 of the payment card also includes a thermochromic pattern 103. The term "thermochromic pattern" is understood to mean a pattern that changes color depending on the temperature.
[0063] The thermochromic pattern 103 extends over the entire surface of the card in this example. In alternative forms to this flat surface, the thermochromic pattern 103 may be partial. The thermochromic pattern 103 may therefore constitute a localized pattern, such as an inscription and / or a shape. In such embodiments, the adhesive layer 101 and the bonding layer 102 are preferentially localized and extend to cover at least the same area as the thermochromic pattern 103.
[0064] The thermochromic pattern 103 is printed on the bonding layer 102. The thermochromic pattern 103 is printed with a thermochromic ink. The bonding layer 102 is suitable for the thermochromic ink used to ensure good adhesion of this ink (and thus the formed thermochromic pattern 103) to the underlying layer 101.
[0065] The thermochromic ink is preferably an acrylic ink.
[0066] Therefore, the thermochromic ink is compatible with the adhesive layer 101 and the tie layer 102 .
[0067] The thermochromic inks used are preferentially water-based, as solvent-based inks tend to damage the microcapsules.
[0068] Thermochromic inks use liquid crystal type active ingredients, in other words they contain liquid crystal compounds, especially in the form of liquid crystal microcapsules.
[0069] Thermochromic inks are typically aqueous solutions containing, in addition to water, liquid crystals, acrylic resins, and optional pigments. The tie layer 102 is suitable for thermochromic inks in that it contains at least 10% by weight, preferably 10% to 30% by weight, and typically 20% by weight, of the same compounds as those listed above, but different from those listed above.
[0070] Liquid crystal phases comprise an intermediate state that exists between a crystalline solid and a completely disordered liquid phase.
[0071] The liquid crystal in this example is a chiral nematic liquid crystal or a cholesteric liquid crystal.
[0072] Liquid crystals are microencapsulated in ink. More precisely, a mixture containing liquid crystals is microencapsulated in ink. A typical mixture of liquid crystals is an optically active oil-based mixture containing several chemicals. In the microencapsulation process, droplets of the oil-based liquid crystal mixture are surrounded by a polymer coating to obtain microcapsules with diameters of 5 to 15 microns. The process then involves combining the microcapsules with a polymer or resin and water to produce the ink.
[0073] Thus, the thermochromic ink contains microcapsules of liquid crystals surrounded by an acrylic matrix, i.e., an aqueous base incorporating acrylic resin and optional pigments. The liquid crystal microcapsules consist of about 80% of the oleic acid liquid crystal mixture inside the microcapsules and about 20% of the dry microcapsule wall material.
[0074] Documents FR 2 322 914, FR 2 361 456, U.S. Pat. No. 4 149 413 and FR 2 386 594 describe examples of typical mixtures of liquid crystals that can be used. Document U.S. Pat. No. 3 697 297 describes examples of microencapsulated liquid crystals that can be used.
[0075] Liquid crystal ink selectively reflects incident light. The liquid crystal changes color when it reaches a certain temperature, called the activation temperature, and continues to change color as the temperature increases. The liquid crystal is transparent when its temperature is outside a predefined temperature range, with the activation temperature as the lower limit and the deactivation temperature as the upper limit. Thus, the liquid crystal is transparent when its temperature is below the activation temperature or above the deactivation temperature. The liquid crystal assumes different colors in the visible spectrum when its temperature is within the predefined temperature range. In the predefined temperature range, the liquid crystal changes color, specifically from red to blue, as the temperature increases.
[0076] Due to the liquid crystal of the thermochromic ink, the thermochromic pattern 103 changes color depending on its temperature.
[0077] The color change of thermochromic ink is reversible, in other words, when the temperature is reduced, the color change is observed in the opposite direction.
[0078] The color change of the thermochromic ink is fully repeatable: a second heating above the activation temperature will again change the color of the thermochromic pattern 103.
[0079] By making the support layer 100 a dark colored layer, preferably a black layer, the visibility of the color reflected by the liquid crystal ink is improved.
[0080] The tie layer 102 ensures good adhesion of the thermochromic pattern 103 to the support layer 100 .
[0081] The bonding layer 102 extending between the adhesive layer 101 and the thermochromic pattern 103 additionally makes it possible to form 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.
[0082] In another exemplary embodiment, a second bonding layer 102 may also be deposited between the thermochromic pattern 103 and the protective layer 104 .
[0083] The front surface 10 of the payment card 1 also includes a protective layer 104, also called an "overlay."
[0084] A protective layer 104 covers the thermochromic pattern 103. The protective layer 104 has the same size and shape as the support.
[0085] The protective layer 104 is, for example, a film.
[0086] The protective layer 104 is made of a thermoplastic material.
[0087] The protective layer 104 is preferably a plastic film, and may be made of, for example, polyvinyl chloride (PVC), polycarbonate (PC), or polyethylene terephthalate glycol (PETG).
[0088] The protective layer 104 is coated to allow adhesion to the rest of the payment card, and is particularly coated with a water-based adhesive.
[0089] The protective layer 104 is configured to protect the payment card from wear and tear. The protective layer 104 also makes it possible to protect the thermochromic pattern.
[0090] The protective layer 104 may be treated against UV radiation or may contain UV absorbers to protect the liquid crystals of the thermochromic pattern from harmful changes due to UV radiation.
[0091] The back surface 11 of the payment card 1, in this example, exhibits the same structure as the front surface 10, with one difference: the back surface 11 of the payment card 1 additionally includes a non-thermochromic pattern 105. The term "non-thermochromic pattern" should be understood to mean a pattern printed with non-thermochromic ink.
[0092] In an alternative form, the back surface 11 of the payment card 1 may not include any thermochromic or non-thermochromic printing, or may include only one of them.
[0093] The non-thermochromic ink can be a water-based ink or an ink that is polymerizable under ultraviolet radiation.
[0094] A non-thermochromic pattern 105 is printed on the second support layer 100 in this example.
[0095] Before lamination, the adhesive layer 101, the bonding layer 102 and the thermochromic pattern 103 of the unlaminated card 1 each have a thickness of, for example, 4 to 10 microns, and in particular the thermochromic pattern 103 has a maximum thickness of 10 microns, preferably 5 to 10 microns.
[0096] The thickness of the protective layer 104 can vary from 40 microns to 100 microns. The thickness of the support layer 100 can reach 350 microns.
[0097] After lamination, payment card 1 loses approximately 5% of its total thickness.
[0098] 4, the smart card includes three support layers 100. A third support layer 100 extending between the first and second support layers 100 may include an RF antenna. This is particularly true in the case of dual interface cards or contactless cards where the RF antenna is connected to, for example, a chip module.
[0099] The process for producing a card, in this example a payment card 1, is as follows and can be applied to one or both sides of a support: the process is directed to producing a card exhibiting a thermochromic pattern having an activation temperature T1 and a deactivation temperature T1'.
[0100] Assembly of the front 10 or back 11 of the payment card 1 is carried out as follows.
[0101] The first step in the process involves providing one of the support layers 100 .
[0102] An adhesive layer 101 is deposited on a support layer 100 .
[0103] Thereafter, a first drying step is performed to dry the adhesive layer 101.
[0104] A tie layer 102 is deposited onto the dried adhesive layer 101 .
[0105] A second drying step is then performed to dry the tie layer 102 .
[0106] A thermochromic pattern 103 is then printed onto the dried tie layer 102 .
[0107] The adhesive layer 101, the tie layer 102 and the thermochromic pattern 103 are deposited or printed by, for example, screen printing, a coating machine, flexography, lithography, rotogravure printing or letterpress printing.
[0108] The thermochromic ink used in this example exhibits an activation temperature T0=T1+δ and a deactivation temperature T0'=T1'+δ, where δ is between 2°C and 5°C, typically 3°C.
[0109] A third drying step is performed to dry the thermochromic pattern 103 .
[0110] A protective plastic layer 104 is then deposited over the thermochromic pattern 103 .
[0111] The protective layer 104 also makes it possible to protect the thermochromic pattern 103 to prevent it from deteriorating during frictional actions to which it may be subjected, which may cause its temperature to increase, for example.
[0112] For the back side 11 of the payment card 1, two intermediate steps are performed after the step of providing the second support layer 100. First, a non-thermochromic pattern 105 is printed onto the second support layer 100. This is followed by a step of drying the non-thermochromic pattern 105.
[0113] The now printed non-thermochromic pattern 105 allows it to be separated from the thermochromic pattern 103 by two layers: adhesive layer 101 and bonding layer 102. In this way, the two layers act as a barrier to prevent the non-thermochromic pattern 105 from damaging the liquid crystal.
[0114] The drying steps each last at least 8 hours, preferably 24 hours.
[0115] The drying temperature is selected depending on the thermochromic ink. The minimum temperature is set to provide a drying function, and the maximum temperature is set to avoid damaging the support layer. The drying process is carried out at, for example, 60°C to 70°C, preferably 65°C.
[0116] The assembly formed by these layers and patterns, which forms the front 10 or back 11 of the payment card 1, is finally laminated.
[0117] The lamination is done under pressure as a hot lamination followed by a cold lamination.
[0118] The lamination parameters, particularly the temperature and pressure, are selected so as not to damage the liquid crystal.
[0119] Hot lamination: 30N / cm 2 ~200N / cm 2 , preferably 120N / cm 2 The pressure is
[0120] The hot lamination is carried out at a temperature of 120°C to 160°C, preferably 125°C.
[0121] Cold lamination: 50N / cm 2 ~300N / cm 2 , preferably 100N / cm 2 The pressure is
[0122] The cold lamination is carried out at a temperature of 10°C to 20°C, preferably 15°C.
[0123] The lamination is carried out for a total duration of 15 to 40 minutes, for example 30 minutes.
[0124] The lamination process reduces the activation temperature of the thermochromic ink by δ degrees, so that the resulting thermochromic pattern after lamination exhibits an activation temperature substantially equal to T1 and a deactivation temperature substantially equal to T1'.
[0125] The above steps, except for the lamination, are repeated twice in this example to obtain the front and back of the payment card 1.
[0126] If the payment card 1 includes three support layers 100, the manufacturing process includes a step that includes providing a third support layer 100. The third support layer 100 may be disposed, for example, between the first and second support layers 100 after laminating the front 10 layer and before laminating the back 11 layer.
[0127] All the steps of printing, assembling the layers and laminating are carried out on a large layer or sheet which, after lamination, is cut into several cards in the desired format, in this case an ID-1 type format, for example, to obtain several cards 1.
[0128] If the card is a smart card, the manufacturing process includes a final step involving the insertion of a chip. The chip is inserted individually for each card. A cavity is formed in the card, for example by a milling machine. The cavity is formed over only a few microns. The cavity is formed in particular up to the antenna of the third support layer 100. The chip is then placed in the cavity and bonded. The chip is brought into contact with the antenna, making it possible to make contact.
[0129] The sequence of steps in the manufacturing of the payment card and the parameters for each step have been selected to obtain a card with satisfactory strength, including at least one thermochromic pattern 103. Due to these selections, the liquid crystal is not damaged and the payment card has the required strength characteristics, despite various manufacturing constraints (use of various adhesives that may penetrate the microcapsules, lamination under pressure and high temperature that may destroy the liquid crystal).
[0130] The resulting payment card 1 can be used as follows:
[0131] The thermochromic pattern 103 can be a security element, such as an inscription of security data, for example a graphic, symbol, string of characters or code. The thermochromic pattern 103 is transparent and is invisible when its temperature is outside a predefined temperature range. When the thermochromic pattern 103 is heated or cooled so that its temperature is within a predefined temperature range, in particular to reach an activation temperature, the thermochromic pattern 103 changes color and the security data becomes visible.
[0132] In this way, the security data, e.g., a cryptogram, becomes invisible to the naked eye when the temperature is outside a predefined temperature range. In particular, the security data becomes invisible to the naked eye when the temperature is below an activation temperature. Because the activation temperature has not been reached, a malicious person observing the payment card cannot fraudulently obtain the security data.
[0133] If the security data in the form of the thermochromic pattern constitutes personal data, also called variable data because it is unique to each cardholder, such as a payment card verification code, then when the user wishes to know the security data, he or she simply heats the thermochromic pattern 103 himself or herself (e.g., by rubbing it) so that the activation temperature is reached.
[0134] If the security data in the form of the thermochromic pattern 103 is an immutable security element, the thermochromic pattern 103 can be revealed at a predetermined temperature to verify the authenticity of the payment card 1. The process according to the present invention is therefore applicable on a large scale, since no individual personalization is incorporated and the pattern is specific, for example, to an institution and / or a batch of cards, particularly by serial number range. Similarly, this embodiment is advantageously applied in the field of identification cards, by incorporating such thermochromic security data therein, for example, in the form of a country-specific design. In this case, the activation temperature can be selected to ensure the transparency of the thermochromic pattern 103 during normal use of the payment card 1. For example, the activation temperature is at least 40°C. The security data printed on the card becomes visible only above this activation temperature.
[0135] In various use cases, the security of the payment card is improved, particularly by adding such thermochromic patterns, due to the fact that perfect counterfeiting is significantly limited and / or the security data is not permanently visible.
[0136] Because thermochromic ink is reversible, the process of revealing or masking security data can be repeated indefinitely throughout the life of the payment card, depending on the needs of its holder for use.
[0137] In another exemplary embodiment, the thermochromic pattern 103, whether variable or not, can be used to mask security data while still allowing for large-scale application of the process according to the present invention. Thus, for the purpose of masking security data, such as a unique code for the cardholder, this security data can be printed on the card using only non-thermochromic ink during the personalization process following the lamination process, with the thermochromic pattern 103 constituting the area beneath the security data printed during personalization. The substrate and the security data are preferentially of the same color so that the security data is invisible outside the predefined temperature range of the thermochromic pattern 103. The choice of black color allows for improved contrast, especially when the thermochromic ink is within the predefined temperature range. The security data is then printed over the thermochromic pattern 103 in such a way that it is invisible outside the predefined temperature range; the security data is therefore printed in the same color as the substrate; the inactive thermochromic pattern 103 is transparent; upon activation of the thermochromic pattern 103 by temperature, it changes color, thereby making the printed security data visible. The thermochromic pattern 103 is transparent when its temperature is outside a predefined temperature range, "masking" the security data from underneath. The thermochromic pattern 103 is colored when its temperature is within a predefined temperature range, making the security data visible. To make the thermochromic pattern transparent and hide the security data, the thermochromic pattern 103 is cooled below its activation temperature or heated above its deactivation temperature. Similarly, this embodiment is particularly advantageously applied to identification cards.
[0138] In this case, by adjusting the properties of the thermochromic ink, a predefined temperature range can be selected that corresponds to the normal operating temperature range of the payment card. Liquid crystals in the cholesteric phase have a helical structure. The transition temperature depends, inter alia, on the helical pitch. Therefore, by changing the helical pitch of the liquid crystal, it is possible to change the activation temperature of the thermochromic pattern 103.
[0139] The term "normal operating temperature range of the payment card" is to be understood to mean, for example, a temperature range of 0°C to 40°C, i.e. a temperature range corresponding to the possible range of ambient temperatures in which the payment card 1 is used. Security data printed on the card will therefore only be visible outside the card's normal operating temperature range.
[0140] Heating of the thermochromic pattern 103 can be achieved 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 hot environment. Cooling of the first pattern can be achieved by stopping the heating, for example by ceasing the rubbing with a finger. Cooling of the thermochromic pattern 103 can also be achieved by placing the payment card 1 in a cold environment.
[0141] The present invention provides a card with improved security whilst allowing for easy and convenient use, in particular due to the speed of activation of the thermochromic pattern.Smart cards also present the advantage of having good mechanical properties.
[0142] Other alternatives, not shown, are described below.
[0143] The smart card may be of a type other than a payment card, for example an identification card, badge or ticket.
[0144] The support may include only one common support layer on the front and back of the card, in other words, a single substrate can be used without additional support layers, said substrate thus serving as a support layer for the deposition and printing of other layers.
[0145] The described smart cards include a thermochromic pattern on each of the front and back sides. A card may include a different number of thermochromic patterns. For example, a card may include one or more thermochromic patterns on only the front or back side.
[0146] The front and back of the smart card may exhibit the same layer and pattern structure.
[0147] The smart card may contain other elements, in particular personalisation elements, graphics or information items made in the protective layer, which may be printed on the protective layer after lamination.
[0148] The smart card may additionally include an ultraviolet filter configured to protect the thermochromic pattern from ultraviolet radiation. The ultraviolet filter may, for example, be incorporated into the protective layer. The protective layer may, for example, include an ultraviolet absorber. Alternatively, the ultraviolet filter may be a layer separate from the protective layer. The smart card may include the ultraviolet filter between the protective layer and the thermochromic pattern.
Claims
1. A laminated card comprising, in order: a thermoplastic support layer (100), an adhesive layer (101), a bonding layer (102), a thermochromic pattern (103) printed by means of a thermochromic ink; a protective plastic layer (104) and wherein the adhesive layer (101) and the tie layer (102) are both water-based or both polymerizable under ultraviolet radiation, and the thermochromic ink comprises a liquid crystal compound.
2. 2. The card of claim 1, wherein the liquid crystal is a chiral nematic liquid crystal.
3. 3. A card according to claim 2, wherein the liquid crystal is contained in microcapsules, the microcapsules having a diameter of less than 50 microns, preferably between 5 and 15 microns.
4. The card according to any one of claims 1 to 3, wherein the bonding layer (102) and the thermochromic ink comprise the same compound.
5. 5. The card of claim 4, wherein the liquid crystal compound constitutes 10% to 30% by weight of the thermochromic ink, preferably 20% by weight of the thermochromic ink.
6. The card according to any one of the preceding claims, wherein the thermochromic ink and the bonding layer (102) have an acrylic matrix.
7. A card according to any one of claims 1 to 6, which is a smart card.
8. 1. A process for producing a laminated card, comprising: - providing a thermoplastic support layer (100); - depositing an adhesive layer (101) on said support layer (100); - depositing a tie layer (102) on the dried adhesive layer (101), wherein the adhesive layer (101) and the tie layer (102) are both water-based and / or both polymerizable under ultraviolet radiation; - printing a thermochromic pattern (103) on the dried tie layer (102) by means of a thermochromic ink, said thermochromic ink comprising a liquid crystal compound; - depositing a protective plastic layer (104) on said dried thermochromic pattern (103); - laminating the assembly; A process involving:
9. The step of laminating includes: - a temperature of 120°C to 160°C, preferably 125°C, and 30 N / cm ２ ~200N / cm ２ , preferably 120 N / cm ２ A partial process of hot laminating under pressure, then - a temperature of 10°C to 20°C, preferably 15°C, and 50 N / cm ２ ~300N / cm ２ , preferably 100 N / cm ２ Partial process of cold laminating under pressure 9. The process of claim 8, comprising:
10. 10. A process according to claim 8 or 9 for producing a laminated card (1) whose thermochromic pattern (103) exhibits an activation temperature T1, said thermochromic printing ink exhibiting an activation temperature T0=T1+δ before hot lamination, where δ is between 2°C and 5°C.