Method for manufacturing a card and card comprising at least one thermochromic pattern

0001The invention relates to a method of manufacturing a card formed of a plurality of layers at least one polymeric material - including polycarbonate rolled under heat and pressure, and such a card.

0002<patcit id="pcit0001" dnum="EP0400220A"><text>EP 0400220</text></patcit> discloses a laminated article for identification (such as an identity card) comprising two sheets or PVC layers of which at least one is transparent, between which is laminated a layer containing thermochromic liquid crystals arranged on a dark contrasting background. These liquid crystals are applied as a water-based ink containing a water-soluble polymeric binder, such as gelatin or polyacrylamide. As noted herein, the hot lamination and pressure PVC sheets bearing the information leads to adhesion problems. This document provides a cleaning step prior to lamination and to remove chemical compounds believed to interfere with adhesion of the different layers together. However, this article was not used in practice.

0003Various other attempts have been made to incorporate thermochromic patterns in cards formed of a plurality of thermoplastic layers laminated under heat and pressure. However, the ink compositions thermochromic known and considered, especially in these applications are aqueous solvent compositions.<patcit id="pcit0002" dnum="EP2322587A"><text>EP2322587</text></patcit> describes an example of a thermochromic ink composition comprising microcapsules incorporating a thermochromic composition and UV absorbers dispersed in an aqueous solvent with a polymeric binder, for example acrylic.

0004Furthermore, many cards forming data carriers and used for identification or security purposes (bank cards, identity cards, driving licenses, individual access cards sites or transport, sheet passport ...) are formed by lamination under heat and pressure a plurality of layers-especially polycarbonate thermoplastic, material having also several advantages in these applications (rigidity, durability, ease and reliability of markings ( variable markings, security reasons ...) ability to perform laser marking ...) -. The inventors have found that the ink compositions to aqueous solvent thermochromic proposed until now are not compatible with the manufacturing processes by hot lamination of such layers of thermoplastic material, and in particular with the hot lamination ( temperature of the order of 150 ° C to 200 ° C) and pressure (of the order of 2.10⁴ Pa) of polycarbonate layers. In fact, these conditions lamination destroy the thermochromic effect provided by the thermochromic ink compositions printed on polycarbonate layers. In addition, irremediably finds adhesion problems polycarbonate layers with each other and the printed thermochromic compositions. Also, the thermochromic ink compositions known have a lifetime limited at best one or two years, which is insufficient in identification and security applications where lifetime of at least 10 years is required (see in particular ISO 24789-1.2 (2012) - "Method of assessment of identification (ID) card Service life"). The same problem arises with synthetic papers and security papers used in security applications (authentication and / or anti-forgery) and / or identification that are often rolled under heat and pressure.

0005It should be noted in this respect that the compositions of thermochromic inks curing under ultraviolet irradiation are not consistent with the hot lamination processes, the thermochromic activity being destroyed under the action of heat and / or in time, and provide a thermochromic effect much less reactive, insufficient in the above applications in which the thermochromic components are thermally insulated from the outside by at least one layer, especially a polycarbonate layer.

0006Furthermore polycarbonate, synthetic papers and fiduciary papers are sensitive to most organic solvents and are therefore not compatible with prints with inks based on organic solvents.

0007Therefore, the proposals that have been made to incorporate thermochromic patterns in the laminated cards under heat and pressure-especially in polycarbonate, synthetic papers and security papers are not so far as not feasible theoretical lessons practice on an industrial or commercial scale, in particular for producing data carriers usable for identification or security.

0008The invention therefore aims to overcome these drawbacks.

0009The invention relates to a manufacturing method according to claim 1.

0010The invention also relates to a card according to claim 12.

0011The thermochromic ink composition simultaneously:<ul><li>is compatible with a hot lamination at a temperature above 150 ° C, typically around 180 ° C,</li><li>can adhere strongly to a layer of thermoplastic material, in particular polycarbonate, and / or a synthetic paper and / or on a security paper,</li><li>not detrimental to adhesion-especially thermoplastic polycarbonate layers after lamination under heat and pressure,</li><li>present a thermochromic effect sufficiently reactive to be able to be activated through the thickness of at least one protective layer, in particular a layer of thermoplastic material-in particular in polycarbonate, or a security film or a synthetic paper or banknote paper layer ,</li><li>presents a persistent thermochromic effect on more than 10 years,</li><li>present a thermochromic effect lightfast and variations and temperature shocks and humidity.</li></ul>

0012The thermochromic ink composition comprises a liquid medium, said solvent, said solvent being aprotic: <ul><li>a dispersion of thermochromic microcapsules incorporating at least one leuco dye, and</li><li>a thermoplastic binder selected from the group consisting of polyacrylic polyesters, polyurethanes, and copolymers thereof.</li></ul>

0013Said solvent therefore for the aprotic solvent group and is especially free of water and is not an aqueous solvent. It should be noted that the term "solvent" is used throughout the text to refer, as the terminology used in the field of ink compositions and printing, the liquid medium forming the basis of the composition thermochromic ink, although the liquid medium is not strictly a solvent in the chemical sense of the term, the thermochromic microcapsules are dispersed in the liquid medium and not dissolved therein.

0014The inventors have found that the use of an aprotic solvent in the thermochromic ink composition allows to obtain thermochromic impressions which are then compatible with a lamination under heat and pressure, of enduring thermochromic effect over many years and responsive enough power is used through at least one ply of thermoplastic material-in particular in polycarbonate that exhibit excellent adhesion to the thermoplastic materials, particularly on rigid thermoplastics-in particular at room temperature on the polycarbonate and not detrimental to the adhesion of layers of plastic materials such as polycarbonate-especially when they are interposed between such layers. The invention also provides thermochromic impressions which are then compatible with synthetic papers and security papers. No clear explanation can be given for this surprising phenomenon found by the inventors. It is however possible that the aprotic nature of the solvent, although the latter is more normally present when printing is hardened (the solvent has been evaporated), plays a role in the higher resistance thermochromic microcapsules to a hot rolled and pressure and / or operation of the leuco dyes. More exactly, it is possible that the protic character aqueous solvents hitherto used in the ink compositions known thermochromic greatly affects the resistance higher thermochromic microcapsules to lamination under heat and pressure and / or operation of leuko- dyes.

0015Said aprotic solvent should also be selected to be compatible with the microcapsules and the binder, and to be compatible with the printing process. Advantageously and according to the invention, the aprotic solvent is selected from the group of solvents printable compositions by screen printing. Advantageously and according to the invention said aprotic solvent comprises at least one of the following characteristics:<ul><li>it is selected from the group aprotic solvent having a dipole moment between 0 and 1.9 Cm,</li><li>is selected from the group of aprotic solvents having a dielectric constant (permittivity relative to vacuum) between 1.5 and 11,</li><li>it is selected from the group of aprotic polar solvents,</li><li>it comprises at least one compound selected from the group consisting of n-alkyl propanoates and glycol polypropylenes (solvents particularly compatible with thermochromic microcapsules melamine formaldehyde).</li></ul>

0016More particularly, in one embodiment advantageously a thermochromic ink composition comprises as a solvent a compound selected from the group consisting of propanoic acid, n-propyl, n-propanoate butyl, n-pentyl propanoate, of ethoxy-3-propanoate, acetate, 1-methoxy-2propyle, 1-propoxy-2-propanol acetate, 1-propoxy-2-propyl, 1-butoxy-2-propanol, 1- (2-methoxy-1-methylethoxy) 2-propanol, acetate 1- (2-methoxy-1-methylethoxy) 2-propyl, 1- (2-propoxy-1-methylethoxy) 2-propanol, and [2- (2-methoxy methylethoxy) methylethoxy] propanol. Other examples are possible.

0017Moreover, the thermoplastic binder is selected in particular depending on the material used as print media for the thermochromic ink composition. It is an advantage of the invention that allow solving the aforementioned problems with a large number of print media that can be used to receive the thermochromic print. Thus the thermochromic ink composition can be optimized for printing on a support selected from the group of thermoplastic materials, synthetic papers and security papers. It should be noted in this regard that the thermochromic ink composition can be optimized for printing on a medium sensitive to solvents such as polycarbonate substrates and security papers.

0018The thermoplastic binder of the thermochromic ink composition can also be optimized for printing on a medium to be laminated under heat and pressure (for example a laminate of thermoplastic layers forming a security card and / or such that identification 'a credit card).

0019The thermoplastic binder of the thermochromic ink composition can also be optimized to have a long service life, in particular of several years, e.g., at least ten years.

0020In particular, by way of example, the thermoplastic of the thermochromic ink binder composition can be optimized for printing on a carrier of a thermoplastic material selected from the group consisting of polycarbonate, PVC, and polyesters (polyethylene of ethylene PET, PETG). Other examples are possible.

0021Preferably the thermochromic ink composition more particularly intended for printing onto a polycarbonate support comprises as binder a thermoplastic resin selected from the group consisting of poly (meth) acrylates and their copolymers.

0022In particular, by way of example, the thermoplastic of the thermochromic ink binder composition can be optimized for printing on a synthetic paper substrate selected from paper sold under the brand Teslin® from PPG, Monroeville, USA, the paper sold under the brand Neobond® by the company Neenah Lahnstein, Lahnstein, Germany, and the paper sold under the brand Polyart® by Arjobex company, Boulogne, France. Other examples are possible.

0023In particular, by way of example, the thermoplastic binder of the thermochromic ink composition may be optimized for printing on a security paper support such as a passport paper, a banknote, a paper identity card, driver paper's license, visa paper, a birth certificate, a paper customs seals, ... other examples are possible.

0024In security applications and / or identification of the invention, the thermoplastic binder of the thermochromic ink composition may also advantageously be selected to reveal Solvent falsification attempts (etching), and in particular a binder comprising a soluble agent in a solvent adhesive (when the thermochromic ink composition is used to print a pattern on a thermochromic adhesive card) as described for example by <patcit id="pcit0003" dnum="EP1109675A"><text>EP 1109675</text></patcit>.

0025Furthermore, another advantage of the thermochromic ink composition is to allow the addition of different additives in the solvent without disturbing the curing of the composition after printing.

0026In particular, preferably the thermochromic ink composition further comprises at least one UV additive selected from the group consisting of absorbing agents for ultraviolet and light stabilizing agents (in particular HALS ( "hindered amine light stabilizers "). such an agent ultraviolet absorber and / or light stabilizer of the thermochromic ink composition is incorporated in said aprotic solvent and is in particular possible separate UV absorbers and / or light stabilizers incorporated in microcapsules . thermochromic Advantageously, the thermochromic ink composition comprises between 1% and 10%-especially between 2% and 5% - by weight of an anti-UV additive.

0027As an anti-UV additive of the thermochromic ink composition, any ultraviolet absorbent may be used and / or light stabilizer compatible with the other constituents of the composition. For example, include the group of 2- (hydroxyphenyl) benzotriazoles (see especially "<nplcit id="ncit0001" npl-type="s"><text>Ultraviolet stabilizers of the 2- (hydroxyphenyl) benzotriazole class: Influence of substituents is patterned and spectra "J. Phys Chem, 1992, 96 (25), pp 10225-10234..</text></nplcit>); the group of 2-hydroxyphenyl-s-triazines (see in particular<patcit id="pcit0004" dnum="US5096489A"><text>US5096489</text></patcit>); and the group of 2,2,6,6-tetramethyl (TMP) (see in particular<nplcit id="ncit0002" npl-type="b"><text>"Oxidation inhibition in organic materials» Jan Pospisil, Peter P. Klemchuk CRC Press, 1989</text></nplcit>). Advantageously and according to the invention, one can choose an ultraviolet absorber in the 2- (2-hydroxyphenyl) -benzotriazole (BTZ) and the 2-hydroxyphenyl-s-triazine (HDT).

0028In an advantageous embodiment and according to the invention, the thermochromic ink composition comprises in said solvent between 15% and 35% by weight of thermochromic microcapsules, between 30% and 45% by weight of thermoplastic binder, between 1% and 10% by weight of at least one anti-UV additive.

0029The thermochromic any pattern can be: text (s), drawing (s), line (s), ... It can also be a solid color (continuous printing on at least one surface portion of a layer the map).

0030Advantageously and according to the invention at least one thermochromic pattern is printed with the thermochromic ink composition so as to be interposed between a surface layer of the board and a layer immediately underlying said surface layer. To do this, at least a thermochromic pattern is printed with the thermochromic ink composition on a surface layer of the card, that is to say on a layer of thermoplastic polycarbonate-in particular in which one face constitutes a free face of the card after lamination under heat and pressure. Such thermochromic pattern is preferably printed on one side of said surface layer opposite to the face of the layer forming the outer free face of the card. Alternatively or in combination, at least a thermochromic pattern is printed with the thermochromic ink composition onto a layer immediately underlying a surface layer of the card, in particular on a face of said underlying layer coming into contact with said surface layer after lamination under heat and pressure.

0031The invention also relates to a method of manufacturing a card and a card characterized in combination by all or some of the features mentioned above or below.

0032Other objects, features and advantages of the invention appear on reading the examples which follow.

EXAMPLE 1 Manufacture of a thermochromic ink composition

0033A thermochromic ink composition is made by dispersing 20% ​​by weight of thermochromic microcapsules in a liquid mixture of a polar aprotic solvent and a thermoplastic resin.

0034The thermochromic ink composition comprises:<ul><li>20% by weight of pigments (microcapsules) thermochromic,</li><li>40% by weight of methyl methacrylate copolymer as a transparent binder,</li><li>26% by weight of 1- (2-methoxy-1-methylethoxy) 2-propanol,</li><li>10% of ethoxy-3-propanoate,</li><li>4% by weight of 2-hydroxyphenyl-s-triazine (UV absorber).</li></ul>

0035Des_microcapsules thermochromic microcapsules are marketed under the brand CHAMELEON® by the company Polychrom Co LTD, Ansan City, Korea.

0036The ultraviolet absorber is marketed under the reference TINUVIN® 400 by BASF, Ludwigshafen, Germany.

0037This ink has a viscosity of 7.0 Pa.s +/- 1 Pa

0038The ink can be printed with silk screens 120 son / cm for fine print outputs frame 80 dpi.

Example 2: production of a polycarbonate card incorporating thermochromic impressions

0039An ink composition obtained according to example 1 is printed in the form of a solid ink on one of the faces of two sheets of polycarbonate whose thickness is of the order of 50 microns.

0040The ink is dried by hot air.

0041printed polycarbonate sheets are associated with five other polycarbonate sheets interposed between the polycarbonate sheets printed so as to form a stack, the printed sides being placed in contact with the underlying sheets of the stack, that is, say not constituting the external faces of the latter. Five polycarbonate sheets forming with the two printed sheets, said stack successively as follows: a sheet of 100 microns of polycarbonate; a sheet of 200 .mu.m in white polycarbonate; a sheet of 200 .mu.m in white polycarbonate; a sheet of 200 .mu.m in white polycarbonate; a sheet of 100 .mu.m of transparent polycarbonate.

0042The set of sheets forming the stack is laminated in a lamination press under the following conditions:<ul><li>1 min up to 180 ° C</li><li>12 min at 180 ° C under 30 N / cm²</li><li>5 min at 180 ° C under 150 N / cm²</li><li>cooling to 26 ° C for 17.5 minutes under 180N / cm².</li></ul>

0043One obtains a map whose total thickness is equal to the sum of polycarbonate sheets of thickness used decreased by about 10%.

0044Thermochromic prints made with the thermochromic ink composition of the invention are thus incorporated into the thickness of the card.

EXAMPLE 3: Adhesion and durability tests

0045Durability tests are performed on polycarbonate cards as manufactured in accordance with Example 2.

0046The adhesion between the different layers of the card is evaluated according to different test protocol: <ul><li>peel measurement according to ISO 10373-90 ° at 300mm / min</li><li>peel measurement after weathering according to ISO 24789-1 and 2 standards,</li><li>bending test according to ISO 24789-1 and 2 standards, 50,000 flexions in length, 50 000 bendings in width,</li><li>bending test after weathering according to ISO 24789-1 standards and 2,</li><li>bending test after exposure to artificial light according to ISO 24789-1 and 2</li></ul>

0047The peel measurement shows that the strength of adhesion between the layers is greater than 3.5 N / cm.

0048In flexion tests no delamination appears at the surrounding polycarbonate layers thermochromic impressions.

Example 4 lightfastness

0049The light resistance of polycarbonate cards as manufactured in accordance with Example 2 was evaluated by measuring the color difference (DE * _Lab) Thermochromic impressions before and after exposure to artificial light. The color measurement is carried out when the thermochromic impressions are in their first non-activated state this is to say in the colored version thermochromic microcapsules.

0050The measurement of color difference is performed with a spectro-colorimeter (Spectropen® (Dr. Lange, Düsseldorf, Germany)) according to the ISO 7724-3 standard.

0051Thermochromic prints are exhibited in three test protocols:<ul><li>UVA exposure: 20h; UVA 340 nm; 60 ° C; 0.72 W / m²/ Nm (ISO 4892)</li><li>Exposure to artificial light according to ICAO standard 3.2 -2006-paragraph 5-14, </li><li>exposure to xenon arc light according to 24789-1 and ISO 2.</li></ul>

0052The color difference DE is less than 10 in the case of exposure to UVA and less than 5 in the case of exposure to artificial light xenon arc type.

0053With reversible thermochromic microcapsules stained with unactivated state and transparent when activated.

0054It is found that the thermochromic activity of the samples exposed with respect to the discoloration temperature range and restaining temperature range is identical to the unexposed samples.

Example 5: Climate held

0055Climate held polycarbonate cards as manufactured according to Example 2 is evaluated according to the following test protocols:<ul><li>exposure to thermal cycling and for stressful storage conditions according to the ICAO standard 3.2-2006 subsection 5.2 ( "thermal cycling method") and Section 5.3 ( "storage temperature stress method"),</li><li>Exposure to high temperatures and humidity, thermal shock and thermal cycle according to ISO 24789-1 and 2, paragraph 5-7 ( "temperature and humidity aging"), paragraph 5-8 ( "shock temperature"), paragraph 5 9 ( "temperature and humidity cycling").</li></ul>

0056For different test protocols, there is no loss of the thermochromic activity in terms of discoloration, change in the range of fading and the beach of recoloring.