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

THERMOCHROMIC INK COMPOSITION

The invention relates to a thermochromic ink composition more particularly intended for cards formed from a plurality of layers made of at least one polymeric material, in particular polycarbonate, hot-rolled and pressurized, synthetic papers and fiduciary papers.

EP 0400220 describes an article laminated for identification purposes (such as an identity card) comprising two sheets or layers of PVC, at least one of which is transparent, between which is laminated a layer containing thermochromic liquid crystals arranged on a dark background. These liquid crystals are applied in the form of an aqueous-based ink containing a polymeric water-soluble binder, for example gelatin or a polyacrylamide. As this document indicates, hot and pressure lamination of the PVC sheets bearing the information causes adhesion problems. This document provides for a cleaning step preceding lamination and aimed at removing the chemical compounds which are supposed to harm the adhesion of the different layers between them. However, this article has not been used in practice.

Various other attempts have been made to incorporate thermochromic patterns into cards formed from a plurality of hot-rolled and pressurized thermoplastic layers. However, the thermochromic ink compositions known and envisaged in particular in these applications are compositions with aqueous solvent. ΕΡ2322587 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.

In addition, numerous cards forming data carriers and used for identification or security purposes (bank cards, identity cards, driving license, individual access cards to sites or public transport, sheet passport ...) are formed by hot lamination and under pressure of a plurality of layers of thermoplastic material - in particular polycarbonate, a material which also has many advantages in these

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WO 2014/184482 2 PCT / FR2O14 / O51O99 applications (rigidity, durability, ease and reliability of markings (variable inscriptions, security reasons, etc.), possibility of performing laser markings, etc.). However, the inventors have found that the compositions of thermochromic ink with aqueous solvent proposed until now are not compatible with the methods of manufacture by hot lamination of such layers of thermoplastic material, and in particular with hot lamination ( temperature of the order of 15O٥C to 2OO٥C) and under pressure (of the order of 2.0 Pa) of polycarbonate layers. Indeed, these lamination conditions destroy the thermochromic effect provided by the thermochromic ink compositions printed on the polycarbonate layers. In addition, there are irretrievably problems of adhesion of the polycarbonate layers to each other and with the thermochromic compositions printed. Also, the known thermochromic ink compositions have a lifetime limited at best to one or two years, which is insufficient in identification or security applications for which a lifespan of at least 10 years is required. (cf. in particular ISO 24789-1,2 (2012) - Method of evaluation of identification (ID) card service life). The same problem arises with synthetic papers and fiduciary papers used in security applications (authentication and / or anti-forgery) and / or identification which are often hot rolled and under pressure.

It should be noted in this respect that the compositions of thermochromic inks which harden under irradiation with ultraviolet rays are also not compatible with the hot lamination processes, the thermochromic activity being destroyed under the action of heat and / or over time, and provide a much less reactive thermochromic effect, insufficient in the abovementioned applications in which the thermochromic components are thermally isolated from the outside by at least one layer, in particular a layer of polycarbonate.

In addition polycarbonate, synthetic papers and fiduciary papers are sensitive to most organic solvents and are not

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WO 2014/184482 3 PCT / FR2O14 / O51099 therefore not compatible with printing with inks based on organic solvents.

Consequently, the proposals which have been made to incorporate thermochromic patterns in hot-rolled and pressurized cards - notably in polycarbonate -, synthetic papers and fiduciary papers constitute to date only theoretical teachings which cannot be realized in practical on an industrial or commercial scale, in particular for manufacturing data carriers usable for identification or security purposes.

The invention therefore aims to overcome these drawbacks by proposing a composition of thermochromic ink which simultaneously:

- is compatible with hot lamination at a temperature above 15O٥C, typically of the order of 18O٥C,

- can adhere strongly to a layer of hermoplastic material, in particular polycarbonate, and / or synthetic paper and / or to fiduciary paper,

- does not harm the adhesion of the layers of thermoplastic material - in particular polycarbonate - after their hot lamination and under pressure,

- has a thermochromic effect which is sufficiently Teactive to be able to be activated through the thickness of at least one protective layer, in particular a layer of thermoplastic material - in particular polycarbonate -, or a safety film or a layer of synthetic paper or paper fiduciary,

- has a persistent thermochromic effect over a period of more than 10 years,

- has a thermochromic effect resistant to light and to variations and shocks in temperature and humidity.

To do this, the invention therefore relates to a thermochromic ink composition comprising, in a liquid medium, known as a solvent:

a dispersion of thermochromic microcapsules incorporating at least one leuco-dye, and

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- A thermoplastic binder chosen from the group forms polyacrylic polyesters, polyurethanes, and their copolymers, characterized in that said solvent is aprotic.

Said solvent therefore belongs to the group of aprotic solvents and is in particular free of water and is not an aqueous solvent. It should be noted that the term solvent is used throughout the text to designate, like the terminology used in the field of ink compositions and printing, the liquid medium forming the base of the composition of thermochromic ink according to the invention, although this liquid medium does not strictly constitute a solvent in the chemical sense of the term, the thermochromic microcapsules being dispersed in this liquid medium and not dissolved in the latter.

The inventors have noted that the use of an aprotic solvent in a thermochromic ink composition according to the invention makes it possible to obtain thermochromic prints which are then compatible with hot and pressure lamination, which have a lasting thermochromic effect. over many years and sufficiently reactive to be able to be used through at least one thickness of thermoplastic material, in particular polycarbonate, which have excellent adhesion to thermoplastic materials, more particularly to rigid thermoplastic materials at room temperature -in particular on polycarbonate- and do not harm the adhesion of layers of such plastic materials -including polycarbonate when interposed between such layers. The invention also makes it possible to obtain thermochromic prints which are then compatible with synthetic papers and fiduciary papers. No clear explanation can be given for this surprising phenomenon observed by the inventors. It is however possible that the aprotic nature of the solvent, although the latter is normally no longer present when the impression is hardened (the solvent having been evaporated), plays a role in the subsequent resistance of the thermochromic microcapsules to hot lamination. and under pressure and / or in the operation of leuco-dyes. More precisely, it is possible that the protic character of the aqueous solvents used until now in the compositions

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WO 2014/184482 5 PCT / FR2O14 / O51099 known thermochromic ink considerably affects the subsequent resistance of thermochromic microcapsules to hot and press lamination and / or the functioning of leuco-dyes.

Said aprotic solvent must also be chosen to be compatible with the microcapsules and with the binder, and to be compatible with the printing technique used. Advantageously and according to the invention, the aprotic solvent is chosen from the group of solvents of the compositions printable by screen printing. Advantageously and according to the invention, said aprotic solvent has at least one of the following characteristics:

- It is chosen from the group of aprotic solvents having a dipole moment between 0 and 1.9 c. m,

it is chosen from the group of aprotic solvents having a dielectric constant (permittivity relative to the vacuum) between 1.5 and 11,

- it is chosen from the group of polar aprotic solvents,

- It contains at least one compound chosen from the group formed by n-alkyl propanoates and glycol propylenes (solvents particularly compatible with thermochromic microcapsules made of melamine formaldehyde).

More particularly, in an advantageous embodiment, a thermochromic ink composition in accordance with the invention comprises, as solvent, a compound chosen from the group formed by n-propyl propanoate, n-butyl propanoate, n propanoate -pentyle, ethyl ethoxy-3propanoate, l-methoxy-2propyl acetate, l-propoxy-2propanol, Lpropoxy-2-propyl acetate, l-butoxy-2-propanol, l - (2-methoxy-lmethylethoxy) 2-propanol, 1- (2-methoxy-1-methylethoxy) 2propyl acetate, 1- (2-propoxy-1-methylethoxy) 2-propanol, and [2- (2-methoxy methylethoxy) methylethoxy] propanol. Other examples are possible.

Furthermore, the thermoplastic binder is chosen in particular as a function of the material serving as a printing medium for the thermochromic ink composition according to the invention, it is an advantage of the invention to allow the above-mentioned problems to be resolved with large number of supports

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WO 2014/184482 6 printing PCT / FR2O14 / O51O99 which can be used to receive thermochromic printing. Thus, a thermochromic ink composition according to the invention can be optimized for printing on a support chosen from the group of thermoplastic materials, synthetic papers, and fiduciary papers. It should be noted in this respect that a thermochromic ink composition according to the invention can be optimized for printing on a support sensitive to solvents such as polycarbonate supports and fiduciary papers.

The thermoplastic binder of a thermochromic ink composition according to the invention can also be optimized for printing on a support intended to be hot rolled and under pressure (for example a laminate of thermoplastic layers forming a security card and / or identification such as a bank card).

The thermoplastic binder of a thermochromic ink composition according to the invention can also be optimized to have a long service life, in particular of several years, for example at least ten years.

In particular, by way of example, the thermoplastic binder of a thermochromic ink composition according to the invention can be optimized for printing on a support made of a thermoplastic material chosen from the group consisting of polycarbonate, PVC, and polyesters (polyethylene terephthalate PET, PETG). Other examples are possible.

Advantageously, a thermochromic ink composition according to the invention more particularly intended for printing on a polycarbonate support comprises, as a binder, a thermoplastic resin chosen from the group formed of poly (meth) acrylates and their copolymers.

In particular, by way of example, the thermoplastic binder of a thermochromic ink composition according to the invention can be optimized for printing on a synthetic paper support chosen from paper sold under the brand Teslin® by the company PPG , Monroeville, USA, the paper sold under the Neobond® brand by the company Neenah Lahnstein,

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Lahnstein, Germany, and the paper marketed under the Polyart® brand by the company Arjobex, Boulogne, France. Other examples are possible.

In particular, by way of example, the thermoplastic binder of a thermochromic ink composition according to the invention can be optimized for printing on a paper made of fiduciary paper, such as passport paper, banknote paper. bank, an ID card paper, a driver's paper, a visa paper, a birth certificate paper, a customs seal paper, ... Other examples are possible.

In the security and / or identification applications of the invention, the thermoplastic binder of a thermochromic ink composition according to the invention can also advantageously be chosen so as to reveal attempts at falsification with solvents (chemical attack ), and in particular a binder incorporating a solvent-soluble agent of an adhesive (when the thermochromic ink composition is used to print a thermochromic pattern on an adhesive card) as described for example by EP 1109675.

Furthermore, another advantage of a thermochromic ink composition according to the invention is to allow the addition of various additives in the solvent without disturbing the hardening of the composition after printing.

In particular, advantageously a thermochromic ink composition according to the invention also comprises at least one anti-UV additive chosen from the group formed by ultraviolet absorbing agents and light stabilizing agents (in particular of the HALS type (“ hindered amine liglit stabilizers ”). Such an ultraviolet absorbing agent and / or light stabilizer of a thermochromic ink composition according to the invention is incorporated into said aprotic solvent, and is in particular distinct from any ultraviolet absorbers and / or incorporated light stabilizers thermochromic microcapsules. Advantageously, a thermochromic ink composition according to the invention comprises between 1% and 10% - in particular between 2% and 5% - by weight of an anti-UV additive.

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As an anti-υν additive of a thermochromic ink composition according to the invention, one can use any ultraviolet absorber and / or light stabilizer compatible with the other constimants of the composition. By way of example, mention may be made of the group of 2- (hydroxyphenyl) ٠ benzotriazoles (cf. in particular Ulraviolet stabilizers of the 2 (hydroxyphenyl) benzotriazole class: influence of substances on structure and spectra ل. Phys. Chem., 1992, 96 (25), PP 10225-10234); the group of 2hydroxyphenyl-s-triazines (cf. in particular US5O96489); and the group of 2,2,6,6tetramethylpiperidines (TMP) (cf. in particular “oxidation inhibition inorganic materials” Jan Pospisil, Peter p. Klemchuk CRC Press, 1989). Advantageously and according to the invention, an ultraviolet absorber can be chosen from the group of 2- (2hydroxyphenyO-benzotriazole (BTZ) and 2-hydroxyphenyl-s-triazine (HDT).

In an advantageous embodiment and in accordance with 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.

The invention extends to a process for manufacturing a card made of thermoplastic material - in particular polycarbonate - comprising at least one step of hot and pressure lamination of a plurality of layers of thermoplastic material - in particular polycarbonate -, characterized in that, before at least one step of hot lamination and under pressure, one prints on at least one layer of thermoplastic material - in particular polycarbonate -, at least one thermochromic pattern with a thermochromic ink composition according to the invention.

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

Advantageously and according to the invention at least one thermochromic pattern is printed with a thermochromic ink composition according to the invention so as to be interposed between a surface layer of the card and

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WO 2014/184482 9 PCT / FR2O14 / O51O99 a layer immediately underlying said surface layer. To do this, at least one thermochromic pattern is printed with a thermochromic ink composition according to the invention on a surface layer of the card, that is to say on a layer of thermoplastic material - in particular polycarbonate - of which 5 one side constitutes a free side of the card after hot lamination and under pressure. Such a thermochromic pattern is advantageously printed on one face of said surface layer opposite to the face of the layer constituting the free external face of the card. As a variant or in combination, at least one thermochromic pattern is printed with a thermochromic ink composition 10 according to the invention on a layer immediately subjacent to a surface layer of the card, in particular on one face of this sub-layer. overlying coming into contact with said surface layer after hot lamination and under pressure.

The invention extends to a card comprising a plurality of layers superimposed on at least one thermoplastic material - in particular polycarbonate - comprising at least one thermochromic pattern formed by printing an ink composition according to the invention.

The invention also relates to a thermochromic ink composition, a method of manufacturing a card and a card characterized in combination by all or some of the characteristics mentioned above or below.

Other objects, characteristics and advantages of the invention will appear on reading the examples which follow.

EXAMPLE 1 manufacture of a thermochromic ink composition

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

The thermochromic ink composition includes:

% by weight of thermochromic pigments (microcapsules).

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- 10% ethyl ethoxy-3-propanoate,% by weight of 2 hydroxyphenyl-s-triazine (ultraviolet absorber).

Thermochromic microcapsules are microcapsules sold under the brand CHAMELEON® by the company Polychrom Co 10 LTD, Ansan City, Korea.

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

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

The ink can be printed with screen printing screens of 15,120 threads / cm allowing fine screen type prints of 80 dpi.

EXAMPLE 2: manufacture of a polycarbonate card incorporating thermochromic prints

An ink composition obtained in accordance with Example 1 is printed in the form of a solid on one side of two sheets of transparent polycarbonate, the thickness of which is of the order of 50 μm.

The ink is dried by hot air.

The printed polycarbonate sheets are associated with five other polycarbonate sheets interposed between the printed polycarbonate sheets so as to form a stack, the printed faces being placed in contact with the underlying sheets of the stack. That is to say, not constituting the outer faces of the latter. The five polycarbonate sheets forming, with the two printed sheets, said stack are successively the following: a 100 μm sheet of transparent polycarbonate; a 200 µm sheet of white polycarbonate; a 200 µm sheet of white polycarbonate; a 30,200 µm sheet of white polycarbonate; a 100 µm sheet of transparent polycarbonate.

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All of the sheets forming this stack are laminated in a lamination press under the following conditions:

- 1 min climb at 18O٥C

- 12 min at 18O٥C under 30N / cm2

- 5 min at 18O٠C under 150 N / cm2

- cooling to 26٠c for 17.5 min under 180N / cm2.

A card is obtained whose total thickness is equal to the sum of the thicknesses of the polycarbonate sheets used, reduced by approximately 10%.

The thermochromic prints produced with the thermochromic ink composition according to the invention are thus incorporated into the thickness of the card.

EXAMPLE 3: adhesion and durability tests

Durability tests are carried out on polycarbonate cards as manufactured in accordance with Example 2.

The adhesion between the different constituent layers of the card is evaluated according to different test protocols:

- peel measurement according to ISO 10373 - 90٥ at 300mm / min,

- peel measurement after climatic aging according to ISO 24789-1 and 2 standards,

- bending test according to ISO 24789-1 and 2 standards, 50,000 bending in the length, 50,000 bending in the width,

- bending test after climatic aging according to ISO 24789-1 and 2 standards,

- bending test after exposure to artificial light according to ISO 24789-1 and 2 standards

The peel measurement shows that the adhesive force between the layers is greater than 3.5 N / cm.

In the bending tests, no delamination appears at the polycarbonate layers surrounding the thermochromic prints.

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EXAMPLE 4: resistance to light

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

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

Thermochromic prints are exposed according to three test protocols:

- exposure to UVA rays: 8 p.m .; UVA 340 nm; 60 ° C; 0.72 w / m²/ nm (ISO 4892 standard),

- exposure to artificial light according to ICAO standard 3.2-2006 paragraph 5-14,

- exposure to xenon arc light according to ISO 24789-1 and 2.

The 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 of the xenon arc type.

With reversible thermochromic microcapsules colored in the inactive state and transparent in the activated state.

It is found that the tliermochromic activity of the exposed samples with regard to the bleaching temperature range and the bleaching temperature range is identical to that of the unexposed samples.

EXAMPLE 5: climatic behavior

The climatic resistance of polycarbonate cards as manufactured in accordance with Example 2 is evaluated according to the following test protocols:

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- exposure to thermal cycles and stressful storage conditions according to ICAO standard 3.2-2006 paragraph 5.2 (thermal cycling method) and paragraph 5.3 (storage temperature stress method),

- exposure to high temperatures and humidity, thermal shock and 5 thermal cycle according to ISO 24789-1 and 2, paragraph 5-7 (temperature and humidity aging), paragraph 5-8 (temperature shock), paragraph 5-9 ( temperature and humidity cycling).

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

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