KR102251250B1 - Process for the surface treatment of a security document and associated security document - Google Patents

Abstract

The present invention includes at least one security print consisting of at least one pattern on at least one side of both sides of a security document, wherein the one side and the at least one related print are covered with a transparent protective coating. It relates to a method for surface treatment of a security document, wherein a varnish containing 0.5% to 10% crystalline nanocellulose based on the weight of the varnish is disposed on the at least one side through printing or coating technology, and the varnish layer is dried. do.

Description

Surface treatment of security documents and related security documents {PROCESS FOR THE SURFACE TREATMENT OF A SECURITY DOCUMENT AND ASSOCIATED SECURITY DOCUMENT}

The present invention relates to the field of secure documents, such as credit documents or similar documents, for example.

The expression "credit document" means all documents, such as bank notes, checks, bank cards, etc., used to transmit a certain amount in the specification of the present invention. The expression "similar document" means any document issued by the administrative office of a state, such as passports, identification cards, driver's licenses, etc., to prove the identity of a person or the right to drive a vehicle. This expression also means any document used to authenticate an object of value, such as a label affixed to luxury clothing. In addition, it means any document used to authenticate tax payment, such as an income stamp.

1 shows a credit document 1, in particular a bank note, to which no protective coating has been attached.

The banknote 1 comprises a cotton substrate 2 having two opposite sides 20, 21. The bank note 1 also has a number of secure prints 3 with at least one pattern on one of the two sides.

In general, security prints 3 of various levels of security are added to banknotes 1 in particular to discourage counterfeiting attempts.

Such security printing 3 is prepared by a series of printing and security processes such as, but not limited to, laser marking or micro-perforation, flexo printing, silkscreen printing, hot marking, dry or wet offset, or intaglio printing. .

The one-step security printing (3) is detectable with the naked eye in daylight or artificial lighting and does not require the use of special devices. Watermarks present in the banknote 1, colored fibers, visible elements in transmitted light, or tactile embossing created by intaglio printing are examples of such first-level elements.

The two-stage security printing (3) is detectable using technically common devices such as ultraviolet or infrared lamps, or polarizing filters. In particular, these secure printings 3 make it possible to check the bank notes 1 in various institutions such as stores and branch banks. Examples of the two-step security printing 3 include patterns or texts printed with ink, fluorescent fibers and magnetic wires that are invisible in sunlight but visible under ultraviolet or infrared rays.

Finally, the three-stage secure printing 3 requires sophisticated equipment and is consequently expensive. These secure prints 3, for example tracers with special spectral features, are primarily inspected by central banks.

Therefore, this is a secure print (3) that can check the bank note (1).

However, one condition necessary to ensure the confirmation of the secure print 3 over time is the good obsolescence of the bank note 1 and the secure print 3.

Therefore, in terms of cost reduction and sustainable development, central banks show increasing interest in the development of banknotes that exhibit extended service life.

A number of studies have been carried out by central banks to elucidate several possible causes for the recovery of banknotes. The causes are, for example, tears, soiling, folded edges, graffiti, loss of stiffness, etc.

However, DE HEIJ Hans. Durable Banknotes: an overview.In: Presentation of the BPC / Paper Committee to the BPC at a presentation of the BPC/Paper Committe in Prague in May 2002. , May 2002, Prague), 60 to 80% of the recovered banknotes (1) are due to soiling. Therefore, the most important cause of the recovery of the bank note 1 is pollution.

Contamination is caused by fats such as sebum, which are naturally present on the surface of human skin. These fats that naturally enter the pores and/or accumulate on the surface of the banknote 1 by weak chemical bonding will contribute to the discoloration of the unique color of the banknote 1. Moreover, the oxidation of the fat accumulated on the surface of the banknote 1 will cause the appearance to become yellowish and then brownish over time, which will cause the banknote 1 to not circulate and lead to collection.

A number of solutions have already been provided by the practitioners in the field, in particular paper manufacturers, for example polyurethane-based or latex-based antifouling coatings on the substrate 2 of the banknote 1.

However, such a coating inevitably does not protect the print quality of the substrate 2 to an optimum level, and does not guarantee the protection of the security print 3, which is essential for verifying the banknote 1.

WO 02051638 discloses a technique consisting of flexographic printing varnishing of the substrate 2 at the final stage of the manufacturing process of the bank note 1. This overprinting varnish improves the contamination resistance of the bank note 1 and thus completely protects the security printing 3.

However, although the method disclosed in WO 02051638 generally improves the contamination resistance of the bank note 1, problems with water repellency and stain repellency still remain in this improvement.

In addition, WO 2013/178986, a document known in the prior art, proposes a security document including a cellulose microfiber base varnish. The cellulose microfibers used in this varnish have a length of 1 to 100 μm and a width and thickness of 5 to 10 nm.

In addition, WO 2012/127110, a document known in the prior art, discloses an iridescent crystalline nanocellulose film for security documents. Such films are obtained, for example, from an aqueous base solution comprising crystalline nanocellulose that adheres to the security document before proceeding to evaporation to form a solid film on the security document. Such a method is described for example in WO 2010/066029.

Therefore, it is an object of the present invention to improve the water repellency and oil repellency of the security document as well as the contamination resistance of the security document, and in particular, a method for surface treatment of a security document to ensure the protection of the security printing essential for the verification of a bank note. It is to solve the above-described disadvantages by proposing.

More precisely, the present invention includes at least one security print consisting of at least one pattern, on at least one side of both sides of a security document, wherein the one side and the at least one associated print are made of a transparent protective coating. One object is to provide a method for surface treatment of a covered security document, and a varnish including crystalline nanocellulose (CNC) in a proportion of 0.5% to 10% based on the weight of the varnish is It is placed on the side through printing or coating techniques, and the varnish layer is dried.

Preferably, a varnish comprising about 1% crystalline nanocellulose is used.

According to an embodiment of the present invention, the varnish is dried under ultraviolet light. According to a variant, the varnish is dried with hot air.

Preferably, the varnish is an epoxide based varnish or an acrylate based varnish.

Preferably, a solution containing cellulose microfibril (CMF) is applied to at least one side of a security document, and then a layer of cellulose microfibres is dried, after which the varnish layer is a layer of cellulose microfibres. Is placed on top.

Preferably, in order to form at least two layers of cellulose microfibres, before proceeding with the arrangement of the varnish layer, a solution containing cellulose microfibres is applied to at least one side of the security document and a layer of cellulose microfibres is applied. The steps of drying are repeated at least once.

In addition, the present invention includes at least one security print composed of at least one pattern on at least one side of both sides of a security document, and the one side and the at least one related print are covered with a transparent protective coating. One object of the present invention is to provide a secure document that is provided, and the coating is characterized in that it comprises at least one layer of varnish layer comprising crystalline nanocellulose in an amount of 0.5% to 10% based on the weight of the varnish.

Preferably, the varnish comprises about 1% crystalline nanocellulose.

Preferably, the varnish is an epoxide based varnish or an acrylate based varnish.

Preferably, the transparent protective coating also comprises a layer of cellulosic microfibres of at least one layer arranged between at least one side of the security document and the varnish layer.

Other features and advantages of the present invention will become apparent from the following detailed description which is to be read by reference to the accompanying drawings, which are wholly illustrative and non-limiting.

1 is a front view schematically showing a part of a bank note before carrying out the method of the present invention.
FIG. 2 is a schematic cross-sectional view of a bank note according to an embodiment of the present invention along the II-II plane of FIG. 1.
FIG. 3 is a schematic cross-sectional view of a bank note according to another embodiment of the present invention, taken along a plane II-II of FIG. 1.
Fig. 4 is a flow chart of a processing method executed on the bank note shown in Fig. 2;
5 is a flowchart of a processing method executed on the bank note shown in FIG. 3;

The security document 1 comprises a substrate 2 made of, for example, cotton-based vellum paper.

According to a variant, the substrate 2 is made of imitation paper comprising a mixture of cotton and natural fibers, for example flax fibers or abaca fibers.

According to another variant, the substrate 2 is made of imitation paper comprising a mixture of cotton and synthetic polymer fibers comprising, for example, polyethylene, polypropylene, polyester, polyamide.

According to another variant, the substrate 2 is made solely of a polymer such as for example biaxially stretched polypropylene.

According to another variant, the substrate 2 is a composite material. That is, the substrate 2 comprises an assembly of layers of natural fiber material and successive layers of a polymer such as polyester, polyamide or biaxially stretched polypropylene.

The security document 1 is, for example, a bank note.

The substrate 2 has two faces 20 and 21 opposite to each other. In the example shown in Figs. 2 and 3, the banknote 1 has a plurality of security prints 3 which are at least one pattern on one side 20 of both sides thereof. According to a variant (not shown), the banknote 1 has one or more secure prints 3 on two sides 20 and 21 of the substrate 2.

The banknote 1 also comprises an optically clear protective coating C covering one or both of the sides 20 and 21 and the associated security print 3.

The protective coating C comprises at least one varnish layer 4 in which crystalline nanocellulose (CNC) is incorporated in a proportion of 0.5% to 10% by weight of the varnish. Crystalline nanocellulose is, for example, in powder form.

In the present specification, the term "varnish" refers to a varnish formed to dry under infrared and/or hot air, or ultraviolet light. For forming the varnish layer 4, for example, acrylic varnishes comprising an aqueous base, varnishes comprising an epoxide base, or varnishes comprising an acrylate base are particularly suitable. Also suitable are varnishes containing a monomer of the cycloaliphatic epoxide family that polymerizes a polyepoxide substrate through an initiator such as an ultraviolet activated onium salt to form the varnish layer 4.

Nanocellulose is an organic material made of cellulose fibers of very small size, especially about 5 to 20 nm. Crystalline nanocellulose (CNC) is distinguished from cellulose microfibers (CMF).

Cellulose microfibers (CMF) are obtained by mechanical exfoliation of pre-bleached fibers, followed by homogenization, microfluidization and micropolishing treatments. The size of the cellulose microfibre (CMF) particles varies depending on the cellulose source from which the particles are extracted. In general, cellulose microfibers (CMF) have a diameter of 50 to 100 nm, a length of 1000 to 2000 nm, and a specific surface area of 10 to 100 m ² /g.

Crystalline nanocellulose (CNC) is obtained from cellulose microfibers (CMF) by chemical treatment of acid hydrolysis. Acid hydrolysis prevents deterioration of the crystalline regions of the cellulose, while destroying the amorphous parts inside and around the cellulose microfibers. Thus, cellulose nanocrystals, also referred to as "whiskers" are obtained. The size of crystalline nanocellulose (CNC) particles varies depending on the cellulose source from which they are extracted. For example, crystalline nanocellulose (CNC) has a diameter of 5 to 10 nm, a length of 100 to 500 nm, and a specific surface area of 500 m ² /g. Thus, crystalline nanocellulose (CNC) is clearly distinguished from cellulose microfibers by its size, in particular its length, being much shorter than that of cellulose microfibers.

Preferably, the layer of varnish and crystalline nanocellulose (CNC) comprises about 1% crystalline nanocellulose (CNC) with respect to the weight of the varnish.

In the example shown in FIG. 2, the protective coating C comprises a varnish and a layer 4 of crystalline nanocellulose (CNC). According to a variant (not shown), the protective coating C comprises a varnish and multiple layers 4 of crystalline nanocellulose (CNC).

The use of crystalline nanocellulose (CNC) as a dopant, i.e., a small amount as an additive to the varnish, has a surprising effect of substantially improving the water repellency and repellency of the banknote (1) as well as the water repellency and repellency while ensuring good mechanical properties. .

The use of nanocellulose is particularly advantageous in that it is produced from natural, renewable, recyclable and biodegradable materials.

The protective coating (C) comprising a layer of varnish and crystalline nanocellulose (CNC) also has the advantage that it is printable by itself and is compatible with skin contact, i.e. it is not toxic or does not cause allergies.

In the example shown in Figure 3, the protective coating (C) is a layer of cellulose microfibers (CMF) arranged between the layer 4 of varnish and crystalline nanocellulose (CNC) and the side 20 of the banknote 1 ( Also includes 5). For example, cellulose microfibers (CMF) are in the form of a gel incorporated in a solvent, especially water or isopropanol. For example, the cellulose microfiber (CMF) gel contains a solid content of 2% of the gel weight when the solvent used is water, and the solid content of 2.5% of the gel weight when the solvent used is isopropanol.

Preferably and as shown in Figure 3, the protective coating (C) is at least two layers of cellulose microstructures arranged between the layer (4) of varnish and crystalline nanocellulose (CNC) and the side (20) of the banknote (1). And layers 5 of fibers (CMF).

The use of layers 5 of cellulose microfibres (CMF) is a combination with a varnish and a layer of crystalline nanocellulose (CNC), a single layer of varnish and a layer of crystalline nanocellulose (CNC) (4). It makes it possible to provide the banknote 1 with more improved pollution prevention properties, water repellency and stain repellency compared to those used. Moreover, the use of layers 5 of cellulose microfibers (CMF) improves the mechanical properties of the banknote 1, in particular tearing resistance.

In addition, it is particularly advantageous to use nanocellulose in that it is produced from natural materials, renewable materials, recyclable materials and biodegradable materials as described above.

A protective coating (C) comprising a layer of at least one layer of cellulose microfibers (CMF) and a layer of varnish and a layer of crystalline nanocellulose (CNC) can be produced by known industrial methods such as coating and printing. There is also the advantage of being compatible with skin contact, i.e. not toxic or allergic.

The surface treatment of the banknote 1 shown in Fig. 2 proceeds as described below.

In the first step 30 shown in Fig. 4, a varnish containing crystalline nanocellulose (CNC) is applied to the sides 20 and 21 of the bank note 1 by printing or coating technology to form a transparent protective coating C. ) Are placed on one or both of them.

Varnishes comprising crystalline nanocellulose (CNC) are applied, for example, by methods of flexo printing, photogravure printing or silkscreen printing, or even air knife coating, curtain coating or roll coating. For example, the varnish layer 4 is applied by the flexographic printing method using ^{15 cm 3} /m ^{2 anilox rolls applying 4 to 5 g/m 2 on average.}

During the second step 31, the varnish layer 4 comprising crystalline nanocellulose (CNC) is dried. According to an embodiment, the varnish layer 4 comprising crystalline nanocellulose (CNC) is dried with ultraviolet rays. This embodiment is particularly advantageous when the varnish is a varnish comprising an epoxide or acrylate base. According to a variant, the varnish layer 4 comprising crystalline nanocellulose (CNC) is dried with hot air. This embodiment is particularly advantageous when the varnish is a varnish comprising an aqueous base.

According to an embodiment (not shown) of the present invention, the first and second steps 30 and 31 are repeated at least once to form two or more layers of varnish and layers 4 of crystalline nanocellulose (CNC). .

The surface treatment of the banknote 1 shown in Fig. 3 proceeds as described below.

In a first step 40 shown in FIG. 5, a solution of a cellulose microfibre (CMF) gel and a solvent is applied to one or both of the sides 20 and 21 of the banknote 1. The banknote 1 may be printed or unprinted in advance.

The solution is applied in the laboratory using, for example, a threaded rod to which a solution containing cellulose microfibre (CMF) gel is attached. Next, the rod is moved along the side 20 or 21 of the bank note 1 in order to distribute the solution evenly. For example, a threaded rod is applied with a layer 5 of solution 36 to a thickness of 36 μm.

According to a variant, the solution is applied to one or both of the sides 20, 21 of the bank note 1 by coating or printing techniques described below. This variant is particularly suitable for industrial manufacturing conditions.

During the second step 41, the layer 5 of cellulose microfibre (CMF) gel is dried. The layer 5 of cellulose microfibrous (CMF) gel is dried, for example by hot air and/or open laboratory air. During drying, the solvent evaporates from the solution and the thickness of the layer 5 decreases.

Preferably and as shown in Fig. 5, the first and second steps 40, 41 are repeated at least once to form layers 5 of two or more cellulose microfibres (CMF) gels.

According to an embodiment of the present invention (not shown), the substrate 2 is then laminated by intaglio printing, for example with or without ink, in order to return a uniform and smooth surface quality to the substrate 2 .

During the third step 42, a varnish comprising crystalline nanocellulose (CNC) is deposited on the layer 5 of cellulose microfibrous Kel, which was finally applied, by printing or coating technique.

The varnish layer 4 comprising crystalline nanocellulose (CNC) is applied, for example, by methods of flexo printing, photogravure printing or silkscreen printing, or even air knife coating, curtain coating or roll coating.

During the fourth step 43, the varnish layer 4 comprising nanocellulose (CNC) is dried. According to an embodiment, the varnish layer 4 comprising nanocellulose (CNC) is dried with ultraviolet rays. This embodiment is particularly advantageous when the varnish is a varnish comprising an epoxide or acrylate base (cationic and radically polymerizable, respectively). According to a variant, the varnish layer 4 comprising crystalline nanocellulose (CNC) is dried with hot air. This embodiment is particularly advantageous when the varnish is a varnish comprising an aqueous base.

According to an embodiment (not shown) of the present invention, the third and fourth steps 42 and 43 are repeated at least once to form two or more layers of varnish and layers 4 of crystalline nanocellulose (CNC). do.

The table below shows the results obtained by the Cobb sizing test, Frisch test, Kit test, and Bentsen permeability test performed on security documents to which various treatments were applied. Is summarized.

"One-sided calendered" means that the substrate is intaglio printed on one side.

By "laminated CMF layers" it is meant that layers of cellulose microfibers (CMF) are intaglio printed without the use of ink.

By "standard varnish" is meant a varnish comprising a monomer of the cycloaliphatic epoxide family that polymerizes a polyepoxide matrix through an initiator such as an ultraviolet activated onium salt.

In the above table, various tests were performed on the calendered side and both sides of each substrate were varnished.

The Cobb sizing test characterizes the water repellency, ie the resistance of the banknote base to the penetration of water, such as moisture in sweat. More precisely, this is the amount of water absorbed by the substrate expressed in ^{g/m 2} over a period of 60 seconds.

The Fritz test characterizes contamination resistance. The Fritz test is carried out for 15 minutes using a vibrating device in which small glass spheres are dispersed on a substrate to form a skin. The contaminant composition is used to determine the fats present in sand, peat, activated carbon, flour, and sebum and glycerin monooleate. Includes. The brightness L* of the substrate for the various zones is measured before and after the substrate is exposed to the contaminating composition. The difference ΔL* obtained between the measurements before and after running the test characterizes the adhesion of the contaminant to the substrate. Therefore, the smaller the difference value, the better the contamination resistance of the substrate.

Kit tests characterize the stain repellency of the substrate. This is a test in which the substrate is exposed to a mixture of fats, especially castor oil and a high boiling point solvent, toluene and n-heptane during the test. By varying the proportions of the listed materials, a composition is obtained in which the viscosity and surface tension change inversely with the impregnation ability. Thus, a composition rich in castor oil is located at the bottom of the scale, whereas a composition rich in solvent is located on the top at the same scale. Typically 12 different compositions are used. The evaluation is carried out visually. It is recognized that a score of 6 or more imparts a satisfactory barrier to fat. The results in this test are highly dependent on the substrate and the surface condition of the secure print covering the substrate.

The ventgen permeability test characterizes the air permeability of the substrate, ie air flow through the substrate at a measuring surface area of ^{10 cm 2.}

The table presented above highlights the advantages conferred by the present invention.

In fact, in this table, crystalline nanocellulose (CNC) as a dopant in the varnish attached to the substrate 2, i.e., incorporated at a low ratio, substantially improves the contamination resistance, water repellency, stain repellency and air permeability of the banknote (1). It is clear that it is done.

In addition, in this table, the combination of varnish containing crystalline nanocellulose (CNC) and layers of cellulose microfibres (CMF) is the combination of a bank note (1) already obtained by attaching a layer (4) of varnish and crystalline nanocellulose (CNC). It is also clear that it further improves properties, in particular stain resistance and stain repellency.

In addition, similar tests conducted on paper containing a varnish layer incorporating cellulose microfibres (CMF) powder indicated that a mixture of varnish and cellulose microfibres (CMF) could not be easily printed. Moreover, these tests did not give important results, in particular with regard to contamination resistance, water repellency, stain repellency and air permeability. Thus, the combination of varnish and crystalline nanocellulose (CNC) gives particularly advantageous results, especially with regard to contamination resistance, water repellency, stain repellency and air permeability, but not in the combination of the same varnish and cellulose microfibres (CMF). Thus, the results in these tests show a special synergistic effect between the varnish and crystalline nanocellulose (CNC), even in small amounts, which does not exist between the varnish and cellulose microfibres (CMF).

Therefore, the present invention has the advantage of proposing a bank note 1 having remarkably improved contamination resistance. Thus, the bank note 1 according to the present invention can remain in circulation for a longer period of time before being returned to the central bank. In addition, this improvement of contamination resistance according to the present invention is economically inexpensive and does not employ complex physical methods that significantly increase the manufacturing cost of the bank note 1. Finally, the natural substances cellulose microfibres (CMF) and crystalline nanocelluloses (CNC) have the obvious advantage of not being on the list of substances that are restricted under the REACH regulation as set out by the European Chemicals Agency (ECHA).

Claims (11)

It includes at least one security print (3) consisting of at least one pattern on at least one side of the two sides (21, 22) of the security document, and the one side and the at least one related security print are transparent. As a method for surface treatment of a security document 1 covered with a protective coating (C),
Arranging (30, 42) a varnish containing crystalline nanocellulose (CNC) on the at least one side 21 by printing or coating technology in a proportion of 0.5% to 10% based on the weight of the varnish, and the varnish A method for surface treatment of a secured document (1), characterized by the step (31, 43) of drying the layer (4). The method of claim 1,
A method for surface treatment of a security document (1), characterized in that a varnish containing 1% of crystalline nanocellulose (CNC) is used. The method of claim 1,
The step of drying the varnish (31, 43) is a method for surface treatment of a security document (1), characterized in that it is carried out under ultraviolet light. The method of claim 1,
The step of drying the varnish (31, 43) is a method for surface treatment of a security document (1), characterized in that it is carried out with hot air. The method of claim 1,
The varnish is an epoxide-based varnish or an acrylate-based varnish. The method according to any one of claims 1 to 5,
Step 40 of applying a solution containing cellulose microfibers (CMF) to at least one side 21 and 22 of the security document 1, followed by drying the layer 5 of cellulose microfibers (CMF). A method for surface treatment of a security document (1), characterized by a step (41), and thereafter disposing (42) the varnish layer (4) on a layer (5) of cellulose microfibers (CMF). The method of claim 6,
In order to form the layers 5 of at least two layers of cellulose microfibres (CMF), prior to the step 42 of arranging the varnish layer 4, at least one side (21, 22) of the security document (1) is The steps (40, 41) of arranging cellulose microfibers (CMF) by coating technology and drying the layer of cellulose microfibers (CMF) are repeated at least once. It includes at least one security print (3) consisting of at least one pattern on at least one side of the two sides (21, 22) of the security document, and the one side and the at least one related security print are transparent. As a security document (1) covered with a protective coating (C),
The coating is a security document (1), characterized in that it comprises a varnish layer (4) of at least one layer containing crystalline nanocellulose (CNC) in a proportion of 0.5% to 10% based on the weight of the varnish. The method of claim 8,
Security document (1), characterized in that the varnish contains 1% crystalline nanocellulose (CNC). The method of claim 8,
Security document (1), characterized in that the varnish is an epoxide-based varnish or an acrylate-based varnish. The method according to any one of claims 8 to 10,
The transparent protective coating (C) also comprises a layer (5) of at least one layer of cellulose microfibres (CMF), arranged between at least one side (21, 22) of the security document and the varnish layer (4). Security document (1), characterized in that.

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