KR20160118240A - Process for the surface treatment of a security document and associated security document - Google Patents

Abstract

The present invention comprises at least one secure print comprising at least one pattern on at least one side of both sides of a secure document, wherein the one side and the at least one associated print are covered with a transparent protective coating A method for surface treatment of a security document, wherein a varnish comprising crystalline nanocrystalline in a ratio of 0.5% to 10% by weight of the varnish is disposed on the at least one side through a printing or coating technique, do.

Description

PROCESS FOR THE SURFACE TREATMENT OF A SECURITY DOCUMENT AND ASSOCIATED SECURITY DOCUMENT [0002]

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

The expression "credit document" means all documents such as a bank note, a check, a bank card, etc. used to transmit a certain amount in the specification of the present invention. The expression "similar document" means any document issued by an administrative authority of the State for the purpose of demonstrating the identity of a person, such as a passport, identity card or driver's license, or the right to drive a vehicle. This expression also refers to any document used to authenticate an object of value, such as a label attached to, for example, luxury apparel. It also means any document used to authenticate tax payments such as income recognition.

Figure 1 shows a credit document (1), in particular a bank note, where no protective coating is attached at all.

The banknote 1 comprises a cotton substrate 2 having two faces 20, 21 opposite to each other. The banknote 1 also has a plurality of secure prints 3 with at least one pattern on one of the sides.

Generally, a security print 3 of various security levels is added to the banknote 1, in particular to dissuade attempts to counterfeit.

This secure print 3 is prepared by a series of printing and security processes such as, but not limited to, laser marking or micro-perforation, flexo printing, silk screen printing, hot marking, dry or wet offset, .

The first level of security printing (3) is detectable by daylight or artificial light and does not require the use of special equipment. The watermark, the non-colored fibers present in the banknote 1, the visible elements in the transmitted light, or the tactile embossing created by intaglio printing are examples of the first stage element.

The two-step security print 3 is detectable using technically common devices such as ultraviolet or infrared lamps or polarizing filters. In particular, these security prints (3) enable identification of banknotes (1) in various institutions such as shops and branch offices. Examples of two-step security printing (3) include patterns or text printed with inks, fluorescent fibers and magnetic wires that are invisible in daylight but visible under ultraviolet or infrared radiation.

Finally, the three-step secure printing (3) requires a sophisticated device and, as a result, is expensive. These security prints (3), for example tracers with special spectral characteristics, are usually checked by the central bank.

Therefore, this is a secure print (3) that identifies the banknote (1).

However, one condition required to ensure the confirmation of the secure print 3 over time is the good aging of the banknote 1 and the secure print 3.

Thus, from the perspective of cost savings and sustainable development, central banks show increasing interest in the development of banknotes that represent extended service life.

A number of studies have been carried out by the central bank to identify the various possible causes for the withdrawal of banknotes. The causes are, for example, tearing, dirty, folded edges, graffiti, loss of stiffness, and the like.

However, a review of the durable banknotes issued by DE HEIJ Hans at the BPC / Paper Committe presentations in Prague in May 2002 (DE HEIJ Hans. Durable Banknotes: an overview. In: Presentation of the BPC / Paper Committee to the BPC , May 2002, Prague), 60 to 80% of the recovered banknotes (1) are due to soiling. Therefore, the most important reason why banknotes (1) are recovered is pollution.

Contamination is due to fats, especially sebum, that naturally exists on the skin surface of a person. These fats, which naturally enter the pores and / or accumulate on the surface of the banknote (1) by weak chemical bonds, will contribute to the discoloration of the banknote (1). Moreover, oxidation of the accumulated fat on the surface of the banknote (1) causes the appearance to turn yellowish and then brownish over time, which will cause the banknote (1) not to circulate but to be recovered.

A number of solutions have already been provided by relevant industry practitioners, notably by paper manufacturers, such as polyurethane bases or latex base antifouling coatings on the substrate 2 of banknote 1, for example.

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

WO 02051638 discloses a technique consisting of flexographic printing varnishes of the substrate (2) at the end of the manufacturing process of the banknote (1). This overprinting varnish improves the fouling resistance of the banknote 1 and thus protects the security print 3 completely.

However, although the method disclosed in WO 02051638 substantially improves the fouling resistance of banknote 1, there are still challenges associated with water repellency and foaming.

WO 2013/178986, also known in the prior art, discloses a security document comprising a cellulose microfiber base varnish. The cellulose microfibers used in this varnish are 1 to 100 mu m in length and 5 to 10 nm in width and thickness.

Also known from the prior art, WO 2012/127110 discloses a pristine crystalline nanocellulose film for security documents. Such a film is obtained, for example, from an aqueous base solution comprising crystalline nano-cellulose adhered to a 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 provide a surface processing method of a security document for improving the repellency of security documents as well as improving the repellency and oil repellency of security documents, To solve the above-mentioned disadvantages.

More precisely, the present invention comprises at least one secure print comprising at least one pattern on at least one of the two sides of a security document, wherein said one face and said at least one associated print are in a transparent protective coating It is an object to provide a method for surface treatment of a covered security document, wherein a varnish comprising crystalline nanocellulose (CNC) in a proportion of 0.5% to 10% by weight of the varnish is applied to the at least one Is disposed through a printing or coating technique on the surface, and the varnish layer is dried.

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

According to one 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 base varnish or an acrylate base varnish.

Preferably, a solution comprising cellulose microfibril (CMF) is applied to at least one side of the security document, and then a layer of cellulose microfibers is dried, after which a layer of cellulose microfibril .

Preferably, a solution comprising cellulose microfibers is applied to at least one side of the security document before proceeding with the placement of the varnish layer, to form layers of at least two layers of cellulose microfibers, and a layer of cellulose microfibers Are repeated at least once.

The invention also includes at least one secure print comprising at least one pattern on at least one side of both sides of the secure document, wherein the one side and the at least one associated print are covered with a transparent protective coating Wherein the coating comprises at least one layer of a varnish layer comprising crystalline nanocrystalline in a proportion of 0.5% to 10% by weight of the varnish.

Preferably, the varnish comprises about 1% crystalline nanocellulose.

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

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

Other features and advantages of the present invention will be apparent from the following detailed description, which is meant to be purely exemplary and non-limiting and should be read with reference to the accompanying drawings.

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

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 a blend of natural fibers, for example flax fibers or abaca fibers, and mixtures of the faces.

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

According to another variant, the substrate 2 is exclusively made of a polymer, for example a biaxially oriented polypropylene.

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

The secure document (1) is, for example, a banknote.

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

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

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

The term "varnish" as used herein means a varnish which is formed to dry under infrared and / or hot wind, or ultraviolet radiation. Varnishes comprising, for example, an acrylic varnish comprising an aqueous base, a varnish comprising an epoxide base, or an acrylate base to form the varnish layer 4 are particularly suitable. Also suitable are varnishes comprising monomers of the cycloaliphatic epoxide family which polymerize the polyepoxide substrate via an initiator such as, for example, 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 peeling of the previously bleached fibers, followed by homogenization, microfluidization and micro-polishing treatments. The size of the cellulose fine fiber (CMF) particles varies with the cellulose source from which the particles are extracted. Generally, the cellulose microfine fibers (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 microfibrils (CMF) by chemical treatment of acid hydrolysis. Acid hydrolysis prevents degradation of the crystalline regions of the cellulose while destroying the amorphous portions inside and around the cellulose microfibers. Thus, a cellulose nanocrystal, also referred to as a "whisker" is obtained. The size of the 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 nanoclusters (CNC) are clearly distinguished from cellulose microfibers by their size, especially their length being much shorter than the length of the cellulose microfibers.

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

In the example shown in Figure 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 plurality of layers 4 of varnish and crystalline nanocellulose (CNC).

The use of crystalline nano-cellulose (CNC) as a dopant in small quantities as an additive in varnishes has the surprising effect of substantially improving the water repellency and foaming properties as well as the antifouling property of the banknote 1 .

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

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

3, the protective coating C comprises a layer of cellulose microfibers (CMF) arranged between the layer 4 of varnish and crystalline nano-cellulose (CNC) and the face 20 of the banknote 1 5). For example, cellulose microfibers (CMF) are in the form of a gel incorporated in a solvent, especially water or isopropanol. For example, a cellulose microfibre (CMF) gel comprises a solids content of 2% of the gel weight when the solvent used is water and a solids content of 2.5% of the gel weight when the solvent used is isopropanol.

Preferably, and as shown in FIG. 3, the protective coating C comprises at least two layers of cellulose microspheres arranged between the layer 4 of varnish and crystalline nanocerulose (CNC) and the face 20 of the banknote 1 And layers (5) of fibers (CMF).

The use of layers 5 of cellulose microfibers (CMF) results in a single layer of varnish and a layer of crystalline nanocellulose (CNC) (4) in combination with a layer of varnish and crystalline nanocellulose (CNC) Thereby making it possible to provide the banknote 1 with a further improved contamination prevention, water repellency and corrosion resistance as compared with those used. Moreover, the use of layers 5 of cellulose microfibers (CMF) improves the mechanical properties of the banknote 1, in particular the tearing resistance.

It is also particularly advantageous to use nanocellulose in that the nanocellulose is produced from natural materials, renewable materials, recyclable materials and biodegradable materials as described above.

A protective coating (C) comprising at least one layer of cellulose microfibers (CMF) and one layer of varnish and a layer of crystalline nanocellulose (CNC) is produced by known industrial methods such as coating and printing And is compatible with skin contact, i.e., it has no toxicity or does not cause allergy.

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

4, a varnish comprising crystalline nano-cellulose (CNC) is applied by a printing or coating technique to the sides 20, 21 of the banknote 1 to form a transparent protective coating (C) Or on both sides thereof.

Varnishes comprising crystalline nano-cellulose (CNC) are applied, for example, by methods of flexographic printing, photogravure printing or silk screen printing, or even by methods of air knife coating, curtain coating or roll coating. For example, the varnish layer 4 is applied by the flexographic method using 15 cm ³ / m ² anilox rolls that apply an average of 4 to 5 g / m ² .

During the second step 31, the varnish layer 4 comprising crystalline nanocellulose (CNC) is dried. According to one embodiment, the varnish layer 4 comprising crystalline nanocellulose (CNC) is dried with ultraviolet light. 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 one 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 crystalline layers of nanocellulose (CNC) .

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

In a first step 40 shown in Figure 5, a solution of cellulose microfibre (CMF) gel and solvent is applied to one or both of the faces 20,21 of the banknote 1. The banknote 1 may be pre-printed or non-printed.

The solution is applied in the laboratory using, for example, a threaded rod with a solution containing cellulose microfibrils (CMF) gel. The bar is then moved along the face 20 or 21 of the banknote 1 to distribute the solution evenly. For example, a threaded bar applies layer 5 of solution 36 to a thickness of 36 [mu] m.

According to a variant, the solution is applied to one or both sides 20, 21 of the banknote 1 by the 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 fine fiber (CMF) gel is dried, for example, by hot air and / or open laboratory air. During drying, the solvent evaporates from solution and the thickness of 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 layers of cellulose microfine (CMF) gels.

According to one embodiment (not shown) of the present invention, the substrate 2 is then laminated by intaglio printing, for example using ink 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 nano-cellulose (CNC) is applied on the layer 5 of the finally applied cellulose microfibre coat by printing or coating techniques.

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

During the fourth step 43, the varnish layer 4 comprising nanocellulose (CNC) is dried. According to one embodiment, the varnish layer 4 comprising nanocellulose (CNC) is dried with ultraviolet light. This embodiment is particularly advantageous when the varnish is a varnish comprising an epoxide or acrylate base (each cationically and radically polymerizable). 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 one embodiment (not shown) of the present invention, the third and fourth steps 42 and 43 are repeated at least once to form layers 4 of two or more layers of varnish and crystalline nanocellulose (CNC) do.

The table below shows the results obtained with the Cobb sizing test, the Fritsch test, the Kit test, and the Bendtsen permeability test performed on the security documents with various treatments. .

"1-side 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 monomers of the cycloaliphatic epoxide family polymerizing the polyepoxide substrate via initiators such as ultraviolet activated onium salts.

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

The cob sizing test characterizes water repellency, ie, the resistance of a bank note to the penetration of water, such as moisture in the sweat. More precisely, this is the amount of water absorbed by the substrate 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 the substrate to form the envelope, which is used to remove the fat present in sand, peat, activated charcoal, flour, and sebum, glycerin monooleate . The brightness L * of the substrate is measured for various zones before and after exposure of the substrate to the contaminant composition. The difference [Delta] L * obtained between the measurements before and after performing the test characterizes the attachment of contaminants to the substrate. Therefore, the smaller the difference value, the better the contamination resistance of the substrate.

The kit test characterizes the aerosol properties of the substrate. This is a test during which the substrate is exposed to a mixture of fats, especially castor oil and high boiling solvents, toluene and n-heptane. By varying the ratios of the listed materials, a composition is obtained in which the viscosity and surface tension vary inversely with the impregnating ability. Thus, the composition in which the castor oil is enriched is located at the bottom of the scale, while the composition in which the solvent is enriched is located at the top in the same scale. In general, twelve different compositions are used. The evaluation is performed visually. It is recognized that a score of 6 or higher gives a satisfactory barrier to lipids. The results in this test are highly dependent on the substrate and the surface conditions of the security print covering the substrate.

The Ventgen permeability test characterizes the air permeability of the substrate, i.e. the air flow through the substrate at a measured surface area of 10 cm ² .

The foregoing table highlights the advantages imposed by the present invention.

Indeed, in this table, it can be seen that the incorporation of crystalline nanocellulose (CNC) as a dopant, i.e., a low proportion, into the varnish deposited on the substrate 2 substantially improves the fouling resistance, water repellency, .

Also in this table, the combination of the layers of the varnish comprising crystalline nano-cellulose (CNC) and the layers of cellulose microfibers (CMF) is obtained by attaching a layer 4 of varnish and crystalline nanocellulose (CNC) It is also clear that it further improves the properties, in particular the fouling resistance and foaming properties.

In addition, similar tests performed on paper comprising a varnish layer incorporating cellulose microfibrillary (CMF) powders have shown that a mixture of varnish and cellulose microfibers (CMF) can not be easily printed. Moreover, these tests did not provide significant results, especially with respect to fouling resistance, water repellency, gas permeability and air permeability. Thus, the combination of a varnish and a crystalline nanocellulose (CNC) provides particularly beneficial results, especially with regard to contamination resistance, water repellency, gas permeability and air permeability, but not in the combination of the same varnish and cellulose microfibers (CMF). Thus, the results in these tests show a special synergy between the varnish and the crystalline nanocellulose (CNC), even in small amounts, which does not exist between the varnish and the cellulose microfibrils (CMF).

Therefore, the present invention has the advantage of proposing banknote 1 with remarkably improved pollution resistance. Thus, the banknote 1 according to the present invention can be kept for a longer period of time before being returned to the central bank. In addition, according to the present invention, this improvement in pollution resistance is economically inexpensive and does not use complicated physical methods that significantly increase the manufacturing cost of the banknote 1. Finally, the natural substances cellulose microfibers (CMF) and crystalline nanocelluloses (CNC) have the obvious advantage that they do not fall under the list of substances restricted under the REACH regulation prescribed by the European Chemicals Management Organization (ECHA).

Claims (11)

At least one security print (3) consisting of at least one pattern on at least one of the two sides (21, 22) of the security document, said one side and said at least one associated security print being transparent A surface treatment method of a security document (1) covered with a protective coating (C)
(30, 42) of a varnish comprising crystalline nanocrystalline (CNC) in a proportion of from 0.5% to 10% by weight of the varnish on said at least one side (21) by a printing or coating technique, And drying the layer (4) (31, 43). The method according to claim 1,
Characterized in that a varnish comprising about 1% of crystalline nanocellulose (CNC) is used. 3. The method according to claim 1 or 2,
Wherein the drying (31, 43) of the varnish is carried out under ultraviolet light. 3. The method according to claim 1 or 2,
Wherein the drying (31, 43) of the varnish is carried out with hot air. 4. The method of any one of the preceding claims,
Wherein the varnish is an epoxide base varnish or an acrylate base varnish. 6. The method according to any one of claims 1 to 5,
(40) of applying a solution comprising cellulose microfibers (CMF) to at least one surface (21, 22) of the security document (1), followed by drying the layer (5) of cellulose microfibers Placing a varnish layer (4) on the layer (5) of the cellulose microfibre (CMF) after step (41), and thereafter (42). The method according to claim 6,
It is preferred that at least one of the surfaces 21 and 22 of the security document 1 is provided with at least two layers before forming the varnish layer 4 to form the layers 5 of at least two layers of cellulose microfibers CMF. Characterized in that the steps (40, 41) of placing the cellulose microfibers (CMF) by a coating technique and drying the layer of cellulose microfibers (CMF) are repeated at least once. At least one security print (3) consisting of at least one pattern on at least one of the two sides (21, 22) of the security document, said one side and said at least one associated security print being transparent A security document (1) covered with a protective coating (C)
Characterized in that the coating comprises at least one layer of varnish layer (4) comprising crystalline nanocellulose (CNC) in a proportion of 0.5% to 10% by weight of the varnish. 9. The method of claim 8,
Characterized in that the varnish comprises about 1% crystalline nanocellulose (CNC). 10. The method according to claim 8 or 9,
Characterized in that the varnish is an epoxide base varnish or an acrylate base varnish. 11. The method according to one of claims 8 to 10,
The transparent protective coating C also comprises a layer 5 of at least one layer of cellulose microfibers (CMF) arranged between at least one side 21, 22 of the security document and the varnish layer 4 (1).

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