KR20190067173A - How to create a secure element - Google Patents

Abstract

The present invention relates to a support made of oriented plastic and a method for producing a security element comprising at least one layer of liquid crystals bearing and orientated by the support, wherein the support is stretched before it is stretched in at least one direction Thereafter, an adhesion primer is depotted and the orientation is such that the support is in an oriented state and the liquid crystals are depotted by printing on the adhesive primer.

Description

How to create a secure element

The present invention relates to security elements for secure documents, and processes for creating the same.

The present invention particularly relates to security elements for bearing liquid crystals.

Liquid crystals, especially cholesteric liquid crystals, are widely used in security elements due to their goniochromatic properties. In order to improve the visibility of the effect of changing the color by the viewing angle, they are generally dark, in particular black, placed in front of the background.

Moreover, security elements in the form of strips, also referred to as security threads, are often incorporated into security documents such as banknotes.

These security elements conventionally include a substrate made of a thermoplastic material, for example PET, which may or may not have demetallized zones in the form of patterns seen in transmitted light.

It is advantageous to provide liquid crystals to these security elements to enhance security by creating optical effects that are visible to the naked eye.

However, depoting of liquid crystals is confronted with a number of problems that are currently solved only through processes that are complex to implement, costly, and impose certain limitations in terms of arrangement.

Thus, practice is known to apply solid state liquid crystals by a transfer process, which has the drawback of limiting the possibilities from the artistic point of view and imposing the presence of liquid crystals in non-metalized zones. This provides coloring in less attractive transmission light and the presence of liquid crystals in nonmetallized zones increases the cost of security without providing any significant benefits in terms of security or art.

The transfer process causes loss of material and lamination steps, which makes the production more complicated.

EP 1 744 904 discloses a substrate comprising a biaxially oriented PET film coated with oriented liquid crystals. This type of structure is not entirely satisfactory in terms of adhesion to the substrate.

Application US 2003189684 describes various processes for orienting liquid crystals.

Application US 20070216518 discloses multilayer structures containing liquid crystals. The superposition of liquid crystals makes structures expensive by increasing the amount of liquid crystals to be used. Generation by a transfer process is preferable.

The application EP 2 073 986 also describes structures with superposition of liquid crystals.

JP 2009-98568 discloses a security element comprising an oriented film made of plastic, which may be biaxially stretched and bearing liquid crystals.

GB 2 527 763 describes an oriented polymer film which may also contain liquid crystals and also sheets comprising an adhesive layer.

WO 2008/116796 relates to a security document comprising a plurality of polymer films comprising an opaque film that undergoes axial stretching. Adhesive layers may be applied to this film by printing. Moreover, the film may comprise liquid crystals.

In particular, to further enhance security elements including liquid crystals and processes for creating them, in order to have available security elements that are used in a manner that allows liquid crystals to adhere well to the substrate and allow full and abundant array optical effects There is a need for

The present invention aims at meeting this need and achieving this by a process for creating a security element comprising a support made of oriented plastic and at least one layer of bearings and oriented liquid crystals by the support And an adhesion primer is deposited before or after the support is stretched in at least one direction and the stretching enables the support to be in an oriented state and the liquid crystals are printed on this adhesive primer by printing Lt; / RTI >

The term "adhesive primer" should be understood to mean any layer that promotes adhesion. Therefore, this expression should not be understood in a restrictive way.

With the present invention, the adhesion of the liquid crystals is improved, and the depoting of the liquid crystals by printing provides many possibilities in terms of the aesthetics and optical effects obtained.

The application of the liquid crystals can be performed according to any pattern, on well-defined regions, thus providing great flexibility in the arrangement of the various securing means within the element. If appropriate, it is possible to obtain a greater variety of color-change effects without penalizing the transparency of the clear text openings.

The present invention makes it possible to avoid the deposition of liquid crystals by transfer, which facilitates the implementation of the process.

Preferably, the bonding primer is depotted prior to the step of stretching the support.

Likewise, the support is oriented in one direction, after which the primer is depotted, and the support is then stretched in the other direction.

Application of the primer prior to stretching the support allows the primer to entrain the stretching of the support and thus further improves the orientation of the liquid crystals.

The support preferably comprises PET, but other materials may be used.

The primer may require crosslinking before application of the liquid crystals, especially when including monomers. The process may thus comprise the step of crosslinking the adhesive primer, preferably after stretching of the support.

The adhesive primer may comprise a polyolefin (or polyalkene), preferably a polyethylene, a polyurethane, a polyester, a polyether, a polycarbonate or a polyacrylic, or a copolymer thereof, have.

The adhesive primer may also comprise at least one olefin (or alkene), urethane, ester, ether, carbonate or acrylic monomer, preferably acrylic monomer, prior to its demoulding, in particular.

Application of the primer may be carried out by any means, and in particular by printing, coating, spraying or co-extrusion.

Printing of the liquid crystals may be performed by any means, and preferably by screen printing, photogravure or flexography. The liquid crystals are deposited after stretching the support.

The process may include printing on an adhesive primer of two different inks, at least one of which includes liquid crystals, rather it is better that both contain liquid crystals and the liquid crystals are preferably cholesteric.

These two inks may be deposited without overlap; The depotated amount is thus limited to only a useful amount.

The reflected haze (hereinafter "haze") effect of the cholesteric liquid crystal layer may be less than the reflective haze effect of the reference security element without a layer of adhesive primer. The reflective haze is responsible for the milky appearance associated with the scattering of low-intensity light with the dominant reflection corresponding to the reflection in the specular direction. Measurements may be performed according to standard ASTM D4039-09 (reapproved in 2015) or ISO 13803: 2014. This allows the visibility of the goniocromatic effect over a wider range of angles, and consequently the masking of the background over a wider angular range.

A dark background may be provided below the layer of liquid crystals, especially on the opposite side of the support. As a variant, a dark background may be provided on the layer of liquid crystals, in particular on the same side of the support. This dark background may be obtained by printing dyes or (absorbent or coherent) pigments. As a variant, the dark background is obtained by metallization, in particular under vacuum or electrochemically or by any other technique for depotating metal, metal oxides or metal oxide salts. The dark background is also preferably supported by an additional support comprising PET, and may be attached to the support by suitable means, in particular by lamination with an adhesive. If appropriate, the additional support is preferably attached to the support at the side of the layer of liquid crystals.

Preferably, the dark background is at least partially overlaid on the layer of liquid crystals.

The dark background is preferably arranged in-register with respect to the printing of the liquid crystals; In particular, a dark background may be superimposed exactly on liquid crystals.

The dark background may be generated before application of the liquid crystals.

The dark background may have a transmittance of less than 80% and is preferably opaque.

The bonding primer is preferably transparent.

Another aspect of the present invention, in accordance with other of its aspects, is a security element for a secure document obtained by a process according to the invention, in particular as defined above, comprising:

a. A support made of a stretched thermoplastic material,

b. An adhesive primer on the surface of the support,

c. And at least one layer of liquid crystals, especially cholesteric liquid crystals, deposited on the adhesive primer by printing.

The security element may include printing of at least two liquid crystal inks that preferably do not overlap with each other.

The adhesion of the layer of liquid crystals to the support, measured according to the Tesa test described below, is preferably equal to two.

Preferably, the layer of liquid crystals is in the form of patterns, in particular of alpha-numeric patterns.

Another point of the present invention is a process for authenticating a security element in accordance with the present invention which includes observing an element that determines whether a goniocromatic effect is observed for incident angles greater than 70 degrees, And generating a piece of information on authenticity based on the authenticity information.

The authentication process may comprise the step of observing the element through a polarizing filter for the purpose of demonstrating the orientation of the support and the adhesive primer, and at least creating a piece of information about the authenticity based on this observation.

The present invention will be more clearly understood from a reading of the following description of the non-limiting examples of implementation thereof, and the accompanying drawings, wherein:
1 is a view from above showing a security element according to the invention,
2 is a longitudinal section along II-II of Fig. 1,
Figure 3 shows the embodiment details of the element,
Figure 4 is a view similar to Figure 1 of an alternative embodiment,
Figure 5 is a longitudinal section of the element of figure 4,
Figure 6 is a view similar to Figure 3 of an embodiment variant of the element;
- Figure 7 illustrates various steps of an example process according to the invention,
8 shows an example of a secure article incorporating a security element according to the invention, and
9 is a diagram illustrating a measurement of "haze" described below.
In the figures, actual proportions are not always considered for clarity.

A security element 10 according to the invention comprising a support 11, an adhesive primer 12 and a layer 13 of liquid crystals depotted by printing on a primer 12 is represented in Figures 1 to 3 .

The layer 13 is formed by two prints 13a, 13b of different colors, which do not overlap each other. In the examples of Figs. 1 to 3, the prints 13a and 13b do not cover the entire surface area of the surface 11a of the support together. Thus, areas 14 that are fluorescent or opaque, which may be used by other security measures, e.g. layers, in particular ink, remain around the prints.

In the examples of Figs. 4 to 6, the prints 13a and 13b cover the entire surface 11a of the support together.

In order to improve the visibility of the liquid crystals, the prints are advantageously superimposed on an opaque background, preferably a dark or reflective background, for example a black background.

As an example, the presence of a dark background in the form of an opaque layer 15 on the support 11 on the opposite side of the layer 13 of liquid crystals is illustrated in Fig. The opaque layer 15 is for example metallized or black ink printing.

The generation of the layer 15 is performed, for example, after the deposition of the layer 13 of liquid crystals.

According to one embodiment variant of Figure 6, the opaque layer 15 is present on the layer of liquid crystals 13 on the same side of the support. The security element is then viewed from the side of the support opposite the layer 13 of liquid crystals.

Support

The support is made of a stretchable thermoplastic material.

Preferably, the support is made of PET, polypropylene or polyethylene.

In order to improve the durability of the security element, an additional support, preferably comprising PET, is attached to the support by any suitable means, in particular by lamination with an adhesive.

An additional support is preferably attached to the support at the side of the layer of liquid crystals. In one variation intended to improve the cohesion of the sandwiches thus formed, the layer of liquid crystals is preferably in the form of patterns, for example covering at least 50% of the surface of the support. The adhesion between the support and the additional support is thus strengthened.

Liquid crystals

Preferably, the liquid crystals are cholesteric liquid crystals (CLCs). As a variant, the liquid crystals are nematic liquid crystals.

Many liquid crystal inks are present in the market and may be used. The ink may be a mixture of cholesteric and nematic liquid crystals in a ratio selected according to the desired color change.

Adhesive primer

The adhesive primer increases the adhesion of the liquid crystals to the support, but without preventing the support from being involved in the orientation of the liquid crystals due to its inherent structure.

The adhesive primer comprises one or more polymers.

The primer may be applied to the support in the form of monomers, in particular olefins (or alkenes), urethanes, esters, ethers, carbonates or acrylics, preferably acrylics, monomers, followed by crosslinking, , Followed by exposure to UV radiation.

Preferably, the chemistry of the primer is chosen to be of best relevance to the liquid crystal ink used. Thus, since many liquid crystal inks are based on acrylate monomers, it is desirable to use primers that are similarly based on acrylate monomers.

The amount of primer to be deposited is selected so that the thickness of the deposit is sufficiently small for the structure of the underlying support to remain active with respect to the orientation of the liquid crystals.

The thickness of the primer is therefore preferably less than 1000 nm, more preferably less than 100 nm.

Orienting the support with the previously presented primer may make it possible to orient the primer and thus allow a larger displacement of the primary.

Other security measures

The security element may comprise, in addition to the liquid crystals, any other security means selected from first-, second- or third-level security means.

that is:

Patterns which are visible in transmitted light and are formed by metallization and / or nonmetallization,

- dyes in particular in the form of printed or mixed with at least one constituent layer of the security element, luminescent pigments, interference pigments,

Photochromic or thermochromic compounds, dyes and / or pigments, in particular in the form of a mixture with at least one constituent layer of a printed form or a security element,

- ultraviolet (UV) absorbers, in particular in the form of a coating, or in combination with at least one constituent layer of a security element,

- interference multilayer structure,

Refractive, birefringent or polarizing layer,

- diffractive structure,

)" 를 생성하는 수단, 예를 들어 이러한 효과는 2 개의 보안 수단의 중첩에 의해, 예를 들어 2 개의 보안 수단의 라인들을 함께 밀접하게 함으로써 생성된 패턴을 드러내는 것이 가능하다,- "Moire effect (

) &Quot;, for example, this effect is possible by overlapping two security measures, for example by revealing the generated pattern by bringing together the lines of the two security measures together,

- Colored filters,

(For example, fluorescence, phosphorescence), absorption (e.g., ultraviolet, visible or infrared), Raman activity, magnetism, microwave interaction, X-ray interaction, or electroconductive properties Readable < / RTI > security means.

Security Elements

The security element according to the invention is advantageously a security thread, foil, patch or film for protecting variable data. It may also be a protective or impregnability film or card.

In the case of a security element consisting of a security thread, the thread may be integrated as windows in a secure sheet, such as banknote 30, as illustrated in FIG. The security element then extends from one edge 31 of the document to the other edge 32.

When the security element is in the form of a thread, its width is for example between 1 and 10 mm and its thickness is between 10 and 100 탆.

In the case of a foil, the security element is applied, for example, by transfer of the paper, film or surface of the card.

The term "patch" refers to a film that does not cover the entire surface of the underlying substrate.

Generation process

According to the invention, the process comprises the step (21) of preparing a film made of plastic, for example by extrusion, as illustrated in Fig. The film may be a single layer or multiple layers.

The process takes at least one stretching step (22) which makes it possible to orient in a first direction. This is, for example, the first stretching in the longitudinal direction (also referred to as the machine direction).

The adhesive primer is then applied in step 23 and the film is then stretched again in step 24, in a direction different from the beginning, for example in the transverse direction (also referred to as the transverse direction).

Finally, the liquid crystals are depressed by printing and coated with an adhesive primer, in this way on the biaxially stretched film, in step (25).

The orientation of the liquid crystals occurs during evaporation of the solvent present in the used ink. This evaporation is preferably carried out by air drying, preferably horizontally, to promote the orientation of the liquid crystals. Preferably, the ink is UV-crosslinkable, and crosslinking following depoting of the ink makes it possible to fix this orientation critically.

Printing is preferably performed with a plurality of liquid-crystal inks which are preferably desirably deposited without overlapping one another. The inks may be deposited in the form of solids or patterns. The term "pattern" refers in particular to any pattern recognizable by the naked eye, for example one or more alphanumeric characters, or an image of an object such as an individual, animal, object, landscape, plant or monument. It may be a halftone raster pattern which is preferably displayed in 3D by a shadow effect by halftone reproduction of the pattern. It may be a given direction, a raster pattern, or preferably a repeating pattern arranged in a checkerboard arrangement.

Printing may be performed by flexography, screen printing or photogravure among other printing techniques that may be used.

In one variation of the process, the film undergoes double stretching in machine and transverse directions after the bonding primer is demoulded. This depoting preferably occurs after the first stretching in the machine direction.

Thus, the following sequence:

- stretching in the machine direction,

- Depotting primer,

- stretching in the transverse direction,

- It is possible to have an elongation in the machine direction.

Authentication process

Authentication of a security element in accordance with the present invention may be performed by observing the element to determine whether a goniocromatic effect is observed for incident angles of 70 degrees or greater and this effect is related to the presence of liquid crystals.

Therefore, it is possible to generate a piece of information about authenticity based at least on this observation.

The authentication may comprise the step of observing the element through the polarizing filter of the support and for the purpose of demonstrating the orientation of the adhesive primer, and at least making up a piece of information about the authenticity based on this observation.

The biaxial orientation of the support may be verified by analyzing the ball refraction of the film in a conventional manner.

A linear polariser, such as a filter to be placed on the security element, may be used, which is rotated by 90 degrees to determine whether there is a change from a darker appearance to a brighter appearance as it rotates.

Examples

The "tesa" test mentioned below is a test for the adhesion of a layer deposited on a substrate, where the adhesive tape is applied to the layer sought to measure the cohesion and adherence to the substrate.

A score of 0 to 2 is obtained according to the percentage of the tested layer that is attached to the tape after its removal:

- 0 indicates the total adhesion to the tape, and thus the zero adhesion to the substrate of the tested layer,

- 1 indicates partial attachment to the tape, and

- 2 shows the absence of adhesion to the tape, and thus the adhesion of the tested layer to the substrate.

Examples 1 to 3 (comparative)

Several PET films have three products, namely:

Cholesteric liquid crystals: 5.29 g

Nematic liquid crystals: 3.11 g

Photoinitiator: 1.6 g

Lt; RTI ID = 0.0 > liquid < / RTI >

The mixture constitutes the ink with an acrylic base containing cholesteric and nematic liquid crystals.

The selected ratio between the cholesteric liquid crystal and the nematic liquid crystal is given in color; In this case, a change from blue to green-yellow by an observation angle is obtained.

Deposition of the liquid crystals is carried out at a coating thickness of 3 microns.

Drying under blown hot air is carried out to align the liquid crystals. The ink is UV crosslinked.

Liquid crystals are observed in front of a dark background.

* Chemical attack: treatment with an acidic solution to produce surface micro-roughness

** Goniocromatic effect: Observed parameters are: Obvious observation of two colors, brightness of color and angle of color change.

The plasma treatment does not provide optimal adhesion, but alignment of the liquid crystals is accurate.

The PET film treated by chemical erosion makes it possible to have good adhesion, but the optical effect is degraded.

Examples 4 (comparative) and 5 to 7 (according to the invention)

Deposition of the liquid crystals is performed as in Examples 1-3 by commercially available liquid crystal inks.

*** Off-line: Application occurs after the steps of stretching the PET film. On-line: Application takes place during the production of the film between at least two steps of stretching the PET film.

The goniocromatic effect is surprisingly conserved for Examples 5-7, despite the presence of an intermediate primer layer between the biaxially oriented PET support that allows alignment with layers of liquid crystals.

The alignment of the liquid crystals is modified by the presence of an adhesive primer. Modification of this alignment makes it possible to increase the visibility of the color-changing effect and to impart on the layer of liquid crystals translucence which makes it possible to limit the visibility of the black background.

The degree of translucency may be determined by measurement of the reflection "haze" according to standard ASTM D4039-09 and ISO13803. It is a measure of haze, that is milky opalescence, shiny or transparent top coat.

On the quality (Class A) surfaces, a brighter appearance and brighter image is expected. Microstructures may be responsible for milky white appearance. This effect is called "Hayes". If microscopic and microscopic defects are present on very shiny surfaces, this results in scattering of low-intensity light with predominant reflection. The dominant part is reflected in the specular direction, and the surface thus appears to be very shiny by the rendering of the image, but is covered with milky and hazy haze.

The "haze" of the layer of liquid crystals on the support according to the present invention may be less than the haze of the layer of liquid crystals on the non-treated PET, resulting in a shininess much smaller than for a layer of liquid crystals on a standard support . Moreover, the reduction of "haze " increases the optical scattering of the layers of liquid crystals and thus enables the goniocromatic effect to be observed over a wide range of angles. Surprisingly, therefore, at the "grazing" angles, the goniocromatic effect is maintained with the support according to the invention, whereas with standard supports the liquid crystals are no longer visible and a dark background is observed, not.

에 따라 조명된다. "헤이즈" 의 측정은 센서 (92) 에 의하여 수행되며, 스펙큘러 광선 (94) (각도 -

) 의 세기에 대응하는 반짝임과는 대조적으로, 광선들 (93) 의 세기에 대응한다.The "haze" measured according to the standard ISO 13803: 2014 of film (1) and film (6) are 274 and 79, respectively. This measurement is illustrated in Fig. 9, in which the support 91 to be measured has an angle < RTI ID = 0.0 >

. The measurement of "haze" is performed by the sensor 92 and the specular ray 94 (angle-

Which corresponds to the intensity of the rays 93, as opposed to the sparkle corresponding to the intensity of the rays 93. [

In order to quantify the increase in the angular extent of the goniocromatic effect, the maximum intensity over the wavelength range of 400 to 700 nm ("intensity" in the table below) It was measured at various angles of observation for illumination at an angle. All intensity measurements shown in the following table are given in arbitrary units corresponding to a given calibration; In particular, the intensities of sample 1 and sample 6 were measured with the same calibration.

The intensity of the sample 6 is greater than the intensity of the sample 1 for the grazing angles of the observations, for example, 10 °, 20 °, 70 ° and 80 °, Note that this reflects visibility over the more extended angular extent of the effect.

Claims (20)

A process for producing a security element comprising a support (11) made of oriented plastic and at least one layer (13) of bearings and oriented liquid crystals by said support,
The adhesive primer (12) is depotted before or after the support is stretched in at least one direction, and the stretching enables the support to be in an oriented state and the liquid crystals are printed on the adhesive primer by printing A process for creating a secure element that is depotted. The method according to claim 1,
Wherein the adhesive primer (12) is deposited prior to the step of stretching the support (11). 3. The method according to claim 1 or 2,
Wherein the support comprises PET. 4. The method according to any one of claims 1 to 3,
The process also includes crosslinking the adhesive primer, preferably after stretching the support. 5. The method according to any one of claims 1 to 4,
Wherein the adhesive primer comprises a polyolefin, a polyurethane, a polyester, a polyether, a polycarbonate or a polyacryl, or a copolymer thereof. 6. The method of claim 5,
Wherein the adhesive primer comprises polyacrylic. 5. The method of claim 4,
Wherein the adhesive primer comprises at least one urethane, ester, ether, carbonate or acrylic monomer prior to its demoulding. 8. The method according to any one of claims 1 to 7,
Wherein the printing of the liquid crystals is performed by screen printing, photogravelling or flexography. 9. The method according to any one of claims 1 to 8,
Wherein the liquid crystals are deposited after stretching of the support. 10. The method according to any one of claims 1 to 9,
Wherein at least one of the two different inks comprises cholesteric liquid crystals, and more preferably both comprise cholesteric liquid crystals, the printing on the adhesive primer of two different inks. 11. The method according to any one of claims 1 to 10,
Wherein the haze effect of said layer of cholesteric liquid crystals is less than the haze effect of a reference security element without a layer of adhesive primer. 12. The method according to any one of claims 1 to 11,
And a dark background below said layer of liquid crystals. 13. The method according to any one of claims 1 to 12,
Wherein the adhesive primer is transparent, a process for creating a secure element. 13. A security element (10) for a secure document obtained by a process for creating a security element according to any one of claims 1 to 13,
a. A support 11 made of a stretched thermoplastic material,
b. The adhesive primer (12) at the surface of the support,
c. And at least one layer (13) of liquid crystals depotted on said adhesive primer by printing. 15. The method of claim 14,
And printing of at least two liquid crystal inks preferably not overlapping each other. 16. The method according to claim 14 or 15,
The adhesion of the layer of liquid crystals to the support measured according to the Tesa test is equal to two. 17. The method according to any one of claims 14 to 16,
Wherein said layer of cholesteric liquid crystals is in the form of a pattern, especially an alpha-numerical pattern. 18. The method according to any one of claims 14 to 17,
Also includes a dark background, a security element. 18. A process for authenticating a security element as claimed in any one of claims 14 to 18,
An observation of the element to determine whether a goniochromatic effect is observed for incident angles greater than or equal to 70 degrees and at least to generate a piece of information about authenticity based on the observation A process for authenticating a secure element, comprising the steps of: 18. A process for authenticating a security element as claimed in any one of claims 14 to 18,
Comprising the steps of observing the element through a polarizing filter for the purpose of demonstrating the orientation of the support and of the adhesive primer, and generating at least a piece of information about the authenticity based on the observation. A process for authenticating.

Images