ES2731365T3 - Security document - Google Patents

Abstract

A security document comprising a layer (12) of the substrate with a security function (11) comprising a first area (11a) and a second area (11b), in which, in both areas (11a, 11b) the Safety function (11) is visible with visible light in a basic color (P) in which, when excited with infrared light, the first area (11a) is visible with visible light in a first color (1) and the second area (11b) is visible with visible light in a second color (2) different from the first color (1), characterized in that the security function (11) is a printing layer consisting of a composition comprising, in the first area ( 11a), a first additional up-conversion luminescence pigment excitable by infrared light and, in the second area (11b) a second additional up-conversion luminescence pigment excitable by infrared light, in which the second additional pigment is different of the first additional pigment.

Description

DESCRIPTION

Security document

Technical field

The disclosure refers to security documents comprising, in particular, a substrate layer with a printed security function.

Background

Security documents comprise various security functions that make them difficult to copy or forge. Security functions may, for example, take the form of a print on a substrate of the document, which is made up of several digits, letters or other graphic symbols. The security functions can be permanent (that is, the same for a group of documents) or customized (that is, individual for each document).

Various known pigments are used in film forming printing positions, which are invisible to the naked eye with visible light, but which are visible when illuminated with an electromagnetic wave with a specific wavelength, different from that of the light spectrum visible (VIS), for example an infrared (IR) light or an ultraviolet (UV) light.

Anti-stoke pigments are known, which show an ascending luminescence - they are invisible to the human eye with visible light but, when they are excited by an infrared light in the range between 900 and 1000 nm they are visible with a specific color, depending on the structure of the pigment and its chemical composition.

The ascending luminescence, which involves the emission of anti-stokes radiation, is produced for the upward conversion of luminescent pigments, when the excited electron of the pigment particle absorbs another quantum of energy in the form of a photon, which causes additional excitation of the electron (it is transferred to an even higher energy band). When the excited electron then returns to its basic state, it emits a photon of energy that is the sum of energy of both absorbed photons, reduced by the energy of the rotating, vibratory excitation of the pigment particle. Therefore, the energy emitted by the pigment particle causes radiation (electromagnetic wave) with a wavelength shorter than the wavelength of the absorbed radiation. Therefore, the emitted radiation is displaced at higher frequencies. In the event that the photons absorbed by the electron of the pigment particle are photons from the infrared radiation frequency, the emitted radiation may exist in the visible light spectrum. The luminescence of upward conversion is observed in some pigments with a crystalline structure doped with ions of rare earth chemical elements: lantanides, that is, chemical elements with an atomic number between 59 and 71 (Ce-Lu).

A PCT patent application WO 9513597 A2 discloses a copy protection device comprising a marking defined by a pair of inks having a colored area continues, substantially flat, seen and illuminated under visible light, but when the area is scanned with and / or illuminated at least one wavelength outside the amplitude of the visible wavelength, a motif that can be detected is generated.

US patent application US 2011298204 A1 discloses a security mark with visible and hidden portions. Each component of the brand is visible in a first lighting state and can be detected in a second lighting state; each component of the second mark is hidden in the first lighting state and can be detected in the second lighting state; Each component of the third mark is visible in the first lighting state and is hidden in the second lighting state. The first lighting state is visible light and the second lighting state is IR or UV light.

A PCT patent application WO 2004050376 A1 discloses a security device comprising two or more regions, in which each region contains a material or a combination of materials in which the two or more regions show substantially the same appearance visible under the first display states and different visible appearances under a few second display states. The second display states comprise a combination of a) visible light and b) substantially any UV wavelength.

In the aforementioned applications, the different visibility of the areas in the IR region is due to the different absorption aspect of the inks used at the wavelength outside the visible wavelength amplitude. For example, prior art inks may have the absorption spectrum shown in Fig. 4A.

It is necessary to obtain a security document with a substrate with a printed security function, which can take advantage of the phenomenon of up-conversion luminescence to secure the document against counterfeiting and that makes possible an unequivocal and simple procedure to verify the authenticity of the document.

Summary

The object of the invention is a security document comprising a substrate layer with a printed security function comprising a first area and a second area, in which in both areas the security function is visible with visible light in a color basic, characterized in that when it is excited with infrared light, the first area is visible with visible light in a first color and the second area is visible with visible light with a color different from the first color, in which the safety function is a layer of printing consisting of a composition comprising, in the first area, a first luminescence pigment of additional upward conversion excitable by infrared light and, in the second area a second luminescence pigment of additional upward conversion excitable by infrared light, in which the second additional pigment is different from the first additional pigment.

The security function may be a printing layer consisting of a composition comprising, in the first area and in the second area, a visible basic pigment with visible light.

Compositions that form a film of the first area and the second area may have the same absorption spectrum over visible and infrared wavelengths.

The AE1-2 difference between the first and second colors in a CIELab space can be equal to at least 5.

The difference AEi -b between the first color and the basic color as well as the difference AE2-B between the second color and the basic color can be equal to at least 5.

The first area may be located on the substrate layer at a certain distance from the second area. The first area on the substrate layer may be adjacent to the second area.

The first area on the substrate layer may be superimposed, at least partially, on the second area. The security function can be located on two layers of substrate.

Brief description of the figures

The security document is presented herein by means of exemplary embodiments shown in a drawing, in which:

Fig. 1A schematically presents a cross section of a first embodiment of a security document.

Fig. 1B schematically presents a cross section of a second embodiment of a security document.

Figs. 2A - 2C schematically present various locations of security printing areas.

Fig. 3 systematically presents pigments used in different areas of security printing.

Detailed description

A security document 10, shown in cross section in the first embodiment in Fig. 1A, comprises a substrate layer 12 with a printing layer 11 applied thereon.

The security document shown in cross section in the second embodiment in Fig. 1B differs from the first embodiment of Fig. 1A in that the printing layer 11 is located between two layers of the material 12, 13 of substrate - for example, is printed on one of the layers 12 and then covered with the second layer 13, in which the two layers are then laminated together.

The substrate layer 12, 13 may consist of various materials, including a single material or more than one type of material. It can take the form of a single layer, a laminate or a composite material. For example, the substrate layer 12, 13 may consist of thermoplastic paper or thermosetting materials or plastics, such as: polycarbonate (PC), polyethylene (PE), polypropylene (PP), acrylonitrile-styrene-butadiene (ABS), poly (methyl methacrylate) (PMMA), poly (styrene-co-acrylonitrile) (SAN), polyvinyl chloride (PVC) or various types of resins, for example phenolic resins or phenolformaldehyde.

The printing layer 11 performs a security function of the document 10. The printing layer 11 is constituted by a composition that forms a film, which can be applied to the substrate 12 by means of various techniques, such as: jet printing ink, offset printing, gravure printing or screen printing.

The printing layer comprises a first area 11a and a second area 11b. In a form of a motif as shown in Fig. 2a, the first area 11a can be applied on the substrate 12 at a certain distance from the second area 11b. In another form of the motif, as shown in Fig. 2B, the first area 11a may be adjacent to the second area 11b. In another additional form of the motif, as shown in Fig. 2C, the first area 11a may partially overlap the second area 11b. Areas 11a, 11b can take various forms, such as graphic symbols, letters or digits.

The printing layer 11 is constituted by a pigmented composition that forms a film, such as a paint, lacquer, enamel or ink. The composition includes visible pigments with visible light and pigments excited by infrared light.

Both areas 11a, 11b comprise a visible basic pigment with visible light (VIS). In addition, the first area 11a comprises an additional infrared light (IR) excitable upward conversion luminescence pigment and a second area 11b comprises a second infrared light (IR) additional upward convertible luminescence pigment. The first additional pigment is different from the second additional pigment.

Preferably, the pigments are uniformly distributed in areas 11a, 11b, so that areas 11a, 11b are visible with visible light (VIS) as surfaces having a uniform color.

As a result, when a security layer 11 printed with visible light is observed, the same basic color B is visible in both areas 11a, 11b, so that the chromatic hue depends on the basic pigment used. However, when the printed security layer 11 is excited by infrared light, the first area 11a is visible with visible light in the first color (1), depending on the first additional pigment used, different from the second color (2) visible on the second area 11b depending on the second additional pigment used. This is shown schematically in Fig. 3.

The first and second additional pigments, preferably, are selected so that the first and second colors, in which these pigments are visible with visible light when excited by infrared light, are sharply different from each other. Preferably, the difference AE1-2 between the first and second colors in a CIELab space is equal to at least 5 and, more preferably to at least 10.

The AE difference is defined generically as:

AE = V (AI ) 2 + (A a ) 2 + ( A b)

where L is the brightness (luminance), a - color from green to violet, b - color from blue to yellow.

The CIELAB definition set out above is defined, for example, by the publication CIE 15.2 (1986) and ISO 11664 -4: 2008.

The first and second additional pigments, preferably, are selected so that the first and second colors are distinctly different from the basic color. Preferably, in the CIElab the difference AEi -b between the first color and the basic color as well as the difference AE2-B between the second color and the basic color is equal to at least 5 and, more preferably to at least 10.

Arbitrary known pigments can be used as the basic pigment for compositions that form a film.

Additional up-conversion luminescence pigments may be based on compounds that incorporate a matrix in the form of a crystalline lattice added with trivalent rare earth elements including: Ho3 +, Er3 +, Gd3 +, Yb3 +, alkaline earth element ions: Ca2 +, Sr2 + , Ba2 +, or concrete transition metals such as Zr4 +, Ti4 +, while, for the creation of matrices of these pigments, concrete halides can be used: NaYF4, YF3, LaF3, oxides for example, Y2O3, ZrO2 or sulfoxides Y2O2S, La2O2S.

The first and second areas, preferably, have substantially the same absorption spectrum, preferably over the entire wavelength amplitude. In particular, they have the same absorption spectrum in the visible amplitude and in the infrared amplitude as shown in Fig. 4B, which presents an absorption spectrum for 4 different compositions that form a film. The term "substantially" should be understood as meaning that the reflectance measured by the spectophotometer in one area is different from the reflectance in another area by no more than 10% and, more preferably, no more than 5% of the absolute value (for example, as shown in Fig. 4B, for 950 nm the lowest reflectance value is approximately 70% of one composition and the highest value is approximately 73% for another composition, therefore the difference is 3%).

In order to detect the safety function, the areas can be illuminated by a laser or by a laser diode of a specific wavelength, for example 980 nm, which causes the excitation of the up-conversion luminescence pigments, so that they result visible with visible light in different colors. On the contrary, when the areas are not illuminated by the specific wavelength that excites the up-conversion pigments, the areas have the same visibility over all wavelengths, according to the absorption spectrum shown in Fig. 4B Therefore, there is no change in the visible color, these areas are already observed with visible light or infrared light.

This contrasts with the prior art, in which the areas that have an absorption spectrum as shown in Fig. 4A, seen by means of an infrared camera, will be visible in different colors.

Compositions that form a film for areas 11a, 11b comprise a color base (which defines the basic color) and an additive of the upconversion component, which has the same basic color for visible light as the color base and which it also comprises a concrete pigment of upward luminescence conversion. The amount of the upstream conversion component may be different, depending on the visibility of the component. In this case, additional components for the composition, such as diluents, can be used to obtain uniform color and structure compositions. The expert without inventive skills in the field will notice specific compositions to obtain specific effects depending on the components used. For example, the following compositions can be used:

Printing compositions on polymer substrates, such as polycarbonate or PVC:

- A: 97% color base, 3% green ascending converter additive;

- B: 71% color base, 25% yellow ascending converter additive, 4% diluent. Compositions for printing on polymer substrates such as polycarbonate or PVC;

- 95% color base 5% green additive conversion additive;

- 73% color base 23% red ascending conversion additive 4% diluent.

Compositions for printing on polymeric substrates, such as polycarbonate or PVC:

- 78% color base 18% yellow additive conversion additive 4% diluent; - 71% color base 25% additive conversion blue ascending 4% diluent.

Compositions to print on a paper substrate:

- 91% transparent base 5% green upconversion additive 4% drying compound;

- 71% transparent base 25% yellow additive conversion up 4% drying compound.

The security document 10 may consist of a banknote, an identity card, a driver's license, a passport, a credit card, a diploma, a certificate or any other known security document. The usefulness of the security document means that the security function is visible to the naked eye as a printed area that has a first color with visible light, while when it is excited by infrared light the amplitude of 900 to 1000 nm is visible as an area of two colors or multiple colors. This makes possible a quick and convenient location of the security function on the substrate of the document, with visible light and, consequently, the verification of the authenticity of the document by lighting the security function with infrared light.

Claims (9)

1. - A security document comprising a layer (12) of the substrate with a security function (11) comprising a first area (11a) and a second area (11b), in which, in both areas (11a, 11b) the safety function (11) is visible with visible light in a basic color (P) in which, when excited with infrared light, the first area (11a) is visible with visible light in a first color (1) and the second area (11b) is visible with visible light in a second color (2) different from the first color (1), characterized in that The security function (11) is a printing layer consisting of a composition comprising, in the first area (11a), a first additional up-conversion luminescence pigment excitable by the infrared light and, in the second area (11b) a second luminescence pigment of additional upward conversion excitable by infrared light, wherein the second additional pigment is different from the first additional pigment. 2. - The security document according to claim 1, wherein the security function (11) is a printing layer consisting of a composition comprising, in the first area (11a) and in the second area (11b ), a basic pigment with visible light. 3. - The security document according to any of the preceding claims, wherein the compositions that form a film of the first area (11a) and the second area (11b) have substantially the same absorption spectrum over the lengths of visible and infrared wave. 4. - The security document according to any of the preceding claims, wherein the difference AE-i-2 between the first and second colors in a CIELab space is equal to at least 5. 5. - The security document according to any of the preceding claims, wherein the AE-ib difference between the first color and the basic color, as well as the AE2-B difference between the second color and the basic color is the same to at least 5. 6. - The security document according to any of the preceding claims, wherein the first area (11a) is located on the substrate layer (12) at a certain distance from the second area (11b). 7. - The security document according to any of the preceding claims, wherein the first area (11a) on the substrate layer (12) is adjacent to the second area (11b). 8. - The security document according to any of the preceding claims, wherein the first area (11a) on the substrate layer (12) overlaps, at least partially, the second area (11b). 9. - The security document according to any of the preceding claims, wherein the security function (11) is located between two layers of a substrate (12, 13).