Document comprising at least two photoluminescent images, security film and protective security method

Abstract

A document (15) includes at least: one first image (5) including at least one photoluminescent pigment which is invisible under illumination in visible light and is visible under illumination by at least one first source (20) of non-visible light emitting in the short ultraviolet domain, one second image including at least one photoluminescent pigment which is invisible under illumination in visible light and is visible under illumination by at least one second source of non-visible light emitting in the long ultraviolet domain, one layer, named a filtering layer, arranged facing the second image and including at least one material, named a filtering material, suitable for allowing the wavelengths emitted by the first source of non-visible light to be filtered without preventing the first image from being seen under illumination by the first light source.

Claims

1. A security film, comprising: at least one first image which is invisible under illumination in visible light and is visible under illumination by at least one first source of non-visible light emitting in a short ultraviolet domain, said first image comprising at least one pigment which is photoluminescent under illumination by said first source of non-visible light, wherein the security film further comprises: at least one second image which is invisible under illumination in visible light and is visible under illumination by at least one second source of non-visible light emitting in a long ultraviolet domain, said second image comprising at least one pigment which is photoluminescent under illumination by said second source of non-visible light, at least one filtering layer, arranged facing said second image and comprising at least one filtering material suitable for allowing the non-visible light emitted by said first source of non-visible light to be filtered without preventing the first image from being seen under illumination by the first light source, further comprising at least one support film on which are arranged said first image and said second image, said filtering layer being arranged between said first image and said second image.

2. The security film according to claim 1, wherein said second image is arranged on top of said first image on said support film.

3. The security film according to claim 1, wherein said support film is transparent.

4. A security film, comprising: at least one first image which is invisible under illumination in visible light and is visible under illumination by at least one first source of non-visible light emitting in a short ultraviolet domain, said first image comprising at least one pigment which is photoluminescent under illumination by said first source of non-visible light, wherein the security film further comprises: at least one second image which is invisible under illumination in visible light and is visible under illumination by at least one second source of non-visible light emitting in a long ultraviolet domain, said second image comprising at least one pigment which is photoluminescent under illumination by said second source of non-visible light, at least one filtering layer, arranged facing said second image and comprising at least one filtering material suitable for allowing the non-visible light emitted by said first source of non-visible light to be filtered without preventing the first image from being seen under illumination by the first light source, wherein said filtering layer forms a support film having a first face on which is arranged said first image, and a second face, different from said first face, on which is arranged said second image.

5. A protective security method for at least one surface portion of a document, in which at least one first image which is invisible under illumination in visible light and is visible under illumination by at least one first source of non-visible light emitting in a short ultraviolet domain is applied to said surface portion, said first image comprising at least one pigment which is photoluminescent under illumination by said first source of non-visible light, wherein at least one second image which is invisible under illumination in visible light and is visible under illumination by at least one second source of non-visible light emitting in a long ultraviolet domain is applied to said surface portion, said second image comprising at least one pigment which is photoluminescent under illumination by said second source of non-visible light, and a filtering layer superposed on said second image and comprising at least one filtering material suitable for allowing the non-visible light emitted by said first source of non-visible light to be filtered without preventing the first image from being seen under illumination by the first light source, wherein the first image is printed on a support film, the filtering layer is applied on top of the first image, the second image is printed on top of the filtering layer, an adhesive layer is applied on top of the second image.

6. The method according to claim 5, wherein each image is printed by a technique selected from screen printing, flexography, offset and photogravure.

7. A protective security method for at least one surface portion of a document, in which at least one first image which is invisible under illumination in visible light and is visible under illumination by at least one first source of non-visible light emitting in a short ultraviolet domain is applied to said surface portion, said first image comprising at least one pigment which is photoluminescent under illumination by said first source of non-visible light, wherein at least one second image which is invisible under illumination in visible light and is visible under illumination by at least one second source of non-visible light emitting in a long ultraviolet domain is applied to said surface portion, said second image comprising at least one pigment which is photoluminescent under illumination by said second source of non-visible light, and a filtering layer is superposed on said second image and comprising at least one filtering material suitable for allowing the non-visible light emitted by said first source of non-visible light to be filtered without preventing the first image from being seen under illumination by the first light source, wherein, in order to apply each image, a plurality of superposed, monochromatic printing layers are printed such that, in an order of receiving the illumination light, they are in an order of blue, red, green of filtering wavelengths and emission peaks of photoluminescent pigments.

Description

(1) Other aims, features and advantages of the invention will become apparent upon reading the following description of one of its preferential embodiments given by way of non-limiting example, and referring to the attached figures in which:

(2) FIG. 1 is schematic, cross-sectional view of a security film in accordance with the invention,

(3) FIG. 2 is schematic, cross-sectional view of an official document in accordance with the invention,

(4) FIGS. 3 to 5 illustrate different steps of a method in accordance with the invention.

(5) For ease of illustration, FIGS. 1 to 5 are not shown to scale. In particular, in FIG. 1, the thicknesses are shown in an exaggerated manner.

(6) A clear protective lacquer 4, in particular one which is transparent to short-wave ultraviolet light and to long-wave ultraviolet light, is printed on a translucent or transparent, opaque, thin support film 2 made of polymer material. The support film 2 is generally selected so as to have a size greater than that of the surface to be covered of the official document to be protected. Alternatively, the support film 2 can be opaque if it is intended to be removed after being transferred to an official document. If it is translucent or transparent (to visible light as well as to short-wave and long-wave ultraviolet light) it can be removed or retained after being transferred to the official document to be protected (the size thereof can thus be adjusted with respect to that of the surface to be covered of the official document to be protected).

(7) Then, a first polychromatic image 5 which is invisible under illumination in visible light and is visible under illumination by at least one first source 20 of non-visible light emitting in the short ultraviolet domain, is printed using three printing compositions comprising pigments which are photoluminescent under illumination by the first source 20 of non-visible light. To this end, three printing compositions are successively printed, forming three layers 6a, 6b and 6c.

(8) After having printed the image 5, a filtering layer 7 is printed directly on top of the image 5, said filtering layer being suitable for allowing the wavelengths emitted by the first source 20 of non-visible light to be filtered without preventing the first image from being seen under illumination by the first light source.

(9) The filtering layer can be formed from at least one material selected from thermoplastic and thermosetting polymeric materials, in particular photocurable polymeric materials.

(10) In a first variant in accordance with the invention, the filtering layer comprises at least one polymer material selected from the group formed of polymer materials suitable for filtering short-wave ultraviolet light, and in particular from the group formed of thermoplastic polymeric materials (in particular polycarbonates, polyesters and polyvinyl chloride (PVC)), thermosetting polymeric materials (in particular polyurethanes) and photocurable polymeric materials (in particular functionalised acrylic resins which are cross-linked or polymerised under ultraviolet radiation or under electron irradiation). The filtering layer comprises in particular at least one such polymer material having a transmittance (measured using a UV-visible spectrophotometer) of less than 30% at wavelengths of less than 300 nm.

(11) In a second variant in accordance with the invention, the filtering layer comprises at least one polymer material selected from the group formed of polymer materials comprising additives suitable for filtering short-wave ultraviolet light, and in particular from the group formed of acrylate and/or methacrylate polymers and copolymers comprising filtering additives selected from among the additives filtering short-wave ultraviolet light such as those of the family of 2-(2-hydroxyphenyl)-benzotriazole (BTZ) or 2-hydroxyphenyl-s-triazine (HPT).

(12) A second polychromatic image 9 which is invisible under illumination in visible light and is visible under illumination by at least one second source 22 of non-visible light emitting in the long ultraviolet domain, is printed directly on top of the filtering layer 7 using three printing compositions comprising pigments which are photoluminescent under illumination by the second source 22 of non-visible light. To this end, three printing compositions are successively printed, forming three layers 8a, 8b and 8c.

(13) Then, an adhesive layer 10 can be applied on top of the second image 9, followed by a film 12 protecting the adhesive.

(14) The thus obtained security film 1 can form a heat transfer, i.e. can be used to apply the security film 1 and to transfer it by hot lamination onto a surface portion of an official document 15, as shown in FIGS. 3 to 5, in particular so as to protect same against being falsified and/or to authenticate the official document and/or the variable or common markings previously printed on this surface portion and/or to ensure the integrity thereof.

(15) A method for making a security film is thus a method in which: at least one first image 5 which is invisible under illumination in visible light and is visible under illumination by at least one first source 20 of non-visible light emitting in the short ultraviolet domain is printed using at least one printing composition comprising at least one pigment which is photoluminescent under illumination by said first source of non-visible light, at least one second image 9 which is invisible under illumination in visible light and is visible under illumination by at least one second source 22 of non-visible light emitting in the long ultraviolet domain is printed using at least one printing composition comprising at least one pigment which is photoluminescent under illumination by said second source of non-visible light, a layer, named filtering layer 7, is arranged facing said second image and comprises at least one material, named filtering material, suitable for allowing the wavelengths emitted by said first source 20 of non-visible light to be filtered without preventing the first image 5 from being seen under illumination by the first light source.

(16) The order of printing the first image and the second image can vary depending on whether each of the three preceding layers were applied successively on a support film or directly on a document to be protected or whether the filtering layer forms a support film.

(17) If the document is a card (e.g. a card comprising at least one polycarbonate layer), the second image 9 can be placed directly on said card or on a film made of polycarbonate, PVC or even PET, which is then itself placed onto said card. In this latter case, the first image 5 will preferably have been placed onto a face of said film made of polycarbonate, PVC or PET (said face being opposite to that on which the second image 9 is placed).

(18) FIG. 2 shows an official document 15 on which the security film 1 was thus transferred after having removed the protective film 12 from the adhesive layer 10. Once the security film 1 is arranged on the official document 15, the support film 2 used as a transfer support film is likewise removed. If present, the protective lacquer 4 thus allows the first polychromatic image 5 to be protected against external events, in particular chemical attacks and climate changes, and likewise increases the resistance thereof to mechanical stresses.

(19) The support film 2 can be, for example, a Fasprotek (FASVER, Baillargues, France)-type film.

(20) Alternatively, the support film 2 can likewise comprise a single layer (not supported by a support and without a protective lacquer layer 4), e.g. a Fasfilm (FASVER, Baillargues, France)-type film. In this case, the continuous layer is, for example, formed of polyethylene terephtalate, of polycarbonate or of polyvinyl chloride and can be used as a filtering layer, the first polychromatic image being printed on a first support face and the second polychromatic image being printed on a second face of the support different from the first face. Therefore, the first image and the second image are printed respectively on one side and on the other side of the support film made of polyethylene terephtalate, of polycarbonate or of polyvinyl chloride and filtering short-wave ultraviolet light. Furthermore, in this latter case, the adhesive layer is not necessary to allow the transfer by hot lamination of the security film 1 to a surface portion of an official document 15.

(21) The photoluminescent pigments used are selected from among fluorescent pigments and phosphorescent pigments. In particular, the photoluminescent pigments used are selected from among mineral pigments, in particular photoluminescent pigments comprising chemical elements belonging to the family of rare earth metals, and organic pigments resistant to the radiation of each source of non-visible light allowing the behaviour of each image over time to be ensured.

(22) FIGS. 3 to 5 show an official document 15 (e.g. an identity card) to which the security film as prepared previously is transferred.

(23) FIG. 3 shows the official document 15 as seen under illumination in visible light (daylight for example). The images 5 and 9 comprise photoluminescent pigments which are thus not visible.

(24) The official document 15 has markings 17, in particular identity data. The markings 17 located on the official document 15 are preferably black and in particular of a colour (or shade) different from the colours of the patterns of the semi-transparent polychromatic images covering them, so that the markings can be easily distinguished by the naked eye (under illumination by a source of non-visible light in short-wave and/or long-wave ultraviolet light).

(25) FIG. 4 shows the official document 15 under short-wave ultraviolet light owing to the source 20 of non-visible light. The image 5 can now be seen (and represents, for example, a pattern such as a butterfly). The image 5 which can be seen under illumination by the source 20 of light emitting in the short ultraviolet domain, emitting in particular at a wavelength in the order of 250 nm, is of a very high quality and allows the details of the represented pattern and its different colours to be clearly distinguished. In particular, no light emission from the underlying image 9 interferes with the viewing of the image 5.

(26) FIG. 5 shows the official document 15 under long-wave ultraviolet light owing to the source 22 of non-visible light. Only the image 9 can now be seen (and represents, for example, a pattern such as a flower). The image 9 which can be seen under illumination by the source 22 of light emitting in the long ultraviolet domain, emitting in particular at a wavelength in the order of 365 nm, is of a very high quality and allows the details of the represented pattern and its different colours to be clearly distinguished.

EXAMPLE 1

(27) A support film which is transparent to short-wave and long-wave ultraviolet light and is formed of polystyrene, as sold by the company VITASHEET GROUP (Italy) under reference Robbex 515PH is selected. A protective lacquer made of polyurethane is printed on this support film and was formed from an aqueous solution comprising a transfer lacquer base sold by TIFLEX (France) under reference 3X9426 and a curing agent with reference 3X9427. The proportion of curing agent added is 45 parts by volume for 100 parts by volume of the base. This printing is effected in a block of colour by screen printing with a mesh of 51 threads/cm so that the applied protective lacquer layer has a thickness between 10 m and 20 m.

(28) A first image is printed on this protective lacquer using three different printing compositions, each being formulated from an ink base suitable for not filtering short-wave ultraviolet light such as an ink base sold by the company TIFLEX (France) under reference LG 111104 Solubilis. The first printing composition comprises blue fluorescent pigments such as those sold by the company MITSUBISHI CHEMICAL CORPORATION (Japan) under reference KX-626A. The second printing composition comprises red fluorescent pigments such as those sold by the company HONEYWELL under reference Lumilux Red CD106. The third printing composition comprises green fluorescent pigments such as those sold by the company HONEYWELL under reference Lumilux Green CD145. This first image contains fluorescent pigments which are visible under short-wave ultraviolet light.

(29) The concentration of blue fluorescent pigments in the first printing composition is 50% by weight relative to the total weight of the first printing composition. The concentration of red fluorescent pigments in the second printing composition is 16.5% by weight relative to the total weight of the second printing composition. The concentration of green fluorescent pigments in the third printing composition is 15% by weight relative to the total weight of the third printing composition.

(30) Following the three printing layers forming the first image which is visible under short-wave ultraviolet light, there is printed a polyurethane-based lacquer comprising a lacquer base such as that sold by the company TIFLEX (France) under reference 3Y0530 vernis S3HN1 (screen printing product) and a catalyst such as that sold by the company TIFLEX (France) under reference 3X9096. The proportion of catalyst added is 53 parts by volume for 100 parts by volume of the lacquer base. The printing is effected in a block of colour by screen printing with a mesh of 77 threads/cm so that the applied protective lacquer layer has a thickness between 8 m and 12 m. A lacquer layer filtering short-wave ultraviolet light is thus obtained.

(31) A second image is printed on this filter using three different printing compositions. The first printing composition is a UVIPRIM ink sold by the company TIFLEX (France) under reference 3Y1150 Bleu. The second printing composition is a UVIPRIM ink sold by the company TIFLEX (France) under reference 3Y0742 Rouge. The third printing composition is a UVIPRIM ink sold by the company TIFLEX (France) under reference 3Y0877 Vert. This second image contains fluorescent pigments which are visible under long-wave ultraviolet light.

(32) Each layer is allowed to dry between each printing step.

(33) Then, a heat-sealable adhesive sold by the company TIFLEX under reference 3Y1836NF (screen printing product) is applied.

(34) Only the first image is observed under illumination by a source of light emitting in the short ultraviolet domain at a wavelength in the order of 250 nm. Only the second image is observed under illumination by a source of light emitting in the long ultraviolet domain at a wavelength in the order of 365 nm.

(35) The invention can comprise a large number of embodiment variants. In particular, it is possible to provide an additional image comprising photoluminescent pigments which are invisible under illumination in visible light and are visible under illumination by at least one infrared light source.