Security feature with optically variable effect

Abstract

Provided herein are a security document with security device, and a method for making the security document. The security device comprises at least one layer or portion of reflective material and at least one layer or portion of transparent or translucent optically variable material, and wherein the transparent or translucent optically variable material are at least partially overlapping in a portion of the security device, thereby producing an optically variable effect in the overlapping portion.

Description

[0001] SECURITY FEATURE WITH OPTICALLY VARIABLE EFFECT

[0002] FIELD OF THE INVENTION

[0003] The invention relates generally to a security feature for security documents. In particular, the present invention provides security devices comprising colour changing dyes, inks or films, for use in printed security documents including but not limited to identification cards, driver’s licenses, passports, and banknotes.

[0004] BACKGROUND

[0005] Security documents such as identification cards, data pages, driver’s licenses, passports and banknotes may include one or more features formed by printing, laser engraving and / or by applying metallization. For example, a security document in the form of an identification card, a driver's license or personal identification sheet of a passport may be made of a thermoplastic polymer substrate and may bear data or a feature that is laser engraved onto the thermoplastic polymer substrate.

[0006] Counterfeits in security documents are quite prevalent due to the demand for fake identification documents for various purposes including underage drinking, access to festivals with age restriction, and illegal activities such as financial frauds and travels. The advancement in digital printing technologies in the new era poses a challenge. The resolution of off-the-shelf inkjet and dye sub printers, availability of papers and polymers that accept high-quality print, and access to all the materials and knowledge through portable devices, make counterfeiters' work more efficient.

[0007] In order to minimize the risk of counterfeiting, it is desirable for the security documents to include security features which are difficult to simulate and easy to verify. In order to render the security document more difficult to copy or counterfeit, security features incorporating optically variable devices may be used. A wide variety of optically variable devices, including interference films and holograms, are available. These can be integrated with other security features such as watermarks, microprinting, and ultraviolet features, thereby creating a multilayered feature.Integration plays a huge role in protecting the optically variable material and the document from alteration or simulation. This is important, as counterfeiters have access to the same materials used by security document manufacturers.

[0008] Examples of products available for creating optically variable devices include special dyes, films and inks. For example, some inks, dyes or films, when applied to a transparent or semi-transparent substrate, may produce a colour shifting effect through different viewing angles, different background colors, or under UV light. As an example, Janus Effect™ ink, produced by H.W. Sands Corporation, may appear green over a white background, but brown over a black background, or may appear pink in ambient light but orange under UV light. As another example, O.V.M™ fiduciary inks from Crime Science Technology (CST) may appear blue over a white background, but green over a dark background; may appear green when viewed under a conventional white light source such as a smartphone flashlight, but the projected shadow appears blue; and / or may fluoresce when viewed under UV light. O.V.M™ fiduciary polycarbonate from CST produces similar effects. These inks or films allow for observation of two colors: one under transmitted light and the second under reflected light. These dyes, inks and films are functional for applications where the substrate is transparent or semi-transparent, such as in the window portion of a security document. See, for example, U.S. Patent No. 12,049,096 (Optical Marking Device), U.S. Patent No. 11,649,563 (Use of 4-bora-3a,4a-diaza-s-lndacenes for the Production of Fluorescent Fibres), U.S. Patent No. 11,186,768 (Use of 4-bora,3a,4a-diaza-s-indacenes for Security Purposes).

[0009] In order to create security features which are more difficult to simulate, inks, dyes or films producing a colour shifting effect may be combined with other elements.

[0010] SUMMARY

[0011] Optically variable materials producing a colour shifting effect may be combined with a reflective material to create a security feature that is difficult to copy.

[0012] For optically variable materials that change colour when viewed under different conditions, for example appearing as one colour when under transmitted light and as a second colour when under reflected light, the colour changing effect may beachieved, for example, in the transparent or semi-transparent window portion of a security document. Thus, when light shines through the transparent portion, one colour is visible, while when the light is reflected (for example due to placement of the transparent portion on a dark-coloured background), a different colour is visible. However, it is not necessary for the security document to include a transparent or semi-transparent window. Rather, the colour changing effect may be achieved with a shiny or reflective material in combination with a transparent or translucent optically variable material. Accordingly, where security document comprising thermoplastic polymer substrate layers further comprises a reflective material and a translucent / transparent optically variable material, such that the reflective material and the optically variable material are at least partially overlapping within the security document, it is possible to see two different colours, depending on the viewing condition, such as the viewing angle.

[0013] In an embodiment, provided herein is a security document comprising a security device, the security document comprising at least three thermoplastic polymer substrate layers, for example at least one white or opaque layer, and at least two transparent or translucent layers. The security device comprises at least one layer or portion of reflective material, and at least one layer or portion of transparent or translucent optically variable material. The reflective layer and the optically variable material are at least partially overlapping in a portion of the security device, thereby producing an optically variable effect in the overlapping portion.

[0014] In an embodiment, the optically variable effect is a colour changing effect. For example, the variability of the optically variable effect may be dependent on the angle at which the security device is viewed.

[0015] In some embodiments, the reflective layer may be a layer of metal foil. As another example, the reflective layer may be all or part of an embedded chip or antenna. In some embodiments, the translucent / transparent optically variable material is applied directly to the reflective layer. In some embodiments, the translucent / transparent optically variable material is applied to or situated adjacent to a thermoplastic polymer substrate layer of the security document. In some embodiments, the translucent / transparent optically variable material is incorporatedinto a thermoplastic polymer substrate layer, for example the substrate layer is or comprises a translucent / transparent optically variable film.

[0016] In some embodiments, the security device further comprises laser-inscribed personalized data. The laser-inscribed personalized data may be coloured by use of optically variable material. On the other hand, in some embodiments, the laser-inscribed personalized data may lack colour, due to laser inscription over a security device with colour changing effect.

[0017] In some embodiments, the security device comprises a half-window or a full window. Provided herein is a method for making a security device in a security document, the security document comprising at least three thermoplastic polymer substrate layers. The method comprises the steps of incorporating a reflective layer into at least a first portion of the security document; incorporating an optically variable material into at least a second portion of the security document; wherein the first and second portions are at least partially overlapping, thereby producing an optically variable effect in the overlapping portion.

[0018] In some embodiments, incorporating the reflective layer comprises complete or selective metallization of the first portion.

[0019] In some embodiments, incorporating the reflective layer comprises embedding a chip and antenna into the security document.

[0020] In some embodiments, incorporating the translucent / transparent optically variable material comprises applying the optically variable material onto the reflective layer. In some embodiments, incorporating the optically variable material comprises applying or incorporated the optically variable material to a thermoplastic substrate layer of the security document.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 illustrates an exemplary optically variable security device in accordance with the present invention. A: no optically variable material is incorporated; B: optically variable material is incorporated, and the security device is viewed at a first angle; C:optically variable material is incorporated, and the security device is viewed at a second angle.

[0023] Figure 2 illustrates an exemplary optically variable security device in accordance with the present invention. A: the security device when viewed at a first angle; B: the security device when viewed at a second angle.

[0024] Figure 3 illustrates an exemplary optically variable security device in accordance with the present invention. A: selective metallization without incorporation of optically variable material; B: selective metallization with optically variable material when viewed at a first angle; C: selective metallization with optically variable material when viewed at a second angle.

[0025] Figure 4 illustrates an exemplary embodiment of a security document, wherein a dye is applied to a first polymer layer, and a reflective material is applied to a second polymer layer.

[0026] Figure 5 illustrates an exemplary embodiment of a security document, wherein both a dye and a reflective material are applied to a single polymer layer.

[0027] Figure 6 illustrates an exemplary embodiment of a security document, wherein a dye layer is between two layers of reflective material.

[0028] DETAILED DESCRIPTION

[0029] As used herein, the term “thermoplastic polymer substrate” refers to thermoplastic polymers which are capable of fusing together under heat and pressure to form a monolithic document. Suitable thermoplastic substrates include polycarbonate or polycarbonate in combination with polyurethane and / or polyethylene terephthalate glycol (PETG). However, other polymers may be suitable as well. Each layer of thermoplastic polymer is sufficiently thick to be self-supporting and individually manipulable during the process of manufacturing the security document. For example, each layer may have a thickness of between 50 pm and 200 pm, or between 100 pm and 200 pm.

[0030] As used herein, the term “reflective material” refers to a material that is capable of reflecting light, including but not limited to a metal foil, a layer of metal which has beendeposited onto a substrate surface, ora chip or antenna. Similarly, the term “reflective layer” refers to a layer of reflective material or a reflective surface of a reflective material.

[0031] Metallization refers to the application of a thin layer of metal by, for example, chemical vapor deposition from a radiation sensitive precursor. In an embodiment, the metal comprises aluminum. Other suitable metals may also be used, such as gold, silver, vanadium, copper, zinc, tin, chromium, or titanium. Alloys of suitable metals may also be used.

[0032] Metallization or selective metallization may be achieved by any method known in the art. For example, a thermoplastic layer may be flood metallized. Optionally, portions of the metallized layer may be cut out and inserted into a security document as a partial layer. As another example, a mask layer, such as a water-soluble mask layer, may be first applied onto a thermoplastic layer in portions which are not to be metallized. Finally, the mask layer is removed.

[0033] As used herein, the term “optically variable material” refers to a material, such as an ink, dye or film, that appears differently depending on the conditions under which it is viewed, such as the angle or quality of light under which it is viewed. The optically variable material is transparent or translucent such that layers behind or beneath the optically variable material are at least partially visible. For example, the optically variable material may produce a colour shifting effect through different viewing angles, different background colors or under UV light.

[0034] The manufacture of the security documents described herein involves collating together layers of thermoplastic polymers, then exposing them to high heat and pressure during lamination. Non-limiting examples of thermoplastic polymers include polycarbonate, polyvinyl chloride, polyethylene terephthalate glycol, and thermoplastic polyurethane. In some embodiments, the thermoplastic polymer is polycarbonate. The thermoplastic polymer softens at about 160 °C, and adjacent layers fuse together during lamination to form a monolithic document. Some layers of thermoplastic polymer may be laser engravable, while others may not be.

[0035] In some embodiments, the addition of personal identification details may occur after the document has been manufactured, i.e. after the lamination has occurred. Forexample, the addition of personal identification details may be achieved by laser inscription.

[0036] In some embodiments, security documents may include an embedded contactless computer chip and antenna which allows the document to be scanned using radio frequency identification (RFID) technology.

[0037] In some embodiments, security documents may include a half-window, namely a portion of the document which, rather than being transparent throughout the entire thickness of the document, is transparent only through a portion of the document, thereby allowing interior layers or features to be seen through the half-window.

[0038] In other embodiments, the security documents may include a full window, namely a portion of the document which is transparent or translucent.

[0039] The translucent / transparent optically variable material may be, for example, an optically variable dye or ink. In other embodiments, the optically variable material is an optically variable thermoplastic film or layer.

[0040] In some embodiments, the reflective layer may be part of an embedded chip and antenna. For example, the chip and antenna may be located in a half-window area of the document, or the chip and antenna may simply be visible beneath one or more transparent thermoplastic layers of the security document. Optically variable material may be applied directly to the surface of the chip, the transparent thermoplastic layers may comprise the optically variable material, or the half-window area may comprise the optically variable material. The chip comprises a reflective surface that, when overlapping with a layer of optically variable material, results in the appearance of two different colours, depending on the viewing angle. The reflective surface of the chip will appear differently, depending on the viewing angle, while the surrounding area, if covered with optically variable material, will not change colour. Replacement of the chip or any alteration can be identified by first-level inspection.

[0041] As illustrated in Figure 1, an optically variable material is applied in a half-window portion of the document. Image A shows a chip in the data page (in a half-window) without optically variable material. Images B and C have optically material incorporated into the document, for example with an optically variable film, dye or ink. Image B shows the security device at first viewing angle, where the reflective portionsof the chip appear light blue, while the surrounding non-reflective portion appears purple. Image C shows the security device at second viewing angle, where the reflective portions of the chip appear reddish purple, while the surrounding non-reflective portion appears purple.

[0042] In some embodiments, a metallized foil may be incorporated behind the optically variable material. This may be achieved by any method known in the art. For example, a thermoplastic substrate layer may be flood metallized, then portions cut out to be inserted into the security document as a partial layer, such that only selected portions of the security document are metallized. Incorporation of the optically variable material may be achieved by various means. For example, the optically variable ink or dye may be printed onto the surface of the metallized substrate layer. As another example, the optically variable material may be included in one of the substrate layers over the metallized substrate layer or portion thereof in the form of an optically variable film. As a further example, a substrate layer over the metallized substrate layer may include a partial layer comprising optically variable material. As yet another example, the optically variable ink or dye may be printed on a substrate layer over the metallized substrate layer or metallized portion.

[0043] The reflective surface of the metallized portion will appear differently coloured depending on the angle at which it is viewed.

[0044] Illustrated in Figure 2 is a sample security document with optically variable dye applied over metallized portions. As shown in image A, the metallized portion appears blue when viewed at a first angle. As shown in image B, the metallized portion appears purple when viewed at a second angle.

[0045] In some embodiments, selective metallization may be used to create an optically variable security feature. For example, a masking layer may be applied to a thermoplastic polymer substrate layer in portions of the substrate which are not to be metallized. The masking layer may be any type of removable mask layer known in the art, including, for example, a water-soluble masking layer. The masking layer may be printed or applied in any suitable manner including, for example, screen or flexographic printing. Optically variable material is then applied or printed in selected areas. The material may be applied in any suitable manner such as, for example,screen or flexographic printing. The thermoplastic polymer substrate layer is then metallized, and finally the masking layer is removed.

[0046] In some embodiments, the translucent or transparent optically variable material is applied to a thermoplastic polymer substrate layer. The thermoplastic polymer substrate layer is then metallized over top of the optically variable material. The thermoplastic polymer substrate layer may be incorporated into the security document or card during the manufacturing process of the document. In some cases, the optically variable material would be visible from one side of the card, and the metallized portion would not be seen directly, but only through the optically variable material. In some cases, the thermoplastic polymer substrate layer may be incorporated such that it appears in a window of the security document, allowing for the metallized portion to be seen from one side of the document, and the optically variable material to be seen from the other side of the document. In some embodiments, the metallized / optically variable portion may overlap between a window and an opaque portion of the security document.

[0047] In some embodiments, a mask layer may be applied to a thermoplastic polymer substrate layer. Subsequently, a translucent or transparent optically variable material is printed onto the thermoplastic polymer substrate layer, for example by flexographic printing. The optically variable material may be applied as a flood coat, or only in selected portions of the substrate layer. Flood metallization is applied, followed by washing to remove the mask layer. The thermoplastic polymer substrate layer may then be incorporated into the security document or card during the manufacturing process of the document. As discussed in the preceding paragraph, the metallized / optically variable portion may be situated in a window of the security document, in an opaque portion of the document, or overlapping between a window and an opaque portion.

[0048] Illustrated in Figure 3 is a security device comprising colour changing dye with selective metallization. Image A shows the result of a selective metallization prior to application of the colour changing dye. Images B and C illustrate the effect of colour changing dye over the metallized area at two viewing angles. The image appears blue when viewed at one angle (B), while it appears green when viewed at a second angle (C).Figures 4 and 5 provide exemplary embodiments of security document construction incorporating translucent ortransparent thermoplastic substrate layers (4), at least one white or opaque thermoplastic substrate layer (2), reflective material (6) and optically variable material (8). In Figure 4, the optically variable material (8) and the reflective material (6) are applied to, or are situated adjacent to, separate transparent or translucent thermoplastic polymer substrate layers (4). In Figure 5, the optically variable material (8) and the reflective material (6) are applied to, or situated adjacent to, the same thermoplastic polymer substrate layer in a transparent region or window (10) of the security document. The optically variable material will be visible on one side, while the reflective material will be visible on the second side in the transparent region. In some embodiments, the reflective material may be laser ablated in order to inscribe personalized information relating to the bearer of the document.

[0049] The combination of a reflective surface, such as metal, with an optically variable material may also be effective for creating difficult-to-copy security features when adding personal identification details (personalization), such as text, image or logo to the security document. In some embodiments, an optically variable material may be applied to or incorporated into a thermoplastic polymer substrate layer of the security document. For example, an optically variable dye or ink may be printed or otherwise applied to the substrate layer, or an optically variable film may be incorporated into the document. The layer is also metallized or selectively metallized so that metallization is situated over or below the optically variable material portion. Once the security document has been formed (e.g. by heating and lamination), personal information may be laser engraved thereupon. The metal layer will be selectively ablated or removed in portions subject to laser engraving. A partial colour changing effect may be achieved - for example, the personalized information will not change colour when viewed at different angles, while the surrounding metallized area will change colour depending on the viewing angle.

[0050] In some embodiments, an optically variable material is situated between two metallic layers. Personalized information may be laser inscribed on one of the metallic surfaces, thus creating a personalized colour changing device whereby the laser inscribed portions exhibit a colour changing effect.Figure 6 provides an exemplary embodiment of security document construction incorporating two reflective material layers (6) and an optically variable material (8). Selective ablation of one of the reflective material layers would produce a colour shift effect due to the presence of the optically variable material and reflective material layer in the laser ablated area.

[0051] The above disclosure and figures are intended to be illustrative and not exhaustive. The description will suggest many variations and alternatives to one of ordinary skill in the art. Those familiar with the art may recognize other equivalents to the specific embodiments described herein within, without departing from the spirit and scope thereof.

Claims

Claims1. A security document comprising a security device, the security document comprising at least three thermoplastic polymer substrate layers; wherein the security device comprises at least one layer or portion of reflective material and at least one layer or portion of transparent or translucent optically variable material, and wherein the transparent or translucent optically variable material are at least partially overlapping in a portion of the security device, thereby producing an optically variable effect in the overlapping portion.

2. The security document of claim 1 , wherein the optically variable effect is a colour changing effect.

3. The security document of claim 1 , wherein the at least one layer or portion of reflective material is a metallized layer.

4. The security document of claim 1 , wherein variability of the optically variable effect is dependent on an angle at which the security device is viewed.

5. The security document of claim 1 , wherein the at least one layer or portion of reflective material comprises an embedded chip and / or antenna.

6. The security document of claim 1 , wherein the optically variable material is applied directly to the at least one layer or portion of reflective material or is situated adjacent to the at least one layer or portion of reflective material.

7. The security document of claim 1 , wherein the optically variable material is applied to a thermoplastic polymer substrate layer or is situated adjacent to a thermoplastic polymer substrate layer of the security document.

8. The security document of claim 1, wherein the security device further comprises laser-inscribed personalized data.

9. The security document of claim 1 , wherein the security device comprises a half-window or a full window.

10. The security document of claim 1, wherein the optically variable material is situated between two reflective layers and wherein one of the two reflective layers is at least partially laser ablated.11.A method for making a security device in a security document comprising at least three thermoplastic polymer substrate layers, the method comprising the steps of: incorporating at least one layer or portion of reflective materialinto at least a first portion of the security document; incorporating at least one layer or portion of a transparent or translucent optically variable material into at least a second portion of the security document; wherein the first and second portions are at least partially overlapping, thereby producing an optically variable effect in the overlapping portion.

12. The method of claim 11, wherein incorporating the at least one layer or portion of reflective material comprises complete or selective metallization of a thermoplastic polymer substrate layer the first portion of the security document.

13. The method of claim 11 , wherein incorporating at least one layer or portion of reflective material comprises embedding a chip and antenna into the security document.

14. The method of claim 11, wherein incorporating the at least one layer or portion of optically variable material comprises applying the optically variable material directly onto the at least one layer or portion of reflective material.

15. The method of claim 11, further comprising laser ablating at least a portion of the at least one layer or portion of reflective material.

16. The method of claim 11, wherein incorporating the at least one layer or portion of optically variable material comprises applying the optically variable material to a thermoplastic polymer substrate layer of the security document.

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