Security substrate and security documents produced therefrom

Abstract

The invention relates to a security substrate for security documents, which is formed based on a laminated structure comprising two BOPP films with appropriate thickness and structure so as to improve durability, enhance tactile feel, and provide advantages in circulation. The security substrate according to the present invention comprises a lower surface and an upper surface. The substrate comprises a laminated structure of two BOPP films bonded together by an adhesive layer. The thickness of the BOPP film layers provides the laminated structure with improved tensile strength compared to the prior art. The coating layers may be applied to one side of the laminated structure, and are preferably applied to both sides of the laminated structure, for example, two coating layers on each side. The thickness of the coating layer, in combination with the laminated structure, provides advantages in terms of tactile feel.

Description

[0001] SECURITY SUBSTRATE AND SECURITY DOCUMENTS PRODUCED

[0002] THEREFROM

[0003] Field of Invention

[0004] The present invention principally relates to the field of security, specifically to substrates for security documents or structures and the like, wherein the substrate is a laminated structure of two polymer films bonded by an adhesive layer having improved strength, tactile response, as well as other advantages, and to security documents produced therefrom.

[0005] Background of Invention

[0006] Security documents, particularly value documents such as banknotes, checks, passports, identification papers, certificates, and licenses, are frequently targeted by counterfeiters and individuals seeking to illegally copy and / or alter any data contained therein.

[0007] Currently, these documents, particularly known banknotes, are produced from a variety of different substrates. These forms of currency include cotton banknotes, polymer banknotes, and hybrid types combining cotton and polymer, also referred to as hybrid banknotes (between paper and polymer).

[0008] Cotton substrates have the advantage of providing a pleasant and familiar tactile feel, being easy to handle and long-used, but they are inferior in durability compared to other types of banknote substrates.

[0009] Polymer substrates offer advantages in terms of durability, ease of cleaning, and moisture resistance. Such substrates are typically produced from Oriented Polypropylene (OPP), and more preferably from Biaxially Oriented Polypropylene (BOPP).

[0010] According to a widely applied prior art, the substrate is formed from a BOPP film structure by means of cast film lamination, followed by biaxial orientation in both transverse and longitudinal directions, wherein the film structure has a thickness of only approximately 75 microns due to technological limitations. According to another prior art disclosed in the International Publication W02004009355A1, a BOPP film structure is formed using bubble technology, wherein two three-layer films are laminated together by heat to produce a five-layer film. The substrate using this film structure is widely applied; however, the film structure also has a thickness of approximately 75 microns. The substrate structure comprising these two layers offers an advantage in tensile strength compared to a single-layer substrate; however, the two layers according to this technology are laminated by heat immediately after extrusion, thus security elements cannot be inserted, nor can any modifications be made between the two films as desired.

[0011] The thickness of approximately 75 microns according to the known solutions, after the application of coating layers such as an opaque layer and an ink-receptive layer, results in the substrate achieving a finished thickness of only slightly above 80 microns. With each coating layer having a thickness of approximately 2 microns, the total thickness of the coated substrate only reaches about 83 microns.

[0012] To achieve the handling feel, tactile response, flexibility, and surface hardness similar to cotton-based banknotes, the substrate thickness after coating needs to exceed approximately 90 microns; however, increasing the number or thickness of the coating layers to reach this thickness compromises the durability of the substrate and increases production costs.

[0013] According to another aspect, security documents, particularly documents of value such as banknotes and checks, are susceptible to counterfeiting. To improve security and prevent counterfeiting or to make counterfeiting more difficult, security documents are often provided with security elements. In particular, in one type of security document known as banknotes, security elements that provide certain visible optical effects for the authentication of the item incorporating such security elements are commonly used.

[0014] In the process of producing banknotes, the above-mentioned substrates are formed and subsequently provided with various pre-fabricated security elements, such as optical diffraction structures, holograms, security features detectable under UV light, etc., or printed on the surface in the form of colored elements or printed patterns.

[0015] Optical diffraction structures and holograms are commonly pre-fabricated as multilayered strips or patches, which are then applied to the surface using an adhesive. The number of layers in the structure of security documents produced from the substrate increases due to the security element itself having a multilayer structure.

[0016] Thus, security documents having such a structure, for example banknotes, suffer from the drawback of being susceptible to delamination; the security elements are easily affected during circulation due to frequent handling, especially when exposed to oil, grease, or interaction with counting machines. In addition, such strip-type security elements are applied in a manner that divides the banknote, which may result in limitations in terms of aesthetics. Colored elements or printed patterns are also easily subject to fading during use.

[0017] Even though a protective coating may be applied, such coating also has a limited thickness, not to mention the need for additional auxiliary steps for its application.

[0018] European Patent Publication EP3986719A1 discloses a substrate comprising a first film and a second film laminated together by an adhesive layer, wherein the security element is an relief structure provided between the films. As a result, the security element is protected from external impact during circulation.

[0019] The substrate disclosed in the above-mentioned document may be composed of cotton, polymer, or a hybrid of cotton and polymer.

[0020] Although the aforementioned patent document mentions that the substrate may be made from polymer, as with other prior art, it does not address issues related to durability, such as insufficient tensile strength, unsatisfactory tactile feel, and a tendency to bend easily in its natural state.

[0021] There exists a need for a substrate that overcomes the aforementioned disadvantages of known substrates.

[0022] Summary of the Invention The objective of the invention is to provide a security substrate for security documents, as well as security documents produced therefrom, wherein the security substrate is based on a laminated structure of two BOPP films with appropriate thickness and configuration, in order to improve durability, enhance tactile feel, and offer advantages in circulation.

[0023] The security substrate according to the present invention comprises a lower surface and an upper surface. The substrate comprises a laminated structure of two BOPP films bonded together by an adhesive layer. The thickness of the BOPP film layers provides the laminated structure with improved tensile strength compared to the prior art. Each BOPP film has a thickness of approximately 40 microns. The coating layers may be applied to one side of the laminated structure, and are preferably applied to both sides of the laminated structure, for example, two coating layers on each side. The coating layer may be an opaque layer and an ink-receptive layer. The thickness of the coating layer, in combination with the laminated structure, provides advantages in terms of tactile feel.

[0024] According to another embodiment, the opaque layer may be omitted and, instead, a first ink-receptive layer is formed with an appropriate thickness and opacity so as to still achieve the advantages of the previous embodiment. This ink-receptive layer is provided above the laminated structure.

[0025] According to a preferred embodiment of the invention, a second opaque layer, a second ink-receptive layer, or only a second substantially opaque ink-receptive layer is formed on the opposite side of the laminated structure. In this case, the thickness of the base substrate may reach that of a cotton substrate, thereby providing a tactile feel similar to that of cotton-based banknotes.

[0026] According to an embodiment, a security element may be incorporated between the two films of the substrate.

[0027] Within the scope of the invention, security documents such as banknotes, checks, or similar documents are also provided and are produced from the aforementioned security substrate by printing onto the ink-receptive layer of the substrate. Brief Description of the Drawings

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, which depict the essential features of the invention. Wherein:

[0029] Fig. 1 is a cross-sectional view illustrating the security substrate for banknote production according to an embodiment of the invention;

[0030] Fig. 2 is a cross-sectional view illustrating the security substrate for banknote production according to another embodiment of the invention;

[0031] Detailed Description of the Invention

[0032] Hereinafter, the present invention is described by specific embodiments and is not intended to limit the scope of the present disclosure. The ranges of values provided in the description are to be interpreted as inclusive of the end points.

[0033] The invention is described herein with reference to a substrate used in the production of security documents, specifically banknotes. However, it is to be understood that the various aspects and embodiments of the substrate according to the invention may be applicable to other types of security documents, provided that they are understood by a person of ordinary skill in the art, including but not limited to: credit cards, checks, passports, identity cards, and the like. Banknotes are merely a typical example selected by the inventor to most clearly illustrate the advantages of the invention as compared to the prior art.

[0034] The substrate 1 according to the present invention, which serves as a substrate for the production of polymer banknotes as illustrated, comprises a laminated structure of two polymer films bonded together by an adhesive layer. Polymeric materials commonly used in the prior art include polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET). However, according to the present invention, the films of the substrate are formed from Bi axially -Oriented Polypropylene ( BOPP).

[0035] With this substrate structure, it is possible to intentionally incorporate features within the interior, between the two BOPP films; for example, a security element may be embedded within the laminated structure, thereby being protected from external influences during circulation.

[0036] According to the present invention, the thickness of each BOPP film is approximately 40 microns. “Approximately 40 microns” as used herein means that a tolerance of 1 micron is permitted, i.e., the thickness of the BOPP film ranges from equal to or greater than 39 microns to less than or equal to 41 microns, and more preferably, is equal to 40 microns. It is preferable that the two BOPP films have equal thickness.

[0037] The thickness of the adhesive layer ranges from 2 to 3 microns. The desired thickness of the laminated structure of the substrate ranges from 80 to 83 microns.

[0038] The inventor has found that, with the BOPP film having a thickness of approximately 40 microns, the strength of the resulting laminated structure is significantly improved. Experiments were conducted with laminated structures in which each BOPP film had a thickness in the range of 32-36 microns, or even 37-38 microns; however, the tensile strength of the resulting laminated structure remained limited and ruptured at approximately 120 MPa.

[0039] The prior art in this technical field has generally focused on substrate thicknesses in the range of 75 microns, as previously mentioned. Patent No. EP3986719A1 also does not disclose the thickness of the film, the thickness of the laminated structure, or the thickness of the substrate.

[0040] The desired substrate structure to be produced is not only capable of improving tensile strength, but must also overcome the drawback of the substrate curling in its natural state, resulting in poor handling feel, thereby providing advantages in circulation as well as other properties, such as substrate opacity.

[0041] For this purpose, the invention provides a substrate comprising a laminated structure of a first BOPP film and a second BOPP film. On at least a film of the laminated structure, at least a coating may be applied, such as two coatings. Although the coating is described as being applied on top of the film layer, it may, as illustrated, be applied on top of the lower film, with the intention that the coating lies on the outer side of the laminated structure.

[0042] The coatings comprise an opaque layer and an ink-receptive layer.

[0043] According to the illustrated embodiment of Fig. 1, the laminated structure comprises a first BOPP film 21 and a second BOPP film 22, which are bonded together by an adhesive layer, and a first opaque layer 23 arranged above the first BOPP film 21 on one side of the laminated structure, with a first ink-receptive layer 25 arranged above the first opaque layer 23.

[0044] According to an embodiment, the substrate 1 further comprises a second opaque layer 24 provided on one side of the first BOPP film 21 opposite to the second BOPP film 22, and a second ink-receptive layer 26 arranged such that the second opaque layer 24 is positioned between the first BOPP film 21 and the second ink-receptive layer 26.

[0045] According to the illustrated embodiment of Fig.. 2, this substrate 1 does not comprise an opaque layer, but instead includes a first substantially opaque ink-receptive layer 25’. A second substantially opaque ink-receptive layer 26’ is also arranged on one side of the first BOPP film, opposite to the first ink-receptive layer 25'.

[0046] According to the illustrated embodiment of Fig. 1, the first and second opaque layers 23 and 24 have a thickness in the range of 2-3 microns, while the first and second ink- receptive layers 25 and 26 have a thickness of approximately 1-2 microns.

[0047] According to the illustrated embodiment of Fig. 2, the first and second substantially opaque ink-receptive layers 25’ and 26', have a thickness of approximately 2-3 microns.

[0048] The owner of this invention has found that, with the thickness of the opaque layer as specified above (according to the embodiment in Fig. 1) and the thickness of the substantially opaque ink-receptive layer as specified above (according to the embodiment in Fig. 2), together with the laminated structure of the two BOPP films with the aforementioned thickness, the resulting substrate provides an improved tactile feel. For example, with a laminated structure having a thickness of approximately 82-83 microns, a first opaque layer 23 with a thickness of 2 microns, and a first ink-receptive layer 25 with a thickness of approximately 2 microns, the resulting substrate has a minimum thickness of 86 microns.

[0049] According to the preferred embodiment, each film has a thickness of 40 microns, the adhesive layer has a thickness of approximately 2 microns, and the substrate further comprises first and second opaque layers 23 and 24, each with a thickness of approximately 2 microns, as well as two ink-receptive layers 25 and 26, each with a thickness of approximately 2 microns. In this case, the substrate has a thickness of approximately 90 microns, which is essentially equivalent to the thickness of a cotton substrate, thereby providing a tactile feel similar to that of cotton-based banknotes.

[0050] Other embodiments may be implemented, for example, the substrate may further comprise a primer layer positioned between the film and the opaque layer, with the primer layer having a thickness of approximately 1 micron, or the thickness of the adhesive layer and opaque layer may be increased to as much as 3 microns.

[0051] Essentially, the laminated structure comprising two BOPP films of the specified thickness provides advantages in terms of tensile strength and thickness, allowing for specific embodiments regarding the number of coating layers to be implemented, which offer advantages over known polymer banknotes.

[0052] A window 27 may be formed on one side of the substrate, in the opaque layer 23 and the ink-receptive layer 25 according to the embodiment shown in Fig. 1, or may be formed in the substantially opaque ink-receptive layer 25' according to the embodiment shown in Fig. 2.

[0053] A window may also be formed on the opposite side of the substrate in a similar manner.

[0054] Other examples may be implemented with the thickness of the films in the laminated structure and the thickness of the opaque layer varying within the aforementioned ranges. Although not all possible embodiments are specifically described, it will be apparent to those of ordinary skill in the art that various alternative dimensions may be implemented without departing from the spirit of the invention.

[0055] In one embodiment, at least one UV-cured coating provided on at least a portion of the surface adjacent to the adhesive layer of at least one of the polymer films, and at least one hologram formed in the said UV-cured coating.

[0056] In an aspect, the present invention provides security documents having a security substrate as described above.

[0057] It should be understood that the invention is not limited to the specific embodiments described in this document, which are provided merely as illustrative examples. Modifications and variations to the embodiments described above may be made without departing from the scope and spirit of the invention. The scope of the present invention is limited only by the appended claims.

Claims

CLAIMS1. A security substrate (1) for security documents, comprising: a first BOPP film (21); a first opaque layer (23) arranged above the first BOPP film (21); a second BOPP film (22) provided between the first opaque layer (23) and the first BOPP film (21); characterized in that: the first BOPP film (21) and the second BOPP film (22) are laminated together by means of an adhesive layer (20), wherein each of the BOPP films (21, 22) has a thickness of approximately 40 microns.

2. The security substrate of claim 1, further comprising: at least one UV-cured coating provided on at least a portion of the surface adjacent to the adhesive layer of at least one of the polymer films; at least one hologram formed in the said UV-cured coating.

3. The security substrate of claims 1 or 2, further comprising a first ink-receptive layer (25) arranged above the first opaque layer (23).

4. The substrate of claims 1, 2 or 3, wherein the substrate further comprises a second opaque layer (24) provided on a side of the first BOPP film (21), opposite to the second BOPP film (22).

5. The substrate of claims 1, 2, 3, or 4, wherein the substrate further comprises a second substantially opaque ink-receptive layer (26') arranged on a side of the first BOPP film (21), opposite to the second BOPP film (22).

6. A security document comprising a security substrate according to any one of the preceding claims.

Images