Graphene based security thread, methods of manufacturing the same and application thereof

Abstract

Graphene based security thread, methods of manufacturing the Same and application thereof. Currency notes comprises of graphene nano-platelets ink (2) based thin coated / printed film / indicia formed on the carrier film (1), graphene nano-platelets ink bands / pattern of variable sizes (21); or embed RFID antenna (5) made from graphene nano-platelets or graphene nano-platelets dots (7) on the substrate, when combined with LC based polymers (4) in form of an overlay will show distinct colour shift. Provided are also a UV curable lacquer / Graphene based lacquer (3) and a PET film (1A).

Description

FIELD OF INVENTION

[0001] The present invention relates to security thread for protection against counterfeiting, more particularly the present invention relates to Graphene nano-platelets based security thread, methods of manufacturing the graphene nano-platelets based security thread and application thereof.BACKGROUND OF THE INVENTION

[0002] There are several key requirements that must be met by a new banknote: esthetics, counterfeit prevention, machine readability, physical durability, and public acceptance. Only banknotes that fulfil these requirements perfectly are capable of establishing themselves long term. It has been the conventional practice to incorporate various security means in these documents. Generally security features are added in the banknotes for anti-counterfeiting purposes. Further, security elements such as intaglio printing, watermarks, covert security features, foil elements, laser marking, security threads and special-effect inks such as use of magnetic inks on metals like aluminum are some of the security features for protection against counterfeiting. The use of metallic coating may result in corrosion and decreased electro conductivity of the security element, when embedded as security thread.

[0003] Intaglio refers to strong denomination colors, striking portraits and ornamental designs, and not least the relief-style embossing are the unmistakable features of this sophisticated printing technique. Watermarks are provided for protection against counterfeiting for hundreds of years. The attractive designs result in the most readily recognized security feature available to the general public for the authentication of banknotes. Covert security elements are integrated into inks, threads, and foils and thereby extend the functionality of these elements to further verification levels. Foil elements are security features that are easy to identify and therefore highly suitable for verifying authenticity. With their eye-catching designs, which are applied to a prominent area of the banknote or security document, they attract the attention of all users. Foil elements enable the creation of flexible designs through the incorporation of gold, copper, or aluminum effects. Laser marking is a laser marking method that uses ultramodern laser technology to individually adapt established security features and thereby create new ones.

[0004] Security threads are an efficient and reliable security element. They are easily recognized by the general public and offer a high level of protection against counterfeiting thanks to the complex techniques used to produce them. Security threads are inserted into the paper at the cylinder mould during the paper production process; either fully covered by the paper or as a window thread that is visible on the surface of the paper at regular intervals. Special-effect inks printing using optically variable special-effect inks produces intriguing security elements that are quickly and easily identifiable and create irreproducible effects. The special-effect inks change their appearance depending on the angle from which they are viewed: they are visible or invisible, or they change color.

[0005] US20170089012A1 discloses a security feature against counterfeiting security printing, in particular banknotes, having at least one graphene quantum dot (GQD) that has a graphene nanoparticle diameter ranging from 0.5 nm to 60 nm, and containing from 1 to 90 layers of graphene, that is disposed in the flexible layer of graphene nanocomposite material, wherein the elastic layer of graphene nanocomposite material comprises at least one layer of graphene arranged directly or on an adhesive layer, preferably a polymer.

[0006] Further US9704080B2, discloses security element for sensitive documents characterized in that it includes at least one graphene layer arranged on a polymer layer where the graphene layer is heterogeneous and forms a pattern characterized by different levels of absorption of electromagnetic radiation, especially infrared radiation, visible light radiation or ultraviolet light passing through the pattern at its various points.

[0007] The prior art, as mentioned above, has been breached by various look-alike methods, and there is a need for a more robust security thread, with additional verifiable features complementing the present overt and covert features. Further, the prior art available discloses a single layer or a single method protection of the banknotes using Graphene that acts as the main active security element. Due to the continuous development of counterfeiting techniques with the constantly improving quality of color photocopiers, digital printing technologies and other printing methods, and in an attempt to protect banknotes from constant counterfeiting, in particular long-life security documents, e.g. banknotes, requires high resistance against counterfeiting or illegal reproduction. Also, the controlled source of raw materials forms an important part in the field of security elements, so as to track and trace the counterfeits.

[0008] WO 2016 / 087485 A1 discloses the preamble of claim 1.

[0009] There exists a need to develop new methods of document protection against illegal copying, by using visual (non-copiable) overt and covert elements, and products produced by complex processes of printing, metalising / demetalising, visible / invisible / UV fluorescent / infrared readable, UV up-convertable coatings, or its combinations. Therefore, in order to overcome or at least mitigate the disadvantages of existing prior art, it is the object of the present invention to provide a multi-pronged system to protect banknotes using graphene nano-platelets as the main feature that is embedded in security thread and method of manufacturing the same and various applications thereof.OBJECTS OF THE PRESENT INVENTION

[0010] The primary object of the present invention is to provide improved graphene nano-platelets based enhanced security threads to protect from the counterfeits, in a multi-pronged manner.

[0011] Another object of the present invention is to provide improved graphene nano-platelets based security threads incorporated with liquid crystal (LC), such that LC can replace color-shifting ink and prevent bank notes counterfeiting. Yet another object of the present invention is to provide a highly counterfeit resistant, machine-readable Security thread for insertion into Bank Note and similar security papers.

[0012] Yet another object of the present invention is to provide improved graphene nano-platelets based security thread without using metal such as aluminum, wherein electro conductivity of the security element increases in the absence of the metallic material.

[0013] Yet another object of the present invention is to provide a problem-solving approach, wherein corrosion by magnetic inks on metals like aluminum is avoided, as the present invention discloses a method of manufacturing an improved graphene nano-platelets based enhanced security thread without using metal, thereby solving the problem associated with corrosion.

[0014] Yet another object of the present invention is to provide higher resistance against counterfeiting or illegal reproduction of security threads by incorporating a rare element like graphene nano-platelets embedded into the security thread, which is sourced from a secure source and is trackable, as part of a multi-pronged strategy.

[0015] Yet another object of the present invention is to provide method of manufacturing improved Graphene nano-platelets based security thread for protection against counterfeits.

[0016] Yet another object of the present invention is to provide Graphene nano-platelets ink bands / pattern, optionally incorporated with magnetic elements of multiple or singular codes of variable sizes and shapes, printed on the security thread, as an enhanced covert / security thread feature for the banknotes that are detected by using, purpose designed sensors / readers.

[0017] Yet another object of the present invention is to print Barcodes / QR Codes / Track & Trace codes using visible or invisible inks made from graphene nano-platelets as security thread feature(s) which are detected / read by using specific readers.

[0018] Yet another object of the present invention is to print Graphene nano-platelets based thin film coating, which is nano thin, so as to be almost clear (rather than opaque / black), on the substrate, to impart additional quality of better mechanical and adhesion properties for subsequent coated functional layers to be used on security thread feature. Higher mechanical properties are required for a nano thread to be inserted in high-speed bank note paper making machines. Adhesion and cohesion properties are required for all the layers of functional coatings, to remain together during the process of Bank Note Paper Making, to ensure proper subsequent adhesion of whole of the security thread to fibres used for bank note paper making.

[0019] Yet another object of the present invention is to provide graphene dots laced with magnetic elements or any other type of machine-readable elements, on the substrate used as security thread feature on the banknotes.

[0020] Yet another object of the present invention is to coat graphene nano-platelets based solution onto a metallic film, as a masking agent, with desired indicia / nano text / graphics / bar-codes, etc., before the process of demetallisation. Graphene has been proven in our experiments as disclosed in the present invention to show better adhesion to metallized film / metal and better resistance to highly alkaline / acidic solvents, being commonly used for demetallisation process, during the manufacture of security threads.

[0021] Optionally, Yet another object of the present invention is to print RFID antenna(s) made from Graphene nano-platelets as security thread feature on the banknotes that are detected / read by using specific readers.

[0022] Yet another object of the present invention is to decrease or eliminate counterfeiting against bank notes or any security documents.

[0023] Yet another object of the present invention is to provide methods of manufacturing this Graphene based security threads and incorporating the same in the banknotes.

[0024] However, the foregoing objects to be achieved will be clear from the following description. In this context it is clarified that the description provided is non-limiting and is only by way of explanation.SUMMARY OF THE INVENTION

[0025] The first aspect of the present invention is to provide an improved graphene-based security thread as described in Claim 1.

[0026] The second aspect of the present invention provides method of manufacturing an improved graphene-based security thread and incorporating the same in the banknotes, as claimed in Claim 12.

[0027] Several ways of incorporating an improved graphene-based security thread in a multi-pronged manner are described herein as mentioned below for securing security paper: i. Graphene nano-platelets ink based thin film coated on the carrier film used as security thread feature on the said security paper; or ii. Graphene nano-platelets ink bands or Graphene nano-platelets ink pattern as security thread feature on the said security paper; or iii. Graphene nano-platelets based dots on the substrate used as security thread feature on the said security paper; or iv. Optionally, embedded RFID antenna made from Graphene nano-platelets as security thread feature on the said security paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Fig.1 is a schematic cross-sectional view of improved Graphene nano-platelets based security thread, wherein Graphene nano-platelets based thin film coating on the substrate used as security thread feature on the banknotes. This Graphene based coating may be flood coating or discreet pattern based print-coating or even an indicia of graphene. This graphene-based layer will be instrumental in displaying the colour shift effect, in discreet places, in the design of high security threads. Fig. 2A-2B is a diagrammatic representation illustrating graphene nano-platelets ink bands / pattern of variable size as security thread, wherein said security thread on the banknotes are detected using UV light. Fig. 3A-3B shows a diagrammatic representation illustrating alternative embodiment of printing RFID antenna (5) made from graphene nano-platelets as security thread, wherein said security thread on banknotes can be detected using specific readers. Fig. 4 is a diagrammatic representation illustrating Graphene nano-platelets (Nanene ®< ) based dots, on the substrate.

[0029] Having described the main features of the invention above, a more detailed and non-limiting description of a preferred embodiment will be given in the following paragraphs with reference to the accompanying drawings.DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention relates to Graphene nano-platelets based security threads, methods of manufacturing the same and application thereof for protection against counterfeiting against bank notes or any security documents.

[0031] Basically, Graphene is a single atomic layer of graphite; a mineral which is an allotrope of carbon that is made up of very tightly bonded carbon atoms organised into a hexagonal lattice. Graphene is unique because of its sp2 hybridisation and very thin atomic thickness (of 0.345 nm). In more complex terms, Graphene is an allotrope of carbon in the form of a plane of sp2-bonded atoms with a molecular bond length of 0.142 nanometers. Layers of graphene stacked on top of each other form graphite, with an interplanar spacing of 0.335 nanometers. The separate layers of graphene in graphite are held together by van der Waals forces. It's amazing properties as the lightest and strongest material, along with its ability to conduct heat and electricity better than anything else, as well as to store memory, has been found to be right mix which when integrated in proper chemistry and when applied at desired locations will result in desired and consistent values, till the end of life of the security thread, before and after insertion into bank note paper or security documents, throughout its circulation life. The right quality and mix will help improve the performance and efficiency of current materials and substances.

[0032] The nanomaterials with properties that are particularly useful in the field of document security against counterfeiting include graphene, which is a flat structure made of carbon atoms connected in hexagons. Graphene shows, among others, linear dependence of dispersion, resulting in a unique light absorption. Light absorption occurs when an electron from the valence band can absorb a photon (the photoelectric effect). This is possible if the energy difference between the point of the valence band and conduction is the same as the energy of the photon. In graphene in the area called "point K" there is linear dispersion dependence and closed energy slot, which means that each wavelength of light (each colour) in the range of from near infrared to ultraviolet light can be absorbed by graphene, as there will always be an electron, which can absorb a photon. Furthermore, the probability of absorbing each wavelength of light is the same. Since the graphene is a single layer material, it absorbs only a very small part of the incident light (2.3%) and thus is a material having a high degree of translucency (transparency), and at the same time a material having a very strong absorption of light (as for such a thin structure).

[0033] The graphene security feature can be transparent or opaque dark in the case of the need to obtain visualisation; it can have a form which is visible to the human eye. This essentially depends upon the laydown of graphene and target end use. Graphene nano-platelets such as (Nanene ®< ), may also be used.

[0034] Graphene nano-platelets is particularly used here as it has been found to have the desired quality, purity and more robust features like conductivity, adhesion properties, cohesion properties, as well as the best opacity which is an important factor when it comes to production of security threads having colour shifting qualities as an overt feature as well as giving an unparalleled advantage when it comes to enhancing the magnetic values and consistency in reading one or multiple magnetic codes on a security thread (covert feature), as disclosed in the present invention.

[0035] The primary aspect of the present invention is to provide improved Graphene nano-platelets based security thread for the purpose of securing security paper used for bank notes., consisting of: a dimensionally stable carrier film (1); a graphene nano-platelets inks (2) coated / printed over the carrier film (1); a UV lacquer / Graphene based lacquer (3) coated over the graphene nano-platelets inks (2) layer; and Liquid crystal film (4) coated over the UV lacquer / Graphene based lacquer (3) layer; characterized in that the graphene nano-platelets inks forms a robust and complex security feature, with adhesion value greater than black ink, increased electro conductivity and that prevents corrosion by eliminating the use of metallic material.

[0036] Further, alternatively printed RFID antenna / barcodes / QR codes etc. made from Graphene nano-platelets based coatings / inks for a robust and complex security thread feature may also me formed. Also, graphene nano-platelets ink bands / pattern of variable size as security thread may be formed, wherein said security thread on the banknotes are detected using UV light.

[0037] Further graphene nano-platelets dots may be provided on the substrate to be used as security thread feature on the banknotes in order to provide higher resistance against counterfeiting against bank notes or any security documents.

[0038] The present invention provides an improved graphene nano-platelets based security thread in a multi-pronged manner for the purpose of security paper like, but not limited to currency notes, characterized in that the said currency notes comprises graphene nano-platelets ink based thin film coated over the carrier film. This Graphene nano-platelets ink-based coating may be flood coated or discreet pattern-based print-coating or even an indicia of graphene over the carrier film. This graphene-based layer will be instrumental in displaying the colour shift effect. Graphene nano-platelets ink bands / pattern of variable sizes as security thread feature may be incorporated in the currency notes; or embedded RFID antenna may be made from graphene nano-platelets as security thread feature on the currency notes; or graphene nano-platelets dots may be made on the substrate used as security thread feature on the currency notes in order to provide higher resistance against counterfeiting against currency notes or any security documents.

[0039] In an embodiment of the present invention there is provided an assembly of improved graphene nano-platelets based security feature, wherein the said security feature can be incorporated in the security thread in a multi-pronged manner for the purpose of security paper like, but not limited to currency notes.

[0040] In another embodiment of the present invention there is provided several ways of incorporating an improved graphene-based security thread in a multi-pronged manner as mentioned below for securing security paper characterized in that the said security paper: i. Graphene nano-platelets ink based thin film formed on the carrier film / substrate used as security thread feature on the said security paper; or ii. Graphene nano-platelets ink bands or Graphene nano-platelets ink pattern(s), indicia is placed on discreet areas to form a web of printed film which is converted into security thread, and inserted into paper on paper machines, this insertion can be done in totality (embedded within the pulp or can be "sewn" in intermittently to show a windowed thread as security thread feature on the said security paper; or iii. Graphene nano-platelets based dots on the substrate used as security. thread feature on the said security paper; or iv. Optionally, embedded RFID antenna or indicia is made from Graphene nano-platelets as security thread feature on the on the said security paper.

[0041] The present invention discloses a problem-solving approach, wherein corrosion by magnetic inks / carbon based black ink is avoided, as the present invention discloses an assembly and a method of manufacturing an improved graphene nano-platelets based enhanced security thread without using metal, such that graphene nanoplatelets mimics the characteristics of magnetic inks / carbon based black ink. Further the present invention is to provide improved graphene nano-platelets based security thread without using metal such as aluminum, wherein electro conductivity of the security element increases in the absence of the metallic material.

[0042] Fig. 1 is a schematic cross-sectional view of improved graphene nano-platelets based security thread. A dimensionally stable carrier film (1), which is made of Polyethylene terephthalate (PET) is selected of a specific micron. The dimensionally stable carrier film (1), which is made of Polyethylene terephthalate (PET) for example may have a thickness ranging from 20 microns to 24 microns, particularly ranging from 15 microns to 18 microns, more particularly ranging from 8 micron to 12 micron, but not limited to the specific micron and can vary depending upon the need of the end user. The carrier film (1) is coated / printed with graphene nano-platelets inks (2) to form a robust and complex security feature, since adhesion value of graphene nano-platelets based ink is more compact in comparison to carbon based black ink. Graphene nano-platelets based thin film coating / printing, which is nano thin, forms an almost clear coating(rather than opaque / black), on the carrier film (1), to impart additional quality of better mechanical and adhesion properties for subsequent coated functional layers to be used on security thread feature. Wherein the graphene nano-platelets based ink thickness may range from 0.5 micron to 5 micron. Further the graphene nano-platelets ink (2) based thin film coated / printed on the carrier film (1) is coated with a layer of U.V curable lacquer / Graphene based lacquer (3) to form a smooth surface. Graphene based lacquers (3) have been found to have better adhesion to filmic substrates, like but not limited to, polyester films based substrates, and has better resistance to strong alkaline or acidic solutions, while producing a high security thread. Further liquid crystal polymers (LC) that can be chiral, nematic / cholesteric or combination thereof and has a specific wavelength in selected; wherein the said liquid crystal polymers forms an LC film (4) once coated on the U.V curable lacquer / Graphene based lacquer (3) by casting / coating / printing. Further the LC film (4) is subsequently dried and curable. A PET(1A) in laminated over the LC film (4)for further use.

[0043] As disclosed in Fig. 1, graphene nano-platelets ink when combined with LC based polymers in form of an overlay will show distinct colour shift, which will provide higher resistance against counterfeiting to bank notes or any security documents, after insertion of such security threads into security paper.

[0044] Fig.1 shows schematic cross-sectional representation illustrating Graphene nano-platelets based ink coating on the carrier film (1) used as security thread feature on the banknotes, wherein Graphene nano-platelets replaces the magnetic metal properties present on the security threads in banknotes, such that Graphene mimics the magnetic property of the metal thereby providing higher tensile strength and greater protection against counterfeiting. The present invention discloses printing graphene nano-platelets based ink coating, which is nano thin, so as to be almost clear (rather than opaque / black), on the substrate, to impart additional quality of better mechanical and adhesion properties for subsequent coated functional layers to be used on security thread feature. This Graphene based coating may be flood coating or discreet pattern-based print-coating or even indicia of Graphene. This layer will also be instrumental in creating the colour shift effect in the high security threads. Fig. 1 illustrates Graphene nano-platelets ink based coating, wherein Graphene nano-platelets ink are deposited on a film of polymeric substrate / a dimensionally stable carrier film (1), wherein the carrier film (1) is coated with a solution containing the Graphene nano-platelets ink, and a preparatory operation is carried out on a surface of the carrier film (1) prior to coating the carrier film (1) with Graphene nano-platelets ink (2), characterized in that the preparatory operation ensures that Graphene ink is deposited on the substrate in a chosen pattern such that when the security thread is produced from the carrier film (1) by cutting the said film, the Graphene ink in the resulting security thread has a specific pattern and provides both a visually discernible security feature and a magnetically detectable security feature. The present invention provides higher resistance against counterfeiting or illegal reproduction of security threads by incorporating a rare element like graphene nano-platelets ink embedded into the security thread, that is trackable, as part of a multi-pronged strategy.

[0045] According to the second embodiment of the present invention, there is provided a method of manufacturing improved Graphene nano-platelets based security elements for protection against counterfeits.

[0046] Generally, higher mechanical properties are required for a nano thread to be inserted in high-speed bank note paper making machines. Adhesion and cohesion properties are required for all the layers of functional coatings, to remain together for example (during the process of Bank Note Paper making, to ensure proper subsequent adhesion of whole of the security thread to fibres used for bank note paper making).

[0047] Graphene nano-platelets ink as disclosed in the present invention has been proven in our experiments as mentioned below to have better adhesion than metallised film / metal and better resistance to highly alkaline / acidic solvents, during the manufacture of security threads.

[0048] Comparison of Graphene nano-platelet based security thread with carbon based Black Ink (generic black ink presently used by colour shift security thread manufacturers):EXPERIMENTAL ANALYSIS:

[0049] SamplesMechanical Properties:Magnetic Ink Coating ( 1 GSM coating)Graphene nano-platelets Based Ink Coating ( 1 GSM coating)Sample 1Magnetic Remanence ( mWb / m)110 -130140 -160Sample 2Magnetic Coercivity ( Oe)150 -170175 -190

[0050] Experimental analysis was carried out, to understand the mechanical property of graphene nano-platelets based ink, wherein said graphene nano-platelets based ink coated on carrier film was compared to the standard magnetic based ink coated on carrier film to be used as security thread.

[0051] SAMPLE 1: Graphene nano-platelets based ink is coated on the carrier film of about 1 GSM coating, and magnetic based ink is coated on the carrier film of about 1 GSM coating. The said coatings where subjected to drying process, subsequently after the drying process mechanical character such as magnetic remanence was studied of both the ink coating on the carrier film. Magnetic remanence of Graphene nano-platelets based ink is found to be about 140 -160 (mWb / m), whereas magnetic remanence of magnetic based ink is found to be about 110 -130 (mWb / m). Thus it can be seen that the magnetic remanence of graphene nano-platelets based ink is far superior to magnetic based ink.

[0052] SAMPLE 2: Graphene nano-platelets based ink is coated on the carrier film of about 1 GSM coating, and magnetic based ink is coated on the carrier film of about 1 GSM coating. The said coatings where subjected to drying process, subsequently after the drying process mechanical character such as magnetic coercivity was studied of both the ink coating on the carrier film. Magnetic coercivity of Graphene nano-platelets based ink is found to be about 175 -190 (0e), whereas magnetic coercivity of magnetic based ink is found to be about 150 -170 (Oe). Thus it can be seen that the magnetic coercivity of graphene nano-platelets based ink is much better than magnetic based ink.INTERPRETATION:

[0053] Graphene has better consistency, opacity and darkness than magnetic / carbon black ink. Graphene based inks have a more even and dimensionally stable surface after printing (when compared to magnetic / carbon based black ink). Graphene based Ink has better electro conductivity and magnetic properties, which enables in quicker reading of magnetised signals (during the process of verification of currency notes).

[0054] The method of manufacturing of improved graphene nano-platelets based security elements / thread for insertion into paper to provide protection against counterfeits, comprising the steps of: taking a dimensionally stable carrier film (1), which is made of Polyethylene terephthalate (PET) having a thickness ranging from 8 microns to 12 micron; printing / coating graphene nano-platelets based inks (2) over the carrier film (1), since adhesion value of graphene nano-platelets based ink is more compact in comparison to black ink; wherein the thickness of graphene nano-platelets inks (2) ranges from 0.5 micron to 5 micron; coating the graphene nano-platelets inks (2) with UV curable lacquer / Graphene based lacquer (3) to form a smooth surface; casting / coating / printing an LC film (4) on the UV curable lacquer / Graphene based lacquer (3); wherein the liquid crystal polymers, can be chiral, nematic / cholesteric or combination thereof and has a specific wavelength; subsequently drying and curing the LC film (4) formed on the UV curable lacquer / Graphene based lacquer (3); laminating a PET (1A) over the LC film (4) coat for further use;

[0055] Graphene based lacquers have been found to have better adhesion to filmic substrates, like but not limited to, polyester films based substrates, and has better resistance to strong alkaline or acidic solutions while producing a high security thread.

[0056] Graphene nano-platelets based thin film coating, which is nano thin, forms an almost clear coat (rather than opaque / black), on the substrate, to impart additional quality of better mechanical and adhesion properties for subsequent coated functional layers to be used on security thread feature.

[0057] Likewise, the aforementioned method of manufacturing can alternatively or optionally be formed by coating Graphene nano-platelets based solution onto a metallic film, as a masking agent, with desired indicia / nano text / graphics / bar-codes, etc, before the process of demetallisation.

[0058] Fig. 2A is a diagrammatic representation illustrating alternative embodiment of graphene nano-platelets ink bands / pattern of variable size as security feature (2') on the security thread (1') that are detected by using UV light. Graphene nano-platelets ink bands / pattern, optionally is incorporated with magnetic elements of multiple or singular codes of variable sizes and shapes, printed on the security thread, as an enhanced covert feature for the banknotes that are detected by using, purpose designed sensors / readers. The security thread (1') comprises of a dimensionally stable carrier film (1) that has been imaged with a pattern for example image such as INDIA printed over the carrier film (1), said carrier film (1) is patterned with graphene nano-platelets ink bands / pattern of variable size as security feature (2') coating composition of variable size to give a coated surface, such that the surface coated with graphene nano-platelets ink have a different properties from the surface not coated with graphene nano-platelets ink. The properties can include one or more of electrical or thermal conductivity, optical properties (such as optical density, color coordinates, etc.), X-ray diffraction, (XRD) pattern, etc.

[0059] Fig. 2B shows a horizontal view of graphene nano-platelets ink bands / pattern of variable size as security feature (2') of the security thread (1') that are detected by using UV light. Wherein graphene nano-platelets ink bands / pattern of variable size as security feature (2') is printed over the carrier film (1) that has been imaged with a pattern containing a lighter portion and a darker portion or a strip pattern. The opacity, color coordinates, and other optical properties of the coating and / or the pattern can be adjusted to achieve a desired degree of visibility of the pattern. The coated image can have different properties from the background area and different portions of the coated image can have different properties from each other.

[0060] The coating composition comprises graphene nano-platelets ink / graphene sheets, and, optionally, at least one binder, at least one carrier, one or more functional additives to adjust the optical properties, conductivity, XRD pattern, or other properties of the coating, and / or one or more additional additives. Functional additives can include electrochromic, photochromic, phosphorescent, fluorescent, pearlescent, thermochromic, metallic, and metallic effect pigments, glitter, UV / IR blockers, etc.

[0061] Fig.3A-3B shows a diagrammatic representation illustrating alternative embodiment of printing RFID antenna (5) made from graphene nano-platelets printed over the carrier film (1) to form the security thread (1') feature to be incorporated in the banknotes, wherein said security feature are detected using specific readers. The two basic components of an RFID tag that are required is a chip (5B) and an antenna (5A). The antenna (5A) acts as a communication link between the RFID tag while the chip (5B) carries out all the necessary protocols, data encoding, reading / writing from memory. For applications in banknotes the memory used in RFIDs should be non-volatile and rewritable in order to effectively complement logic and sensing elements to provide the desired circuit functionality. Further it should be cheap, flexible, robust and have good retention properties. And fabricating such memory devices on banknotes has been the biggest hurdle so far.

[0062] Graphene being a 2D nanomaterial with outstanding properties such as high charge mobility, zero band gap, high thermal conduction, high mechanical strength, high surface area and excellent biocompatibility. Due to these remarkable properties of graphene, it has a great potential to provide high conductive inks, which can be integrated with the flexible and transparent substrate to produce chemically stable, mechanically flexible and lost cost RF products.

[0063] Fig.3A illustrates embed RFID antenna (5) made from graphene nano-platelets of security thread (1') feature on the banknotes that are detected by using specific reader, wherein graphene-based antennas RFID application, is achieved through rolling compression method. A graphene-based RFID is printed on the carrier film (1) by using inkjet printing. Graphene, being the strongest, thinnest and most conductive material, could dramatically increase the conductivity of RFID tags. In addition, Graphene can deliver far cheaper devices by printing onto materials like paper or plastic, rather than more expensive metals such as aluminum or copper. Made from compressed Graphene ink, the antenna is flexible, environmentally friendly and could be cheaply mass-produced, paving the way for wearable wireless devices and sensors. Optionally Fig.3B illustrates embed RFID antenna (5) made from Graphene nano-platelets on carrier film (1) feature on the banknotes that are detected by using specific readers, wherein the RFID antenna ends are connected to each other by aluminum / metal / copper connector (6) formed during the process of de metallization.

[0064] Optionally, printing of barcodes / QR Codes / Track &Trace codes using visible or invisible inks made from Graphene nano-platelets can also be done as security thread feature(s) which are detected / read by using specific readers.

[0065] Fig.4 shows a diagrammatic representation illustrating Graphene nano-platelets based dots (7), on the carrier film (1), which can be Graphene based flood coating or discreet pattern based print-coating or even an indicia of Graphene. This Graphene based carbon black layer will also be instrumental in displaying the colour shift effect, in discreet places, in the design of high security threads. Optionally Graphene dots laced, on the substrate used as security thread feature on the banknotes can also be added as an additional security feature.

[0066] The present invention provides several ways of incorporating an improved graphene-based security thread in a multi-pronged manner as mentioned below for securing security paper characterized in that the said security paper; i. Graphene nano-platelets ink based thin film coated on the carrier film / substrate used as security thread feature on the said security paper; or ii. Graphene nano-platelets ink bands or Graphene nano-platelets ink pattern(s), indicia is placed on discreet areas to form a web of printed film which is converted into security thread, and inserted into paper on paper machines, this insertion can be done in totality (embedded within the pulp or can be "sewn" in intermittently to show a windowed thread as security thread feature on the said security paper; or iii. Graphene nano-platelets based dots on the substrate used as security thread feature on the said security paper; or iv. Optionally, embedded RFID antenna or indicia is made from Graphene nano-platelets as security thread feature on the said security paper.

[0067] Film or substrate may include, but are not limited to, flexible and / or stretchable materials, silicones and other elastomers and other polymeric materials, metals (such as aluminum, copper, steel, stainless steel, etc.), adhesives, fabrics (including cloths) and textiles (such as cotton, wool, polyesters, rayon, etc.), clothing, glasses and other minerals, ceramics, silicon surfaces, wood, paper, cardboard, paperboard, cellulose-based materials, glassine, labels, silicon and other semiconductors, laminates, corrugated materials, concrete, bricks, and other building materials, etc. Substrates can in the form of films, papers, wafers, larger three-dimensional objects, etc.

[0068] The films can have been treated with other materials before the images are applied. Examples include substrates (such as PET) coated with indium tin oxide, antimony tin oxide, etc. They can be woven, nonwoven, in mesh form; etc.

[0069] The film can be paper-based materials generally (including paper, paperboard, cardboard, glassine, etc.). Paper-based materials can be surface treated. Examples of surface treatments include coatings such as polymeric coatings, which can include PET, polyethylene, polypropylene, acetates, nitrocellulose, etc. Coatings can be adhesives. The paper-based materials can be of sized. The dimensionally stable carrier film, which is made of Polyethylene terephthalate (PET) for example may have a thickness ranging from 20 microns to 24 microns, particularly ranging from 15 microns to 18 microns, more particularly ranging from 8 micron to 12 micron, but not limited to the specific micron and can vary depending upon the need of the end user.

[0070] The pattern and coating composition can be applied using any suitable method, including, but not limited to, painting, coating, printing, pouring, spin casting, solution casting, dip coating, powder coating, by syringe or pipette, spray coating, curtain coating, lamination, co-extrusion, electrospray deposition, ink-jet printing, spin coating, thermal transfer (including laser transfer) methods, doctor blade printing, wire rod printing, screen printing, rotary screen printing, gravure printing, lithographic printing, intaglio printing, digital printing, capillary printing, offset printing, microprinting, electrohydrodynamic (EHD) printing, flexographic printing, pad printing, stamping, tampon printing, pad printing, stencil, wire rod, xerography, microcontact printing, dip pen nanolithography, laser printing, drawing, writing, coloring, via pen, or similar means, etc. The pattern and / or coating composition can be applied in multiple layers or via multiple passes or multiple methods.

[0071] The pattern can be made from any suitable medium including, but not limited to, paints, inks, varnishes, toners and other solid or powder-based printing media, inkjet inks, water-based inks and coatings, solvent based inks and coatings, graphic inks, UV- curable inks, flexographic inks, screen inks, offset inks, gravure inks, pencils and pens, chalk and other minerals, crayons, markers (e.g. felt tip pens, permanent markers, magic markers, highlighters, Sharpies, etc.), waxes, etc. In some embodiments, the media can use carbon-based dyes and / or pigments, colored dyes and / or pigments, materials that are pigment / dye-free, materials that are binder-free, etc. Two or more media can be used and may overlap each other.

[0072] There is no limitation to the formation of pattern. They can be continuous or amorphous, in the form of designs, shapes, lines, characters (such as letters, numbers, symbols, etc.), lines, bar codes (including two-dimensional and three-dimensional bar codes, etc.), arbitrary designs and patterns, etc. They can have a uniform or non- uniform thickness. The over coating may be applied such that it covers some or all of the image and little to none of the background areas.

[0073] The presence of the underlying pattern can be detected by a user using methods such as measuring electrical and / or thermal conductivity, optical density, color coordinates, XRD patterns, etc. A variety of devices, including handheld, wireless, etc. devices can be used. Any suitable color coordinates system (such as Lab) can be used.

[0074] In some embodiments, if the pattern is formed using different densities and / or thicknesses of a coating, ink, toner, etc. in different areas of the pattern, the coated surface can have different properties. If the pattern is formed using different coatings, inks, toners, etc. in different areas of the pattern, the coated surface can have different properties in those areas. The variable properties in different portions of the pattern can be used to create a distinctive signature in the security thread and provide an additional layer of security.

[0075] The above description is intended to describe the preferred embodiments of the invention in sufficient detail to enable those skilled in the art to practice the invention. The above description is intended to be illustrative and should not be interpreted as limiting the scope of the invention. Those skilled in the art to which the invention relates will appreciate that many variations of the described example implementations and other implementations exist within the scope of the claimed invention.

Claims

1. An improved graphene based security thread for securing security paper consisting of: - a dimensionally stable carrier film (1); - a graphene nano-platelets inks (2) coated / printed over the carrier film (1); and - a UV curable lacquer / Graphene based lacquer (3) coated over the graphene nano-platelets inks (2) layer; the thread being characterised in that it further consists of - a Liquid crystal film (4) coated over the UV curable lacquer / Graphene based lacquer (3) layer; and - a PET film (1A) laminated over the Liquid crystal film (4).

2. The improved graphene based security thread as claimed in claim 1, wherein the security thread comprises ink bands / pattern of variable size as security feature (2') formed on the security thread (1') consisting of: - a dimensionally stable carrier film (1), wherein said dimensionally stable carrier film (1) is patterned with graphene nano-platelets ink (2') coating composition of variable size to give a coated surface.

3. The improved graphene based security thread as claimed in claim 1, wherein the security thread comprises RFID antenna (5) of graphene nano-platelets made on security thread (1'), and wherein optionally at least one of the following applies: (i) the RFID antenna (5) of graphene nano-platelets is printed on the carrier film (1) by using inkjet printing, said RFID antenna (5) may be detected using specific readers, wherein the RFID antenna ends are connected to each other by aluminum / metal / copper connector (6); and (ii) two basic components of an RFID tag required are the chip (5B) that carries out all the necessary protocols, data encoding, reading / writing from memory and an antenna (5A) that acts as a communication link between the RFID tag.

4. The improved graphene based security thread as claimed in claim 1, wherein the security thread comprises Graphene nano-platelet based dots (7), on the carrier film (1), that is Graphene based, and is flood coating or discreet pattern based print-coating or even an indicia of Graphene.

5. The improved graphene based security thread as claimed in claim 1, wherein the security thread comprises Graphene nano-platelets based dots (7), on the carrier film (1), and may be laced with magnetic elements or any other types of machine readable elements.

6. The improved graphene based security thread as claimed in claim 1, comprising a film or substrate which may include, but is not limited to, flexible and / or stretchable materials, silicones and other elastomers and other polymeric materials, metals (such as aluminum, copper, steel, stainless steel, etc.), adhesives, fabrics (including cloths) and textiles (such as cotton, wool, polyesters, rayon, etc.), clothing, glasses and other minerals, ceramics, silicon surfaces, wood, paper, cardboard, paperboard, cellulose-based materials, glassine, labels, silicon and other semiconductors, laminates, corrugated materials, concrete, bricks, and other building materials.

7. The improved graphene based security thread as claimed in claim 1, wherein the substrates are in the form of films, papers, wafers, larger three-dimensional objects.

8. The improved graphene based security thread as claimed in claim 1, comprising a film that may be paper-based materials such as paper, paperboard, cardboard, glassine, PET, polyethylene, polypropylene, acetates, nitrocellulose.

9. The improved graphene based security thread as claimed in claim 1, comprising substrates such as PET, that may be surface treated with indium tin oxide, antimony tin oxide.

10. The improved graphene based security thread as claimed in claim 1 or claim 2, wherein the graphene-based pattern and / or graphene-based coating composition is applied using a method, selected from: painting, coating, printing, pouring, spin casting, solution casting, dip coating, powder coating, by syringe or pipette, spray coating, curtain coating, lamination, co-extrusion, electro spray deposition, ink-jet printing, spin coating, thermal transfer (including laser transfer) methods, doctor blade printing, wire rod printing, screen printing, rotary screen printing, gravure printing, lithographic printing, intaglio printing, digital printing, capillary printing, offset printing, microprinting, electrohydro dynamic (EHD) printing, flexographic printing, pad printing, stamping, tampon printing, pad printing, stencil, wire rod, xerography, microcontact printing, dip pen nanolithography, laser printing, drawing, writing, coloring, via pen.

11. The improved graphene based security thread as claimed in claim 1 or claim 2, wherein the graphene-based pattern and / or graphene-based coating composition: (i) is applied using a suitable medium including, but not limited to, paints, inks, varnishes, toners and other solid or powder-based printing media, inkjet inks, water-based inks and coatings, solvent based inks and coatings, graphic inks, UV- curable inks, flexographic inks, screen inks, offset inks, gravure inks, pencils and pens, chalk and other minerals, crayons, markers, waxes, carbon-based dyes and / or pigments, colored dyes and / or pigments, materials that are pigment / dye-free, and materials that are binder-free; and / or (ii) is at least one of continuous, amorphous, and uniform or non- uniform in thickness, and may be in the form of one or more of designs, shapes, lines, characters, lines, bar codes, arbitrary designs and patterns.

12. A method of manufacturing an improved graphene nano-platelets based security thread as claimed in claim 1, comprises the steps of: - taking a dimensionally stable carrier film (1), which is made of Polyethylene terephthalate (PET); - printing / coating graphene nano-platelets inks (2) over the carrier film (1), since adhesion value of graphene nano-platelets based ink is more compact in comparison to black ink; - coating the graphene nano-platelets inks (2) with UV curable lacquer / Graphene based lacquer (3) to form a smooth surface; - casting / coating / printing an LC film (4) on the UV curable lacquer / Graphene based lacquer (3); wherein the liquid crystal polymers, can be chiral, nematic / cholesteric or combination thereof and has a specific wavelength; and - subsequently drying and curing the LC film (4) formed on the UV curable lacquer / Graphene based lacquer (3); - laminating a PET (1A) over the LC film (4) for further use.

13. The method of manufacturing an improved graphene nano-platelets based security thread as claimed in claim 12, wherein at least one of the following applies: (i) the thickness of a dimensionally stable carrier film (1) ranges from 20 to 24 micron, particularly from 15 to 18 micron and more particularly from 8 micron to 12 micron; and (ii) the thickness of the graphene nano-platelets based ink ranges from 0.5 micron to 5 micron.

14. The method of manufacturing an improved graphene nano-platelets based security thread as claimed in any of claims 1 to 11, the method further comprising incorporating the graphene nano-platelets based security thread into security paper in one or more of the following manners: i. using the Graphene nano-platelets ink based thin film coated on the carrier film / substrate as security thread feature on the said security paper; or ii. placing Graphene nano-platelets ink bands or Graphene nano-platelets ink pattern(s), indicia on discreet areas to form a web of printed film which is converted into security thread, and inserted into paper on paper machines, this insertion can be done in totality (embedded within the pulp or can be "sewn" in intermittently to show a windowed thread as security thread feature on the said security paper; or iii. using Graphene nano-platelets based dots on the substrate as security thread feature on the said security paper; or iv. making embedded RFID antenna or indicia from Graphene nano-platelets as security thread feature on the said security paper.

15. The method of manufacturing an improved graphene nano-platelets based security thread as claimed in claim 12, wherein said graphene nano-platelets based thin film coating, which is nano thin, forms an almost clear coat on the substrate, to impart additional quality of better mechanical and adhesion properties for subsequent coated functional layers to be used on security thread feature.

Images