1 AUTHENTICABLE SECURITY ELEMENT FIELD OF THE INVENTION 5 The present invention relates to authenticable security elements including electrical circuits sensitive to at least one trigger condition for security purposes, and methods of their manufacture. BACKGROUND TO THE INVENTION 10 Counterfeiters rapidly adjust their techniques to overcome new and improved security elements in security documents. Thus there is the need to introduce more complex security elements to ensure the security of security documents from counterfeiters. It is also well known to use a plurality of 15 techniques to make a security element more complex and more difficult to counterfeit. The use of radio frequency identification, henceforth known as RFID, is well known in applications related to tracking and access management of goods. 20 RFID is the use of radio frequency electromagnetic fields in a wireless and contact-less system to read data from a tag on a product or other object for identification and tracking. Typically, the RFID tag, also known as a RFID transponder, may be located on products to track their progress through a production line or in identification cards or passports to identify a person's 25 identity. A typical RFID tag may include an electrical or integrated circuit which may store and process information and may also modulate and de-modulate an RF signal as well as other functions. RFID tags are also known for including an 30 antenna for sending and receiving the RF signals.
2 However, it has been also known that it is possible to counterfeit a RFID tag and thus these RFID tags may not have an adequate level of security. Improvements in the security of RFID tags have proposed the use of an 5 item that has an RFID transponder and a second data element, such at the device disclosed in the document WO 2005/124673. The second data element may include a bar code that duplicates the information of the RFID transponder. The bar code may be printed in a non-visible ink. 10 However, the disadvantage of this invention is that it does not increase the security of the RFID transponder itself, but primarily protects the security of the coded information and the information overall. SUMMARY OF THE INVENTION 15 According to a first aspect of the invention, there is provided a security element for the authentication of a security device or document including: an electrical circuit; at least part of the electrical circuit printed with an ink sensitive to at least one predetermined trigger condition; and 20 wherein when the at least one trigger condition is applied to the security element, the at least one trigger condition causes a predetermined change in electrical conductivity enabling authentication of the security device or document. This security element provides the advantage of requiring a trigger condition prior to being able to authenticate the security device or document 25 making it more difficult to counterfeit. The authenticity of the security device may then be communicated to a user by a variety of communication means. The communication means may include electromagnetic radiation or wireless communication, preferably in the form of radio frequency electromagnetic fields. Thus, the security element may include a RFID tag which allows a RFID tag 30 reader to authenticate the security element by determining if the security device 3 has been triggered by the trigger condition allowing a user to determine if the security element has been authenticated. The security element may also include an electrical circuit that is sensitive to force so that the at least one trigger condition may be selected to be force. 5 Thus, to authenticate a security element, external force can be applied to the security element, either manually or with a tool or other device. Additionally, the electrical circuit of the security element may be sensitive to force, if the electrical circuit is printed with an ink where the ink may be a force sensitive ink. 10 Preferably, the at least one trigger condition is selected from one of a number of trigger conditions including temperature. Thus, when heat at a temperature or a range of temperatures is applied to the security device or document, the device or document may be authenticated by the activation of the electrical circuit of the security element. 15 The security element may include an electrical circuit that is sensitive to temperature by printing the circuit in a temperature sensitive ink. The security element may include that the electrical circuit may also be sensitive to temperature by including a thermal switch. The thermal switch may be activated by a predetermined temperature. The thermal switch may include a gap or break 20 in the electrical circuit which may at least partially include temperature sensitive material wherein when the gap is exposed to heat at a predetermined temperature, the material including the thermal switch expands closing the gap and causing a predetermined change in the electrical conductivity, restoring electrical continuity of the electrical circuit, and consequently activating the 25 electrical circuit. The gap may include temperature sensitive material. Thus a standard electrical circuit may be made sensitive to temperature with the use of a temperature sensitive ink or a thermal switch, increasing the difficulty of counterfeiting the security element.
4 Once the electrical circuit has been activated by the at least one trigger condition, in this case, temperature, the authentication of the security element may then be communicated to a user by a communication means. The communication means include electromagnetic radiation including wireless 5 communication, preferably in the form of radio frequency radiation. A security element that is sensitive to a trigger condition of a temperature may be triggered where the source of temperature includes a source of heat such as sunlight. This allows the security device or document including the security element to be authenticated with a readily available source of stimuli. 10 Preferably, the at least one trigger condition may also be selected from a range of trigger conditions including electromagnetic radiation. In a circuit that has temperature sensitive ink or a thermal switch, the electromagnetic radiation produces the heat necessary to achieve a predetermined temperature to cause a predetermined change in the conductivity of the circuit or to close the gap or to 15 switch the thermal switch. Preferably, the electromagnetic radiation is a broadband source of electromagnetic radiation such as sunlight or may be a specific wavelength of electromagnetic radiation or may be a specific range of electromagnetic radiation. Preferably, the electromagnetic radiation is microwave radiation. The 20 electromagnetic radiation may be applied as a beam of radiation. This allows for a range of trigger conditions chosen that may allow an added layer of complexity to the security element. Alternatively, the security element may be made by printing the electrical circuit in an ink where the ink is photoconductive. Preferably, the photoconductive 25 ink includes one of or any combination of a selection of suitable materials for optoelectronic application. To increase the difficulty of counterfeiting the security element, the security element may be sensitive to at least two trigger conditions wherein the at least 5 two trigger conditions are from any combination of a selection of temperature, force or electromagnetic radiation. For even more difficulty in counterfeiting the security element, the security element may be made sensitive to three trigger conditions wherein the three 5 trigger conditions are a temperature, force or electromagnetic radiation. In addition, the security element may also be sensitive to electric or magnetic fields. As an added layer of security, the security element of any of the above embodiments may include that the electrical circuit be printed in an ink, where the 10 ink includes a phosphorescent material. This will allow the ink to glow when viewed under an ultraviolet (UV) light, further authenticating the security element and thus adding even more difficulty to the ability of the security element to be counterfeited. This may be included or combined with any one or more of the trigger conditions in the security element. 15 The security element of any of the above aspects or embodiments may be included in any security device or document, specifically a banknote. The security element may or may not be visible on the security device or document. According to a further aspect of the invention, there is provided a method of manufacturing a security element for authentication of a security device or 20 document including the steps of: providing an electrical circuit; printing at least part of the electrical circuit with an ink sensitive to at least one predetermined trigger condition; and wherein when the at least one trigger condition is applied to the security 25 element, the at least one trigger condition causes a predetermined change in electrical conductivity enabling authentication of the security device or document. This method provides the advantage of being able manufacture a security element to authenticate the security device or document making it more difficult to 6 counterfeit. The authenticity of the security device may then be communicated to a user by a variety of communication means. The communication means may include electromagnetic radiation including wireless communication, preferably in the form of radio frequency radiation. Thus, the method may include the step of 5 providing a RFID tag which allows a RFID tag reader to determine if the security device has been triggered by the at least one trigger condition allowing a user to determine if the security element has been authenticated. Additionally, the method may include the step of providing that the at least one trigger condition is force. Preferably, the method includes the step of 10 providing that the ink may be a force sensitive ink. Thus, to authenticate a security element, external force can be applied to the security element, either manually or with a tool or other device. In one embodiment, the method provides that at least one trigger condition is temperature. Preferably, the electrical circuit may be printed in a temperature 15 sensitive ink or may include a thermal switch in series with the circuit. The thermal switch may include a gap or is at least partially includes temperature sensitive material. Specifically, the thermal switch may activate at a predetermined temperature. The method includes that the step of printing the thermal switch by printing a gap in the electrical circuit wherein when the gap is exposed to a 20 predetermined amount of heat, the gap closes or temperature sensitive material further conducts, increasing the electrical conductivity, restoring the electrical continuity of the circuit and consequently activating the circuit. The method includes providing a security element that may be sensitive to a trigger condition of temperature that may be triggered where the source of 25 temperature includes a source of heat such as sunlight or other electromagnetic radiation, which may be applied as a beam. This allows the security device or document including the security element to be authenticated with a readily available source of stimuli. Alternatively, the method includes that the at least one trigger condition is 30 electromagnetic radiation. In a circuit that has temperature sensitive ink or a 7 thermal switch, the electromagnetic radiation produces the predetermined temperature necessary to cause a predetermined change in the electrical conductivity of the circuit or to close the gap or to switch the thermal switch. Preferably, the method includes that the electromagnetic radiation is broadband 5 radiation, such as sunlight. Even more preferably, the electromagnetic radiation may be a specific wavelength of electromagnetic radiation or may be in a specific range of electromagnetic wavelengths. Preferably, the method includes that the electromagnetic radiation is microwave radiation. This allows for a range of trigger conditions chosen that may allow an added layer of complexity to the security 10 element. Preferably, the method includes that the electrical circuit is printed in a photoconductive ink which may include one of or any combination of a selection of suitable material for optoelectronic application. To increase the difficulty of counterfeiting the security element, the method 15 of manufacturing the security element may include the step of including that the security element be sensitive to at least two trigger conditions wherein the at least two trigger conditions are from any combination of a selection of temperature, force or electromagnetic radiation. For even more difficulty in counterfeiting the security element, the method 20 of manufacturing the security element may include the step of including that the security element may be made sensitive to three trigger conditions wherein the three trigger conditions are temperature, force or electromagnetic radiation. In addition, the method of manufacturing the security element may also include that the security element may be made sensitive to electric or magnetic 25 fields. As a further alternative, the method of manufacturing the security element may further include that the electrical circuit includes a phosphorescent material. This will allow the ink to glow in the dark after it is exposed to ultraviolet (UV) light for some time, further authenticating the security element and thus adding even 8 more difficulty to the ability of the security element to be counterfeited. This may be included or combined with any one or more of the trigger conditions in the security element. Further aspects of the invention relate to methods of manufacturing any of 5 the above aspects or embodiments of the security element, as well as methods of manufacture of a security document, such as a banknote including any embodiment of the security element. BRIEF DESCRIPTION OF THE DRAWINGS 10 In order that the present invention may be more readily understood, a preferred embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: 15 Figure 1 is a view of a security element in the proximity of a trigger condition in accordance with a preferred embodiment of the present invention; Figure 2 is a view of an internal view of a security element including an electrical circuit in accordance with a preferred embodiment of the present 20 invention; and Figure 3 is a view of a bank note including the security element in accordance with a preferred embodiment of the present invention. 25 DESCRIPTION OF PREFERRED EMBODIMENT Referring now to Figure 1, there is shown a view of a security element 2, according to a preferred embodiment of the present invention. The security element 2 includes an electrical circuit 4 that is printed in an electrically 9 conductive ink. The electrical circuit 4 is designed to respond to a change of a predetermined amount or change in the amount of electrical conductivity in part or all of the electrical circuit 4, and consequently activating the electrical circuit 4. A pre-prepared trigger condition A which is adapted to cause the change in 5 electrical conductivity, activates the electrical circuit 4 to communicate to a user to confirm the authenticity of the security element 2. In Figure 1, a particular trigger condition A is applied, which then causes the change of the electrical conductivity of at least part of or all of the electrical 10 circuit 4, where the predetermined amount or predetermined change of the electrical conductivity is at the value or within the predetermined range of values as expected. The electrical circuit 4 is activated and this then indicates that the correct trigger condition A has been detected or enables the circuit to carry out authentication functions. Thus the security element 2 is authenticated. 15 Thus it is envisaged that the invention may be utilised in the following way, the user of the security document may apply a trigger condition to the security document. The trigger condition activates the electrical circuit by changing the electrical conductivity of the circuit, which may then activate the circuit which can 20 communicate to the user that the security element is genuine. This may occur if the electrical circuit includes at least a part of the circuit that undergoes a phase transformation such that the part of the circuit changes from a resistive semiconductor phase to a conductive phase, consequently changing the electrical conductivity of the circuit. The communication means may include an 25 electromagnetic radiation, including a phosphorescent glow or wireless communication such as radiofrequency radiation. In this embodiment of the invention, the security element 2 also includes a communication means of a RFID transponder. The RFID transponder may be an 30 'active' or 'passive' transponder, in other words, may or may not include an integrated circuit. When the security element 2 has been authenticated, a signal may be sent using the communication means of the transponder to a user or location in the general vicinity, verifying that the security element 2 is authentic.
10 The trigger condition A may be a particular environmental parameter, such as a force, a temperature or electromagnetic radiation including light or microwave radiation. 5 For instance, if the electrical circuit 4 or the ink used in the printing of electrical circuit 4 is sensitive to force, then the trigger condition A, may be a predetermined force or range of forces. In this embodiment of the invention, the presence of the predetermined force or range of forces will cause a 10 predetermined change in the electrical conductivity of at least part of the electrical circuit 4. If the change or amount of electrical conductivity of the electrical circuit 4 is at the value or within the expected predetermined range of values, the electrical circuit is activated to verify that the security element 2 is genuine. A signal via a communication means, for example, electromagnetic radiation, 15 including radiofrequency radiation of the RFID transponder can be then sent to a person or location in the general vicinity, indicating that the security element 2 is genuine. The external force may be applied to the security element manually or with a specific tool. 20 Similarly, trigger condition B may be a predetermined temperature. Thus if the electrical circuit 4 or the ink of the electrical circuit 4 is sensitive to temperature, the trigger condition B changes a predetermined change in the electrical conductivity of at least part of the electrical circuit 4. If the change or value of electrical conductivity of the electrical circuit 4 is at the value or within the 25 predetermined range of values as expected, this then verifies that the security element 2 is genuine. A signal via the communication means, such as a RFID transponder can be then sent to a person or location in the general vicinity, indicating that the security element 2 is genuine. 30 Similarly again, the trigger condition C may be a source of electromagnetic radiation, such as light. The light be of a broadband spectrum from a source such as sunlight or may be of a narrow band of light or even a particular wavelength of light. The electromagnetic radiation may include microwave radiation. Thus if the 11 electrical circuit 4 or the ink of the electrical circuit 4 is sensitive to temperature, the trigger condition C may heat up the ink sufficiently to cause a predetermined change the electrical conductivity of at least part of the electrical circuit 4. If the change or value of electrical conductivity of the electrical circuit 4 is at the value 5 or within the predetermined range of values as expected, this then verifies that the security element 2 is genuine. A signal via the communication means, such as a RFID transponder can be then sent to a person or location in the general vicinity, indicating that the security element 2 is genuine. 10 Thus, in this embodiment of the invention, trigger condition C is a source of electromagnetic radiation. Thus, if the printed electrical circuit 4 or the ink used to print the electrical circuit 4 is photosensitive such that the trigger condition C changes the electrical conductivity of the electrical circuit 4 to a specific value or within the predetermined range of values as expected, consequently activating 15 the electrical circuit 4. This then verifies that the security element 2 is genuine. A signal via the communication means, such as a RFID transponder can be then sent to a person or location in the general vicinity, indicating that the security element 2 is genuine. In addition, the electrical circuit 4 may also be sensitive to electric or magnetic fields, such that the electric or magnetic fields may also 20 change the electrical conductivity of the electrical circuit 4. Referring now to Figure 2, there is shown a security element 2, in yet another embodiment of the present invention. Security element 2 includes a part of the electrical circuit 4 that is sensitive to temperature, in particular to trigger 25 condition B which is a specific temperature or a range of temperatures. Part of electrical circuit 4 includes a thermal switch 6 in the line of the electrical circuit 4. The thermal switch 6 may be a break in the line of the electrical circuit 4. In this embodiment, the electrical circuit 4 is printed. When trigger condition B affects thermal switch 6, the temperature causes the material of the thermal switch to 30 change phase, causing a predetermined change in electrical conductivity or restoring electrical continuity to the circuit 4. The electrical circuit 4 then is, activated and thus verifies the authenticity of the security element 2. Moreover, a 12 signal may be sent via the RFID transponder can be then sent to a person or location in the general vicinity, indicating that the security element 2 is genuine. In this embodiment of the invention, the ink may include one of or any 5 combination of a selection of suitable material from the optoelectronic group of materials. It will be understood that a person skilled in the art would be able to substitute any material as would be necessarily to modify or improve the invention without departing from the scope of the present invention. 10 Alternatively, trigger condition C in the form of broadband or narrow band electromagnetic radiation, such as sunlight or microwave radiation, may also sufficiently heat the thermal switch 6 in the line of the electrical circuit 4. Thus, when trigger condition C affects thermal switch 6, the electromagnetic radiation may cause a rise in temperature causing the material of the thermal switch to 15 change phase, causing a predetermined change in electrical conductivity or restoring electrical continuity to the circuit 4. The thermal switch may also include temperature sensitive material. The electrical circuit 4 then is, activated and thus verifies the authenticity of the security element 2. Moreover, a signal may be sent via the RFID transponder can be then sent to a person or location in the general 20 vicinity, indicating that the security element 2 is genuine. Referring now to Figure 3, a further specific embodiment of the invention is shown. In this figure, a security element 2 is included within the layers of a bank note 8. The bank note 8 may then be verified by locating the bank note 8 in the 25 proximity of any trigger condition A, B or C as in the following examples. Example 1: Trigger condition A is a force that is applied to bank note 8. The security element 2 of bank note 8 includes an electrical circuit 4 that is sensitive to force. In particular, electrical circuit 4 is printed with force sensitive 30 ink. The force subsequently causes the electrical conductivity of the force sensitive ink of electrical circuit 4 to change. If the electrical circuit 4 detects that the electrical conductivity is now at a specific electrical conductivity or within a range of specific electrical conductivities, this activates the electrical circuit and 13 verifies the authenticity of the bank note 8. Consequently, the electrical circuit 4 then sends a signal via communication means of the RFID transponder to the general vicinity or a user indicating that the authenticity of the bank note 8 has been verified. 5 Example 2: Bank note 8 may be exposed to trigger condition B. A bank note 8 includes a temperature sensitive electrical circuit 4 which may undergo a phase transformation on application of heat subsequently causing a predetermined change in electrical conductivity or restoring continuity. Electrical 10 circuit 4 may instead include a thermal switch, known as a gap in the line of an electrical circuit 4 which is also may change electrical conductivities upon the application of thermal energy. Again, when electrical circuit 4 detects trigger condition B, this activates the electrical circuit and verifies the authenticity of bank note 8 and a signal is sent via a RFID transponder. The gap may also include 15 temperature sensitive material. Example 3: Similarly to the above examples, bank note 8 may be exposed to trigger condition C, a radiation source, which could be a broad band source or a laser beam operating at one or more specific wavelengths. .Exposure to 20 sunlight or a specific laser radiation will heat up the thermal switch changing its phase to conduct electricity. This then restores electrical continuity or causes a predetermined change in the electrical conductivity in the circuit element 4 and the security element 2 activating and consequently, verifying the authenticity of bank note 8. 25 Example 4: As in the above examples 1 and 2, a bank note 8 includes an electrical circuit 4 that is both force and temperature sensitive. Thus both trigger condition A or B or A and B may be used to verify the bank note 8. In addition, the electrical circuit 4 may also be sensitive to electric or magnetic fields. 30 Example 5: As in the above examples 2 and 3, a bank note 8 includes an electrical circuit 4 that is both light and temperature sensitive. Thus both trigger 14 condition B or C or B and C may be used to verify the bank note 8. In addition, the electrical circuit 4 may also be sensitive to electric or magnetic fields. Example 6: As in the above examples 1 and 3, a bank note 8 includes an 5 electrical circuit 4 that is both force and temperature sensitive. Thus both trigger condition A or C or A and C may be used to verify the bank note 8. In addition, the electrical circuit 4 may also be sensitive to electric or magnetic fields. Example 7: As in the above examples 1 and 2 and 3, a bank note 8 10 includes an electrical circuit 4 that is force, light and temperature sensitive. Thus at least one of trigger conditions A, B or C, or any combination of trigger conditions may be used to verify the bank note 8. In addition, the electrical circuit 4 may also be sensitive to electric or magnetic fields. 15 In any embodiment of the invention as described above, the conductive ink used in the printing of the electrical circuit 4 may also include a phosphorescent material. The addition of the phosphorescent material causes the colour phosphorescent material and subsequently the conductive ink to glow under the application of illumination, such as ultraviolet radiation causing the ink and thus 20 electrical circuit to communicate to the user of the authenticity of the security document by means of a phosphorescent glow. Thus, in conjunction with at least one of the possible scenarios with a security element sensitive to any or all of trigger conditions A, B or C, the phosphorescent material adds an extra security element to any of the embodiments above. 25 Further, it is expected that while the security element is visible in the figures 1 to 3, that the security element of the security device and document may not be visible or may be hidden as part of the artwork included on the security device or document in any embodiment of the present invention. 30 Further modifications and improvements may be made without departing from the scope of the present invention. For example, the security element may include a data element that is adapted to store data, an antenna adapted to 15 receive and send electromagnetic radiation. Further, the electrical circuit of the security element 2 may be adapted to modulate or de-modulate an electromagnetic signal. As a further example, the communication means that communicates to the user of the security document of the authenticity of the 5 security document, may be any form of electromagnetic radiation, such as a phosphorescent glow or wireless communication including radiofrequency radiation. Further examples of modifications may relate to the printing process or 10 processes. For example, the electrical circuit may be printed in a gravure or flexographic printing process. Furthermore, the security elements of each embodiment described above may be understood to be applicable to a variety of security document 15 applications, as well as, but limited to security bank notes, cheques, certificates, travel documents, academic transcripts, identity cards, deed of title and passports. It may also applicable to other security applications such as authentication of products and devices, where authentication may be preferable or necessary. Other possible applications of the security element may be in 20 supply chain and logistic-control of products and/or services.