GB2571790A

GB2571790A - Short-ranged radio frequency communication device

Info

Publication number: GB2571790A
Application number: GB1803846.3A
Authority: GB
Inventors: Whelan Sean; Maccarthy Niall; Doust Alexander
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-03-09
Filing date: 2018-03-09
Publication date: 2019-09-11
Also published as: WO2019171019A1; GB201803846D0

Abstract

A short-range radio frequency (RF) communications device 5, e.g. an RFID tag or card, comprises a compliant foam layer (Fig.5, 27) and a flexible substrate 6 between first and second flexible outer layers (Fig.5, 10 & 11). The flexible substrate supports one or more organic light emitting diodes (OLED(s)) 8, a flexible integrated circuit 9, and an antenna 7 for short-range radio frequency communications, e.g. near-field (NFC). The flexible integrated circuit is configured to harvest power from the RF signals received from the antenna, and to convert the harvested power into a driving signal 16 supplied to each organic light emitting diode to control light emission. The organic LEDs emit light in response to a driving signal amplitude of 3.5V or less. A method of fabricating the short-range RF communications device comprises depositing, e.g. by printing, the one or more organic light emitting diodes and the antenna on the flexible substrate, mounting the flexible integrated circuit on the flexible substrate, and laminating the flexible substrate and compliant foam layer between the first and second outer layers. The RF communication device may also comprise one or more input devices (Fig.10, 44) and/or a non-volatile storage element 19 to store local data, and may be configured to transmit a signal using the antenna.

Description

(57) A short-range radio frequency (RF) communications device 5, e.g. an RFID tag or card, comprises a compliant foam layer (Fig.5, 27) and a flexible substrate 6 between first and second flexible outer layers (Fig.5, 10 & 11). The flexible substrate supports one or more organic light emitting diodes (OLED(s)) 8, a flexible integrated circuit 9, and an antenna 7 for short-range radio frequency communications, e.g. near-field (NFC). The flexible integrated circuit is configured to harvest power from the RF signals received from the antenna, and to convert the harvested power into a driving signal 16 supplied to each organic light emitting diode to control light emission. The organic LEDs emit light in response to a driving signal amplitude of 3.5V or less. A method of fabricating the short-range RF communications device comprises depositing, e.g. by printing, the one or more organic light emitting diodes and the antenna on the flexible substrate, mounting the flexible integrated circuit on the flexible substrate, and laminating the flexible substrate and compliant foam layer between the first and second outer layers. The RF communication device may also comprise one or more input devices (Fig. 10, 44) and/or a non-volatile storage element 19 to store local data, and may be configured to transmit a signal using the antenna.

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Article


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Short-range radio frequency communication device

Field of the invention

The present invention relates to a short-range radio frequency communication device including an organic light emitting diode which is powered by harvesting power from radio frequency signals.

Background

Short-range radio frequency communication reading devices and corresponding radio 10 frequency identity (RFID) tags may be useful for several applications. One type of short-range radio frequency communication is referred to as near field communication (NFC) and RFID tags for use with NFC communications may be referred to as NFC tags. NFC readers and NFC tags have been deployed in mass transit systems in which users may pay for travel by simply holding a card including a NFC tag near to a reader 15 on a bus, a train, a train platform and so forth. Contactless payment systems may also use NFC technology. NFC tags may be included in paper or cardboard packaging to assist in stock or cargo tracking by an operative using a handheld NFC reading device. Similarly, NFC tags may be included in shipment labels affixed to parcels or other mail items to assist in tracking and tracing mail items in transit.

RFID tags may be active or passive. Active RFID tags are connected to a power source such as a battery, and may transmit signals even in the absence of an RFID reader. Passive RFID tags do not include a battery or similar power source, and operate using power harvested from signals transmitted by an RFID reader using an embedded 25 antenna. Passive RFID tags have the advantage of not requiring a separate power source such as a battery.

In some applications, operation of an RFID system may not be transparent to a user. Displays have been added to items including passive RFID tags to provide increased feedback to a user. For example, US 2010/0052908 At, US 2011/0279242 At and

CN 104167160 A describe passive, stable display elements, for example electrophoretic, electrochromic or cholesteric liquid crystal displays, operated using power harvested from signals transmitted by an RFID reader. US 2010/0052908 At also describes RFID tags including batteries for powering active devices.

Summary

According to a first aspect of the invention, there is provided a short-range radio frequency communication device including first and second flexible outer layers, a compliant foam layer between the first and second outer layers and a flexible substrate 5 between the first and second outer layers. The flexible substrate supports an antenna configured for short-range radio frequency communications. The flexible substrate also supports one or more organic light emitting diodes. The flexible substrate also supports a flexible integrated circuit configured to receive radio frequency signals from the antenna, harvest power from the radio frequency signals received by the antenna, 10 and convert harvested power into a driving signal for the organic light emitting diodes.

The flexible integrated circuit is also configured to, for each organic light emitting diode, control light emission by supplying the driving signal to the organic light emitting diode. Each organic light emitting diode is configured to emit light in response to receiving a driving signal having an amplitude of less than or equal to 3.5 V.

The flexible integrated circuit may be configured to transmit a signal using the antenna.

The flexible integrated circuit may be configured to receive a radio frequency signal encoding external data from the antenna.

The flexible integrated circuit may include a non-volatile storage element configured to store local data.

The antenna and the one or more organic light emitting diodes may be deposited 25 directly onto the substrate.

The flexible integrated circuit may be configured to control the light emission of each organic light emitting diode in dependence upon the external data and/or local data.

Each organic light emitting diode may include an electron injection layer comprising an n-doped polymer, the polymer comprising one or more arylene repeat units.

The electron injection layer may be in direct contact with an aluminium electrode.

Each organic light emitting diode may include a layer of sodium fluoride.

-3The antenna and/or the one or more organic light emitting diodes may be formed by printing.

At least one conductive feature of the antenna and at least one conductive feature of the one or more organic light emitting diodes may have been formed in a first common process step.

At least one insulating feature of the antenna and at least one insulating feature of the one or more organic light emitting diodes may have been formed in a second common 10 process step.

The device may also include one or more input devices.

Each organic light emitting diode may draw a power density of less than 50 mW.cnr² at 15 a luminance of 400 Cd.nr².

According to a second aspect of the invention, there is provided a method of fabricating a short-range radio frequency communication device, including depositing one or more organic light emitting diodes and an antenna configured for short-range radio frequency communications on a flexible substrate. The method also includes mounting a flexible integrated circuit on the flexible substrate. The method also includes laminating the flexible substrate and a compliant foam layer between a first outer layer and a second outer layer. The flexible integrated circuit is configured to receive radio frequency signals from the antenna, to harvest power from the radio frequency signals received by the antenna, and to convert harvested power into a driving signal for the organic light emitting diodes. The flexible integrated circuit is configured to, for each organic light emitting diode, control light emission by supplying the driving signal to the organic light emitting diode. Each organic light emitting diode is configured to emit light in response to a driving signal having an amplitude of less than or equal to 3.5 V.

Depositing the one or more organic light emitting diodes and the antenna may include printing the one or more organic light emitting diodes and the antenna.

Printing may include inkjet printing, gravure printing, flexographic printing, or slot die 35 coating.

-4At least one conductive feature of the antenna and at least one conductive feature of the one or more organic light emitting diodes maybe formed in a first common process step.

At least one insulating feature of the antenna and at least one insulating feature of the one or more organic light emitting diodes maybe produced in a second common process step.

Depositing the one or more organic light emitting diodes and the antenna may include 10 depositing a first patterned conductive layer on the substrate, depositing an insulating mask layer over the first conductive layer, wherein the insulating mask layer defines the emitting areas of the one or more organic light emitting diodes, depositing the active layers of the one or more organic light emitting diodes over the insulating mask layer, depositing a second conductive layer over the active layers, the insulating mask layer 15 and/or the substrate, and depositing an encapsulation layer over the one or more light emitting diodes.

Mounting a flexible integrated circuit on the flexible substrate may include applying conductive glue or ink to a plurality of contact pads deposited on the substrate, each 20 contact pad connected to the one or more organic light emitting diodes or the antenna via conductive traces. Mounting a flexible integrated circuit on the flexible substrate may also include placing the flexible integrated circuit on the substrate such that a second plurality of contact pads on the flexible integrated circuit are aligned with the contact pads deposited on the substrate.

Mounting a flexible integrated circuit on the flexible substrate may include applying an anisotropic conductive film over a plurality of contact pads deposited on the substrate, each contact pad connected to the one or more organic light emitting diodes or the antenna via conductive traces. Mounting a flexible integrated circuit on the flexible 30 substrate may also include placing the flexible integrated circuit on the substrate such that a second plurality of contact pads on the flexible integrated circuit are aligned with the contact pads deposited on the substrate.

The method may be carried out in a roll-to-roll process.

-5Brief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a short-range radio frequency communication system including a reading device and a short-range radio frequency communication device;

Figure 2 illustrates a short-range radio frequency communication device incorporated within a pre-payment card;

Figure 3 is a cross-sectional view of a short-range radio frequency communication device;

io Figure 4 illustrates bending a short-range radio frequency communication device including a planarizing layer;

Figure 5 illustrates bending a short-range radio frequency communication device including a compliant foam layer;

Figure 6 is a cross-sectional view of packaging for an organic light emitting diode;

Figure 7 is a cross-sectional view of an organic light emitting diode;

Figure 8 shows luminance-voltage characteristics for organic light emitting diodes;

Figure 9 illustrates an example method of interaction between the reading device and short-range radio frequency communication device shown in Figure 1;

Figure 10 is a schematic view of a modified short-range radio frequency communication 20 device;

Figure 11 is a process-flow diagram for an example method of making a short-range radio frequency communication device;

Figures 12A to 12F illustrate plan views of intermediate steps in a method of making a short-range radio frequency communication device;

Figures 13A to 13G illustrate cross-sectional views of intermediate steps in a method of making a short-range radio frequency communication device; and

Figure 14 illustrates a system for making short-range radio frequency communication devices in a roll-to-roll process.

Detailed Description of Certain Embodiments

In the following, like parts are denoted by like reference numbers.

Passive, stable (for example bi-stable) display elements which do not emit light such as, for example, electrophoretic displays or electrochromic displays only require energy in 35 order to switch the state of a display element. This can allow the displayed information to be retained even when no power is available. However, electrophoretic or

-6electrochromic displays can have slow response times. Furthermore, in some applications it maybe undesirable for information to remain on display when a device is not being actively used. For example, a user of a debit or credit payment card may appreciate being able to see their remaining account balance or credit at the time of, or 5 just after, completing a transaction. However, for reasons of privacy a user may not want to have their remaining account balance or credit viewable on their card at all times. Moreover, a passive non-emitting display requires ambient light in order to be viewed.

Organic light emitting diodes (OLEDs) typically have faster response times than electrophoretic displays or electrochromic displays. Furthermore, because organic light emitting diodes do not display information when unpowered, the privacy issues arising from passive non-emitting display types are not a concern. Moreover, organic light emitting diodes may be viewed in conditions where there is little or no ambient light.

There are several barriers to providing organic light emitting diodes which can be powered by a short-range radio frequency signals. For example, organic light emitting diodes typically require power densities and voltages which may be difficult to supply from commonly used short-range radio frequency communication systems such as 20 NFC.

The present disclosure is concerned with a device including one or more organic light emitting diodes which can be powered using short-range radio frequency signals. Devices described herein may include organic light emitting diodes (Figure 7) which are 25 capable of operating with sufficient current efficiency in a low-voltage drive regime.

Flexible electronic devices often require encapsulation within exterior layers in order to protect the circuit elements, and also in some instances to provide planarization for aesthetic purposes. However, laminating multiple flexible layers together reduces the 30 flexibility of the overall laminate, often considerably. The laminated flexible layers are bonded to one another and mechanically constrain each another so that all the bonded layers deform with respect to a common neutral axis. This results in increased straining in most of the layers for a given bending radius. Increased straining of a flexible electronics layer may lead to more rapid degradation of a flexible electronic 35 device and/or failure of the flexible electronic device at a larger bend radius than would be possible for the un-encapsulated flexible electronic device.

-ΊThe present disclosure is also concerned with a flexible electronic device which is encapsulated with a structure which permits a reduction in strain of the flexible electric device for a given bending radius, as compared to a conventionally laminated flexible electronic device.

Referring to Figure 1, a short-range radio frequency communication system 1 is shown.

The system 1 includes a reading device 2 which includes a short-range radio frequency communication transmitter 3 configured to transmit radio frequency signals 4. The radio frequency signals 4 may encode data, for example by modulating a carrier signal. The transmitter 3 operates at a low power level and has a short effective range. In other words, the power level of the transmitter 3 is such that a receiver will be unable to reliably detect the radio frequency signals 4 unless the distance separating the transmitter 3 and such a receiver is short. Short range may be in the range of up to cm. The transmitter 3 may be a near field communication (NFC) transmitter, for example conforming to ISO/IEC 14443, and/or ISO/IEC 18000-3 standards. The transmitter 3 periodically transmits polling signals (also sometime as referred to as “interrogation” signals) and monitors for replies from any RFID tags which have moved 20 into the transmitter 3 interrogation range.

The reading device 2 may be housed within a mobile communications terminal (not shown). The reading device 2 may be statically mounted at a location such as, for example, at or near a bus stop, train platform, advertising poster, point of sale display 25 and so forth. The reading device 2 may be mounted to a vehicle such as, for example, a bus, train, tram and so forth.

The system 1 includes a short-range radio frequency communication device 5 which includes a flexible substrate 6. An antenna 7 configured for short-range radio frequency communications, one or more organic light emitting diodes 8 and a flexible integrated circuit 9 are supported on the substrate 6. The flexible integrated circuit 9 is configured to receive radio frequency electrical signals 18 from the antenna 7. The flexible integrated circuit 9 includes a driving module 13 and a control module 15. The driving module 13 is configured to harvest power from radio frequency signals 4 received by the antenna 7, and to convert such harvested power into a first driving signal 14 for the control module 15. The control module 15 is configured to, for each

-8given organic light emitting diode 8, control light emission by supplying a second driving signal 16 to the given organic light emitting diode 8.

The one or more organic light emitting diodes 8 are configured to emit light in response 5 to receiving the second driving signal(s) 16. Each organic light emitting diode 8 is configured to emit light in response to a second driving signal 16 having an amplitude of less than or equal to 3.5 V.

The driving module 13 and the control module 15 maybe provided as separate, flexible components mounted to the flexible integrated circuit 9. Alternatively, the driving module 13 and the control module 15 may be provided as a single, integrated flexible component. For example, the driving module 13 and the control module 15 may be provided by a single, thin semiconductor device produced using, for example, back side polishing or comparable thinning techniques. The flexible integrated circuit 9 may also include additional, discrete electronic components in addition to the driving module 13 and the control module 15. For example, one or more resistors, capacitors, diodes, thin film transistors and so forth. Any such additional, discrete electronic components are preferable flexible.

Referring also to Figures 2 and 3, further details of the short-range radio frequency communication device 5 are shown.

The short-range radio frequency communication device 5 includes first and second flexible outer layers 10,11 (also referred to as exterior layers). A compliant foam layer

12 and the flexible substrate 6 are laminated between the first and second outer layers

10,11. The compliant foam layer 12 provides several advantages. Firstly, the foam layer 12 serves to smooth over components such as the flexible integrated circuit 9 which may protrude from the substrate 6, so as to conceal the morphology of the substrate 6 and components supported thereon. In other words, the foam layer 12 may function as a planarizing layer. In Figure 3, the antenna 7 and the one or more organic light emitting diodes 8 are not shown. However, the antenna 7 and the one or more organic light emitting diodes 8 may also protrude from the substrate 6 to the same, or a greater extent, than the flexible integrated circuit 9. For example, an encapsulation structure of the one or more organic light emitting diodes 8 may protrude from the flexible substrate 6. The foam layer 12 may be open cell or closed cell. Preferably the

-9foam layer 12 may be closed cell to provide better encapsulation of the flexible substrate 6.

As mentioned hereinbefore, the substrate 6 is flexible. A flexible substrate 6 is made of a material which may be bent to a radius of curvature of 100 mm or less without undergoing permanent deformation or damage. Substrates 6 with greater flexibility maybe used such as, for example, substrates 6 capable of bending to radii of 50 mm or less, 40 mm or less, 30 mm or less, 20 mm or less, 10 mm or less, or 5 mm or less without experiencing permanent deformation or damage. For example, a flexible material may be capable of withstanding bending to a bend radius of 10 mm for at least one thousand cycles of bending and unbending without experiencing permanent deformation or damage. The substrate 6 maybe formed of polyethylene naphthalate (PEN).

Although the substrate 6 is flexible, the minimum bend radius of the device 5 overall may be less than the minimum bend radius of the substrate 6 alone, because the minimum bend radius of the device 5 also depends on the bend radius of the substrate 6 which the antenna 7, the one or more organic light emitting diodes 8 and/or the flexible integrated circuit 9 can sustain without damage. The device 5 overall is flexible, and may be bent to a radius of curvature of too mm or less without undergoing permanent deformation or damage to the antenna 7, the one or more organic light emitting diodes 8 or the flexible integrated circuit 9. In some examples, the device 5 maybe bent to radii of 50 mm or less, 40 mm or less, 30 mm or less, 20 mm or less, 10 mm or less, or 5 mm or less without radii of 50 mm or less, 40 mm or less, 30 mm or less, 20 mm or less, 10 mm or less, or 5 mm or less without experiencing permanent deformation or damage. For example, a flexible element such as a flexible organic light emitting diode 8, the antenna 7 or the flexible integrated circuit 9, may be capable of withstanding bending to a bend radius of 10 mm for at least one thousand cycles of bending and unbending, without experiencing permanent deformation or damage.

The antenna 7 is formed by a conductive track 17 disposed on a surface of the flexible substrate 6. The antenna 7 geometry is configured to receive electromagnetic signals 4 originating at short-ranges. For example, the antenna 7 maybe configured to couple to coils (not shown) of a transmitter 3. The antenna 7 may be configured for NFC, for example to conform to ISO/IEC 14443 and/or ISO/IEC 18000-3 standards. When the antenna 7 receives electromagnetic signals 4, corresponding electronic signals 18 are

- 10 induced in the antenna 7 conductive track 17. The antenna 7 is connected to both the driving module 13 and the control module 15 of the flexible integrated circuit 9. The electromagnetic signals 4 are preferably radio frequency. The conductive tracks 17 of the antenna 7 may take the form of metal tracks printed onto the flexible substrate 6.

In the example shown in Figure 1, the one or more organic light-emitting diodes 8 and the flexible integrated circuit 9 are provided over separate areas of the substrate 6. However, in other examples the conductive tracks 17 of the antenna 7 may surround one or both of the one or more organic light-emitting diodes 8 and the flexible integrated circuit 9.

The control module 15 of the flexible integrated circuit 9 receives and processes electronic signals 18 and extracts data encoded in the corresponding electromagnetic signals 4. In some examples the device 5 and flexible integrated circuit 9 only receive 15 electromagnetic signals 4. However, in other examples the device 5 and flexible integrated circuit 9 may also use the antenna 7 to send electromagnetic signals encoding data back to the reading device 2. The mechanism by which the device 5 sends signals to the reading device 2 typically depends on the frequency of electromagnetic signals 4 which the transmitter 3 is configured to use. For low to high 20 radio frequency electromagnetic signals 4, the separation between the transmitter 3 and antenna 7 may be considerably less than one wavelength. The antenna 7 of the device 5 maybe inductively coupled to an antenna (not shown) of the transmitter 3. As a result of such coupling, modulating the electrical loading of the transmitter 3 by the antenna 7 can be detected by the transmitter 3. For ultra-high radio frequency signals 25 4 the separation between transmitter 3 and antenna 7 may correspond to one or more wavelengths. When the transmitter 3 uses ultra-high radio frequency signals 4, the device 5 may send signals encoding data to the reading device 2 using a backscattering mechanism. In some examples, the control module 15 of the flexible integrated circuit 9 may simply drive the antenna 7 to emit electromagnetic signals 5. However, this may 30 require a prohibitive amount of power for many passive devices 5.

In addition to external data received encoded in radio frequency signals 4, the control module 15 of the flexible integrated circuit 9 may also include non-volatile storage 19 for storing local data. Local data may include, for example, information for uniquely 35 identifying the device 5. Local data may include authentication information in the form of queries and corresponding responses which allow the reading device 2 and the device

- 11 5 to authenticate one another. Local data may include information about an object in which the device 5 is incorporated, or to which the device 5 has been attached or applied. The control module 15 may store external data received from the reading device 2 directly into the non-volatile storage 19. The control module 15 may modify and/or overwrite some or all of the local data stored in the non-volatile storage 19 based on external data encoded by radio frequency signals 4.

The driving module 13 of the flexible integrated circuit 9 is configured to harvest power from the electronic radio frequency signals 18 and to convert harvested power into the 10 first driving signal 14 for powering the control module 15. The first driving signal 14 does not include power from any source other than the harvested power. Preferably, the first driving signal 14 is a DC voltage having sufficient amplitude to exceed a voltage threshold Vt of the one or more organic light emitting diodes 8. The voltage threshold V_T of an organic light emitting diode 8 is the minimum voltage which must be applied 15 across the organic light emitting diode 8 to cause emission of photons, i.e. to illuminate the organic light emitting diode 8. Whether provided as a separate component or integrated with the control module 15, the driving module 13 may include at least a rectifier (not shown), for example in the form of one or more diodes. The driving module 13 may also include one or more capacitances arranged to reduce oscillations 20 (also referred to as ripples) in the first driving signal 14.

In order to harvest sufficient power to power the control module 15 and to enable the one or more organic light emitting diodes 8 to be illuminated, the device 5 will need to be within a threshold distance of the transmitter 3. The threshold distance will typically be less than a maximum range of the transmitter 3. The threshold distance maybe 2 cm or less.

The control module 15 of the flexible integrated circuit 9 is configured to control the light emission of each organic light emitting diode 8 by supplying second driving 30 signals 16 to illuminate some or all of the one or organic light emitting diodes 8. In some examples, the second driving signals 16 may be identical to the first driving signals 14. In other examples, the second driving signals 16 may correspond to modulation of the first driving signals 14 by the control module 15, for example to cause one or more organic light-emitting diodes 8 to blink or flash. Which of the one or more 35 organic light-emitting diodes are illuminated may be determined in dependence on

- 12 external data encoded by the radio frequency signals 4 and/or local data stored in the non-volatile storage 19.

In one example, each organic light emitting diode 8 may be connected to the driving signal 14 via a transistor (not shown) which is controlled by the control module 15. In other examples, the control module 15 may be provided by a flexible micro-controller or flexible microprocessor. A single flexible micro-controller may provide the functions of the driving module 13 and the control module 15. In still further examples, each organic light emitting diode 8 may be integrated with a thin-film transistor or organic 10 thin-film transistor configured to connect the organic light emitting diode 8 to first or second driving signals 14,16 when the transistor is switched on. In such examples, the control module 15 will control the one or more integrated thin-film transistors or organic thin-film transistors.

The device 5 may include any number of organic light emitting diodes 8. Preferably, the voltage threshold V_T of the organic light emitting diodes 8 is less than or equal to 3.5 V. Preferably the voltage threshold of the organic light emitting diodes 8 is no more than 5 V. Preferably, each organic light emitting diode 8 draws a power density of less than 50 mW.cnr² at a luminance of 400 Cd.nr².

Flexible organic light emitting diode 8 structures which are operable in this low voltage driving regime are described further hereinafter (see Figures 6 and 7). A low voltage threshold V_T is important because the peak voltage induced in the antenna 7 may typically be quite low. For example, the peak voltage induced in an NFC antenna during operation can be of the order of 3 to 5 V. Although the driving module 13 of the flexible integrated circuit 9 can be configured to increase the voltage, some power will be lost in the conversion and the current for driving the one or more light emitting diodes 8 (which is typically expected to be proportional to the illumination intensity) would be decreased even if the power could be kept constant.

In some examples, the device 5 may include a single organic light emitting diode 8. Individual organic light emitting diodes 8 may be of any shape, for example, organic light emitting diodes 8 may take the shape of letters, numerals or other symbols. Alternatively, the device 5 may include a number of organic light emitting diodes 8 in 35 the form of pixels arranged to form a display or an array. The electroluminescent elements 8 may be addressable and illuminable by the control module 15 of the flexible

-13integrated circuit individually, in groups, or in a combination of individual and group addressing.

The antenna 7 and the one or more organic light emitting diodes 8 are deposited directly onto the flexible substrate 6. Preferably, the antenna 7 and the one or more organic light emitting diodes 8 are printed onto the flexible substrate 6. The substrate 6 may take the form of one or more thin and flexible polyimide layers. The conductive tracks 17 forming the antenna 7, and other conductive tracks connecting the flexible integrated circuit 9 and the one or more organic light emitting diodes 8 may also be printed using conductive inks such as, for example, metal based or polymer based conductive inks. Alternatively, the conductive tracks 17 forming the antenna 7, and other conductive tracks connecting the flexible integrated circuit 9 and the one or more organic light emitting diodes 8 may instead by formed by foil stamping, or any other suitable methods. At least one conductive feature of the antenna 7 and at least one conductive feature of the one or more organic light emitting diodes 8 may be produced in the same process step.

Transistors (not shown) for controlling illumination of the one or more organic lightemitting diodes 8 may be provided by organic thin-film transistors printed on the 20 substrate 6. Organic thin-film transistors printed on the substrate 6 may be integrated with the corresponding organic light-emitting diodes 8.

The device 5 may be incorporated within, attached to, or applied to a wide variety of different objects. For example, the device 5 maybe incorporated into a debit or credit 25 payment card. Payment cards increasingly include NFC chips to allow contactless payments. Using the device 5, payment cards may be provided with further functionality such as, for example, an organic light-emitting diode display 8 to show the user of the payment card their remaining account balance or credit after completing a transaction.

The device 5 may be incorporated into a pre-payment card such as a public transport card to pay for buses, trams, trains and the like. The flexible integrated circuit 9 of a pre-payment card may store a unique identifier in the non-volatile storage 19. When a user wishes to pay for a ticket, for example a bus ticket, they may place the pre-payment 35 card near to a reading device 3 on the bus or at a bus stop. The reading device 2 reads the unique identifier (subject to authentication) and deducts the cost of the ticket from

-14an account corresponding to the pre-payment card. Typically, the balance associated with each pre-payment card will be stored on a server (not shown) for security reasons. However, the reading device 2 could transmit the remaining balance after paying for a ticket to the device 5, which may display the remaining balance to the user using an organic light-emitting diode display 8.

The device 5 may be incorporated within a business card. When a receiver of the business card scans the business card using a NFC reader built into their mobile phone, the flexible integrated circuit 9 may send contact information of the business card 10 provider to the mobile phone and may illuminate an organic light-emitting diode 8 in the shape of a business logo or name. In this way, a business card may be provided with a memorable “stand-out” effect.

The device 5 may be incorporated into a lottery ticket. For example, a user may select 15 numbers at a vendor site and the vendor can use a reading device 2 to store the selected numbers into the non-volatile memory 19 of the flexible integrated circuit 9 of a device 5 incorporated in the ticket, in addition to printing the numbers on the ticket. After the lottery draw, the ticket holder could check whether they have won a prize by placing the ticket on or next to a reading device 2 at a vendor site. The reading device 2 can read the stored numbers, check them against the winning numbers, and send data to the device 5 indicating whether the ticket has won a prize. If the ticket has won a prize then this may be indicated to the ticket holder by illuminating one or more organic light emitting diodes 8.

The device 5 may be incorporated within playing cards, models and/or boards for playing a game. The device 5 may be incorporated into a label for products and/or produce. The preceding examples are non-exhaustive.

Referring in particular to Figures 2 and 3, an example of a pre-payment card 20 30 incorporating the device 5 is shown.

As described hereinbefore, the substrate 6 of the device 5 and the foam layer 12 are encapsulated by, or laminated between the first and second outer layers 10,11. The first and second outer layers 10,11 may each take the form of one or more layers formed 35 from a protective polymer layer which is suitable to protect the substrate 6 from water, moisture and/or air. The second outer layer 11 is shown peeled back in Figure 2. The

-ι₅outer layers 10,11 cover and conceal the antenna 7, the one or more organic light emitting diodes 8 and the flexible integrated circuit 9. The foam layer 12 provides planarization such that the profiles of the antenna 7, the one or more organic lightemitting diodes 8 and the flexible integrated circuit 9 are not visible through the outer 5 layers 10,11. A region of the second outer layer 11 is transparent and provides a window 21 through which the organic light emitting diodes 8 can emit light. The device 5 incorporated into the pre-payment card 20 is an NFC device. In the example prepayment card 20 shown in Figure 2, the one or more organic light emitting diodes 8 are arranged in the form of a seven-segment display 22 for displaying numerals. The outer 10 layers 10,11 may be decorated with indicia 23 indicating the purpose of the prepayment card 20 and other contextual information, graphics, logos and so forth.

The pre-payment card 20 shown in Figure 2 is a pre-payment card 20 for a public transportation network. A user of the pre-payment card 20 can place the pre-payment 15 card 20 proximate to reading devices 2 located on buses, trains, trams, bus stops, train platforms and so forth. The reading device 2 reads the identity of the pre-payment card 20 and the cost of a ticket is deducted from an account associated with the pre-payment card 20. At the same time, the seven segment display 22 is illuminated to indicate to the user of the pre-payment card the amount of their remaining balance. For security 20 reasons, the balance of an account is typically held on a server (not shown) which is in communication with the reading device 2. However, account balance information may also be duplicated in the non-volatile storage of the flexible integrated circuit 9. This can allow a user to check their balance even when they are not close to a reading device 2 associated with the public transportation network. For example, a user may use an 25 NFC reader built into their mobile phone to power the pre-payment card 20 so that they may view their remaining balance on the display 22. In this way, the user can avoid unnecessary queuing to check their balance at a counter or card top-up payment machine, or embarrassment from boarding a bus or train, or reaching a barrier, without having sufficient balance to pay for a ticket.

The system 1 can be made secure and private. For example, the device 5 and the reading device 5 may perform an authentication when NFC communication is initiated. If the reading device 2 is authenticated as belonging to the public transportation network, then the flexible integrated circuit 9 may permit write access to the non35 volatile storage 19 so that the local copy of the balance information may be updated. If the reading device 2 is not authenticated as belonging to the public transportation

-16network, then the flexible integrated circuit 9 may restrict access to the non-volatile storage 19 to read-only. The pre-payment card 20 may also be paired with a users’ mobile telephone, so that the balance is only displayed in response to an authenticated communication with the users’ mobile telephone. In this way, the users’ balance can be viewed using an NFC reader in a way which preserves the users’ privacy. Similar authentication methods are preferable when the device 5 is incorporated into a debit or credit payment card.

Further details of communications between a device 5 and a reading device 2 are explained hereinafter (Figure 9).

Referring also to Figures 4 and 5, a strain reduction afforded by the foam layer 12 shall be discussed.

Referring in particular to Figure 4, a plate-like flexible device 24 is shown. The platelike flexible device 24 is the same as the device 5, except that instead of the foam layer 12 the plate-like flexible device 24 includes a planarizing layer 25 which has a comparable Youngs modulus and compressibility to the outer layers 10,11 and the flexible substrate 6. For example, the planarizing layer 25 may take the form of a polymer layer such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), a cured epoxy resin and so forth.

When the plate-like flexible device 24 is bent to some radius of curvature, all of the layers 11, 6, 25,10 of the plate-like flexible device 24 bend together with respect to the 25 same implied origin of the bending, as expected for conventional beam/plate bending.

For example, the edges 27, 28 of the plate-like flexible device 24 remain approximately flat. The plate-like flexible device 24 is only free of strain along a neutral axis 26. The further the antenna 7, the one or more organic light emitting diodes 8 and the flexible integrated circuit 9 are from the neutral axis 26, the more strain they experience. The 30 precise location of the neutral axis 26 depends on the relative geometries and Youngs moduli of the materials of the outer layers 10,11, the substrate 6, the planarizing layer 25 and so forth.

Referring in particular to Figure 5, the foam layer 12 is formed of a polymeric or elastomeric foam having a relatively low Youngs modulus compared to the materials of the outer layers 10,11 and/or substrate 6. The foam layer 12 is also highly compressible

-17due to the ability of cell walls/struts forming the foam to deform into the pores of the foam layer 12. The foam layer 12 is also very resilient, and may elastically recover its original shape following very large net strains. This is possible because the individual cell walls/struts do not themselves experience high strains.

As a result of the significant differences in mechanical properties between the foam layer 12 and the outer layers 10,11 and/or substrate 6, the conventional assumptions of beam/plate bending do not hold for the device 5. Instead, as shown in Figure 5, the first outer layer 10 is not constrained to bend with the second outer layer 11 and substrate 6 about the same implied origin. Instead, the first outer layer 10 may bend to a given bending radius about a first implied origin, whilst the second outer layer 11 and substrate 6 may bend to the same bending radius with respect to a second implied origin which is offset from the first implied origin. Consequently, the edges 27, 28 of the device 5 may deform as a result of shearing of the foam layer 12. This behaviour is possible because the foam layer 12 may reversibly sustain relatively large shear displacements, local compressions/expansions and so forth.

Although the outer layers 10,11, the substrate 11 and supported components 7, 8, 9 will still experience strains from the bending, these strains may be relatively reduced. This 20 may occur because the neutral axis for the second outer layer 11 and the substrate 6 may be closer to the substrate 6 as compared to the plate-like flexible device 24. The strain on the substrate 11 and supported components 7, 8, 9 maybe further reduced if a second foam layer (not shown) is included between the substrate 6 and the second outer layer 11. In order to permit light from the one or more organic light emitting 25 diodes 8 to exit the device 5, any such second foam layer (not shown) would need to be either transparent or include a window (not shown) corresponding to the window 21.

Reducing the peak strain experienced by the device 5 for bending to a given bending radius may improve the flexibility of the device 5 and also improve the number of 30 bending/unbending cycles which the antenna 7, the one or more organic light emitting diodes 8 and/or the flexible integrated circuit 9 can sustain (to a given bend radius) before fatigue damage occurs.

Organic light-emitting diodes

Referring also to Figure 6, an exemplary organic light emitting diode 27 which maybe powered using short-range radio frequency signals 4 is shown.

-18The exemplary organic light emitting diode 27 is deposited onto a transparent, flexible substrate 6, for example in the form of a layer of polyethylene naphthalate (PEN) having a thickness of 125 pm (in the z direction shown in Figure 6). The substrate 6 has 5 first and second surfaces 28, 29 and the organic light emitting diode 27 is deposited onto the first surface 28. A foil 30 is laminated over the first surface 28 of the substrate 6 and the exemplary organic light emitting diode 27 using a layer of adhesive 31. The foil 30 is in the form of an aluminium foil having a thickness of 20 pm. The foil 30 is provided for the purpose of sealing the organic light emitting diode 27 against the environment, and the foil 30 is not used as an electrode. The adhesive 31 takes the form of a pressure-sensitive adhesive having a thickness of approximately 25 pm. An optional additional encapsulation layer 32 may be laminated over the foil 30.

Alternatively, the foil 30 may directly contact the foam layer 12.

When used, the additional encapsulation layer 32 may take the form of a layer of polyethylene terephthalate (PET) having a thickness of 25 pm. The additional encapsulation layer 32 may be chemically or thermally bonded to the foil 30, or alternatively the foil 30 maybe deposited onto or chemically/thermally bonded to the additional encapsulation layer 32 before the foil 30 is adhered to the substrate 6 and organic light emitting diode 27. The organic light emitting diode 27 emits light through the transparent, flexible substrate 6, i.e. from the first surface 28 towards the second surface 29 and away from the foil 30 (in the negative z direction shown in Figure 6).

The second outer layer 11 is laminated covering the second surface 29 of the substrate 6 using a layer of transparent adhesive 33. The second outer layer 11 is transparent at 25 least within a region corresponding to the emission area of the exemplary organic light emitting diode 27. The second outer layer 11 may take the form of a layer of polyethylene terephthalate (PET), and the layer of transparent adhesive 33 may take the form of a pressure-sensitive adhesive having a thickness of approximately 25 pm.

The additional encapsulation layer 32 and adhesive layer 31 maybe transparent or opaque.

Transparency is relative to the emission wavelength of the organic light emitting diode

27. A material maybe considered transparent if it transmits 70% or more of light at the emission wavelength of the organic light emitting diode 27. In other examples, a material may be considered transparent if it transmits 50% or more of light at the emission wavelength.

-19The organic light emitting diode 27 comprises an anode, a cathode and an organic lightemitting layer between the anode and the cathode. One or more further layers maybe provided between the anode and cathode including, without limitation, charge5 transporting, charge-blocking and charge-injecting layers.

Referring also to Figure 7, the structure of the exemplary organic light emitting diode 27 is shown.

The anode is provided by a transparent electrode 34 supported on the first surface 28 of the transparent, flexible substrate 6. The transparent electrode 34 provides the anode and takes the form of a layer of indium tin oxide (ITO) having a thickness of around nm.

The cathode is provided by an electron injection layer 35 supported directly on a top electrode 36. The top electrode 36 takes the form of an aluminium electrode having a thickness of around 200 nm. The electron injection layer 35 has a thickness of 10 nm and comprises or consists of an n-doped, non-polymeric or polymeric electrontransporting material. The electron-transporting material is preferably a polymer comprising one or more arylene repeat units, optionally one or more repeat units selected from fluorene, phenylene and anthracene. Suitable n-dopants are 2,3dihydro-iH-benzoimidazoles, optionally i,3-Dimethyl-2-phenyl-2,3-dihydro-iHbenzoimidazole (DMBI) and 4-(2,3-Dihydro-i,3-dimethyl-iH-benzimidazol-2yl)-N,N-dimethylbenzenamine (N-DMBI). The top electrode 32 takes the form of an aluminium electrode having a thickness of around 200 nm. The electron injection layer 35 and top electrode 36 are arranged with the electron injection layer 35 facing the transparent electrode 34.

Alight emitting layer 37 comprising one or more light-emitting materials is arranged between the transparent electrode 34 (anode) and the electron injection layer 35 (cathode). Light-emitting materials maybe fluorescent materials, phosphorescent materials or a mixture of fluorescent and phosphorescent materials. Preferred lightemitting polymers are conjugated polymers, more preferably polyfluorenes, examples of which are described in Bernius, Μ. T., Inbasekaran, M., O'Brien, J. and Wu, W.,

Progress with Light-Emitting Polymers. Adv. Mater., 12 1737-1750, 2000, the contents of which are incorporated herein by reference. The light-emitting layer 37 may

- 20 comprise a host material and a fluorescent or phosphorescent light-emitting dopant. Preferred phosphorescent dopants are row two or row three transition metal complexes, preferably complexes of ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum or gold, most preferably complexes of iridium.

The particular material selected for the light emitting layer 37 depends on the desired emission wavelength of the exemplary organic light emitting diode 27.

A hole injection layer 38 is supported on the transparent electrode 34, between the transparent electrode 34 (anode) and the light emitting layer 37. The hole injection layer 38 takes the form of a layer of a conducting organic material having a thickness of around 50 nm. Preferred conducting organic materials are polyethylenedioxythiophene (PEDOT) doped with a polyacid, for example polystyrene sulfonic acid (PSS); and polythiophenes, for example Plexcore ® available from

Plextronics, Inc.

A hole transport layer 39 is supported on the hole injection layer 38, between the hole injection layer 38 and the light emitting layer 37. The hole transport layer 39 takes the form of a layer having a thickness of 22 nm and comprising or consisting of a polymeric 20 or non-polymeric hole-transporting material. The hole-transporting material is preferably an aromatic amine or a polymer comprising arylamine repeat units. Exemplary hole-transporting polymers are as described in WO 99/54385, WO 2005/049546 and WO 2013/108022, the contents of which are incorporated herein by reference.

The exemplary organic light emitting diode 27 is operable in a low drive voltage regime. For example, the voltage threshold V_T is preferably 3.5 V or less, and no more than 5 V. Combined with relatively high current efficiency, the capability to be driven by relatively low voltages enables the organic light emitting diode 27 to be powered using 30 energy from radio frequency signals 4 received by the antenna 7 of the device 5.

In other embodiments, the cathode may be in direct contact with the light-emitting layer. In these embodiments, the cathode may comprise a first layer of a metal compound having a first surface in direct contact with the light-emitting layer and an 35 opposing second surface in direct contact with a second layer comprising or consisting

- 21 of a conducting material. The metal compound may be a metal fluoride, more preferably an alkali or alkali earth fluoride such as, for example, LiF, NaF or KF.

Preferably, the second layer consists of a metal, more preferably a metal having a work function of more than 3.5 eV, preferably at least 4.0 eV, most preferably aluminium.

A third layer comprising or consisting of a metal having a work function of more than 3.5 eV, preferably at least 4.0 eV may be adjacent to the second layer.

Work functions of elemental metals are as given in the CRC Handbook of Chemistry and Physics, 87^th Edition, 12-114. For any given element, the first listed work function 10 value applies if more than one work function value is listed.

A preferred cathode is Al.

Referring also to Figure 8, first and second luminance-voltage characteristics 40, 41 for exemplary organic light emitting diodes 27 are shown. The first and second luminance15 voltage characteristics 40, 41 are plotted against a base ten logarithmic y-axis.

A first luminance-voltage characteristic 40 corresponds to a flexible organic light emitting diode 27 which emits blue light. The first luminance-voltage characteristic 40 has a voltage threshold V_T of around 2.75 V. A second luminance-voltage characteristic 20 41 corresponds to a flexible organic light emitting diode 27 which emits white light.

The second luminance-voltage characteristic 41 has a voltage threshold V_T of around

2.25 V. The flexibility of the blue and white organic light emitting diodes 27 corresponding to the first and second luminance-voltage characteristics 40,41 maybe sufficient to withstand bending to a 10 mm bend radius.

The minimum voltage threshold Vt for light emission typically does not produce sufficient luminance to be easily observed by the human eye, except in dark ambient conditions. A voltage threshold for observable light emissions, V_Obs, may be determined based on a desired luminance value 42. For example the desired luminance value 42 30 shown in Figure 8 is 400 Cd. nr² (candelas per square meter of organic light emitting diode 27). To reach the desired luminance value 42, the blue organic light emitting diode 27 may be driven at V_Obs ~ 3 V, and the white organic light emitting diode 27 may be driven at V_Obs ~ 4·9 V. Thus, both the blue and white flexible organic light emitting diodes 27 may be driven using voltages in the range of 3 to 5 V. The precise value of the

- 22 desired luminance value 42 will vary with the intended application, and need not be 400 Cd.nr². The power density of both the blue and white flexible organic light emitting diodes 27 is less than 50 mW.cnr² (milliwatts per square cm of organic light emitting diode) when the luminance is 400 Cd.nr².

Method of using the device

In use, the device 5 is both activated and powered by positioning the device 5 close to the transmitter 3 of a reading device 2. The device 5 may need to be closer to the transmitter 3 than would be required for conventional RFID tag interrogation using antenna load coupling or backscattering, in order to provide a sufficient amplitude of radio frequency signals 4 to power the one or more organic light-emitting diodes 8.

Referring also to Figure 9, a method of controlling illumination of the one or more organic light emitting diodes 8 is shown.

The transmitter 3 of a reading device 2 periodically transmits polling queries in the form of radio frequency signals 4 to determine whether a device 5 or other RFID tagged object is within the interrogation range of the reading device 2 (step Si).

When the device 5 is within interrogation range, the antenna 7 receives the radio frequency signals 4 corresponding to the polling queries, and the device 5 acknowledges the polling query (step S2). The method by which the device 5 provides an acknowledging signal depends on the frequency used and may be, for example, antenna load coupling, backscattering or a separate transmission of radio frequency signals 4 (if 25 the power available to the device 5 is sufficient). In systems 1 which do not use security and which are intended merely to allow a reading device 2 to identify a device 5, the acknowledgement message may take the form of an identifier which uniquely identifies the device 5.

Once the reading device 2 receives an acknowledgement, if the system 1 uses security features, one or more rounds of authentication queries and responses maybe conducted (step S3). For example, the reading device 2 transmits radio frequency signals 4 encoding a query. The control module 15 of the flexible integrated circuit 9 checks the non-volatile storage 19 for a reply matching the query and sends the reply to 35 the reading device 2. If the reply received matches a correct reply, then the device 5 and reading device 2 are authenticated and further data exchange may be carried out.

-23The system 1 may use one or more rounds of queries and responses to perform authentication.

The hereinbefore described example of a debit or credit payment card would utilise authentication to confirm that a payment card was a valid payment card.

Authentication could also be used to confirm that an NFC reader included in a mobile telephone is authorised to display the remaining account balance or credit using an electroluminescent element display 8 of the device 5. If the system 1 is not secured, the authentication step (step S3) may be omitted.

The reading device 2 may transmit radio frequency signals 4 for exchanging data with the device 5 (step S4). Depending upon the system 1, data exchange maybe one directional or bi-directional. The reading device 2 may transmit radio frequency signals 4 encoding data. Alternatively, the reading device 2 may simply transmit a 15 radio frequency signal 4 in the form of a carrier wave in order to power the device 5 so that the device 5 can send a reply including data retrieved from the non-volatile storage

19. For example, the reading device 2 can transmit radio frequency signals 4 which encode data by modulating a carrier wave, then continue broadcasting the carrier wave to provide power for the device 5 to reply using antenna load coupling, backscattering 20 or by transmitting radio frequency signals 4 (depending on the power available and the frequency of operation). The exchanged data maybe an identifier which uniquely identifies the device 5.

In the hereinbefore described example of a debit or credit payment card, after a vendor 25 reading device 2 has authenticated a transaction, the vendor reading device 2 may send the device an updated balance for displaying to the payment card user.

The control module 15 of the flexible integrated circuit 9 may perform processing (step S5), for example, to decode the data received from the reading device 2.

The control module 15 of the flexible integrated circuit 9 causes the second driving signal 16 to be supplied to one, some, or all of the one or more organic light emitting diodes 8 (step S6). The specific organic light emitting diodes 8 illuminated in this way may be dependent on data received from the reading device 2 (step S4), retrieved from 35 the non-volatile storage 19 and/or any intermediate processing (step S5) performed by the control module 15.

-24Referring also to Figure to, a modified device 43 is shown.

The modified device 43 is the same as the device 5 except that the modified device 43 5 further includes one or more input devices 44 supported on the flexible substrate 6.

For example, one or more input devices 44 in the form of capacitive touch pads maybe printed onto the substrate 6. Input devices 44 may provide additional functionality to the modified device 43. For example, illumination of one or more organic lightemitting diodes 8 may be made conditional on a user actuating an input device 44 10 concurrently with interrogation by the reading device 2. Alternatively, the modified device 43 may be configured such that a user actuating an input device 44 concurrently with interrogation by the reading device 2 suppresses illumination of one or more organic light emitting diodes 8. The functions of the input device(s) 44 need not be linked solely to whether or not to illuminate the organic light-emitting diodes 8. For 15 example, if the modified device 43 is embedded in a payment card, then authorisation of a transaction may be made conditional upon a user actuating an input device 44. In this way, unauthorised reading of the payment card when stored in a users’ wallet or pocket can be prevented.

Method of fabricating the device

In general, a method of fabricating the short-range radio frequency communication device 5 includes depositing the one or more organic light emitting diodes 8 and the antenna 7 configured for short-range radio frequency communications on the flexible substrate 6. The method also includes mounting the flexible integrated circuit 9 on the 25 flexible substrate 6. The flexible integrated circuit 9 may be mounted before, during or after the deposition of the one or more organic light emitting diodes 8 and the antenna 7. However, depending on the deposition method(s) used, it maybe convenient to mount the flexible integrated circuit 9 after the deposition of the one or more organic light emitting diodes 8 and the antenna 7. The method also includes laminating the 30 flexible substrate 6 and the compliant foam layer 12 between the first outer layer 10 and the second outer layer 11.

As described hereinbefore, the flexible integrated circuit 9 is configured to receive radio frequency signals 4 from antenna 7, to harvest power from the radio frequency signal 4, 35 to convert harvested power into a driving signal 16 for the one or more organic light emitting diodes 8 and, for each organic light emitting diode 8, control light emission by

-25supplying the driving signal 16 to the organic light emitting diode 8. As described hereinbefore, the one or more organic light emitting diodes 8 are configured to emit light in response to receiving the a driving signal 16 having an amplitude of less than or equal to 3.5 V.

Referring also to Figure 11, an exemplary method of fabricating the device 5 will be explained.

A first conductive layer is deposited onto the substrate 6 (step S7). The first conductive layer may be formed by printing conductive ink or paste such as, for example, metal or carbon based conductive inks. The first conductive layer may be ink-jet printed, screen printing, gravure printed, flexographic printed, slot die coated and so forth. In general, the choice of printing technique may depend on the desired resolution of features and on the volume of devices 5 to be produced.

The first conductive layer need not be printed, and may alternatively by formed by foil stamping. In a further alternative, the first conductive layer maybe formed by sputtering or evaporation of metals through a mask.

Referring also to Figure 12A, an example of a substrate 6 is shown in a top view following deposition of the first conductive layer. Referring also to Figure 13A, a crosssection is shown along the line A-A’ in Figure 12A.

A common transparent electrode 45 is deposited to provide the transparent electrode

34 of an exemplary organic light emitting diode 27. The common transparent electrode is connected by a conductive trace to a contact pad 46 for connection to the flexible integrated circuit 9. Also deposited in the first conductive layer are first and second antenna contact pads 47,48, which are connected by conductive traces to respective contact pads 49, 50 for connection to the flexible integrated circuit 9. Optionally, the first conductive layer may further include one or more capacitive touchpads 51 connected by conductive traces to respective contact pads 52 for connection to the flexible integrated circuit 9. The capacitive touchpads 51 are one example of input devices 44. In this way, features of the antenna 7, the one or more organic light emitting diodes 8 and optionally the input devices 44 maybe co-deposited in a single processing step.

- 26 An insulating mask layer is deposited over the first conductive layer (step S8). The insulating mask layer layer may be formed by printing ink or paste such as, for example, insulating resins or other insulating polymeric materials. The insulating mask layer may be ink-jet printed, screen printing, gravure printed, flexographic 5 printed, slot die coated and so forth. In general, the choice of printing technique may depend on the desired resolution of features and on the volume of devices 5 to be produced.

Referring also to Figure 12B, an example of a substrate 6 is shown in a top view following deposition of the insulating mask layer. Referring also to Figure 13B, a crosssection is shown along the line A-A’ in Figure 12B.

A pixel definition portion 53 of the insulating mask layer is deposited over the common transparent electrode 45. The pixel definition portion 53 includes a number of windows 54 which define the emitting areas of a corresponding number of organic light-emitting diodes 8. The pixel definition portion 53 extends beyond the edges of the common transparent electrode 45 in order to provide insulation of later deposited cathode pixel electrodes 57 (Figure 12D). In the example shown in Figure 12, the organic light-emitting diodes 8 take the form of a seven segment display, but other shapes of emission areas may be used to provide the one or more organic light-emitting diodes 8. The insulating mask layer also includes one or more antenna trace insulting portions 55. The conductive track 17 providing the antenna 7 preferably includes several loops or coils, and the antenna trace insulting portions 55 serve to insulate the conductive tracks 17 where these intersect the conductive traces connecting the first and second antenna contact pads 47, 48 to the respective contact pads 49,50. In the example shown in Figure 12, a single antenna trace insulting portion 55 is provided over the conductive trace connecting the first antenna contact pad 47 to the respective contact pad 49, but in other examples further antenna trace insulting portions 55 may be deposited. In this way, features of the antenna 7 and the one or more organic light emitting diodes 8 may be provided in a common deposition step.

One or more active layers 56 are deposited onto the insulating mask layer (step S9). The one or more active layers 56 may be formed by printing inks or pastes. The one or more active layers 56 maybe ink-jet printed, screen printing, gravure printed, flexographic printed, slot die coated and so forth. In general, the choice of printing technique may depend on the desired resolution of features and on the volume of devices 5 to be produced.

The one or more active layers 56 include at least a light emitting polymer layer 37.

Depending on the materials of the anode, cathode and the light emitting polymer layer

37, the one or more active layers 56 may also include one or more of an electron injection layer 35, a hole injection layer 38 and a hole transport layer 39.

Referring also to Figure 12C, an example of a substrate 6 is shown in a top view following deposition of the one or more active layers 56. Referring also to Figure 13C, a cross-section is shown along the line A-A’ in Figure 12C.

In the example shown in Figure 12, the one or more active layers 56 are deposited over a continuous area roughly corresponding to the common transparent electrode 45.

However, in other examples the one or more active layers 56 may be deposited over two of more areas, for example, the one or more active layers 56 may be deposited within, or overlapping, the windows 54 through the pixel definition portion 53. In this way, different organic light emitting diodes 8 may be provided with different light emitting polymer layers in order to emit light of different colours.

A second conductive layer is deposited (step S10). The second conductive layer may be formed by printing conductive ink or paste such as, for example, metal or carbon based conductive inks. The second conductive layer may be ink-jet printed, screen printing, gravure printed, flexographic printed, slot die coated and so forth. In general, the 25 choice of printing technique may depend on the desired resolution of features and on the volume of devices 5 to be produced.

The second conductive layer need not be printed, and may alternatively by formed by foil stamping. In a further alternative, the second conductive layer maybe formed by 30 sputtering or evaporation of metals through a mask.

Referring also to Figure 12D, an example of a substrate 6 is shown in a top view following deposition of the first conductive layer. Referring also to Figure 13D, a crosssection is shown along the line A-A’ in Figure 12D.

- 28 Cathode pixel electrodes 57 are deposited over the one or more active material layers 56. Each cathode pixel electrode 57 corresponds in location, shape and approximate area to an underlying window 54 in the pixel definition portion 53. Each cathode pixel electrode 57 may extend beyond the underlying window 54. The cathode pixel electrodes 57 are connected by conductive traces to contact pads 58 for connection to the flexible integrated circuit 9. The conductive track 17 providing the antenna 7 is also deposited as part of the second conductive layer. The conductive track 17 starts and ends on the antenna contact pads 47,48. The conductive track 17 is insulated from the conductive traces connecting the antenna contact pads 47, 48 to the respective contact 10 pads 49,50 by one or more antenna trace insulating portions 55.

A conductive adhesive layer is deposited (step S11). The conductive adhesive layer may be formed by printing conductive ink or paste such as, for example, metal or carbon based conductive adhesives. The conductive adhesive layer maybe ink-jet printed, screen printing, gravure printed, flexographic printed, slot die coated and so forth. In general, the choice of printing technique may depend on the desired resolution of features and on the volume of devices 5 to be produced.

The conductive adhesive layer need not be printed, and may alternatively be formed by laminating an anisotropic conductive film having adhesive properties over the appropriate portion of the substrate 6.

Referring also to Figure 12E, an example of a substrate 6 is shown in a top view following deposition of the conductive adhesive layer. Referring also to Figure 13E, a 25 cross-section is shown along the line A-A’ in Figure 12E.

In the example shown in Figure 12, conductive adhesive 59 is deposited onto each of the contact pads 46,49,50,52,58 for connecting to the flexible integrated circuit 9. In other examples, an anisotropic conductive film (not shown) may be applied to cover 30 each of the contact pads 46, 49,50, 52,58 for connecting of the flexible integrated circuit 9.

The flexible integrated circuit 9 is placed on and mounted to the substrate 6 (step S12). The flexible integrated circuit 9 may be emplaced using a pick-and-place machine (not 35 shown) which obtains the flexible integrated circuits 9 from an adjacent web, tape or hopper. The flexible integrated circuit 9 is placed so that contacts 60 of the flexible

-29integrated circuit 9 are aligned with the contact pads 46, 49, 50,52,58 to provide electrical connections. Encapsulation layers for the one or more organic light emitting diodes 8 are laminated to cover and protect the one or more active layers 57 from moisture and other environmental factors (step S13).

Referring also to Figure 12F, an example of a substrate 6 is shown in a top view following mounting of the flexible integrated circuit 9 and encapsulation of the one or more organic light emitting diodes 8. Referring also to Figure 13F, a cross-section is shown along the line A-A’ in Figure 12F.

The encapsulation may take the form of the foil 30, which is laminated over the cathode pixel electrodes 57 and the one or more active layers 56 using a layer of pressure sensitive adhesive 31. Preferably the pressure sensitive adhesive 31 is provided on the foil 30 to simplify the application of the foil 30.

The substrate 6 and the foam layer 12 are laminated between the first and second outer layers 10,11 (step S14). The foam layer 12 maybe pre-adhered to the first outer layer for simplicity, or the foam layer maybe provided as a separate sheet which is stacked with the substrate 6 before lamination with the first and second outer layers 10,11. The 20 laminated layers may be adhered using layers of adhesive. Alternatively, the foam layer and the outer layers 10,11 may be thermoplastic and laminating may comprise applying heat and pressure to bond the device 5 layers together. In some examples, a second compliant foam layer (not shown) is laminated between the substrate 6 and the second outer layer 11, which may further improve flexibility and resilience of the electronic device 5.

Referring also to Figure 13G, a cross-section of the device 5 is shown following lamination of the foam layer 12 and outer layers 10,11.

Referring also to Figure 14, the method of fabricating the devices 5 maybe implemented using a roll-to-roll system 61.

The substrate 6 maybe provided from a substrate supply roll/drum 62. The substrate 6 is fed through a pair of feed rollers 63 and into a first deposition stage 64. The first deposition stage 64 applies the first conductive layer using a printing or foil stamping process as described hereinbefore. For example, the first deposition stage 64 may

-30apply the common electrode 45, the first and second antenna contacts 47,48 and the contact pads 46, 49, 50.

From the first deposition state 64, the substrate 6 moves on to a second deposition stage 65 which prints the insulating mask layer as described hereinbefore. For example, the second deposition stage 65 may apply the pixel definition portion 53 and one or more antenna trace insulating portions 55.

The one or more active layers 56 are printed by a third deposition stage 66. Depending 10 on the number of active layers 35,37, 38, 39, the third deposition stage 66 may include more than one printing process. Successive printing of active layers 35,37, 38, 39 may use orthogonal solvents to prevent dissolution of underlying layers. Additionally and/or alternatively, the third deposition stage 66 may include UV sources to provide cross-linking/curing of underlying active layers 35, 37, 38, 39 before deposition of the 15 subsequent active layers 35,37, 38, 39.

The second conductive layer is printed by a fourth deposition stage 67. The fourth deposition stage 67 applies the second conductive layer using a printing or foil stamping process as described hereinbefore. For example, the fourth deposition stage 20 67 may apply the cathode pixel electrodes 57 and the conductive track 17.

An encapsulation stage 68 laminates a foil 30 over the one or more light emitting diodes 8. An encapsulation supply roller 69 provides a web or tape 70 supporting predefined regions of foil 30 coated with a pressure sensitive adhesive 31. The tape 70 is 25 passed with the substrate 6 through transfer rollers 71 to transfer the foil 30 to the substrate 6. The used/spent tape 70 is wound up on a spent roller 72. The transfer rollers 71 apply pressure, and optionally heat, to bond the foil 30 over the one or more light-emitting diodes 8.

A first mounting stage 73 laminates an anisotropic conductive film 74 provided from an anisotropic conductive film supply roller 75 over contact pads for connecting the flexible integrated circuit 9. The anisotropic conductive film 74 is passed with the substrate 6 through transfer rollers 76 to transfer the anisotropic conductive film 74 to the substrate 6. The used/spent anisotropic conductive film 74 is wound up on a spent roller 77. The transfer rollers 76 apply pressure, and optionally heat, to bond the anisotropic conductive film 74 to the substrate 6.

-31A second mounting stage 78 is a pick-and-place machine. The second mounting stage includes a hopper (not shown) holding flexible integrated circuits 9 or is fed with a tape or web (not shown) holding the flexible integrated circuits 9. Following placement of the flexible integrated circuit 9, the substrate 6 may be passed through transfer roller to apply pressure and optionally heat to ensure good adhesion of the flexible integrated circuit 9 to the substrate 6 and good electrical contact between the contacts 60 and the contact pads 46, 49,50, 52,58.

In a lamination stage 80, the outer layers 10,11, the foam layer 12 and the substrate 6 are passed between lamination rollers 81 which apply pressure, and optionally heat, to the layers 6,10,11,12. The first outer layer 10 is provided from a first outer layer supply roller 82. Similarly, the second outer layer 11 is provided from a second outer layer supply roller 83. The foam layer 12 is supplied from a foam supply roller 84. In other examples, the foam layer 12 may be pre-attached to the first outer layer 10, so that only the first outer layer supply roller 82 is needed. Optionally, a second foam layer (not shown) may be provided between the substrate 6 and the second outer layer 11, or pre-bonded to the second outer layer 11.

A continuous layer 85 of finished devices 5 is spooled up onto a take-up roller 86. Alternatively, the continuous layer 85 could be passed through a die-cut roller pair (not shown) to cut out the individual devices 5. This may depend upon whether further processing is needed to apply, for example, indicia 23 to the devices 5.

For high throughout/high volume productions, the first to fourth deposition stages 64, 65, 66, 67 may use a continuous roller printing technique such as a gravure or flexographic printing. In other examples where greater flexibility in the device 5 layout is needed, ink-jet printing or slot die coating maybe preferred.

Modifications

It will be appreciated that many modifications may be made to the embodiments hereinbefore described. Such modifications may involve equivalent and other features which are already known in the design, manufacture and use of organic light emitting diodes and/or short-range radio frequency communication devices, and which maybe 35 used instead of or in addition to features already described herein. Features of one embodiment may be replaced or supplemented by features of another embodiment.

-32The flexible substrate 6 need not be a single piece of material, and the flexible substrate 6 maybe made up or two or more separate substrates joined, bonded or laminated to one another.

Preferably, the antenna 7 and the one or more organic light-emitting diodes 8 are printed onto the same flexible substrate 6. Alternatively, the one or more light-emitting diodes 8 may be printed onto a separate substrate (not shown) which is then laminated to the flexible substrate 6.

In the example shown in Figure 2, the pre-payment card 20 includes a single window

21. However, a second outer layer 11 may include more than one window 21, for example a second outer layer 11 may include as many windows 21 as there are organic light-emitting diodes 8. Windows 21 need not be transparent, and may instead be provided as through holes of the second outer layer 11.

The organic light emitting diodes 8 may alternatively be top-emitting, in which case windows 21 should be provided in the first outer layer 10, and the foam layer 12 should be either transparent or be provided between the substrate 6 and the second outer layer 20 11.

The one or more organic light-emitting diodes 8 need not be grouped in one region of the substrate 6 or on only one side of the substrate 6, and may be distributed across front and/or reverse faces of the substrate 6, either individually or in groups.

Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combination of features disclosed herein either explicitly or implicitly or any generalization thereof, whether or 30 not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicant hereby gives notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

-33Claims

Claims

-33Claims

1. A short-range radio frequency communication device comprising:

first and second flexible outer layers;

5 a compliant foam layer between the first and second outer layers;

a flexible substrate between the first and second outer layers, the flexible substrate supporting:

an antenna configured for short-range radio frequency communications;

one or more organic light emitting diodes; and io a flexible integrated circuit configured to:

receive radio frequency signals from the antenna harvest power from the radio frequency signals received by the antenna;

convert harvested power into a driving signal for the organic light 15 emitting diodes;

for each organic light emitting diode, control light emission by supplying the driving signal to the organic light emitting diode;

wherein each organic light emitting diode is configured to emit light in response to receiving a driving signal having an amplitude of less than or equal to 3.5 V.
2. A device according to claim 1, wherein the flexible integrated circuit is configured to transmit a signal using the antenna.
3. A device according to claims 1 or 2, wherein the flexible integrated circuit is

25 configured to receive a radio frequency signal encoding external data from the antenna.
4. A device according to any preceding claim, wherein the flexible integrated circuit comprises a non-volatile storage element configured to store local data.

30 5. A device according to any preceding claim, wherein the antenna and the one or more organic light emitting diodes are deposited directly onto the substrate.

6. A device according to any one of claims 3 or 4, wherein the flexible integrated circuit is configured to control the light emission of each organic light emitting diode in 35 dependence upon the external data and/or local data.

-347- A device according to any preceding claim, wherein each organic light emitting diode comprises an electron injection layer comprising an n-doped polymer, the polymer comprising one or more arylene repeat units.
5 8. A device according to claim 7, wherein the electron injection layer is in direct contact with an aluminium electrode.
9. A device according to claim any one of claims 1 to 8, wherein each organic light emitting diode comprises a layer of sodium fluoride.
10. A device according to any preceding claim, wherein the antenna and/or the one or more organic light emitting diodes are formed by printing.
11. A device according to any preceding claim, wherein at least one conductive

15 feature of the antenna and at least one conductive feature of the one or more organic light emitting diodes are formed in a first common process step.
12. A device according to any preceding claim, wherein at least one insulating feature of the antenna and at least one insulating feature of the one or more organic

20 light emitting diodes are formed in a second common process step.
13. A device according to any preceding claim, further comprising one or more input devices.

25
14. A device according to any preceding claim, wherein each organic light emitting diode draws a power density of less than 50 mW.cnr² at a luminance of 400 Cd.nr².
15. A method of fabricating a short-range radio frequency communication device, comprising:

30 depositing one or more organic light emitting diodes and an antenna configured for short-range radio frequency communications on a flexible substrate;

mounting a flexible integrated circuit on the flexible substrate; laminating the flexible substrate and a compliant foam layer between a first outer layer and a second outer layer;

35 wherein the flexible integrated circuit is configured to receive radio frequency signals from the antenna, to harvest power from the radio frequency signals received by

-35the antenna, to convert harvested power into a driving signal for the organic light emitting diodes and, for each organic light emitting diode, control light emission by supplying the driving signal to the organic light emitting diode wherein each organic light emitting diode is configured to emit light in response 5 to a driving signal having an amplitude of less than or equal to 3.5 V.
16. A method according to claim 15, wherein depositing the one or more organic light emitting diodes and the antenna comprises printing the one or more organic light emitting diodes and the antenna.
17. A method according to claim 16, wherein printing comprises inkjet printing, gravure printing, flexographic printing, or slot die coating.
18. A method according to any one of claims 15 to 17, wherein at least one

15 conductive feature of the antenna and at least one conductive feature of the one or more organic light emitting diodes are formed in a first common process step.
19. A method according to any one of claims 15 to 18, wherein at least one insulating feature of the antenna and at least one insulating feature of the one or more
20 organic light emitting diodes are produced in a second common process step.

20. A method according to any one of claims 15 to 19, wherein depositing the one or more organic light emitting diodes and the antenna comprises:

depositing a first patterned conductive layer on the substrate;

25 depositing an insulating mask layer over the first conductive layer, wherein the insulating mask layer defines the emitting areas of the one or more organic light emitting diodes;

depositing the active layers of the one or more organic light emitting diodes over the insulating mask layer;

30 depositing a second conductive layer over the active layers, the insulating mask layer and/or the substrate;

depositing an encapsulation layer over the one or more light emitting diodes.
21. A method according to any one of claims 15 to 20, wherein mounting a flexible 35 integrated circuit on the flexible substrate comprises:

applying conductive glue or ink to a plurality of contact pads deposited on the substrate, each contact pad connected to the one or more organic light emitting diodes or the antenna via conductive traces; and placing the flexible integrated circuit on the substrate such that a second

5 plurality of contact pads on the flexible integrated circuit are aligned with the contact pads deposited on the substrate.
22. A method according to any one of claims 15 to 20, wherein mounting a flexible integrated circuit on the flexible substrate comprises:

10 applying an anisotropic conductive film over a plurality of contact pads deposited on the substrate, each contact pad connected to the one or more organic light emitting diodes or the antenna via conductive traces; and placing the flexible integrated circuit on the substrate such that a second plurality of contact pads on the flexible integrated circuit are aligned with the contact 15 pads deposited on the substrate.
23. A method according to any one of claims 15 to 22, wherein the method is carried out in a roll-to-roll process.