Radio frequency identification device with visual indicator

BACKGROUND OF THE INVENTION

00011. Technical Field of the Invention

0002The invention relates to radio frequency identification (RFID) devices.

00032. Description of the Related Art

0004Radio frequency identification (RFID) tags and labels (collectively referred to herein as “devices”) are widely used to associate an object with an identification code. RFID devices generally have a combination of antennas and analog and/or digital electronics, which may include for example communications electronics, data memory, and control logic. For example, RFID tags are used in conjunction with security-locks in cars, for access control to buildings, and for tracking inventory and parcels. Some examples of RFID tags and labels appear in U.S. Pat. Nos. 6,107,920, 6,206,292, and 6,262,692, all of which are hereby incorporated by reference in their entireties.

0005As noted above, RFID devices are generally categorized as labels or tags. RFID labels are RFID devices that are adhesively or otherwise have a surface that is attached directly to objects. RFID tags, in contrast, are secured to objects by other means, for example by use of a plastic fastener, string or other fastening means. Nevertheless, RFID devices are referred to herein somewhat interchangeably as “tags” or “labels.”

0006In activating, reading, and/or detecting RFID devices, radio frequency (RF) fields are generally sent over a relatively long range, that is, over intervening free space. Thus detection of devices is accomplished over a significantly-sized region, and spatial discrimination in reading and detection of devices may be difficult.

0007One concern that has been raised regarding RFID devices is that their ability to be read over relatively long distances may implicate privacy concerns for people having objects with RFID devices attached thereto or otherwise coupled thereto. It will be appreciated that concerns about possible tracking or other privacy-related issues may inhibit some users from employing RFID devices. Accordingly, it will be appreciated that it would be desirable for RFID devices to avoid the above problems.

SUMMARY OF THE INVENTION

0008According to an aspect of the invention, an RFID device includes a display that selectively shows one or more visual indicators. Display of the one or more visual indicators may be actuated based on an operating state of the RFID device.

0009According to another aspect of the invention an RFID device includes an electrochromic display that is operatively coupled to a chip of the device.

0010According to still another aspect of the invention, an RFID device includes a display for displaying a visual indication of the disabling of operation of the RFID device.

0011According to a further aspect of the invention, an RFID device includes a display for displaying a visual indicator that is readable only using light outside of the wavelength range normally viewable by humans (i.e., ultraviolet light and/or infrared light).

0012According to a still further aspect of the invention, an RFID device includes: a chip; an antenna operatively coupled to the chip; and a display operatively coupled to the chip. The antenna is configured for receiving energy to power the chip. The antenna is configured to receive information signals to be passed on to the chip. The display includes a visual indicator that provides a visual indication of an operative state of the device.

0013According to another aspect of the invention, an RFID device includes: a chip; an antenna operatively coupled to the chip; and a display operatively coupled to the chip. The antenna is configured to receive information signals to be passed on to the chip. The display includes a visual indicator that provides a visual indication that normal operation of the device is disabled.

0014According to yet another aspect of the invention, a method of using a radio frequency identification (RFID) device includes the steps of: disabling normal operation of the device, thereby placing the device in a disabled state; and displaying a visual indication on a display of the device, wherein the visual indication indicates the disabled state.

0015To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0016In the annexed drawings, which are not necessarily to scale:

0017<figref idref="DRAWINGS">FIG. 1</figref> is an oblique view of a RFID device in accordance with the present invention;

0018<figref idref="DRAWINGS">FIG. 2</figref> is a block diagram of one possible configuration of the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0019<figref idref="DRAWINGS">FIG. 3</figref> is a schematic diagram showing interaction of an RFID reader/detector, and the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0020<figref idref="DRAWINGS">FIG. 4A</figref> is a schematic illustration of an alternate configuration of the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0021<figref idref="DRAWINGS">FIG. 4B</figref> is a schematic illustration of a voltage multiplier that may be part of an RFID device in accordance with the present invention;

0022<figref idref="DRAWINGS">FIG. 4C</figref> is a schematic illustration of a voltage converter that may be part of an RFID device in accordance with the present invention;

0023<figref idref="DRAWINGS">FIG. 4D</figref> is another possible configuration of the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0024<figref idref="DRAWINGS">FIG. 5</figref> is a high-level flowchart illustrating some steps in the operation of the display of the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0025<figref idref="DRAWINGS">FIG. 6</figref> schematically illustrates an electrochromic display for possible use with the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0026<figref idref="DRAWINGS">FIG. 7</figref> schematically illustrates a liquid crystal display for possible use with the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0027<figref idref="DRAWINGS">FIG. 8</figref> is a plan view of an RFID device, in accordance with the present invention, that utilizes a thermochromic display;

0028<figref idref="DRAWINGS">FIG. 9</figref> is a schematic diagram illustrating configuration of a chemically-reactive-material display, for possible use with the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0029<figref idref="DRAWINGS">FIGS. 10 and 11</figref> illustrate two possible visual indicators that may be displayed in use of the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>;

0030<figref idref="DRAWINGS">FIGS. 12 and 13</figref> respectively illustrate obscured and revealed information that is part of a display that is usable with the RFID device of <figref idref="DRAWINGS">FIG. 1</figref>; and

0031<figref idref="DRAWINGS">FIG. 14</figref> schematically illustrates another type of RFID device, with a display that integrated with an antenna and a chip, in accordance with the present invention.

DETAILED DESCRIPTION

0032An RFID device includes a chip, an antenna operatively coupled to the chip, and a visual indicator operatively coupled to the chip. The visual indicator provides a visual indication of an operative state of the device. The visual indication may be human readable and/or machine readable, and may provide visual indication that is dependent on a change in an operative state of the device. The operative state that triggers the visual indication may include a state in which the chip has temporarily or permanently been rendered inoperative or disabled, that is, in which the chip no longer responds to, or otherwise interacts with, ordinary incoming RF signals such as from a device reader. The visual indicator may be included in a display that functions by any of a variety of suitable mechanisms, such as by use of electrochromic materials, thermochromic materials, liquid crystals, or chemically-reactive materials. The visual indication may include any of a wide variety of human-readable or machine-readable indications, for example, including words, symbols, and/or colors, and/or by hiding and/or revealing underlying human-readable or machine-readable indicia. The display that includes the visual indicator may have a single changeable element, or may have multiple elements. Displays with multiple elements may be configured to show different combinations of elements to provide visual indications of different operative states of the RFID device. The device with the visual indicator may be used to communicate a wide variety of different information on operative states, for a wide variety of different purposes. One possible use for the RFID device is to provide a visual indication when the device is rendered permanently inoperative following the receipt by the device of a signal indicating that the device is to disable itself from further operation. Such a visual indication of device inoperability may aid in allaying privacy-based concerns regarding RFID devices.

0033Referring to <figref idref="DRAWINGS">FIG. 1</figref>, an RFID device <b>10</b> includes a chip <b>12</b>, an antenna <b>14</b> coupled to the chip <b>12</b>, and a display <b>16</b> coupled to the chip <b>12</b>. The display <b>16</b> includes a visual indicator <b>18</b> for providing a human-readable and/or machine-readable visual indication of an operative state of the RFID device <b>10</b>. The visual indicator <b>18</b> may indicate an operative state of the chip <b>12</b>. All of the components <b>12</b>-<b>18</b> of the RFID device <b>10</b> may be mounted on a suitable substrate <b>20</b>.

0034A “transponder chip” or “chip” is defined as a device for providing suitable interaction, through an antenna, for communication with an external device, such as a reader. A chip may include any of a variety of suitable electrical components, such as resistors, capacitors, inductors, batteries, memory devices, and processors. It will be appreciated that a large variety of transponder chips for RFID devices are widely known. The term “transponder chip” is intended to encompass the broad range of such devices, which may vary widely in complexity and functionality.

0035The antenna <b>14</b> may be any of a variety of suitable types of antennas for RFID devices. Examples of suitable types of antennas include dipole antennas, loop antennas, slot antennas, coil antennas, and hybrid antennas combining structures and characteristics of various antenna types.

0036The chip <b>12</b> and the antenna <b>14</b> may interact with a communication device, such as an RFID device reader or detector, in a variety of suitable ways. The RFID device <b>10</b> may be a fully passive device, in which the antenna <b>14</b> receives signals which, when rectified, provide power for the chip <b>12</b>, and, if required provide commands from the reader to the chip in the form of amplitude modulation of the signal. To send a signal from the RFID device to the reader, the device modulates its input impedance with a data-carrying signal. For low frequency tags, those operating at typically 125 kHz and 13.56 MHz, the effect of this modulation is best described as an increase in the load presented to the reader transmitter, for high frequency signals, such as those in the band 902-928 MHz, it is usually described as a form of reflection or backscatter modulation.

0037Alternatively, the RFID device <b>10</b> may be a semi-passive RFID device. As with a fully passive RFID device, a semi-passive RFID device does not generate its own radio signals. However, unlike the fully passive device, in the semi-passive device the logic functions of the chip <b>12</b>, and the communication functions of the chip <b>12</b>, are powered by a battery or other energy storage device. Communication with a semi-passive device is similar to communication with a fully passive device, in that in both devices communication from the device occurs by reflection of an incident signal back to a device reader or detector.

0038Another alternative for the RFID device <b>10</b> is an active RFID device. An active device contains its own power source, such as a battery, for providing power to the chip <b>12</b>, and for transmitting signals from the chip <b>12</b>, via the antenna <b>14</b>.

0039The communication by RF signals of the RFID device <b>10</b> with external devices is referred to herein as normal operation of the RFID device <b>10</b>. This normal operation may be accomplished by reflecting of signals (for passive and semi-passive devices) or by the transmitting of signals (for active devices). An RFID device that is rendered by internal mechanisms temporarily or permanently unable to send signals (by reflecting or transmission) is referred to herein as being disabled.

0040The display <b>16</b> may be any of a variety of suitable types of displays. Examples of such displays include electrochromic displays, thermochromic displays, liquid crystal displays (LCDs), and displays containing chemically-reactive materials. At least some of these types of displays are discussed in greater detail below. The display <b>16</b> may have its own power source, such as from a battery or a capacitor. Alternatively, or in addition, the display <b>16</b> may utilize the same active or passive power source used to power the chip <b>12</b>.

0041The visual indicator <b>18</b> may include any of a wide variety of types of visual elements that are readable or otherwise detectable by human vision and/or machine vision. The visual indicator may include a plurality of separately or simultaneously actuatable elements, or may alternatively be a single element. The visual indicator <b>18</b> provided may include display of one or more symbols, such as the display of letters or words. Alternatively, or in addition, the visual indicator <b>18</b> may include graphic elements, such as stylized pictures. The visual indicator <b>18</b> may include a change of color, either alone or in addition to the display of other types of visual elements. The visual indicator <b>18</b> may also include a change in emissivity of a material, for example, revealing or obscuring visible indicia, such as printed matter, that are underneath the display <b>16</b>. Such indicia, for example, including bar code elements, may be printed on the substrate <b>20</b>. It will be appreciated that color change in the visual indicator <b>18</b> may be used to obscure or reveal underlying material, for example, visual elements printed in a similar color. The visual indicator <b>18</b> may involve visual material which may be viewed under ordinary human-visible light. Alternatively or in addition, the visual indicator <b>18</b> may involve material that is visually-readable only in other sorts of light, such as infrared light or ultraviolet light. A further possibility for the visual indicator <b>18</b> is an indicator such as a bar code that is visually detectable by humans, but is only meaningfully deciphered (read) by or with the assistance of machines or devices.

0042The RFID device <b>10</b> may include a wide variety of other layers and/or components. For example, the RFID device <b>10</b> may be a label that includes an adhesive layer with a peelable cover layer. As another example, the RFID device <b>10</b> may include protective layers for protecting the operative components of the device, and/or may include a printable layer or region, for example, for including a bar code or other information.

0043<figref idref="DRAWINGS">FIG. 2</figref> shows a block diagram of one possible configuration of a fully passive version of the RFID device <b>10</b>. <figref idref="DRAWINGS">FIG. 3</figref> schematically illustrates interaction between an RFID device reader or detector <b>22</b>, and the RFID device <b>10</b> of <figref idref="DRAWINGS">FIG. 2</figref>. Antenna elements <b>30</b> and <b>32</b> of the device <b>10</b> receive signals <b>34</b> and <b>36</b> sent by the device reader <b>22</b>. The signals sent by the device reader <b>22</b> include an unmodulated continuous-wave RF power signal <b>34</b>, and an amplitude modulated RF instruction signal <b>36</b>. The unmodulated power signal <b>34</b> provides power to the RFID device <b>10</b>, while the instruction signal <b>36</b> provides commands to the chip <b>12</b> of the device <b>10</b>. The signals <b>34</b> and <b>36</b> may be sequentially emitted by the reader <b>22</b>, in order to power the device <b>10</b>, and to interrogate or command the RFID device <b>10</b>. Alternatively, in the situation where a reduced amplitude modulation depth data signal is used, the device <b>10</b> may receive power and commands simultaneously.

0044Both of the signal types <b>34</b> and <b>36</b> are received by the antenna elements <b>30</b> and <b>32</b> of the device <b>10</b>. The element <b>32</b> acts as a power ground for the device <b>10</b>. Signals from the antenna element <b>30</b> pass through a rectifier <b>40</b>, and into a chip logic block <b>41</b>. Specifically, the incoming signal from the rectifier <b>40</b> enters the chip logic block <b>41</b> through a power port <b>42</b> and a data in port <b>44</b>. The data out port <b>48</b> of the logic block <b>41</b> may be coupled to a modulation transistor <b>50</b> for changing impedance of the device <b>10</b>. The modulation transistor <b>50</b> is coupled to both of the antenna elements <b>30</b> and <b>32</b>. The incoming power signal <b>34</b> provides power for operating the chip logic block <b>41</b>. The logic block <b>41</b> acts upon commands that are received by the incoming instruction signal <b>36</b>. These instructions may involve having the logic block <b>41</b> modify a register in a memory location <b>56</b>. Instructions may also involve sending a signal through the data out port <b>48</b> to modulate impedance through the modulation transistor <b>50</b>. This change in impedance may be detected by the reader/detector <b>22</b> in its effect on the unmodulated power signal <b>34</b>. The antenna element <b>32</b>, which functions as a power ground, is also coupled to a ground port <b>60</b> of the logic block <b>41</b>.

0045The logic block <b>41</b> may be configured such that when a predetermined value is placed in a memory location <b>56</b>, a switch <b>62</b> is tripped to provide high voltage through a power output port <b>64</b> and to the display <b>16</b>. (A predetermined input signal may be used to put the value in the memory location <b>56</b>.) The “high voltage” supplied through the power output port may be a rectified supply voltage, such as at around 1-2 volts. The display <b>16</b> is also coupled to the ground port <b>60</b>. Providing high voltage through the power output port <b>64</b> causes a change in a visual indicator <b>18</b> of the display. Thus, the device <b>10</b> is configured such that writing of a predetermined value to the memory location <b>56</b> also results in display of the visual indicator <b>18</b>.

0046The signal sent to the RFID device <b>10</b> to trigger display of the visual indicator <b>18</b> may be a “kill” or “self-destruct” signal that disables operation of the logic <b>41</b> of the chip <b>12</b>. Examples of such signals may be found in Technical Report: 13.56 MHz ISM Band Class 1 Radio Frequency Identification Tag Interface Specification: Candidate Recommendation, Version 1.0.0 (describing a Destroy command); Draft Protocol Specification For a 900 MHZ Class 0 Radio Frequency Identification Tag (describing a Kill function); and Technical Report: 860 MHz-930 MHz Class I Radio Frequency Identification Tag Radio Frequency &amp; Logical Communication Interface Specification Candidate Recommendation, Version 1.0.1. All of these reports are published by the Auto-ID Center of the Massachusetts Institute of Technology, all are available on line at www.epcglobalinc.org, and all are incorporate herein by reference.

0047The above-described de-activation of the chip <b>12</b> may be a reversible or irreversible operation. Further, the device <b>10</b> may be configured so that only some of kill or disable signals trigger activation of the display <b>16</b>. For example, the device <b>10</b> may be configured so that a password, key, or other specific type of kill command triggers activation of the display <b>16</b>.

0048<figref idref="DRAWINGS">FIG. 4A</figref> illustrates one possible alternate configuration for providing switchable power to the display <b>16</b>, through a pair of input/output ports <b>65</b> and <b>66</b> that are part of the logic block <b>41</b>. A pair of field effect transistors <b>67</b> and <b>68</b> are coupled to a system supply voltage Vdd and a system ground voltage Vss. An internal driver <b>69</b> of the logic block <b>41</b> provides signals X and Y to the field effect transistors <b>67</b> and <b>68</b> to direct the desired voltage to the ports <b>65</b> and <b>66</b>. The signals X and Y may configure the field effect transistors <b>67</b> and <b>68</b> to provide the same voltage, either Vdd or Vss, to both of the ports <b>65</b> and <b>66</b>, providing no voltage difference across the display <b>16</b>. The signals X and Y may also be used to provide a voltage difference across the ports <b>65</b> and <b>66</b> in either direction (and thus across the display <b>16</b> as well), with the supply voltage Vdd supplied to either port, and with ground voltage supplied to the other port. Thus the display <b>16</b> may be driven in either direction.

0049Various forms of voltage converters or voltage multipliers may also be used as part of the device <b>10</b>, as illustrated in <figref idref="DRAWINGS">FIGS. 4B and 4C</figref>, to increase the supply voltage of the device <b>10</b>. The voltage multiplier <b>70</b> shown in <figref idref="DRAWINGS">FIG. 4B</figref> shows a field effect transistor <b>72</b> coupled to a supply voltage Vdd and a ground voltage Vss. A pair of diodes <b>74</b> and <b>75</b> and a pair of capacitors <b>76</b> and <b>77</b> are used to increase the output voltage <b>78</b> of the voltage multiplier. Depending upon the input signal X to the field effect transistor <b>72</b>, the output voltage <b>78</b> may be up to two times the supply voltage Vdd. The output voltage <b>78</b> may be used to drive the display <b>16</b> (<figref idref="DRAWINGS">FIG. 4A</figref>), or may be fed to further voltage multipliers.

0050<figref idref="DRAWINGS">FIG. 4C</figref> illustrates a voltage converter <b>80</b> that includes an inductor <b>82</b> coupled to a supply voltage Vdd. A transistor <b>83</b> is coupled to output from the inductor <b>82</b> and to a ground voltage Vss. A diode <b>84</b> and an output capacitor <b>86</b> also make up part of the voltage converter <b>80</b>. The transistor <b>83</b> sequentially shorts the inductor <b>82</b> across the supply voltage Vdd and the ground voltage Vss. As the current through the inductor <b>82</b> changes, it generates a voltage proportional to the rate of change of the current. This change in voltage charges the output capacitor <b>86</b> to a higher voltage, resulting in a higher output voltage <b>88</b> for the voltage converter <b>80</b>.

0051The voltage converters <b>70</b> and <b>80</b> may be incorporated into the device <b>10</b> in any of a variety of suitable ways. The converters <b>70</b> and <b>80</b> may be parts of the chip <b>12</b>, or may alternatively be separate from the chip <b>12</b>. Multiple converters may be utilized, for example being placed in series, to achieve a desired voltage for driving the chip <b>12</b> and/or the display <b>16</b>.

0052<figref idref="DRAWINGS">FIG. 4D</figref> shows a variation of the passive device of <figref idref="DRAWINGS">FIG. 2</figref>, in which an energy storage device <b>90</b>, such as a battery or capacitor, is added. The energy storage device <b>90</b> is configured so as to be coupled to the display <b>16</b> when a display control switch <b>92</b> is activated. Energy in the energy storage device <b>90</b> may be used in driving operation of the display <b>16</b>. The device <b>10</b> may be configured so that the energy storage device <b>90</b> is charged or re-charged as excess power (beyond what is needed to operate the chip <b>12</b>) is received by the antenna elements <b>30</b> and <b>32</b>. A voltage converter <b>94</b>, such as the voltage multiplier <b>79</b> (<figref idref="DRAWINGS">FIG. 4B</figref>) or the voltage converter <b>80</b> (<figref idref="DRAWINGS">FIG. 4C</figref>), may be included to provide increased voltage to the display <b>16</b>, and to the energy storage device <b>90</b>.

0053The passive devices <b>10</b> described are but a few of the wide variety of possible configurations for the RFID device <b>10</b>. The devices illustrated in <figref idref="DRAWINGS">FIGS. 2 and 4</figref> show a configuration suitable for use with UHF RF energy. It will be appreciated that other suitable configurations may be utilized at that frequency or at other suitable frequencies.

0054Although the RFID devices <b>10</b> in <figref idref="DRAWINGS">FIGS. 2 and 4</figref> are described above as fully passive devices, it will be appreciated that the device in <figref idref="DRAWINGS">FIG. 4</figref> may correspond to a semi-passive device, where the energy storage device <b>70</b> provides power to the chip <b>12</b>, as well as providing power to the display <b>16</b>. It will be appreciated that the attachments of the chip <b>12</b> and the energy storage device <b>70</b>, both tuned to the display <b>16</b>, may also be made part of an active RFID device.

0055<figref idref="DRAWINGS">FIG. 5</figref> shows a high-level flowchart of one possible sequence of events in operation of the passive RFID device <b>10</b> shown in <figref idref="DRAWINGS">FIGS. 2 and 4</figref>. In step <b>100</b> the RFID device <b>10</b> maintains itself in a loop, while waiting for an instruction signal to be received to de-activate operation of the chip <b>12</b>. It will be appreciated that other operations of the RFID device <b>10</b> may be accomplished while in this loop. Once an instruction signal is received to de-activate the chip <b>12</b>, a change is made in the memory block or location <b>56</b>, as indicated in step <b>102</b>. In step <b>104</b>, power is provided to the display <b>16</b> through the power out port <b>64</b>. The power may be the same high voltage as used for operation of the chip <b>12</b>. This power may be provided by the power signal <b>34</b> received through the antenna elements <b>30</b> and <b>32</b>. Alternatively, for a semi-passive chip, the power for operation of the chip <b>12</b> may be provided by an energy storage device, such as a battery or capacitor, that is built into the chip <b>12</b>, or is elsewhere in the RFID device <b>10</b>. As another alternative, there may be a specific energy storage device <b>70</b> for powering the display <b>16</b>. The powering of the display <b>16</b> activates or actuates the visual indicator <b>18</b>, providing a visual indication of the change of state of the operation of the RFID device <b>10</b>. Finally, in step <b>88</b>, impedance of the device <b>10</b> may be modulated by sending a signal through the data out port <b>48</b> to the modulation transistor <b>50</b>.

0056The steps in the flowchart of <figref idref="DRAWINGS">FIG. 5</figref> are but one way that the RFID device <b>10</b> of <figref idref="DRAWINGS">FIGS. 2 and 4</figref> may be operated. It will be appreciated that the steps shown in <figref idref="DRAWINGS">FIG. 5</figref> may occur in a different order, or that some of the steps may be augmented or omitted, if suitable. As an example of an additional step that may be part of such an operation, the chip <b>12</b> may be configured to send a signal (either by reflection or transmission) confirming that the predetermined signal (such a “kill” signal instructing the chip <b>12</b> to disable the device <b>10</b>) has been received and acted upon by the device <b>10</b>.

0057The providing of a power input to the display <b>16</b> may be accomplished in a wide variety of suitable ways. One way is to configure the chip <b>12</b> so that when a triggering signal is received, high voltage is provided to and maintained to the display <b>16</b>. This allows possible refreshing of the high voltage provided to the display <b>16</b>, when the device <b>10</b> receives more power from the power signal <b>34</b> of the reader/detector <b>22</b>. Such a configuration may be desirable where the display <b>16</b> is of a type that may benefit from periodic refreshing.

0058Another way of configuring the device <b>10</b> is to provide the high voltage to the display <b>16</b> for only a limited period of time. This configuration may be suitable for use when actuation of the display <b>16</b> involves an irreversible process, for example, the mixing of chemicals. Removal of the high voltage from the display <b>16</b> may be desirable to prevent damage to other parts of the device <b>10</b>, or to prevent undesirable effects on the display <b>16</b>.

0059The visual indicator <b>18</b> may undergo a permanent (irreversible) change when power is applied to the display <b>16</b>, which makes a permanent visually-readable display. As one alternative, the change in the visual indicator <b>18</b> may be permanent, but may be only intermittently displayable, such as being displayable only when power is applied to the RFID device <b>10</b> by having it in proximity to a reader <b>22</b> that is emitting an unmodulated power signal <b>34</b>. As a further alternative, the visual indicator <b>18</b> may undergo a reversible change when power is applied to the display <b>16</b>. Some other process, such as sending a different power signal to the display <b>16</b>, may cause reversal of the indication provided by the visual indicator <b>18</b>.

0060The energy storage device <b>70</b> may be part of the display <b>16</b>, may be part of the chip <b>12</b>, or may be a separate part of the RFID device <b>10</b>. The energy storage device <b>70</b> may be a printed super capacitor or a printed battery. The energy storage device <b>70</b> may be a traditional battery, for example flexible thin-film batteries sold by Cymbet Corporation of Elk Ridge, Minn., USA, which are described further in International Publication WO 01/73864, which is hereby incorporated by reference in its entirety.

0061What follows now are descriptions of some possible mechanisms for use in the display <b>16</b>. <figref idref="DRAWINGS">FIG. 6</figref> illustrates an electrochromic display <b>116</b> that is one version of the display <b>16</b>. The electrochromic display <b>116</b> includes a film <b>120</b> upon which there is an electrolyte <b>122</b>. On the electrolyte <b>122</b> there are electrochromic material portions <b>124</b> and <b>126</b>. The electrochromic material portions <b>124</b> and <b>126</b> may be configured to have the desired shape for the visual indicator <b>18</b> (<figref idref="DRAWINGS">FIG. 1</figref>). Conductive ink portions <b>128</b> and <b>130</b> are atop respective of the electrochromic material portions <b>124</b> and <b>126</b>. A power supply <b>132</b> is coupled to the conductive ink portions <b>128</b> and <b>130</b>, to provide a potential across the conductive ink portions <b>128</b> and <b>130</b>. When electric current flows from the power supply <b>132</b>, the electrochromic materials <b>124</b> and <b>126</b> become black and stay black. The electrochromic display <b>116</b> requires an electrical current on the order of a few small amps, with a voltage on the order of 0.5V. The electrochromic display <b>116</b> allows complex shapes, such as multiple letters, to be displayed in a single step. The display in the electrochromic display <b>116</b> may be reversed by reversing the current flow between the electrodes of the display <b>116</b>.

0062The electrochromic display <b>116</b> may have other suitable elements, such as suitable electrodes, and suitable layers for providing protection to the operative portions of the display <b>116</b>. Suitable electrochromic materials include electrochromic metal oxides such as WO₃and antimony-doped tin oxide. It will be appreciated that a wide variety of other well-known electrochromic materials, such as suitable metals, viologens, or intrinsically conductive polymers, may be employed. The conductive ink <b>128</b> and <b>130</b> may be a silver ink. Some or all of the layers of the electrochromic display <b>116</b> may be printable layers. Further details regarding electrochromic displays may be found in International Publication No. WO 01/37244, in U.S. Patent Publication No. 2002/0171081, and in U.S. Pat. Nos. 4,723,656, and 4,225,216. The entire disclosures of the above patents and publications are incorporated herein by reference.

0063<figref idref="DRAWINGS">FIG. 7</figref> shows an alternative configuration for the display <b>16</b>, a liquid crystal display <b>146</b>. The liquid crystal display <b>146</b> includes a pair of films <b>148</b> and <b>150</b>, for example being plastic films, which enclose the working parts of the display <b>146</b>. The films <b>148</b> and <b>150</b> may enclose a pair of electrodes <b>152</b> and <b>154</b>, which are coupled to a power supply <b>156</b>. Between the electrodes <b>152</b> and <b>154</b> are spacers <b>160</b>, such as small plastic spheres, and a liquid crystal material <b>164</b>. The liquid crystal material <b>164</b> may be a suitable liquid crystal material, such as a suitable cholesteric liquid crystal material, that maintains a desired state once an electric field is applied. One of the electrodes <b>152</b> may be a transparent electrode, for example being an indium tin oxide electrode. The other electrode <b>154</b> may be made of silver ink with carbon particles added. The electrode <b>154</b> may include coloration so that it is color-matched to a scattered mode of the liquid crystal material <b>164</b>. Alternatively, both of the electrodes <b>152</b> and <b>154</b> may be substantially transparent.

0064The liquid crystal material <b>164</b> may have two states, a first state where the molecules are randomly oriented, and in which light is scattered and the material is opaque; and a second state in which the liquid crystal molecules are oriented in the direction of an applied electric field across the electrodes <b>152</b> and <b>154</b>, making the liquid crystal material <b>164</b> substantially transparent. The display <b>146</b> may be changed from one state to another by applying a sufficient potential from the power generator <b>156</b>, across the electrodes <b>152</b> and <b>154</b>, to cause the liquid crystal material <b>164</b> to re-orient itself. Thus, the liquid crystal material <b>164</b> may selectively be substantially opaque or substantially transparent, either obscuring or revealing the underlying material of the electrode <b>154</b>. Thus, for instance, color in the electrode <b>154</b> may either be obscured or displayed. It will be appreciated that indicia, such as words or symbols, may be printed in the electrode <b>154</b>, or elsewhere on the film <b>150</b> (if the electrode <b>154</b> is substantially transparent), with the indicia being selectively revealed or obscured by changing the state of the liquid crystal material <b>164</b>.

0065One example of a suitable reflective and bi-stable liquid crystal material is a Surface Stabilized Cholesteric liquid crystal or SSChLC, having the following formulation: 82.1% liquid crystal ZLI-5400-100 (Merck), 5.7% chiral compounds ZLI-4572 (Merck), and 12.2% CB-15. Spacers of 5 microns may be used to define the cellgap. Both substrates may be coated with a polyimide, e.g., the Nissan Chemical's polyimide SE-610. An absorber may be applied on the bottom surface of the device. Such a device displays either green or black.

0066The above technology may be modified to display white and black, with the liquid crystal mixture having the following formulation: 80.8% liquid crystal ZLI-5400-100 (Merck), 5.5% chiral compounds ZLI-4572 (Merck), and 13.7% ZLI-3786 (Merck). Further details regarding liquid crystal materials may be found in U.S. Pat. Nos. 5,251,048 and 5,625,477, both of which are herein incorporated by reference in their entireties.

0067<figref idref="DRAWINGS">FIG. 8</figref> illustrates a thermochromic display <b>176</b> that may be used as yet another alternative for the display <b>16</b>. The thermochromic display <b>176</b> includes a resistive track <b>180</b> of conductive material, and a thermochromic material <b>184</b> on at least part of the resistive track <b>180</b>. The resistive track <b>180</b> is coupled to contacts of the chip <b>12</b>. Providing power to the resistive track <b>180</b> causes current flow in the track <b>180</b> that heats the conductive material, and the nearby thermochromic material <b>184</b>. This heating may cause a color change in the thermochromic material <b>184</b>, thus providing a visual indicator.

0068An example of a suitable thermochromic material is a material sold under the designation R45 Matsui, Inc. by Matsui Chemical Company of Kyoto, Japan. It will be appreciated that many other suitable thermochromic materials are available, and that thermochromic materials may be selected with any of a wide variety of characteristics. It will further be appreciated that the visual change in the thermochromic material <b>184</b> is temporary, and fades soon after current is no longer applied to the resistive track <b>180</b>. However, it will be appreciated that the thermochromic display <b>176</b> may be configured so that the visual indicia is refreshable. That is, whenever power is applied to the RFID device <b>10</b>, currents may flow anew through the resistive track <b>180</b>, thereby heating and again changing color of the thermochromic material <b>184</b>. Further details concerning thermochromic displays may be found in U.S. Pat. No. 5,600,231, which is herein incorporated by reference in its entirety.

0069<figref idref="DRAWINGS">FIG. 9</figref> illustrates still another possible configuration for the display <b>16</b>, in this case a display <b>216</b> that involves mixing of two chemically-reactive materials. The display <b>216</b> includes an indicator material <b>218</b>, a diffusion control layer <b>220</b>, a barrier layer <b>222</b> that is coupled to a power supply <b>226</b>, and a reactive layer <b>230</b>. A color change in the display <b>216</b> occurs when the reactant material <b>230</b> and the indicator material <b>218</b> are mixed together. The barrier layer <b>222</b> initially prevents passage of the reactant layer <b>230</b>. The barrier layer <b>222</b> may be a suitable material, such as a wax, that loses its structural material when heated. When power is applied, using the power supply <b>226</b>, across the barrier <b>222</b>, the barrier <b>222</b> breaks down, allowing passage of the reactant material <b>230</b>. The reactant <b>230</b> diffuses through the diffusion control layer <b>220</b>, and eventually reaches the indicator material <b>218</b>. Once the reactant material <b>230</b> reaches the indicator material <b>218</b>, a color change occurs in the indicator <b>218</b>, due to a chemical reaction. The diffusion control layer <b>220</b> controls the timing and rate of the reaction between the reactant <b>230</b> and the indicator <b>218</b>. Many well-known chemically-reactive pairs of materials may be utilized. The chemically-reactive material display <b>216</b> may be on the order of a few microns thick.

0070As another possibility, the display <b>16</b> may have multiple segments connected in parallel, all of initially the same color. Certain of the segments may have a small amount of a suitable chemical inhibitor added to them as they are printed. When a voltage is applied across the display, only those segments without the inhibitor change color, displaying a desired visual indicator. The segments may be such that chemical analysis (and destruction of the device) would be required to determine a priori which of the segments contain the inhibitor. Such a display may be provide additional security against determination of the visual indicator by tampering with the device <b>10</b>.

0071It will be appreciated that other types of displays are possible for use as part of the display <b>16</b>. For example, ferrofluids may be utilized. Ferrofluids are fluids that change in appearance or become visible with the application of a magnetic field. Examples of such fluids are described in U.S. Patent Publication No. 2004/0074973, the disclosure of which is herein incorporated by reference. It may also be possible to utilize electrophoretic displays.

0072It will be appreciated that other elements, for instance, color filters, may be added to the displays described above, in order to achieve desired visual effects. Other types of elements may also be included to provide various visual effects. For example, additional visual effects, such as color change and intermittently flashing elements, may be achieved.

0073It will be appreciated that a wide variety of symbols may be displayed as a visual indicator, in order to indicate a wide variety of different information. <figref idref="DRAWINGS">FIG. 10</figref> shows an example of an indicator <b>318</b> (a letter “X”), which may be displayed to indicate inoperability of an RFID device.

0074<figref idref="DRAWINGS">FIG. 11</figref> illustrates another example, in which a discount or sale price <b>320</b> is displayed as a visual indicator when a suitable instruction is sent to the RFID device <b>10</b>. It will be appreciated that displaying indicia indicating a discount may be used as part of a promotional theme, for instance, in order to encourage customer involvement. Another possibility is that a bar code could be changed to represent a modified identity for a product, so that a new price is associated with the product during a checkout process.

0075Use of visual indicators may also be useful in theft-prevention, and in merchandise authentication. The function within the RFID device <b>10</b> may be instituted when an object coupled to the device is sold, such that either a permanent visual indicator is displayed, or a refreshable visual indicator is displayed. Return for refund of improperly acquired merchandise may thus be prevented, as the merchandise may lack the permanent or transient (refreshable) visual indicator indicating that a proper sale has been made. Additionally, a display may be configured to provide a visual indicator indicating an intended source for a product. Such a visual indicator may aid in preventing sale of gray market goods.

0076As illustrated in <figref idref="DRAWINGS">FIGS. 12 and 13</figref>, the visual indicator may be used to make information available only upon actuation of the display <b>16</b>. As indicated in <figref idref="DRAWINGS">FIG. 12</figref>, the display <b>16</b> may obscure certain underlying information, such as underlying printed information. Once the display <b>16</b> has been activated, for instance by de-activating functionality of the chip <b>12</b> of the RFID device <b>10</b> (<figref idref="DRAWINGS">FIG. 1</figref>), the display <b>16</b> may display underlying informational material, such as a product serial number <b>330</b>.

0077<figref idref="DRAWINGS">FIG. 14</figref> shows another embodiment, wherein an RFID device <b>410</b> has a chip <b>412</b> that has an antenna <b>414</b> and a display built on the chip <b>412</b>. On an upper surface <b>420</b> of the chip <b>412</b> is the antenna <b>414</b>, which may be a coil antenna, a low frequency antenna, or a high frequency antenna. The antenna <b>414</b> is operatively coupled to the chip <b>412</b>. A ground electrode <b>422</b> and an input/output electrode <b>424</b> of the display <b>416</b> are also coupled to corresponding ports of the chip <b>412</b>. The ground electrode <b>422</b> may be a transparent electrode, made of a suitable material such as indium tin oxide. A display material <b>426</b> is between the electrodes <b>422</b> and <b>424</b>, such that when a voltage difference is applied across the electrodes <b>422</b> and <b>424</b>, a visual indicator is displayed in the display <b>416</b>.

0078The RFID device <b>410</b> provides a compact and unobtrusive way of indicating a change of state of the device <b>410</b>. The display material <b>426</b> may be a suitable UV responsive material. The device <b>410</b> may be configured such that the material <b>426</b> is visible against an object, such as a salable product, only under certain conditions, such as when the object has not bee properly sold, registered, or cleared, for example.

0079Another potential application for the RFID device <b>10</b> with the visual display <b>16</b> is in the area of RFID devices in labels attached to air cargo containers. It is often required that the operability of such devices be disabled during aircraft flight, because of concerns that operable RFID devices may interfere with aircraft operations, such as interfering with operation of aircraft control systems or aircraft communications systems. Having a visual indication of the state of operability of the RFID devices may facilitate confirming that the devices are disabled prior to aircraft flight, such as by sending signals to the devices causing the devices to temporarily suspend normal operations, for example by entering a “sleep” mode. The visual indicator may also facilitate confirmation of resumption of normal device operating state. Resumption of the normal device operating state may be accomplished, for example, by the sending to the device of a special “wake up” signal.

0080A further possible application for the RFID device <b>10</b> is in making numbers or symbols on a lottery ticket or other form of gambling media, visible on command. The command to change state may be such that it is only issued when payment has been authorized (such as at an electronic point of sale terminal), when money has been transferred to the lottery operator, and when a predetermined change display code, particular to that ticket or other form, is received back from a lottery or authenticating company.

0081Another possible application is in a re-usable transportation ticket, such as a bus or train ticket or fare card. The display <b>16</b> of a device <b>10</b> incorporated into such a ticket or fare card may display an indication of the number of rides remaining or amount of fares still chargeable on the ticket or card. Such a display may be a simple color change device that (for example) switches from green to yellow to red as the available fare amount of the ticket or card is used up. Of course, more precise information may be displayable by more complicated displays. Such a display may be reversible as the fare amount of the ticket or card is replenished.

0082Software or other products may be shipped including an RFID device <b>10</b> that obscures a code necessary for use of the object. The device <b>10</b> may be configured to have its state changed at a point of sale, so as to make the code visible, thus making the product usable. Theft or other diversion of such products may thus be prevented, as the products are practically useless without the code. As a further precaution, the device <b>10</b> may be configured so that any attempt to remove the obscuring layer damages the underlying code, such as an underlying printed code.

0083It will be appreciated from the foregoing that the visual indicator <b>18</b> of the display <b>16</b> may be used in a wide variety of applications, to communicate information as triggered by some state of operation of the RFID device <b>10</b>. The information may involve the operability of the chip <b>12</b> or of the device <b>10</b> as a whole, or alternatively may simply indicate the state of an internal memory location or logic block of the chip <b>12</b>. The visual indicator <b>18</b> may be used to directly communicate information regarding the operative state of the RFID device <b>10</b>. Alternatively, or in addition, the visual indicator <b>18</b> may be used to communicate a wide variety of additional information, such as information that is for some reason not to be initially known by a viewer of the RFID device <b>10</b>.

0084Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.