WO2005020192A1 - Radio-scannable label for controlling a continuous cold chain - Google Patents

Abstract

The invention relates to a radio-scannable label (TAG) for contactless scanning by means of a writer/reader and at least one microcontroller (MC) provided with electrical means and connected to an antenna (ANT). The inventive radio-scannable label comprises at least one temperature measuring cell (Z1-Zn). Said temperature measuring cells are electrically connected to the microcontroller and irreversibly modify the electrical characteristic (R, C) thereof when an associated pre-determinable temperature (T1-Tn) is exceeded. The electrical means of the label detect the respective modification of the electrical characteristic, determine a maximum exceeded temperature value, and send a corresponding data value to the writer/reader. In a particular form of embodiment, the temperature measuring cell comprises a substrate (SUB) with microcapsules. The measuring process can be initiated by means of a current pulse by a security layer (SI) bordering the substrate.

Description

RADIO-INQUIRABLE LABEL FOR CONTROLLING A CONTINUOUS COOLING CHAIN

Radio-interrogable label, in particular for checking a continuous cold chain when transporting or storing chilled or frozen food

The invention relates to a radio-interrogable label for contactless interrogation with a read / write device and with at least one microcontroller, which is connected to an antenna. The invention further relates to the use of such a label in the food industry and to an identification system with a read / write device and at least one radio-questionable label. From US 4,996,104 a temperature-dependent material and a label for application to temperature-sensitive foods is known, which is provided with such a material. The material is provided with a dye and has a large number of so-called microcapsules, which burst when the label is printed. When a predeterminable temperature is exceeded, the material liquefies and dissolves to form a colored trace, which indicates that the predeterminable temperature has been exceeded.

Temperature-sensitive foods include cold food such as Dairy products, vegetables etc. as well as frozen foods such as frozen fish, frozen meat etc. understood.

The disadvantage here is that with a large number of superimposed foods, such as, for example, during the transport of the foods in a container, during storage in a food store or during the sales display, the critical storage temperature of a food is exceeded is not recognizable at a glance. In this case the are temperature sensitive To inspect food individually by hand, and to sort out foods that have a trace of color. This is cumbersome, error-prone and time-consuming.

It is therefore an object of the invention to provide a label which allows automated and reliable checking of chilled or frozen foods for compliance with a continuous cold chain.

The object is achieved according to the invention with a radio-interrogable label for contactless interrogation with a read / write device according to the features of patent claim 1.

The radio-questionable label has at least one microcontroller with electrical means, an antenna that is electrically connected to the microcontroller, and one or more temperature measurement lines. The temperature measuring cells are electrically connected to the microcontroller and irreversibly change their electrical properties when a respective predeterminable temperature is exceeded. The electrical means of the label detect the respective change in the electrical property, determine a maximum temperature value exceeded and send a corresponding data value to the read / write device. The microcontroller is an advantageous possible embodiment of an electronic control unit for controlling the radio-questionable label. The electrical means are e.g. a microprogram or a software routine, which e.g. be carried out by an electronic switching mechanism of the microcontroller.

This is associated with the great advantage that automated detection of chilled or deep-frozen foodstuffs is possible with a view to exceeding a maximum temperature. This is advantageously also possible with a large number of food items lying one above the other in a container. As a result, an automatic downstream sorting of the detected food items is possible, so that they can no longer be traded, sold and therefore not consumed.

A large number of temperature measuring cells can advantageously be used to determine the degree of temperature overshoot, and, if the temperature is critical for the respective food, is slightly exceeded, it can also be offered as a discounted product or as a product with a shortened expiry date.

In one embodiment, the temperature measuring cells have a substrate with a minimum conductivity, which melts when a predetermined temperature is exceeded.

This advantageously allows the change in the electrical property of the temperature measuring cells to be measured, since their changes in terms of the electrical property, such as electrical resistance and electrical capacitance, can be measured in a simple manner. A change in resistance can e.g. be measured using an analog comparator circuit. A change in electrical capacity can e.g. can be measured by measuring the associated time at a constant charging current of the capacitance and comparing it with a reference value.

In a further embodiment, the substrate for detecting the respective change in the electrical property forms at least one conductive connection between at least two conductive electrodes if the substrate has a wetting effect in the molten state. In a complementary sense, the substrate connects at least two conductive electrodes to detect the respective change in the electrical property, at least one conductive connection being interrupted if the substrate does not have a wetting effect in the molten state. Whether a liquid, such as the above-mentioned substrate in the molten state, has a wetting or non-wetting effect, ie whether the liquid tends to flow on a carrier material or strives to contract depends essentially on the material pairing

Liquid and carrier. For example, a certain roughness of the wearer, e.g. in the case of a fleece, the wetting process due to the capillary effect.

In particular, the respective temperature measuring cell has a changed electrical capacitance and / or a changed electrical resistance as a detectable change in the electrical properties when at least one electrical connection is formed or interrupted. A change in the electrical resistance can advantageously be measured if the substrate contains a small proportion of a conductive substance, in particular a salt dissolved in water, e.g. NaCl, or has an electrolyte. If an electrical connection between two conductive electrodes is interrupted by contraction of the substrate during melting, a measuring current impressed between the two electrodes is also interrupted. Even if the substrate were electrically non-conductive, a change in capacitance of the temperature measuring cell would be detectable, since the substrate acts like a dielectric of a capacitor between two electrically conductive electrodes and consequently changes in shape of the substrate also change the associated dielectric value.

A hydrocarbon such as e.g. an alkane, in particular a dodecane, can be used. The

Properties and advantages of dodecane are sufficiently described in the above-mentioned US 4,996,104.

In a preferred embodiment, the respective substrate of a temperature measuring cell has a different one

Melting temperature, such as in a temperature range from -25 ° C to 10 ° C. For example, for frozen foods such as for fish or seafood, it is important to determine whether a temperature of -18 ° C has been exceeded. For dairy products, for example, it is important to exceed a temperature of 6 ° C. Depending on the food, a temperature range in 1 ° C steps around a critical temperature "around" can be useful. For the deep-freeze mentioned above, this would be, for example, nine temperature cells with a measuring range of -22 ° C, -21 ° C, .., -15 ° C, -14 ° C. To determine the respective substrate melting point, for example alkanes with different valences and with different melting temperatures, such as undecane, tridecane, tetradecane, pentadecane, etc., or mixtures of these can be used in order to be able to set a predefinable melting point as precisely as possible. Another possibility is, for example, to determine the melting temperature of the substrate

Volume ratio of a hydrocarbon and a conductive substance to set.

In a further embodiment, the substrate has a dye. This can also be optically advantageous

Exceeding a predeterminable critical temperature can be determined by the colored substrate.

In a preferred embodiment, the substrate is embedded in microcapsules with a diameter in a range from 1 to 50 μm. The microcapsules preferably have a shell made of gelatin or of a material with comparable physical properties.

This has the great advantage that the substrate can be applied to the radio-questionable label during production, even at room temperature. Although the previously exemplary hydrocarbons of the substrate are in the liquid state, the substrate is prevented from flowing or contracting through the shell of the microcapsules. The effect of the substrate to form a possible change in the electrical properties of a Temperature measuring cell can advantageously only be enabled or initiated when the radio-questionable label has been attached to or on a refrigerated or frozen food item to be monitored and the radio-questionable label itself has then cooled below the temperature to be monitored. The microcapsules burst by means of mechanical pressure on, for example, a specially marked optical marking of the radio-questionable label. If the temperature to be monitored were exceeded, the substrate would now advantageously flow away or contract.

For the reproducibility of the previous process, microcapsules with a diameter in a range from 5 to 10 μm have been found to be advantageous.

In a particular embodiment, the circuit elements of the radio-questionable label consist mainly of organic compounds which can be printed on a plastic carrier layer of the radio-questionable label.

By means of a printing process, e.g. an inkjet printing process, these are then printed on the carrier layer. Such flexible transponders are also referred to as "smart labels" or "integrated plastic chips" (IPC). The printable organic compounds are conductive, insulating or semiconducting with regard to their electrical properties. The conductor tracks applied to the plastic carrier layer and / or the circuit elements made of mainly organic connections that can be printed on the plastic carrier layer have e.g. a thickness of 30 µm. The energy and data transmission between the transponder and the read / write device is preferably carried out in an inductively coupled manner.

A radio-questionable label can be advantageous in large

Quantities and i. for the monolithic process are manufactured significantly cheaper. In addition, the radio questionable labels are flexible and can be offered as "tear-off goods", rolled up on a roll.

The substrate is preferably embedded between two flat and electrically insulating layers and surrounded by at least two conductive electrodes. The flat and electrically insulating layers and the adjacent electrically conductive electrodes thus form a closed chamber or a reservoir for the embedded substrate. The substrate is thus protected from environmental influences.

In a special embodiment, at least one of the conductive electrodes forms a channel. When the substrate melts, this channel acts like a capillary tube. The substrate flows through this tube and at the end of the

Channel creates a conductive connection in a contact area with another conductive electrode. In the opposite sense, i.e. in the non-wetting case of the substrate, a previously filled or printed channel can correspondingly empty during melting and dissolve a previously existing conductive connection.

In a special and preferred embodiment of the radio-interrogable label, an electrically conductive fuse layer is installed, printed or can be inserted there in the channel. This securing position seals the channel. According to the invention, this securing position, which i.Vgl. to the flat and low-resistance conductive layers of the electrodes is high-resistance, release the channel by means of a current pulse. The fuse position acts like an electrical fuse, which "burns out" in the event of overcurrent and irreversibly destroys the membrane separating the channel.

The fuse channel is advantageously connected to at least two of the conductive electrodes. A current pulse can then enter the microcontroller via further electrical means Safety channel can be fed. Successful "burnout" of the fuse layer can be queried by querying one of the electrically conductive electrodes when it is connected to the fuse layer. If necessary, for example if the fuse position has not yet been destroyed, a further current pulse can be fed in controlled by the microcontroller.

The data and energy transmission is preferably carried out by inductively coupled means, e.g. based on the ISO / IEC 15693 or 14443 standard.

The electronic circuit parts of the radio-interrogable label are advantageously supplied with electrical energy for the duration of the data transmission and for the duration of the data reception via the magnetic field emitted by the read / write device. As a result, a battery in the radio-interrogable label can advantageously be dispensed with.

When reading, i.e. when receiving data, at least the maximum temperature value exceeded can be determined in the temperature measuring cells and a corresponding data value can be received.

When sending data, for example, a command from the read / write device can be sent to the microcontroller of the radio-interrogable label to release the above-mentioned fuse position in the channel in one or more temperature measuring cells. This is preferably done by feeding the electrical energy stored in the resonant circuit from the antenna coil and from the storage capacitor. For example, the entire energy content of the storage capacitor can be connected to the associated electrodes of the fuse position as a short current pulse with a relatively high current value of a few amperes via a transistor that can be controlled by the microcontroller. Alternatively, it is also possible to attach a separate induction coil on the radio-interrogable label, into which a high-frequency and very strong magnetic field can be briefly induced by means of a "safety pistol". The high alternating current induced in the induction coil then quickly melts the fuse position.

To release the temperature measurement in the above Sense would be e.g. punching a hole in the radio-questionable label is also conceivable, e.g. then initiate the temperature measurement process by penetrating oxygen. Another possibility would be e.g. initialization with UV light. Finally, it would be a possibility that if a predeterminable temperature, e.g. the melting or boiling point of a substrate, the respective substrate runs out or runs out of the punched hole.

The above Labels which can be queried by radio can be used in an identification system with a read / write device and can also be used advantageously in the food industry.

The invention is explained in more detail with reference to the following figures. It shows

1 shows an exemplary structure of a radio-interrogable label on an inductively coupled basis in a top view,

2 shows an exemplary measuring circuit for detecting the changed resistance of a temperature measuring cell,

3 shows an exemplary structure of a temperature measuring cell with a securing position according to the invention in a plan view, and

4: the exemplary temperature measuring cell from FIG. 3 in a sectional view. 1 shows a top view of an example of a structure of a radio-questionable label TAG on an inductively coupled basis, which can be queried or read out by means of a read / write device (not shown). A microcontroller MC, in particular an RFID chip, can be seen inside the radio-questionable tag TAG. A spiral coil antenna ANT is connected to this. The coil antenna ANT and MikrocontroUer MC form a so-called transponder TAG. The coil antenna ANT itself consists of a conductor track applied, for example vapor-deposited, on a carrier layer. The microcontroller MC is also connected to temperature measuring cells T1-TN via connecting lines +, -, ln. The temperature measuring cells Zl-Zn are also surrounded by a measuring circuit MB (not shown further) in order to enable them to be read out. The positive and negative supply voltage are designated with + and -.

2 shows an exemplary measuring circuit for detecting the changed resistance R of a temperature measuring cell ZI. In accordance with the circuit symbol, the temperature measuring cell ZI was shown as a resistor. The reference symbol Tl, which is entered to the right and subscripted to the reference symbol R, is intended to indicate the temperature Tl at which the resistance R of the temperature measuring cell Tl changes irreversibly according to the invention. A self-conducting transistor TR, which acts like a load resistor, is connected in series with the temperature measuring cell ZI for measurement purposes. The measuring circuit is supplied via the two supply voltages +, -, A2. The voltage drop across the temperature measuring cell ZI is evaluated via connection 1, AI fed back to the microcontroller MC. If the resistance R of the temperature measuring cell ZI changes, the amount of the returned voltage also changes. 3 shows an exemplary structure of a temperature measuring cell Zl-Zn with a securing position SI according to the invention in a plan view. In the example of the present figure, the electrical circuit elements, electrodes AI, A2, A3, LFl, LF2 TL etc. are made of an organic material and printed on an insulating carrier layer TL. The electrical connections A1-A3 to the microcontroller MC are designed as electrically conductive electrodes, ie as electrically conductive surfaces LF1, LF2. Inside the temperature measuring cell Zl-Zn is a substrate SUB according to the

Invention embedded between the carrier layer TL and an insulating layer ISO covering the substrate SUB. This can be seen in the example of FIG. 4 in the associated sectional illustration. In the example, the substrate SUB is enclosed by two conductive electrodes A2, A3, these forming a channel KAN toward the right side of the figure. The channel KAN is separated from the actual reservoir of the substrate SUB by a securing layer SI (see FIG. 4). A gap LU is also shown between the two electrodes A2, A3 for electrical isolation. Instead of the printable material of the electrodes A2, A3, this space is filled by the overlying and also printable electrically insulating insulation layer ISO. In this way, the entire inner space is filled and sealed with the substrate SUB.

If, according to the invention, a current pulse is now passed through the connections A2, A3, it flows through the fuse position SI and destroys it. When the critical predeterminable temperature T2-Tn is exceeded, the substrate SUB now flows into the channel KAN. In a contact area KB, the substrate SUB now electrically connects the electrodes A2, A3 to the electrode AI if it has a certain electrical conductivity. The electrically established connection can now be measured using the line AI, 1 fed back to the microcontroller MC. As already described at the beginning, it is advantageous if the substrate SUB consists of microcapsules, which are burst after reaching a temperature below a predeterminable temperature Tl-Tn, for example by means of a mechanical pressure. As a result, the actual temperature monitoring process is only started.

FIG. 4 finally shows the exemplary temperature measuring cell Zl-Zn from FIG. 3 in a sectional illustration. The separating effect of the securing layer SI with respect to the substrate SUB can be clearly seen. The direction of the arrow shows the direction in which the substrate SUB would spread in the channel KAN if the fuse layer SI was severed. The two electrical connections A2, AI would then be electrically connected in the contact area KB. In the example of Figure 4 that is

Substrate SUB with microcapsules not yet mechanically burst is shown.

Claims

claims 1. Radio-interrogable label (TAG) for contactless interrogation with a read / write device, the radio-interrogable label (TAG) at least having a) a microcontroller (MC) with electrical means, b) an antenna (ANT) which is electrically connected to the microcontroller (MC), c) one or more temperature measuring cells (Zl-Zn) which are electrically connected to the microcontroller (MC) (1-n) and which, when an associated predeterminable temperature (Tl-Tn) is exceeded, irreversibly their electrical properties (R, C) change, and d) the electrical means, which detect the respective change in the electrical property (R, C), determine a maximum temperature value (Tl, .., Tn) and send a corresponding data value to the read / write device. 2. Radio-interrogable label (TAG) according to claim 1, wherein the temperature measuring cell (Zl-Zn) has a substrate (SUB) with a minimum conductivity, which melts when a predetermined temperature (Tl-Tn) is exceeded. 3. Radio-interrogable label (TAG) according to claim 2, wherein the substrate (SUB) for detecting the respective change in the electrical property forms at least one conductive connection between at least two conductive electrodes (AI-A3) if the substrate (SUB) is in the molten state has a wetting effect. 4. radio-interrogable label (TAG) according to claim 2, wherein the substrate (SUB) for detecting the respective change in the electrical property (R, C) connects at least two conductive electrodes (AI-A3), at least one conductive connection then being interrupted, if the substrate (SUB) is not wetting in the molten state. 5. Radio-interrogable label (TAG) according to claim 3 or 4, wherein the respective temperature measuring cell (Zl-Zn) with training or interruption of at least one electrical connection, a changed electrical capacitance (C) and / or a changed electrical resistance (R) as a detectable change in the electrical properties (R, C). A radio interrogatable label (TAG) according to one of the preceding claims 2 to 5, wherein the substrate (SUB) is made of a hydrocarbon such as e.g. consists of an alkane, in particular a dodecane. 7. radio-interrogable label (TAG) according to claim 6, wherein the substrate (SUB) has a small proportion of a conductive substance, in particular a salt dissolved in water or an electrolyte. 8. radio-interrogable label (TAG) according to claim 7, wherein the melting temperature (Tl-Tn) of the substrate (SUB) is adjustable from the volume ratio of a hydrocarbon and a conductive substance. 9. radio-interrogable label (TAG) according to one of the preceding claims 2 to 8, wherein the melting point of the substrate (SUB) is in a range from -25 ° C to 10 ° C. 10. Radio-interrogable label (TAG) according to one of the preceding claims 2 to 9, wherein the substrate (SUB) has a dye. 11. radio-interrogable label (TAG) according to one of the preceding claims to 2 to 10, wherein the substrate (SUB) is embedded in microcapsules with a diameter in a range from 1 to 50 microns. 12. Radio-interrogatable label (TAG) claims 11, wherein the substrate (SUB) is embedded in microcapsules with a diameter in a range from 5 to 10 μm. 13. Radio-interrogable label (TAG) according to claim 11 or 12, wherein the microcapsules have a shell made of gelatin or of a material with comparable physical properties. 14. Radio-interrogable label (TAG) according to one of the preceding claims, with circuit elements (MC, ANT, LFl, LF2, AI, A2, A3) made mainly of organic compounds, which on a plastic carrier layer (TL) of the radio-interrogable label (TAG) are printable. 15. Radio-interrogable label (TAG) according to one of the preceding claims 2 to 14, wherein the substrate (SUB) is embedded between two flat and electrically insulating layers (TL, ISO) and is surrounded by at least two conductive electrodes (AI-A3). 16. Radio-interrogatable label (TAG) according to claim 15, wherein at least one of the conductive electrodes (A2, A3) forms a channel (KAN). 17. radio-interrogable label (TAG) according to claim 16, wherein in the channel (KAN) a conductive fuse layer. (SI) can be introduced, which seals the channel (KAN), whereby the channel (KAN) can be released by means of a current pulse through the fuse position (SI). 18. Radio-interrogable label (TAG) according to claim 17, wherein the security channel (KAN) is connected to at least two of the conductive electrodes (A2, A3). 19. Radio-interrogable label (TAG) according to claim 17 and 18, wherein the microcontroller (MC) has further electrical means for feeding the current pulse into the security channel (SI). 20. Radio-interrogable label (TAG) according to one of the preceding claims with an inductively coupled data and energy transmission. 21. Use of a radio-questionable label (TAG) according to one of the preceding claims in the food industry. 22. Identification system with a read / write device and at least one radio-questionable label (TAG) according to one of the preceding claims 1 to 20.