Abstract:
The invention relates to an activation device for temperature-sensitive and/or time-sensitive indicators for product labeling, said indicators being activated by UV light and said device comprising a UV light source. The device is equipped with a controller/regulator, which can be used to control and/or regulate the irradiation period and/or the irradiation intensity of the UV light source.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/EP2006/010164, filed Oct. 20, 2006, and which claims the benefit of German Patent Application No. 102005051470.7, filed Oct. 21, 2005, the disclosures of both applications being incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to an activation device for temperature-sensitive and/or time-sensitive indicators activatable by UV light for product labeling, comprising a UV light source device. 
     The invention further relates to a device for the provision of activated temperature-sensitive and/or time-sensitive indicators for product labeling. 
     The invention furthermore relates to a method for the activation of a temperature-sensitive and/or time-sensitive indicator activatable by UV light for product labeling. 
     A substrate is known from DE 198 03 208 C2 for the packaging of or for the application onto aging-sensitive and temperature-sensitive products having a time/temperature indicator arranged in the region of the substrate, with the time/temperature indicator being a time/temperature indicator whose starting time can be set as desired defined by light radiation, with the indicator containing a matrix and at least one reversible, rechargeable crystalline indicator which is embedded therein and which has photochromic properties on the basis of transfer reactions. 
     After the activation of the time/temperature indicator via light, and in particular UV light, the color of the indicator changes in dependence on the time and on the temperature. A product labeling can thereby be provided, with the color of the indicator corresponding to the freshness and the quality of the product. 
     SUMMARY OF THE INVENTION 
     It is an underlying object of the present invention to provide an activation device of the initially named kind with which activated indicators can be provided in a simple manner. 
     This object is satisfied in accordance with the invention with the activation device of the initially named kind in that a control/regulation device is provided via which the radiation time and/or the radiation strength of the UV light source device can be controlled and/or regulated. 
     The time dependence and/or temperature dependence of the “deenergizing” after the activation can be set by the control/regulation of the radiation time and/or radiation strength. Time integrator properties or time/temperature integrator properties of the indicator can thereby be set via the activation device. An adaptation to a product to be labeled is thereby possible. For example, products which spoil faster can be provided with correspondingly activated indicators which deenergize “faster”. 
     The aging and/or any contamination of the UV light source device with respect to the UV light radiation can also be taken into account by the control/regulation device. A feedback loop can be realized via which the radiation strength and/or radiation time of the UV light source device can be readjusted such that the aging and/or contamination is compensated. 
     The object is furthermore satisfied in accordance with the invention in that the UV light source device includes at least one UV light emitting diode. UV light emitting diodes can be controlled in a simple manner and have low space requirements. The activation device can thereby be designed in a space-saving manner. It can thereby be integrated, for example, into a labeling device and in particular a hand-held labeling device. Furthermore, UV light emitting diodes have a relatively low electrical energy consumption. The radiated light can furthermore be focused in a simple manner. Indicators can be activated in a simple manner in a continuous process. 
     It is generally possible for the control of the radiation time and/or radiation strength to take place via diaphragms which are moved mechanically. It is advantageous for the light generation at the UV light source device to be able to be controlled and/or regulated by the control/regulation device. No mechanical elements then have to be provided. Such a control/regulation of the light generation can be carried out in a simple manner when the UV light source device includes UV light emitting diodes. 
     It is favorable for the electrical action on the UV light source device to be able to be controlled and/or regulated by the control/regulation device. The electrical action can be varied in a simple manner. When the UV light source device includes UV light emitting diodes, the radiation strength can thereby be set in a simple manner (by the current) and the radiation time can be set in a simple manner (by being acted on or by not being acted on). 
     The radiation time can in be particular be adjusted between 0.05 s and 20 s, and preferably between 0.1 s and 10 s, by the control/regulation device. The indicator properties of an activated indicator can thereby be set directly. 
     For the same reason, it is favorable if the radiation strength can be adjusted by the control/regulation device between 25 mW/cm 2  and 400 mW/cm 2  and in particular between 50 mW/cm 2  and 200 mW/cm 2 . 
     Provision can be made for the UV light source device to radiate UV light in the wavelength range between 300 nm and 430 nm and in particular in the wavelength range between 350 nm and 380 nm. Known indicator materials can thereby be activated in a reliable manner. 
     It is favorable for a plurality of UV light emitting diodes to be arranged in one or more rows. A large areal region can thereby be illuminated with the UV light emitting diodes. An indicator can thereby in turn be activated reliably over its total surface and/or a plurality of indicators can be activated simultaneously. 
     It is favorable when at least one photo sensor is provided. This photo sensor can determine the radiation strength or radiation time of the UV light source device. It is thereby made possible to calibrate the UV light source device, for example. An exact control/regulation of the radiation strength/radiation time is thereby in turn also achievable over a long period. 
     The at least one photo sensor is in particular arranged facing the UV light source device and/or a reference light source device to enable an effective detection of radiated light. A reference light source device can be provided which, for example, has the same light emitting diode type as the UV light source device; in a parallel aging process and/or with equal contamination of the light emitting diodes, the UV light source device can be calibrated with reference to the measurement results for the reference light source device. 
     It is favorable when the UV light source device and the at least one photo sensor are arranged such that indicators to be activated can be passed between them. The at least one photo sensor can be arranged such that it is itself not shaded by indicators or by a carrier of indicators. It can also be arranged such that it only becomes effective (i.e. is radiated) when no indicators (which are in particular arranged at labels) are passed through. A calibration procedure and/or checking procedure of the UV light source device can then be carried out, for example, before insertion of a new label tape. 
     It is preferred for the UV light source device and/or a reference light source device to have memory means for the storage of the operating time of the UV light source device and/or of the reference light source device, in particular for the storage of the operating hour count. The memory means can, for example, be non-volatile memory means, in particular a memory module arranged on a board, preferably an EEPROM. An advanced aging of the UV light source device and/or of the reference light source device can thereby be recognized on which a readjustment is no longer sensible. The memory means and the UV light source device and/or the reference light source device are preferably arranged on a common board so that, on a defect in the UV light source device and/or in the reference light source device or on the reaching of a specific and/or maximum desired operating time, the memory means and the UV light source device and/or the reference light device can be replaced together. It is particularly preferred for the control/regulation device to be arranged on a board and for the UV light source device and/or a reference light source device to be arranged on a further board separate therefrom. 
     It is favorable for at least one checking sensor to be provided for the testing of the activation of indicators. A check can thereby be made whether an indicator was actually activated or was activated “properly” after passing through the activation device. The calibration and the function of the UV light source device can in turn thereby be checked. A feedback loop for the control/regulation of the UV light source device can be realized based on the measurement results of the checking sensor. 
     The at least one checking sensor is in particular arranged after the UV light source device to enable an effective check. 
     If the indicator has photochromic properties, the at least one checking sensor is preferably a color sensor. A check can be made via a color sensor whether an indicator has reached the desired color after the activation. The conditions of specific color valencies (for example RGB values) and the color density can in particular be measured by a color sensor. 
     It is favorable for an indicator to adopt a specific color by activation, with the color varying in dependence on the time and/or the temperature after the activation. Corresponding indicator materials are described in DE 198 03 208 C2, to which reference is expressly made. The activation result can then be checked in a simple manner by a color sensor. 
     It is furthermore an underlying object of the invention to provide a device for the provision of activated temperature-sensitive and/or time-sensitive indicators for product labeling which has a simple structure. 
     This object is satisfied in accordance with the invention in that an activation device in accordance with the invention is provided. 
     The activation device is in particular an application device for a UV protection filter. As a rule, indicator materials are reversible with respect to the UV light activation. The total system is made irreversible by the application of a UV protection filter onto an activated indicator since a subsequent UV light activation is no longer possible. The corresponding indicator thereby becomes secure against manipulation; that is, the time integrator properties or temperature integrator properties or time/temperature integrator properties can no longer subsequently be influenced by UV light radiation. 
     It is favorable when a receiver is provided for a stock of activatable indicators. It is thereby made possible to activate a large number of indicators in a short time period to provide indicators for product labeling, which are activated, in a simple and fast manner. The indicators can be activated in a continuous process. 
     The receiver is in particular designed to hold a roll. The roll is in particular a label roll. It includes, for example, a carrier tape on which labels with indicators are arranged or the roll itself is formed by a label tape, with indicators being arranged on the label tape. The labels can be self-adhesive. 
     The indicators are in particular arranged at labels. Self-adhesive or non-self-adhesive labels can thereby be provided by means of which products can be labeled. 
     It is favorable in this process for the labels to be able to be printed and in particular to be able to be printed outside an indicator. Additional data such as product data can thereby also be printed on the labels. The labels can, for example, be printed via thermal printing; they can be printable via thermal transfer or via direct thermal printing. Other printing methods such as ink jet printing are also possible, for example. 
     The labels are in particular formed at a label tape or on a carrier tape. The labels are, for example, arranged at a label tape without carrier (linerless tape). For this purpose, the labels must be provided with a corresponding non-stick coating if they have an adhesive side. A UV protection filter must be able to stick to the non-stick coating. It is also possible to arrange adhesive labels on a carrier tape (liner). 
     It is favorable if a dispensing device is provided for the dispensing of labels. Labels which are provided with an activated indicator can thereby be removed from the device or be provided by it in a simple manner. An applicator device for the application of labels to a product/product packaging can be arranged downstream of the dispensing device. The labels can then be attached, in particular automatically, to products/product packaging, for example, which are moved past on a conveyor belt. 
     It is furthermore an object of the invention to provide a method of the initially named kind which permits variability with respect to the use of the product labeling. 
     This object is satisfied in accordance with the invention in that the indicator is radiated with UV light and in that the radiation time and/or radiation strength is controlled and/or regulated for the setting of the temperature sensitivity and/or time sensitivity of the indicator. 
     An operator can then set the time integrator properties or temperature integrator properties or time/temperature integrator properties of indicators, adapted to the product to be labeled, via influencing a control/regulation device. An indicator material can then be activated variably at least within specific limits. 
     It is favorable when the indicator is illuminated via at least one UV light emitting diode. The method can thereby be carried out in a simple manner. 
     The electrical action on the at least one light emitting diode is in particular controlled and/or regulated for the control/regulation of the radiation time and/or radiation strength. The light generation at the light emitting diode can thereby be set in a simple manner. 
     It is furthermore favorable for the emission of the UV light source to be measured by at least one photo sensor. The system can thereby be calibrated in order thus in turn to be able to carry out a precisely adjusted activation of an indicator. 
     It is furthermore favorable for an activation of the indicator to be checked by a checking sensor. In particular a color of the indicator is checked after the activation. A readjustment of a light source for the UV radiation can also be carried out, i.e. a calibration can be carried out, via the detection result of the checking sensor. 
     The following description of preferred embodiments serves for the more detailed explanation of the invention in conjunction with the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a first embodiment of a device for the provision of activated indicators for product labeling; 
         FIG. 2  is a schematic representation of a second embodiment of a device for the provision of indicators for product labeling; 
         FIG. 3  is an enlarged schematic perspective view taken from region A of  FIGS. 1 and 2 ; and 
         FIG. 4  is a schematic representation of embodiments of an indicator, illustrating its time dependence and temperature dependence after the activation. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of a device for the provision of activated temperature-sensitive and/or time-sensitive indicators for product labeling, which is shown in  FIG. 1  and is designated there by  10 , comprises an activation device  12  for the activation of indicators. The activation device  12  has a UV light source device  14  by which indicators to be activated can be illuminated by UV light. The UV light source device  14  is formed by means of UV light emitting diodes  16  ( FIG. 3 ). The light emitting diodes  16  are arranged in one or more rows  18   a ,  18   b ,  18   c . The UV light emitting diodes  16  are preferably arranged on a straight line  20  within a row. Different rows  18   a ,  18   b ,  18   c  are preferably aligned parallel to one another. 
     The UV light source device  14  is arranged such that a specific areal region can be illuminated by the UV light source device  14 . Indicators  22  can be guided through this areal region. The indicators  22  are in particular arranged at a carrier  24 , with the carrier  24  preferably being a (printable) label  26 . A label  26  can already be printed with one or more comparison fields for an indicator  22 ; a comparison field is, for example, designed as a comparison color field. It is possible in this connection for the labels  26  to be separate or to form a contiguous label tape. It is furthermore possible for the carriers  24  for the indicators  22  again to be arranged on a carrier tape  28  themselves. The labels  26  are, for example, self-adhesive and the carrier tape  28  forms a liner. 
     It is generally also possible for the labels  26  to be made free of carrier tape as linerless labels. 
     The activation device  12  comprises a control/regulation apparatus  30  by which the light emission of the UV light source device  14  can be controlled and/or regulated with respect to radiation time and radiation strength (intensity). The control/regulation device  30  in particular controls and/or regulates the light generation at the UV light emitting diodes  16  themselves. For this purpose, the current acting on the UV light source device  14  is controlled or regulated to be able to set the intensity of radiation and the radiation time. 
     Provision is made in this connection for the radiation time to be adjustable at least for a period between 0.05 s and 20 s, and preferably between 0.1 s and 10 s, and for the intensity of radiation furthermore to be adjustable at least in a range between 25 mW/cm 2  and 400 mW/cm 2 , and preferably between 50 mW/cm 2  up to 200 mW/cm 2 . 
     The wavelength of the light which is emitted by the UV light emitting diodes  16  preferably lies between 350 nm and 380 nm. 
     At least one UV light sensitive photo sensor  32  is associated with the UV light source device  14 . This at least one photo sensor  32  is arranged opposite the UV light source device  14 , with the indicators  22  being able to be guided through between the UV light source device  14  and the photo sensor  32 . The radiation intensity/radiation time of the UV light source device  14  can be checked by the photo sensor  32 . A calibration of the activation apparatus  12  can thereby be carried out, for example, before the insertion of a new label tape. A check can also be made by the photo sensor  32  (for example before insertion of a new label tape) whether light is being emitted at all from the UV light source device  14 . A problem with the UV light source device  14  can thereby be recognized. 
     A reference light source device  33  can also be provided which is preferably controlled in the same manner as the UV light source device  14 . The reference light source device  14  in particular has one or more UV light emitting diodes of the same construction as the light source device  14 . A photo sensor  35  is associated with the reference light source device  35  and is radiated by it. The photo sensor  35  and the reference light source device  33  are arranged such that the beam acting on the photo sensor  35  is not shadowed by labels being led through. For this purpose, at least the photo sensor  35  or at least the reference light source device  33  is arranged to the side of the carrier tape  28  so that UV radiation emitted by the reference light source device  33  in the direction of the photo sensor  35  is not blocked by the carrier tape  28 . Since the reference light source device  33  substantially has the same properties as the UV light source device  14 , the latter can be monitored—indirectly—constantly by the photo sensor  35  and can be readjusted as necessary. Generally, a photo sensor  35  arranged to the side of the carrier tape  28  can, however, also be associated with the UV light source device  14  itself, which must then be designed and arranged such that an at least small portion of the emitted light is not incident onto the carrier tape  28 , but onto the photo sensor  35 . 
     The activation device  12  furthermore comprises at least one checking sensor  34  which is arranged, with respect to the carrier or carriers  24  for the indicators  22 , on the same side as the UV light source device  14 . This checking sensor  34  is in particular a color sensor. A check can be made by it after the UV light source device  14  whether an activation actually took place and in the required degree, that is, whether the desired energy transfer to the indicators  22  has actually taken place. Defective and/or incorrectly exposed indicators  22  can hereby be recognized and eliminated. An automatically working or manually operable external checking sensor can also be provided, instead of or in addition to the checking sensor  34  disposed downstream of the UV light source device  14 , to check the correct activation at least randomly. It is generally also possible for a checking sensor to be integrated into a printing device explained in more detail in the following. 
     For example, a control loop can be realized with the help of the photo sensor  32  and/or  35  and the control/regulation device  30 , and the aging and/or a contamination of the light sources of the UV light source device  14  (that is, the UV light emitting diodes  16 ) is automatically eliminated by it in that the intensity of radiation and/or the radiation time is readjusted automatically in accordance with the aging and/or the contamination. 
     It is generally also possible for no photo sensor  32  or  35  and only one checking sensor  34  to be provided which, together with the control/regulation device  30 , forms a control loop via which the aging and/or a contamination of the light sources of the UV light source device  14  is automatically eliminated. 
     The photo sensor  32  (and optionally the photo sensor  35 ) and the checking sensor  34  transfer their sensor signals to the control/regulation device  30  via corresponding lines. This transmits its control signals or regulation signals to the UV light source device  14  via a corresponding line. 
     The device  10  comprises a receiver  36  to hold a roll  38 . The roll  38  is, for example, a carrier tape roll with a carrier tape  28  which can be unwound and on which the indicators  22  are arranged at corresponding carriers  24  (for example labels  26 ). The carrier tape  28  is guided between the UV light source device  14  and the photo sensor  32  and is guided past the checking sensor  34 . 
     The receiver  36  comprises a holding mandrel  40  for the roll  38 , for example. 
     Generally, different types of indicators can be provided which in particular differ with respect to their color and/or the radiation energy required for the activation. Different types of indicators can, for example, be used for different types of meat. Indicators of one kind can in each case be wound up on a roll  38 , with different kinds of rolls differing by the type of their indicators. It can then be ensured by means of the photo sensor  32  or  35  or of the photo sensors  32 ,  35  that the energy transfer desired for the respective indicator type takes place. It is made possible by the combination of one or two photo sensors  32 ,  35  and a checking sensor  34  to determine whether a “correct” roll was inserted for the product to be labeled in each case with the corresponding indicators  22 . It can initially be ensured in this connection by means of the photo sensor or photo sensors  32 ,  35  that the energy transfer desired for the respective indicator type takes place. After the activation, a coloration and/or intensity value of the indicators  22  can be determined by means of the checking sensor  34 , for example. If the value found differs from the expected value for the respective indicator type, it can be concluded, in particular if other error sources are eliminated, that an “incorrect” roll had been inserted. 
     A holding device  42  can be provided which in particular comprises a holding mandrel  44  by which a roll  46  with a wound-on carrier band is held. 
     The device  10  comprises a guide element  48  via which the carrier tape  28  is guided to the holding device  42 . A dispenser device  50  for labels is formed at or in the proximity of the guide element  48 . Labels  51  can be peeled off the carrier tape  28  at the dispenser device  50  and can be removed from the device  10 . (The device  10  is then a labeling device.) The dispenser device  50 , for example, comprises a wedge-shaped element  52  with a dispensing edge  54 . 
     The roll  46  is formed by a label-free carrier tape, that is, a carrier tape, which is label-free due to peeling off of labels  51  at the dispenser device  50 . 
     An applicator device  55  can be arranged after the dispensing device  50  and labels  51  can be applied to products or product packaging via it. An automatic label application can thereby be realized. Labels (with activated indicators  22 ) are, for example, automatically applied to products/product packaging which are guided on a conveyor belt. 
     The applicator device  55  is made, for example, as a blow applicator, plunger applicator or pressing applicator. 
     Provision can be made for the holding device  42  to be driven by a drive  56  to wind up the carrier tape accordingly. 
     It is also possible for the labels themselves to form a tape so that no carrier tape is provided (linerless labels). The guidance of the corresponding label tape in the device  10  is then made such that elements of the guide, which come into contact with an adhesive side of the label tape if the labels are self-adhesive, are provided with an anti-stick coating. 
     The device  10  comprises at least one printing device  58 . The printing device  58  itself has a print head  60  and a mating element and in particular a print roll. The guide element  48  is in particular made as a print roll. 
     The device  10  moreover has an application device  62  by which a UV protective filter can be applied to an indicator  22  after its activation. A protection of an indicator against manipulation is achieved by the UV protective filter; an indicator  22  cannot be activated again after application of the protective filter so that the device  10  provides irreversibly activated indicators  22 . 
     A UV protective filter can be applied to an indicator  22  via a tape  64  via the application device  62 , with the tape having corresponding UV protective filter properties. The application device  62  comprises for this purpose a tape guiding device  66  via which the tape  64  can be guided such that UV protective filters can be applied to the activated indicators  22 . 
     The tape  64  comprises, for example, a UV protective filter and is made transparent; it can also be self-adhesive. It is applied to respective applicators  22  in part elements (as labels) or continuously. 
     The tape guiding device  66 , for example, comprises a first roll holder  68  and a second roll holder  70 . A tape roll can be placed onto the first roll holder  68  and the tape can be unwound from there. A roll can be wound up via the second roll holder  70 . The second roll holder  70  is driven, for example. 
     The device  10  can be made in compact form. It is made as a hand-held device, for example. It can also be integrated into a labeler with an applicator device  55 . Labels can then be provided having activating indicators  22  and can be applied automatically to products/product packaging. 
     In a second embodiment of a device in accordance with the invention, which is shown in  FIG. 2  and is designated by  72  there, an activation device  12  is provided which is generally configured the same as the activation device  12  of the device  10 . The same reference numerals are therefore used for this activation apparatus of the device  72 . 
     The receiver for a roll  38  is likewise made the same so that the same reference numerals are used. The dispenser device is also generally made the same as described above. 
     The device  72  comprises a tape guiding device  74  for a transfer tape  76 . The transfer tape  76  is a thermal transfer tape, for example. 
     The tape guiding device  74  has a first roll holder  78  and a second roll holder  80  between which the transfer tape  76  is guided. The transfer tape  76  is in particular unwound from a roll which is seated at the first roll holder  78  and can be wound up at a roll which is seated on the second roll holder  80 . The second roll holder  80  is driven by a drive  82 , for example. 
     The device  72  comprises a printing device  84  having a print head  86  and a print roll as a mating element  88 . Labels  26  at a label tape or on a carrier tape  28  are guided between the print head  86  and the mating element  88 . 
     The tape guiding device  74  is made such that the transfer tape  76  is led past the print head  86 . The transfer tape  76  comprises a UV protective filter material. It can then be applied to corresponding activated indicators  22  by the print head  86 . 
     The print head  86  can be controlled such that UV protective filter material can be applied directly onto the indicator  22  in accordance with its geometrical dimensions. 
     It is generally possible in this connection (if the transfer tape  76  is suitable for it) also to print corresponding labels  26  with information such as product information outside the indicator  22  by the printing device  84 . 
     It is also possible for a second printing device  90  to be provided in addition to the printing device  84  (first printing device) which can be arranged between the printing device  84  and the activation device  12  or can be arranged downstream of the printing device  84 . The second printing device  90  in particular comprises a print head  92  and a mating element  94 . Information can be printed on labels  26  by the second printing device  90  independently of the printing device  84 . 
     Provision can also be made for the device  72  to provide labels having indicators  22  which are activated, provided with UV protective filters and are coupled into a labeling apparatus with a printing device in order to print the labels outside the indicators  22  with information such as product data. It is favorable in this case for the apparatus  72  not to provide individual labels, but a tape such as a label tape or a carrier tape  28  with non-peeled labels. 
     The apparatus  10  and  72  work as follows: 
     An indicator  22  is made from a material which can be activated by UV light and is temperature-sensitive and time-sensitive; that is, after the material has been stimulated, the deenergizing depends on the time after the stimulation and on the temperature. The indicator  22  is in particular a time/temperature indicator having an integration effect with respect to time and temperature. The starting time is determined by the activation time. 
     Examples for indicator materials are rechargeable, crystalline indicators embedded into a matrix and having photochromic properties based on transfer reactions. Such materials are described, for example, in DE 198 03 208 C2, to which reference is expressly made. 
     An indicator can, for example, have different colors depending on the time and on the temperature. Provision can be made for at least one fixed comparison color field to be arranged at an indicator  96  ( FIG. 4 ) so that the status can immediately be recognized with the eyes. For example, a first dark color field  98  is provided which indicates the color directly after the activation. A second color field  100  can be provided which indicates the color after a medium time period—under the same temperature conditions. A third color field  102  can be provided which indicates the color after a longer time period—under the same temperature conditions. The colors of the color fields  98 ,  100  and  102  are fixed. The color of the first color field, for example, symbolizes a “fresh” state; the color of the second color field  100  a “medium” state; and the color of the third color field  102  symbolizes a “no longer fresh” state, for example. 
     If only one comparison color field is provided, it symbolizes a state “to be used”, for example. 
     The color-changing indicator  96  is, for example, circular with the color fields  98 ,  100  and  102  surrounding the indicator in the manner of a ring segment. 
     The color of the indicator  96  changes in accordance with the activation time/temperature integral, as indicated in  FIG. 4 . At higher temperatures, the color of the indicator  96  changes faster than at lower temperatures with time. 
     Such an activated indicator  96  can be used for product labeling. After application of a corresponding product labeling with an indicator  96 , this indicator  96  runs through the same time development and temperature development as the product labeled by the indicator  96 ; that is, it is subject to the same time conditions and temperature conditions. The state of the product and in particular the degree of freshness of the product can thereby be visualized by the temperature-sensitive and time-sensitive indicator  96 . Foodstuffs can thereby, for example, be labeled with respect to their degree of freshness. 
     The start time is set by the time of activation. The indicators  96  are supplied to the activation apparatus  12  for this purpose, where an activation by UV light takes place. Due to the activation by UV light, transfer reactions are, for example, photochemically induced in the indicator material, with fading times of different lengths being able to be achieved in dependence on the bonding strength of an acceptor of the transferred species in the acceptor material (cf. DE 198 03 208 C2). 
     The intensity of radiation and/or the radiation time of the radiation with UV light of corresponding indicators  22 ,  96  can be set by the control/regulation device  30 . The time sensitivity and/or temperature sensitivity of an activated indicator  22  can thereby be set in at least a certain range. For example, with an increased intensity of radiation, a longer fading time can be achieved (with respect to the same temperature conditions). An operator can therefore set the desired properties via the control/regulation device  30 . 
     A calibration of the UV light source device  14  can be carried out via the photo sensor  32  and a monitoring can be made of whether a defect is present with respect to the lighting. 
     A check can be made via the checking sensor  34 , which is in particular a color sensor, of whether an indicator  22  has reached the desired color by the activation. 
     A UV protective filter is applied to an activated indicator  22  by the application device  62  or the printing device  84  (which serves as an application device). The indicator  22  is thereby made safe against manipulation since a repeated activation by UV light is no longer possible; that is, the activation is made irreversible by the UV protective filter. A repeated UV light activation would only be possible by removal of the UV protective filter (which results in a destruction of the indicator  22 ). 
     Provision can also be made for a UV protective filter to be applied to the comparison color field or fields. The color comparability can in particular thereby be optimized when a UV protective filter is not completely transparent for light in the visible spectrum. 
     The UV protective filter is applied to the indicators  22  via a tape, with the tape being able to be applied directly or (as described with reference to the apparatus  72 ) with a transfer of UV protective filter material taking place from the transfer tape  76  to an activated indicator  22 . The transfer tape  76  is in particular a thermal transfer tape, such as a carbon tape, on which corresponding UV protective filter material is arranged. 
     It is transferred onto the indicator  22  via the printing device  84  having the print head  86 . The print head  86  can be controlled such that UV protective filter material is “printed” onto the indicator  22  in accordance with the geometrical dimensions thereof. 
     The present components of a labeling apparatus having a thermal transfer printing apparatus can thereby be used to arrange a UV protective filter on indicators  22 . 
     The indicators  22  are arranged on carriers  24  such as labels  26 . The labels  26  are in turn arranged on a carrier tape  28  or are themselves formed on a label tape. The indicators  22  are guided past the UV light source device  14  for activation. The UV protective filter material is applied after activation. 
     Provision can be made for the corresponding labels  26  to be printed with information such as product data outside the indicators  22 . This printing can take place by the apparatus  72  itself (by the second printing device  90  there) or outside the apparatus  72 . 
     It is generally also possible, if a suitable transfer tape  76  is present, for a printing of the labels  26  to take place outside the indicators  22  by the printing device  84 . 
     It is also possible for labels  26  provided by the device  72  and provided with activated indicators  22  to be supplied to a labeling device in which they are printed.