Patent Publication Number: US-2019171402-A1

Title: Electronic shelf label system and display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-232683, filed Dec. 4, 2017, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to an electronic shelf label system and a display device. 
     BACKGROUND 
     In general, for example, shelf labels on which names, prices, and the like of products are printed (displayed) are attached to display shelves on which products for sales are displayed in stores such as retail stores and supermarkets. 
     If a product price is changed in such a store, for example, the shelf label on which the pre-changed price is printed needs to be replaced with a shelf label on which a changed price is printed, which requires much labor. 
     Recently, a system of displaying data (hereinafter called product data) such as names and prices of products for sales in the store on electric shelf labels (electronic tags) (hereinafter called an electronic shelf label system) is well known. 
     The electronic shelf label system includes a server device which centrally manages the product data, and can display the product data on the electronic shelf labels by transmitting product data of the products to the electronic shelf labels corresponding to the products from the server device. 
     Such an electronic shelf label system can flexibly correspond to the above-mentioned change of product prices and the like without labor. 
     In the electronic shelf label system, however, works such as exchange of electric cells of the electronic shelf labels or charging of batteries are required and the convenience is small in this point. 
     SUMMARY 
     The present application relates generally to an electronic shelf label system and a display device. 
     According to one embodiment, a display device being enable communication with an external device is provided. The display device includes a display panel, a controller, a battery, and a power supply circuit. The controller is configured to control the display panel so as to display product data related to a product. The battery is configured to store electric power operating the display device. The power supply circuit is configured to supply electric power to the battery. The electric power is obtained by the communication with the external device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration for explanation of an example of usage of a display device according to a first embodiment. 
         FIG. 2  is a block diagram showing an example of a configuration of an electronic shelf label system. 
         FIG. 3  is a diagram for explanation of an example of a configuration of an electrophoretic display panel. 
         FIG. 4  is a diagram for explanation of the electrophoretic display panel when displaying white color. 
         FIG. 5  is a diagram for explanation of the electrophoretic display panel when displaying black color. 
         FIG. 6  is a sequence chart showing an example of a processing procedure of displaying product data on a display device in the electronic shelf label system. 
         FIG. 7  is a sequence chart showing an example of a processing procedure of charging a battery of the display device in the electronic shelf label system. 
         FIG. 8  is a chart for explanation of an example of a time band in which the battery of the display device is charged. 
         FIG. 9  is a chart for explanation of an example of a time band in which the battery of the display device is charged. 
         FIG. 10  is a block diagram showing an example of a configuration of an electronic shelf label system according to a second embodiment. 
         FIG. 11  is a sequence chart showing an example of a processing procedure when charging a battery of the display device in the electronic shelf label system. 
         FIG. 12  is a sequence chart showing an example of a processing procedure of urging product data to blink on a specific display device  10 . 
         FIG. 13  is a block diagram showing an example of a configuration of an electronic shelf label system according to a third embodiment. 
         FIG. 14  is a block diagram showing an example of a configuration of an electronic shelf label system according to a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a display device being enable communication with an external device includes a display panel, a controller, a battery and a power supply circuit. The controller is configured to control the display panel so as to display product data related to a product. The battery is configured to store electric power operating the display device. The power supply circuit is configured to supply electric power to the battery. The electric power is obtained by the communication with the external device. 
     Embodiments will be described hereinafter with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is an illustration for explanation of an example of usage of a display device according to the present embodiment. As shown in  FIG. 1 , display devices  10  according to the present embodiment are attached to display shelves on which products are displayed in, for example, stores such as retail stores and supermarkets. As shown in  FIG. 1 , the display devices  10  are attached to the display shelves for the respective products. 
     The display devices  10  are, for example, electronic shelf labels including display panels, which display data of the products arranged close to the display devices  10  (hereinafter referred to as product data). The product data displayed on the display devices  10  include, for example, names, prices, and the like of the products but may include the other data. 
     Each of the display devices  10  includes a communication function and is connected to an external device such as a server device so as to enable communication with the device, which is not shown in  FIG. 1 . An electronic shelf label system (ESL system) includes the display devices  10  and the server device. The server device of the electronic shelf label system is, for example, an information processing device such as a personal computer (PC) which manages the product data displayed on each of the display devices  10  (display panel). 
       FIG. 2  is a block diagram showing a configuration of the electronic shelf label system (the display device  10  and the server device  20 ).  FIG. 2  shows only one display device  10  for convenience, and illustration of the other display devices  10  is omitted. Each of the display devices  10  included in the electronic shelf label system includes the same configuration as that of the display device  10  shown in  FIG. 2 . 
     The display device  10  includes a display module  11 , a controller  12 , a battery  13 , a communication module  14 , and a converting circuit (power supply circuit)  15 . 
     The display module  11  includes a display panel to display the product data, a display driver IC to drive the display panel, and the like. In the present embodiment, for example, an electrophoretic display panel having a display retaining property explained below is used as the display panel included in the display module  11 . 
     The controller  12  includes, for example, a System on a Chip (SoC) or a microcomputer to control operations of the whole display device  10 . The product data can be displayed on the display panel under control of the controller  12 . 
     The battery  13  is a power storage unit configured to store electric power operating the display device  10 . The display device  10  can be operated with the electric power stored in the battery  13  (i.e., the electric power supplied from the battery  13 ). The display device  10  includes the battery  13  in the present embodiment, but the display device  10  may include a power storage unit, different from battery  13 , capable of storing the electric power operating the display device  10  and may include, for example, a capacitor or the like as the power storage unit. 
     The communication module  14  includes an antenna and the like for communication with the above-explained server device  20 . The antenna is used to receive, for example, the product data managed by the server device  20 . More specifically, the antenna receives radio waves (hereinafter referred to radio waves for display) transmitted from the server device  20  for displaying the product data on the display panel. The radio waves for display are radio waves modulated with the product data which are to be displayed on the display device  10 . In this case, the controller  12  executes control to acquire the product data from the radio waves for display by demodulating the radio waves for display received by the antenna and to display the product data on the display panel. 
     The display device  10  according to the present embodiment is capable of, for example, charging the battery  13  with the electric power obtained by the communication with the server device  20  (i.e., supplying the electric power to the battery  13 ). 
     More specifically, the antenna included in the above-explained communication module  14  receives, for example, radio waves transmitted from the server device  20  to supply the electric power to the battery  13  (hereinafter referred to as radio waves for feeding). The converting circuit  15  converts the radio waves for feeding received by the antenna into the electric power and supplies the electric power to the battery  13 . 
     The server device (ESL server)  20  is connected to the display device  10  so as to communicate with the display device  10 . As shown in  FIG. 2 , the server device  20  includes a storage  21 , a controller  22 , a communication module  23 , and an output circuit  24 . 
     The product data managed by the server device  20  are stored in the storage  21  as explained above. The product data are stored in association with an ID (hereinafter referred to as a display device ID) to identify the display device  10  which is to display the product data, in the storage  21 . 
     The controller  22  transmits the above-explained radio waves for display (i.e., radio waves modulated by the product data) to the display device  10  via the communication module  23  (antenna). 
     In addition, the controller  22  transmits the above-explained radio waves for feeding to the display device  10  via the communication module  23 . 
     The controller  22  also executes control of transmission timing of the radio waves for display and the radio waves for feeding. 
     The output circuit  24  outputs, for example, an alert in response to the feeding (status) to the battery  13  included in the display device  10  as explained below. 
     In the display device  10  according to the present embodiment, the electrophoretic display panel is used as the display panel, and the electrophoretic display panel will be explained below in brief. 
     The display panel of the display device  10  according to the present embodiment is assumed to adopt, for example, electrophoretic scheme of secondary particle based microcapsule type. On such a display panel, the product data can be displayed by the electrophoretic phenomenon of particles dispersed in a liquid (solvent). The electrophoretic phenomenon is a phenomenon in which particles are disperse in a liquid, an electric field is applied to the particles, and the particles are thereby made electrophoretic in the liquid by the Coulomb force. For example, positively or negatively charged white (pigment) particles (electrophoretic particles) and negatively or positively charged black (pigment) (electrophoretic particles) can be dispersed in an achromatic and transparent liquid, and white, black and shades of gray can be displayed in accordance with the polarity, magnitude and time of the applied voltage. 
     The configuration of the electrophoretic display panel will be hereinafter explained with reference to  FIG. 3 . As shown in  FIG. 3 , for example, the electrophoretic display panel includes a first substrate  101  and a second substrate  102 , the first substrate  101  includes pixel electrodes  103  on the second substrate  102  side. In contrast, the second substrate  102  includes a flat common electrode  104  on the first substrate  101  side. 
     In the electrophoretic display panel, microcapsules  110  are disposed to be sandwiched between the pixel electrodes  103  and the common electrode  104 . 
     The achromatic transparent liquid, white electrophoretic particles  111 , and black electrophoretic particles  112  are sealed in the microcapsules  110 . It is assumed that in the present embodiment, for example, the white electrophoretic particles  111  are charged negatively (−) and the black electrophoretic particles  112  are charged positively (+). 
     In such an electrophoretic display panel, white or black color can be displayed in accordance with a potential difference between the pixel electrodes  103  and the common electrode  104 . 
     For example, if the electric potential of the pixel electrodes  103  is lower than the electric potential of the common electrode  104 , in a case where the second substrate (transparent substrate)  102  side is the display surface, the white electrophoretic particles  111  charged negatively are attracted to the common electrode  104  side and the black electrophoretic particles  112  charged positively are attracted to the pixel electrode  103  side as shown in  FIG. 4 , and white color can be thereby displayed on the display surface. 
     In contrast, if the electric potential of the pixel electrodes  103  is higher than the electric potential of the common electrode  104 , the white electrophoretic particles  111  are attracted to the pixel electrode  103  side and the black electrophoretic particles  112  are attracted to the common electrode  104  side as shown in  FIG. 5 , and black color can be thereby displayed on the display surface. 
     Since such an electrophoretic display panel has the display retaining property as explained above, for example, display of the product data can be maintained without supplying the electric power once the product data are displayed, and reduction in the power consumption can be implemented. 
     The electrophoretic scheme of secondary particle based microcapsule type is explained but a display panel employing the other scheme may be used in the present embodiment. For example, the liquid and the electrophoretic particles may be sealed not in the microcapsules but (in a layer) between the pixel electrodes  103  and the common electrode  104 . 
     In addition, it has been explained that the display panel in the present embodiment is the electrophoretic display panel, but the display panel is not limited to the electrophoretic display panel and may be, for example, a reflective liquid crystal display panel or the like. 
     Next, operations of the electronic shelf label system (display device  10  and server device  20 ) according to the present embodiment will be explained. 
     First, a processing procedure of displaying the product data on the display device  10  (i.e., rewriting the product data of the display devices  10 ) in the electronic shelf label system will be explained with reference to a sequence chart shown in  FIG. 6 . 
     It is assumed that the product data are displayed on the display panel by the above-explained display retaining property. In this case, the display device  10  (the controller  12 ) periodically transmits an inquiry of requirement for rewriting the product data to the server device  20  (step S 1 ). The inquiry transmitted in step S 1  is assumed to include a display device ID to identify the display device  10  transmitting the inquiry, and the like. 
     This inquiry (display device ID) is transmitted and received via the communication module  14  of the display device  10  and the communication module  23  (antenna), similarly to the product data. Data transmitted between the display device  10  and the server device  20 , which will be explained below, are transmitted and receive in the same manner. 
     If the server device  20  (the controller  22 ) receives the inquiry from the display device  10  via the communication module  23 , the controller  22  determines whether rewriting the product data on the display device  10  identified with the display device ID included in the inquiry (hereinafter referred to as target display device  10 ) is necessary or not. For example, if the current time reaches the time to rewrite the product data, the controller  22  determines that rewriting the product data on the target display device  10  is necessary. The time to rewrite the product data may be preset in, for example, the server device  20 . In addition, if rewriting the product data is instructed by a manager, an employee, or the like of the store, the controller  22  may determine that rewriting the product data is necessary. 
     If it is determined that rewriting the product data is necessary, the controller  22  acquires the product data to be displayed on the target display device  10  from the storage  21  (step S 2 ). The product data to be displayed on the target display device  10  are stored in association with the display device ID indicating the target display device  10  in the storage  21  as explained above. Therefore, the controller  22  acquires the product data stored in the storage  21  in association with the display device ID included in the received inquiry. 
     In this case, the controller  22  transmits the product data acquired in step S 2  to the target display device  10  (step S 3 ). In this case, the controller  22  transmits the radio waves acquired by modulating a predetermined carrier with the product data acquired in step S 2 , as radio waves for display, from the communication module  23  (antenna) to the display device  10 . The radio waves for display are transmitted in a frequency band of, for example, 2.4 GHz or the like. 
     If the processing in step S 3  is executed, the communication module  14  (antenna) receives the radio waves for display transmitted from the server device  20  (controller  22 ). The controller  12  acquires the product data from the radio waves for display by demodulating the radio waves for display received by the communication module  14  and displays the product data on the display panel included in the display module  11  (step S 4 ). 
     In the present embodiment, for example, the product data displayed on the display panel can be rewritten at appropriate timing by executing the above-explained processing shown in  FIG. 6 . If it is determined that rewriting the product data in the server device  20  unnecessary, the processing in  FIG. 6  is terminated. 
     The only processing executed between one display device  10  and the server device  20  has been explained with reference to  FIG. 6 , but the processing shown in  FIG. 6  is executed between all of the display devices  10  attached to the display shelves in the store (i.e., all of the display devices  10  included in the electronic shelf label system) and the server device  20 . In this case, for example, the inquiry explained in step S 1  shown in  FIG. 6  is assumed to be transmitted at the timing of causing no interference between the display devices  10 . 
     The display device  10  according to the present embodiment includes a battery  13  and operates with the electric power supplied from the battery  13 . For this reason, in the present embodiment, the battery  13  needs to be charged on the display device  10 . 
     However, since a number of display devices  10  are used in the electronic shelf label system, work of charging the battery  13  for each of the display devices  10  may be very complicated and may require much labor. 
     In the present embodiment, the battery  13  of each display device  10  is charged by wireless feed. More specifically, the display device  10  charges the battery  13  by supplying the electric power obtained by the communication with the server device  20  (external device) to the battery  13 . 
     A processing procedure of charging the battery  13  included in the display device  10  of the electronic shelf label system will be explained with reference to a sequence chart shown in  FIG. 7 . 
     In the present embodiment, for example, the server device  20  (controller  22 ) periodically requires the data on the display device  10  via the communication module  23  (step S 11 ). The display device  10  serving as the data requirement destination in step S 11  is hereinafter referred to as the target display device  10 . 
     The controller  12  included in the target display device  10  acquires the amount of electric power (hereinafter referred to as remaining battery) stored in the battery  13  included in the target display device  10  in response to the requirement from the server device  20  (step S 12 ). 
     If the processing in step S 12  is executed, the controller  12  transmits (the data indicating) the remaining battery acquired in step S 12  to the server device  20  in response to the requirement from the server device  20  (step S 13 ). 
     Next, the controller  22  included in the server device  20  receives (acquires) the remaining battery transmitted in step S 13  via the communication module  23 . The controller  22  executes feed determination, based on the received remaining battery (step S 14 ). The feed determination is the processing for determining whether the electric power needs to be fed to the battery  13  included in the target display device  10  (i.e., the battery  13  needs to be charged) or not and, for example, if the remaining battery is lower than a predetermined value, it is determined that the electric power needs to be fed to the battery  13 . 
     If it is determined that the electric power needs to be fed to the battery  13 , the controller  22  starts feeding the electric power to the battery  13  (i.e., charging the battery  13 ) (step S 15 ). 
     In this case, the controller  22  transmits the radio waves for feeding to feed (supply) the electric power to the battery  13  to the target display devices  10  via the communication module  23  (step S 16 ). 
     The communication module  14  (antenna) included in the display device  10  receives the radio waves for feeding transmitted from the server device  20  (controller  22 ). The converting circuit  15  includes a rectifier circuit which converts the radio waves for feeding received by the communication module  14  into electric power (DC power) and outputs the DC power as a power source voltage. The electric power is thereby supplied to the battery  13  and the battery  13  is charged (step S 17 ). 
     The display device  10  according to the present embodiment can charge the battery  13  by executing communication with the server device  20  (i.e., receiving the radio waves for feeding from the server device  20 ) as explained above. The radio waves for feeding are assumed to be, for example, radio waves having the frequency fixed. According to this, the power receiving efficiency can be improved by designing the antenna on the power receiving side for an exclusive frequency. Therefore, the charging efficiency of the battery  13  can be improved. In addition, the radio waves for display and the radio wave for feeding include data indicating the type of the radio waves (signals), and the display device  10  is capable of distinguishing the radio waves for display and the radio wave for feed, based on the data. 
     If it is determined that the electric power does not need to be fed to the battery  13  in the above-explained feed determination in step S 14 , the processing shown in  FIG. 7  is terminated. 
     For example, feeding to the battery  13  included in the target display device  10  (i.e., the processing in steps S 16  and S 17 ) is continued for a predetermined period. In other words, feeding is terminated when a predetermined period has passed (step S 18 ). In this case, the controller  22  included in the server device  20  stops transmission of the radio waves for feeding. 
     If the processing in step S 18  is executed, the controller  22  requires the remaining battery of the target display device  10  via the communication module  23  (step S 19 ). 
     The controller  12  included in the target display device  10  acquires the remaining battery in response to the requirement from the server device  20  (step S 20 ). 
     If the processing in step S 20  is executed, the controller  12  transmits (the data indicating) the remaining battery acquired in step S 12  to the server device  20  in response to the requirement from the server device  20  (step S 21 ). 
     Next, the controller  22  included in the server device  20  receives the remaining battery transmitted in step S 21  via the communication module  23 . The controller  22  executes abnormality determination, based on the received remaining battery (step S 22 ). The abnormality determination is the processing for determining whether abnormality occurs in feeding (power supply) to the battery  13  included in the target display device  10  or not. In the abnormality determination, for example, if the received remaining battery is smaller than a predetermined value (i.e., the battery  13  is not sufficiently charged by the processing in steps S 15  to S 17 ), it is determined that abnormality occurs in feeding to the battery  13 . In the abnormality determination, for example, if a difference between the remaining battery acquired in step S 12  and the remaining battery acquired in step S 20  is smaller than a predetermined value, it may be determined that abnormality occurs in feeding to the battery  13 . 
     If it is determined that abnormality occurs in feeding to the battery  13 , the output circuit  24  outputs alert to notify the manager, employee or the like of the store of the abnormality, under control of the controller  22  (step S 23 ). 
     According to the above-explained processing in steps S 19  to S 23 , alert can be output in a case where, for example, the battery  13  is not appropriately charged by the processing in steps S 15  to S 17 . 
     If it is determined that abnormality does not occur in feeding to the battery  13  in the abnormality determination in step S 22 , the processing shown in  FIG. 7  is terminated. 
     Charging the battery  13  included in one display device  10  has been explained with reference to  FIG. 7 , but the processing shown in  FIG. 7  is executed between all of the display devices  10  attached to the display shelves in the store (i.e., all of the display devices  10  included in the electronic shelf label system) and the server device  20 . 
     In the present embodiment as explained above, the electric power obtained by the communication between the display device  10  and the server device  20  (external device) is supplied to the battery  13  (storage). More specifically, the display device  10  includes the antenna (communication module  14 ) which receives the radio waves transmitted from the server device  20 , converts the radio waves received by the antenna into electric power, and supplies the electric power to the battery  13 . 
     The above-explained antenna is configured to receive the radio waves for display (first radio waves) and the radio waves for feeding (second radio waves). If the radio waves for display are received by the antenna, the product data acquired from the radio waves for display are displayed on the display panel. If the radio waves for feeding are received by the antenna, the battery  13  is charged by converting the radio waves for feeding into electric power. 
     In the present embodiment with such a configuration, since the work of individually exchanging the batteries  13  of the respective display devices  10  in the electronic shelf label system does not need to be executed, convenience of the electronic shelf label system can be improved. 
     In the present embodiment, charging the batteries  13  of the respective display devices  10  by periodically executing the above-explained processing shown in  FIG. 7  has been explained, but the processing shown in  FIG. 7  may be executed in a predetermined time zone alone. 
     As shown in  FIG. 8 , it is assumed that business hours of the store where the display devices  10  according to the present embodiment are attached to the display shelves are ten o&#39;clock to twenty-two o&#39;clock. In the electronic shelf label system, for example, the product data displayed on all of the display devices  10  are often rewritten before the business hours. 
     In this case, the above-explained processing shown in  FIG. 7  may be executed in the time band (charging time) except for the business hours of the store and the time to rewrite the product data before the business hours (i.e., the time necessary to rewrite the product data in all of the display devices  10 ). 
     In addition, as shown in  FIG. 9 , the communication is periodically executed between the display devices  10  and the server device  20  during the business hours and the rewriting time. The communication shown in  FIG. 9  includes, for example, processing in step S 1  shown in  FIG. 6  (i.e., an inquiry on necessity to rewrite the product data from the display devices  10  to the server device  20 ). 
     As explained with reference to  FIG. 6 , if it is determined that rewriting the product data is necessary as a result of the inquiry on the necessity to rewrite the product data from the display devices  10  to the server device  20 , the product data displayed on the display devices  10  are rewritten by executing the processing in steps S 2  to S 4 . 
     In the present embodiment, the batteries  13  of the display devices  10  may be charged in the time other than the charging time except for the business hours and the rewriting time before the business hours shown in  FIG. 8  (i.e., during the business hours and the rewriting time). For example, the batteries  13  may be charged in the time (time band) other than the period when the communication is executed between the display devices  10  and the server device  20  and the period when the product data displayed on the display devices  10  are rewritten as shown in  FIG. 9 . 
     In the present embodiment, feeding can be appropriately executed for the only battery  13  that requires feeding by executing the feed determination in step S 14  shown in  FIG. 7 , but the battery  13  may be fed in, for example, a predetermined time band (or periodically) without executing the feed determination. In this case, the processing in steps S 11  to S 13  shown in  FIG. 7  can be omitted. 
     In addition, in the present embodiment, it can be notified that the battery  13  cannot be appropriately fed (or the battery  13  is not charged) (i.e., alert can be output) by executing the abnormality determination in step S 22  shown in  FIG. 7 , but the abnormality determination may not be executed. In this case, the processing in steps S 19  to S 23  shown in  FIG. 7  can be omitted. 
     In the present embodiment, the above-explained configuration is employed since the work such as charging each of the display devices  10  (the batteries  13 ) is unnecessary, but the display device  10  is preferably operated in the manner of saving the power. If the electrophoretic display panel is used as the display panel for displaying the product data as explained above, the display device  10  may be operated in the power saving mode (sleep mode) at the time other than, for example, the time to rewrite the product data displayed on the display device  10  or the time to charge the battery  13  of the display device  10 , since display of the product data can be maintained without supplying electric power by the display retaining property. 
     In addition, in the present embodiment, the radio waves for feeding received by the display device  10  (antenna) are converted into the electric power, which is supplied to the battery  13 , but, for example, the electric power may be supplied to the battery  13  with an induced current caused by the electromagnetic induction when the antenna receives the radio waves for feeding. 
     That is, the present embodiment can be applied to the electronic shelf label system and the display device  10  having a configuration of supplying the electric power obtained by the communication with the external device such as the server device  20  to the power storage unit such as the battery  13 . 
     In the present embodiment, the external device executing communication with the display device  10  when charging with the battery  13  is the server device  20 . However, for example, if a mesh network capable of communication between the display devices  10  is constructed, the batteries  13  of the display devices  10  can be charged by transmitting and receiving the radio waves for feeding between the display devices  10 . 
     Second Embodiment 
     Next, a second embodiment will be explained.  FIG. 10  is a block diagram showing an example of a configuration of an electronic shelf label system according to the present embodiment. In  FIG. 10 , the same elements as those shown in  FIG. 2  are denoted by the same reference numerals and their detailed descriptions are omitted. Different elements from  FIG. 2  will be hereinafter explained mainly. In addition,  FIG. 10  shows only one display device  10  for convenience, and illustration of the other display devices  10  is omitted. 
     As shown in  FIG. 10 , an electronic shelf label system according to the present embodiment is different from the above-explained first embodiment in that the electronic shelf label system includes a terminal  30  dedicated to feeding besides the display device  10  and the server device  20 . 
     The terminal  30  is a dedicated terminal device which transmits radio waves for supplying the electric power (radio waves for feeding) to a battery  13  included in the display device  10 . 
     The radio waves for feeding transmitted by the terminal  30  are received by a communication module  14  (antenna). A converting circuit  15  converts the radio waves for feeding received from the terminal  30  by the antenna into the electric power and supplies the electric power to the battery  13 . 
     Next, operations of the electronic shelf label system (display device  10 , server device  20 , and terminal  30 ) according to the present embodiment will be explained. Processing of rewriting the product data of the display device  10  in the electronic shelf label system is the same as the above-explained processing shown in  FIG. 6 , and its detailed explanations are omitted. 
     A processing procedure of charging the battery  13  included in the display device  10  of the electronic shelf label system will be explained with reference to a sequence chart shown in  FIG. 11 . 
     First, processing in steps S 31  to S 34  corresponding to the processing in steps S 11  to S 14  shown in  FIG. 7  is executed. The display device  10  serving as a requirement destination of data (remaining battery) in step S 31  is referred to as a target display device  10 . 
     If it is determined that the electric power needs to be fed to the battery  13  in the feed determination in step S 34 , the server device  20  (the controller  22 ) requires feeding to the battery  13  to the terminal  30  (step S 35 ). 
     If the processing in step S 35  is executed, the terminal  30  is activated in response to the requirement from the server device  20  (step S 36 ). 
     Next, the terminal  30  transmits the radio waves for feeding to feed (supply) the electric power to the battery  13  to the target display devices  10  (step S 37 ). 
     The communication module  14  (antenna) included in the display device  10  receives the radio waves for feeding transmitted from the terminal  30 . The converting circuit  15  converts the radio waves for feeding received by the antenna into the electric power and supplies the electric power to the battery. The battery  13  is thereby charged (step S 38 ). 
     The display device  10  according to the present embodiment can charge the battery  13  by executing communication with the terminal  30  (i.e., receiving the radio waves for feeding from the terminal  30 ) as explained above. The radio waves for feeding transmitted from the terminal  30  are radio waves having a higher strength than, for example, the radio waves transmitted from the server device  20 . 
     For example, if it is determined that the electric power does not need to be fed to the battery  13  in the feed determination in step S 34 , the processing shown in  FIG. 11  is terminated. 
     For example, feeding to the battery  13  included in the target display device  10  (i.e., the processing in steps S 37  and S 38 ) is continued for a predetermined period. In other words, feeding is terminated when a predetermined period has passed. In this case, the terminal  30  (the operation of the terminal  30 ) is stopped (step S 39 ). The terminal  30  may be automatically stopped when a predetermined period has passed or may be stopped when stopping feeding to the battery  13  is required by the server device  20 . 
     As explained above, if the terminal  30  is stopped (i.e., if feeding is terminated), processing in steps S 40  to S 44  corresponding to the processing in steps S 19  to S 23  shown in  FIG. 7  is executed. If it is determined that abnormality does not occur in feeding to the battery  13  in the abnormality determination in step S 43 , the processing shown in  FIG. 11  is terminated. 
     Charging the battery  13  included in one display device  10  has been explained with reference to  FIG. 11 , but the processing shown in  FIG. 11  is executed between all of the display devices  10  attached to the display shelves in the store (i.e., all of the display devices  10  included in the electronic shelf label system) and the server device  20 . 
     As explained above, in the present embodiment, the display device  10  is connected to the server device  20  and the terminal  30  dedicated to feeding so as to enable communication, and the communication module  14  (antenna) receives radio waves for display (first radio waves) from the server device  20  and receives radio waves for feeding (second radio waves) from the terminal  30 . If the radio waves for display are received by the antenna, the product data acquired from the radio waves for display are displayed on the display panel. If the radio waves for feeding are received by the antenna, the battery  13  is charged by converting the radio waves for feeding into electric power. 
     The above-explained terminal  30  is a dedicated terminal device prepared to feed the electric power to the battery  13  of the display device  10 , and is configured to emit (transmit) radio waves stronger than the radio waves for feeding transmitted from the server device  20  as explained above in the first embodiment. In the present embodiment, the battery  13  of the display device  10  can be charged more efficiently than the first embodiment by transmitting the radio waves for feeding from the terminal  30 . 
     For example, the terminal  30  may be configured to have directivity. Since the terminal  30  having the directivity is capable of emitting strong radio waves in a specific direction, the efficiency of charging, for example, the battery  13  of the display device  10  located in the specific direction can be further improved. 
     In the present embodiment, for example, if the products related to the product data displayed on a specific display device  10  (i.e., the products disposed near the display device  10 ) are sale-priced products, the product data displayed by the display device  10  may be urged to blink. 
     A processing procedure of urging the product data to blink on the specific display device  10  (hereinafter referred to target display device  10 ) will be explained with reference to a sequence chart shown in  FIG. 12 . 
     If the product data are urged to blink on the target display device  10  as explained above, the server device  20  (the controller  22 ) instructs the target display device  10  to start the operation in a mode of urging the product data to blink (hereinafter referred to as sales mode) (step S 51 ). For example, the start of the operation in the sales mode is assumed to be instructed if a time preset in the server device  20  (i.e., a sales mode start time) comes. 
     In this case, blinking the product data in accordance with the instruction from the server device  20  is started on the target display device  10  (step S 52 ). 
     Blinking the product data on the target display device  10  is implemented by alternately transmitting the radio waves for display to display the product data and the radio waves to make the product data undisplayed (radio waves for non-display) from the server device  20  to the target display device  10  (i.e., repeating display and non-display of the product data). 
     As explained above, if blinking the product data on the target display device  10  is started, processing in steps S 53  to S 56  corresponding to the processing in steps S 35  to S 38  shown in  FIG. 11  is executed. According to this, the battery  13  included in the target display device  10  is charged with the radio waves for feeding transmitted from the terminal  30 . The radio waves for display and the radio waves for non-display are alternately transmitted in the blink of the product data while, in step S 55 , the radio waves for feeding are transmitted between transmission (timing) of the radio waves for display and the radio waves for non-display. 
     If the product data are urged to blink as explained above, the operations of urging the product data to be displayed in accordance with reception of the radio waves for display and urging the product data to be undisplayed in accordance with reception of the radio waves for non-display need to be repeated on the target display device  10 . For this reason, power consumption on the target display device  10  is increased as compared with that in a case of maintaining the display of the product data based on the above-explained display retaining property. 
     Therefore, if the product data are urged to blink on the target display device  10 , the battery  13  of the target display device  10  having larger power consumption is preferably charged efficiently by transmitting the radio waves for feeding to the target display device  10  by the terminal  30  having the directivity as explained above. 
     The server device  20  (the controller  22 ) instructs termination of the operation in the above-explained sales mode (step S 57 ). For example, termination of the operation in the sales mode is assumed to be instructed, if a predetermined period has passed after the start of operation in the sales mode has been notified, or if a preset time (sales mode termination time) has come. 
     In this case, blinking the product data in accordance with the instruction from the server device  20  is terminated on the target display device  10  (step S 58 ). 
     If the processing in step S 58  is executed, the server device  20  notifies the terminal  30  that the operation in the sales mode has been terminated (step S 59 ). 
     The terminal  30  stops its operation in response to the notification from the server device  20  (step S 60 ). 
     According to the above-explained processing shown in  FIG. 12 , for example, even in a case of urging the product data to blink on a specific display device  10 , the battery  13  of the display device  10  can be charged appropriately. 
     If the target display device  10  is operated in the above-explained sales mode, the sales price (i.e., a price lower than an ordinary price) is often urged to blink as the product data on the target display device  10 . For this reason, if the processing in  FIG. 12  is terminated (i.e., blink of the product data is terminated), the product data are rewritten to display the ordinary price on the target display device  10  by executing the above-mentioned processing shown in  FIG. 6 . 
     In addition, in the processing shown in  FIG. 12 , the radio waves for display and the radio waves for non-display for the product data are alternately transmitted from the server device  20  to the target display device  10 . If the radio waves for display are received by the target display device  10 , the product data are displayed. If the radio waves for non-display are received, the product data are made undisplayed. Therefore, blink of the product data is implemented. To charge the battery  13  of the target display device  10  in this case, the terminal  30  needs to transmit the radio waves for feeding to the display device  10  at timing different from the timing of the radio waves for display and the radio waves for non-display. 
     In contrast, if a storage device such as a memory is provided in the target display device  10 , for example, control of preliminarily storing in the memory the product data acquired from the radio waves for display transmitted by the server device  20  in the start of operation in the sales mode, and repeating the display and non-display of the product data on the target display device  10  side using the product data stored in the memory (i.e., urging the product data to blink), can be executed. In such a configuration, since the target display device  10  does not need to repeat receiving the radio waves for display and the radio waves for non-display, the terminal  30  can transmit the radio waves for feeding to the target display device  10  at any time and the charging efficiency can be improved. 
     In the present embodiment, the terminal  30  which transmits the radio waves for feeding is prepared independently of the server device  20  but, if the terminal  30  is installed at a predetermined place, the intensity of the radio waves for feeding received by the predetermined display device  10  is often lowered due to the distance from the terminal  30  or its environment, and the charging efficiency of the battery  13  of the display device  10  is often lowered. 
     For this reason, in the present embodiment, the terminal  30  may be installed on, for example, a cart moving inside a store or held by a clerk moving inside the store. Furthermore, a mobile body equipped with the terminal  30  may automatically move inside the store. According to such a configuration, for example, reduction in the charging efficiency of the battery  13  according to the position where the display device  10  is attached, or the like can be suppressed. In addition, feeding can be executed in a state where each display device  10  and the terminal  30  are made to be more close to each other, and improvement of the charging efficiency can be attempted. 
     In addition, even if the terminal  30  is installed at a predetermined position, reduction in the charging efficiency of the battery  13  of the display device  10  may be suppressed by installing a relay equipment which relays the radio waves for feeding between the display device  10  attached to a position where, for example, the intensity of the radio waves for feeding is lowered, and the terminal  30 . The relay equipment may be installed on a cart or the like as explained above. 
     Third Embodiment 
     Next, a third embodiment will be explained.  FIG. 13  is a block diagram showing an example of a configuration of an electronic shelf label system according to the present embodiment. In  FIG. 13 , the same elements as those shown in  FIG. 2  are denoted by the same reference numerals and their detailed descriptions are omitted. Different elements from  FIG. 2  will be hereinafter explained mainly. In addition,  FIG. 13  shows only one display device  10  for convenience, and illustration of the other display devices  10  is omitted. 
     As shown in  FIG. 13 , the electronic shelf label system according to the present embodiment is different from the above-explained first embodiment in that the display device  10  includes a first communication module  14   a  and a second communication module  14   b , and the server device  20  includes a first communication module  23   a  and a second communication module  23   b.    
     The first communication module  14   a  included in the display device  10  includes a first antenna to communicate with the server device  20 . The first antenna receives radio waves for display transmitted from the server device  20  to display the product data managed by the server device  20  on the display panel. 
     The second communication module  14   b  included in the display device  10  includes a second antenna to communicate with the server device  20 . The second antenna receives the radio waves for feeding transmitted from the server device  20  to supply the electric power to the battery  13  includes in the display device  10 . 
     In the present embodiment, the controller  22  included in the server device  20  transmits the radio waves for display to the display device  10  via a first communication module  23   a . In addition, the controller  22  transmits the radio waves for feeding to the display device  10  via a second communication module  23   b.    
     That is, in the electronic shelf label system of the present embodiment, each of the display device  10  and the server device  20  includes a communication module (first communication module  14   a  and first communication module  23   a ) for transmission and reception of the radio waves for display, and a communication module (second communication module  14   b  and second communication module  23   b ) for transmission and reception of the radio waves for feeding. 
     In the present embodiment, the radio waves for display transmitted from the server device  20  via the first communication module  23   a  are received by the first communication module  14   a  (first antenna) of the display devices  10  and the radio waves for feeding transmitted from the server device  20  via the second communication module  23   b  are received by the second communication module  14   b  (second antenna) of the display devices  10 , but other operations of the electronic shelf label system according to the present embodiment are the same as the above-explained first embodiment. Therefore, their detailed explanations are omitted. 
     In the present embodiment as explained above, the display device  10  includes the first antenna (first communication module  14   a ) configured to receive the radio waves for display (first radio waves) transmitted from the server device  20  (first communication module  23   a ), and the second antenna (second communication module  14   b ) configured to receive the radio waves for feeding (second radio waves) transmitted from the server device  20 . 
     In the present embodiment with such a configuration, since the radio waves for feeding can be received by the second antenna without receiving an influence from the radio waves for display, the battery  13  can be charged efficiently. 
     In the present embodiment, for example, the radio waves for display and the radio waves for feeding may be transmitted on different channels to avoid interference between the radio waves for display and the radio waves for feeding. 
     In addition, in the present embodiment, the radio waves for feeding are transmitted from the server device  20  via the second communication module  23   b , but the radio waves for feeding may be transmitted from the terminal  30  dedicated to feeding as explained in the second embodiment. 
     Fourth Embodiment 
     Next, a fourth embodiment will be explained.  FIG. 14  is a block diagram showing an example of a configuration of an electronic shelf label system according to the present embodiment. In  FIG. 14 , the same elements as those shown in  FIG. 2  are denoted by the same reference numerals and their detailed descriptions are omitted. Different elements from  FIG. 2  will be hereinafter explained mainly. In addition,  FIG. 14  shows only one display device  10  for convenience, and illustration of the other display devices  10  is omitted. 
     As shown in  FIG. 14 , an electronic shelf label system according to the present embodiment is different from the above-explained first embodiment in that a controller  12  and a converting circuit  15  are integrated in the display device  10 . 
     Operations of the electronic shelf label system according to the present embodiment are the same as those of the above-explained first embodiment, and their detailed explanations are omitted. In the present embodiment, display of the product data and charging of the battery  13  are changed by the controller  12  and, for example, the battery  13  is charged in a remaining time other than the time for rewriting the product data on the display device  10 . 
     In the present embodiment, the controller  12  and the converting circuit  15  of the display device  10  are integrated as explained above, and downsizing of the display device  10  can be implemented as compared with the above-explained first embodiment. 
     The present embodiment may be applied to the above-explained second and third embodiments. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.