JP2008191588A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display with which an after image phenomenon is prevented, while suppressing the increase in the power consumption of the liquid crystal display, using a cholesteric liquid crystal. <P>SOLUTION: The liquid crystal display device 1 in which the cholesteric liquid crystal 16 with memory properties is used, and in which at least starting of a display and changing of the display are performed by a display driving conducted with temporary application of a voltage, and the display drive comprises a combination of an image refresh drive, conducted in advance and a display draw driving, conducted in succession to the image refresh driving, comprises a temperature detection means 13 for detecting the ambient temperature of the liquid crystal display device 1 and a control means 14 for controlling the display drive. In the liquid crystal display 1; a control means 14 for controlling the display drive, when a predetermined condition, based on the time elapsed after the previous display drive and the temperature detected with the temperature detection means 13 is satisfied, in addition to the time from starting to the changing of the display. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device using a cholesteric liquid crystal having memory properties.

  In stores such as supermarkets and retail stores, it is necessary to display product information such as the name and price of the product to be sold, and the operation of displaying this product information on the product has been performed manually by hand, and the work efficiency It was a problem in terms of work costs. Therefore, an electronic shelf label system that electronically displays product information for this product has been proposed. In this electronic shelf label system, product information such as the name and price of the product is transmitted from the shelf label server and displayed on the electronic shelf label installed in the vicinity of the displayed product.

  The above-described electronic shelf label system needs to cope with various types of products displayed in stores such as supermarkets and retail stores, and therefore, a large number of electronic shelf labels are used. In addition, since it is required to keep the cost as low as possible, construction and maintenance are required easily. For this reason, battery driving using a button battery or the like is adopted for the electronic shelf label.

  Therefore, from the viewpoint of cost and maintenance, it is required to extend the life of the battery of the electronic shelf label as much as possible. For this reason, it is required to reduce the power consumption of the electronic shelf label as much as possible. Therefore, the display device for the electronic shelf label uses a cholesteric liquid crystal which has a memory property and can suppress power consumption.

  The display principle of the cholesteric liquid crystal is a mechanism for performing display using two different molecular orientations due to phase transition. That is, the liquid crystal molecules of the cholesteric liquid crystal have a helical shape, and reflect light (selective reflection) with light having a specific wavelength by this helical structure. For this reason, when the spiral axis is directed in the display surface direction, the light of a specific wavelength is reflected (planar state). Further, when a voltage is applied and the spiral axis is directed in a direction laying with respect to the display surface, the light is transmitted through the cell (focal conic state).

  The cholesteric liquid crystal having such a display principle has a feature that the state of the helical axis is maintained even when the application of voltage is stopped. That is, after the voltage is temporarily applied to drive the display of the cholesteric liquid crystal, the display is continued as it is even if the application of the voltage to the cholesteric liquid crystal is stopped. Therefore, a display device with low power consumption can be configured by using cholesteric liquid crystal.

  However, the cholesteric liquid crystal has a problem that an afterimage phenomenon occurs in which a previous image is not completely erased when another image is displayed after being left for a long time in a constant display state. This afterimage phenomenon occurs as the time for which it is left for a long time, and occurs in a shorter time as the ambient temperature increases.

  In order to prevent the occurrence of the afterimage phenomenon, it is necessary to perform a screen refresh drive for refreshing the display as the display drive of the cholesteric liquid crystal before the afterimage phenomenon occurs. For this reason, various proposals have been made regarding a method of performing the screen refresh drive (see, for example, Patent Document 1).

Patent Document 1 relates to a driving method of a memory type cholesteric liquid crystal display device. This Patent Document 1 counts the time from display update, and when a predetermined time is reached, as display driving of cholesteric liquid crystal, A cholesteric liquid crystal driving method is described in which a screen refresh drive that applies a voltage so as to be in a focal conic state is followed by a display drawing drive that applies a voltage so as to display normal display data.
JP 2002-14325 A

  As described above, the afterimage phenomenon in the cholesteric liquid crystal increases as the time for which the cholesteric liquid crystal is left is increased, and occurs in a shorter time as the ambient temperature of the cholesteric liquid crystal increases. However, in the driving method of the cholesteric liquid crystal display device described in Patent Document 1, the time from the update of the display is simply counted regardless of the ambient temperature of the cholesteric liquid crystal, and when the predetermined time is reached, the screen refresh driving and display are performed. Display driving for performing drawing driving is executed.

  Therefore, assuming that the ambient temperature is the highest and setting the display drive to be executed so as to conform to this state, the object cannot be achieved. As a result, when the ambient temperature is low, the number of times that the display drive is executed becomes larger than the minimum number of times that is originally required, and the power consumed to drive the cholesteric liquid crystal increases. Therefore, an electronic shelf label using cholesteric liquid crystal is used. There was a problem that the battery life of the battery was shortened.

  Accordingly, the present invention has been made to solve the above problem, and provides a liquid crystal display device capable of preventing an afterimage phenomenon while suppressing an increase in power consumption of a liquid crystal display device using cholesteric liquid crystals. It is something to be offered.

  The liquid crystal display device of the present invention is a liquid crystal display device using a cholesteric liquid crystal having a memory property. In this liquid crystal display device, at least display start and display change are performed by display driving performed by temporarily applying a voltage, and this display driving includes screen refresh driving performed earlier and screen refresh driving performed. It is configured in combination with display drawing driving that is subsequently performed.

   The liquid crystal display device includes a temperature detection unit that detects the ambient temperature of the liquid crystal display device, and a control unit that controls display driving. In addition to the display start and the display change, this control means is also used when a predetermined condition is satisfied that includes the elapsed time since the previous display drive and the temperature detected by the temperature detection means. It is characterized by performing display driving when it arrives.

  According to the above-described liquid crystal display device, display drive is performed when a time point when a predetermined condition having elapsed time and ambient temperature of the liquid crystal display device as an element is satisfied after the previous display drive is performed. Therefore, since it is possible to set the optimum predetermined condition based on the ambient temperature of the liquid crystal display device, it is possible to minimize the number of times of display driving, while suppressing an increase in power consumption of the liquid crystal display device, The afterimage phenomenon can be prevented.

  In the above liquid crystal display device, it is preferable that the time when the predetermined condition is satisfied is earlier when the temperature detected by the temperature detecting means is higher than when the temperature is low.

  As described above, the afterimage phenomenon in the cholesteric liquid crystal occurs in a shorter time as the ambient temperature of the cholesteric liquid crystal increases. Thus, by doing the above, it is possible to set an optimal predetermined condition based on the ambient temperature of the liquid crystal display device, and to minimize the number of times of display driving. For this reason, it is possible to prevent the afterimage phenomenon while suppressing an increase in power consumption of the liquid crystal display device.

   Specifically, the liquid crystal display device may be configured as follows. That is, first, a stepwise temperature rank is determined in advance for the temperature detected by the temperature detecting means, and a weighting coefficient corresponding to each temperature rank is determined.

  Then, the control means integrates the weighting coefficient corresponding to the temperature rank corresponding to the temperature detected by the temperature detection means periodically at a constant time interval after the previous display driving, and accumulates the weighting coefficient. Find the sum of the weighting factors, which is the sum. When the sum of the weight coefficients exceeds a predetermined number, the predetermined condition is satisfied and display driving is performed.

  As the above control means, a microprocessor is generally used. However, since the processing method as described above is suitable for processing by software, a liquid crystal display device suitable for processing by the microprocessor is configured. can do.

  Specifically, in the liquid crystal display device configured as described above, it is recommended that the weighting factor increases as the temperature rank corresponding to the weighting factor increases.

  By doing so, a liquid crystal display device having a suitable processing method can be configured as a countermeasure against the afterimage phenomenon in which the afterimage phenomenon occurs in a shorter time as the ambient temperature of the cholesteric liquid crystal increases.

  In the above-mentioned liquid crystal display device using cholesteric liquid crystal having memory properties, for example, when the background is black, if the entire surface of the surface of the liquid crystal display device is in the above-described focal conic state, light incident from the surface Is absorbed by the background and becomes dark. Further, when the entire screen on the surface of the liquid crystal display device is in the above-described planar state, light incident from the surface is reflected to be in a bright state. An actual display image is formed by mixing the dark state and the bright state.

  Therefore, in the present specification, in the liquid crystal display device using the cholesteric liquid crystal, the screen on the surface of the liquid crystal display device, which is performed to form a display image based on actual image data, has the dark state and the bright state described above. The drive that results in a mixed state is referred to as display drawing drive.

  Further, in the above liquid crystal display device using cholesteric liquid crystal, the driving is performed so that the entire screen surface of the liquid crystal display device is in a focal conic state, or the entire screen surface is in a planar state, or the screen is displayed. There can be three types of display, that is, display by drawing driving and driving that makes the light and dark state completely reversed. Such driving is effective as a countermeasure for preventing an afterimage phenomenon caused by continuously displaying the same display image for a long time in a liquid crystal display device using a cholesteric liquid crystal. Therefore, in this specification, these drivings are generally referred to as screen refresh driving.

  In this specification, as the screen refresh drive, the drive that brings the entire surface of the surface of the liquid crystal display device into the focal conic state is referred to as focal conic drive, and the drive that enters the planar state is referred to as planar drive. Called. In addition, since the display is driven in such a way that the display is completely opposite to the display by the display drawing drive, the image data used for the display drawing drive is performed using the inverted image data. This is called image data driving.

  Therefore, it is preferable to use any one of focal conic driving, planar driving, and inverted image data driving as the screen refresh driving in the liquid crystal display device. Alternatively, at least two of focal conic driving, planar driving, and reverse image data driving may be combined.

  According to the present invention, the liquid crystal display device of the present invention includes temperature detecting means for detecting the ambient temperature of the liquid crystal display device and control means for controlling display driving. In addition to the time when the display is started and the time when the display is changed, the control means has arrived at the time when a predetermined condition having the elapsed time and the temperature detected by the temperature detection means is satisfied after the previous display driving. When this happens, display drive is performed.

  Therefore, after the previous display drive, the display drive is performed when a time point when a predetermined condition having the elapsed time and the ambient temperature of the liquid crystal display device as elements is satisfied. Therefore, since it is possible to set the optimum predetermined condition based on the ambient temperature of the liquid crystal display device, it is possible to minimize the number of times of display driving, while suppressing an increase in power consumption of the liquid crystal display device, The afterimage phenomenon can be prevented.

  Further, the time when the above predetermined condition is satisfied comes earlier when the temperature detected by the temperature detecting means is higher than when the temperature is low. Since the afterimage phenomenon in the cholesteric liquid crystal occurs in a shorter time as the ambient temperature of the cholesteric liquid crystal increases, an optimum predetermined condition based on the ambient temperature of the liquid crystal display device can be set in this way. Accordingly, the number of display driving operations can be minimized, and an afterimage phenomenon can be prevented while suppressing an increase in power consumption of the liquid crystal display device.

  Further, in the liquid crystal display device of the present invention, specifically, after the previous display driving, the weighting coefficient corresponding to the temperature rank corresponding to the temperature detected by the temperature detecting means is periodically set at regular time intervals. Integration is performed to obtain a weighting factor sum that is a cumulative sum of the weighting factors. Then, it is assumed that the predetermined condition is satisfied when the obtained total weighting factor is used as the predetermined condition and the total weighting coefficient is equal to or greater than a predetermined number. Since such a processing method is suitable for processing by software, a liquid crystal display device suitable for processing by a microprocessor can be configured.

  The weighting factor increases as the temperature rank corresponding to the weighting factor increases. Therefore, as a countermeasure against the afterimage phenomenon that the afterimage phenomenon occurs in a shorter time as the ambient temperature of the cholesteric liquid crystal becomes higher, a liquid crystal display device having a suitable processing method can be configured.

  Next, a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. As described above, in the electronic shelf label system proposed as a system to be introduced in a store such as a supermarket or a retail store, an electronic shelf label using a cholesteric liquid crystal having a memory property and capable of suppressing power consumption is used. It has been.

  Therefore, in this embodiment, as an explanation of the liquid crystal display device of the present invention, an explanation will be given using an electronic shelf label in which this cholesteric liquid crystal is used. This electronic shelf label is configured by adding functions necessary for an electronic shelf label system to the function of the liquid crystal display device of the present invention in which cholesteric liquid crystal is used.

  FIG. 1 is a schematic diagram showing an overall configuration of an electronic shelf label system 100 using the electronic shelf label 1 in the present embodiment. Referring to FIG. 1, the electronic shelf label system 100 is roughly divided into a plurality of electronic shelf labels 1, 1,. The electronic shelf label system 100 includes a shelf label server 2 that transmits to the tag 1 and is connected to a POS system 200 installed in the store via a LAN.

  The POS system 200 includes a store server 6 for managing product information, sales information, ordering information, etc., a plurality of POS terminals 7, 7,... It comprises one or a plurality of wireless LAN access points 8 for performing wireless communication with the handy terminal 9, and these store server 6, each POS terminal 7, 7,. Connected by.

  The electronic shelf label system 100 includes a shelf label server 2, a base station 3, which is a repeater, or a plurality of transceivers 4, 4,... And a large number of electronic shelf labels 1, 1,. It is configured. Among these, the shelf label server 2 is installed in a backyard of a store such as a supermarket, and is connected to the base station 3, the store server 6, and the POS terminal 7 via a LAN.

  In addition, the shelf label server 2 obtains information about the product (product name, product code, sales price, unit price, special price information, etc.) from the store server 6, and creates display information to be displayed on the electronic shelf label 1. It has a function of transmitting data to the electronic shelf label 1 via the base station 3 and the transceiver 4. The base station 3 also has a function of controlling data between the shelf label server 2 and the transceiver 4 and a function of communicating with the electronic shelf label 1 as a transceiver. The transceiver 4 has a function of transmitting and receiving with the electronic shelf label 1. The electronic shelf label 1 has a function of receiving commands and data from the transceiver 4 and displaying product information.

  FIG. 2 is a functional block diagram of the shelf label server 2. In FIG. 2, a shelf label server 2 includes a control unit 21 that controls the entire server, a memory unit 22 such as a ROM that stores a control program, a CD-ROM / RAM, a DVD-RAM, a hard disk (HD), an IC memory, and the like. An external storage unit 23, a display unit 24 including an LCD, an input unit 25 including a mouse, a keyboard, a touch panel, a communication unit 26 for performing communication via a LAN, and a power supply unit 27 for supplying power to these units. The parts other than the power supply part 27 are connected by a bus line 28. Information regarding the product, identification information (ID) of the electronic shelf label, management information associated with the identification information, and the like are stored in the external storage unit 23 described above.

  FIG. 3 is a functional block diagram of the electronic shelf label 1. In FIG. 3, the electronic shelf label 1 uses a battery 11 that constitutes a power supply unit, an LCD power supply circuit 12 that generates LCD power, a temperature sensor 13, a control IC 14 that controls the electronic shelf label 1, an antenna 15, and a cholesteric LCD. The display panel 16, a COMMON driver 17 that drives the display panel 16, and a SEGMENT driver 18 that also drives the display panel 16.

  Among these, the control IC 14 includes a CPU 141 for controlling the electronic shelf label 1, a ROM 142 for storing a control program, a RAM 143 for storing data to be displayed on the display panel 16, an RTC (Real Time Clock) 144 for measuring the current time, The control signal and LCD drive of the A / D converter (ADC) 145 for inputting the voltage of the battery 11 and the output detected by the temperature sensor 13 to the control IC 14, the RF circuit 146 which is a wireless communication unit, and the LCD power supply circuit 12 It is composed of an I / O circuit 147 that outputs a signal.

  The battery 11 is supplied to the LCD power circuit 12 and the control IC 14. The temperature sensor 13 is used to detect the ambient temperature of the electronic shelf label 1. The temperature detected by the temperature sensor 13 is used for display drive control for the display panel 16 of the electronic shelf label 1 described later.

  The LCD power supply circuit 12 is a circuit that converts the power supplied from the battery 11 into a power supply for driving the display panel 16 composed of an LCD. The power supply voltage suitable for LCD driving is generated based on the voltage of the battery 11 input to the control IC 14 and the temperature detected by the temperature sensor 13. In other words, the CPU 141 of the control IC 14 generates a control signal for generating an optimum voltage, and sends this control signal from the I / O circuit 147 to the LCD power supply circuit 12, so that the LCD power supply circuit 12 is suitable for driving the LCD. A power supply voltage is generated. By controlling the LCD power supply circuit 12 with a control signal, a voltage for driving the display on the display panel 16 of the electronic shelf label 1 is applied and stopped, which will be described later.

  The control IC 14 communicates with the shelf label server 2 via the RF circuit 146, the antenna 15, and the transceiver 4. Display data transmitted from the shelf label server 2 is stored in the RAM 143. The control IC 14 reads data necessary for display on the display panel 16 from the RAM 143 and outputs the data to the COMMON driver 17 and the SEGMENT driver 18 via the I / O circuit 147. Then, a signal is sent from the COMMON driver 17 and the SEGMENT driver 18 to the cholesteric LCD, and information about the product is displayed on the cholesteric LCD. A cholesteric LCD has a plurality of display areas between opposed glass substrates, and liquid crystals of different display colors are injected into each of the display areas.

  4A and 4B are external views of the electronic shelf label 1. FIG. The electronic shelf label 1 has a case body 1 </ b> A that is horizontally long, and the entire front surface is a horizontally long display panel 16. On the display panel 16, product information as shown in FIG. 4A or 4B and management information (information of a management table T described later) can be switched and displayed. Normally, when the product is arranged in the vicinity of the product, product information as shown in FIG. When the employee wants to confirm the management information of the product, the product information screen shown in the figure is switched to the management information screen (not shown) by pressing a switching button (not shown) or an instruction from the handy terminal 9. It is like that. When the management information is confirmed and used again as the electronic shelf label 1, if the switch button is operated again or the handy terminal 9 is used again, the management information screen again displays FIG. ) Or the product information screen shown in (b).

  In the present embodiment, as described above, a cholesteric liquid crystal having a memory property is used for the display panel 16 of the electronic shelf label 1. The display principle of the cholesteric liquid crystal is a mechanism for performing display using two different molecular orientations due to phase transition. That is, the liquid crystal molecules of the cholesteric liquid crystal have a helical shape, and reflect light (selective reflection) with light having a specific wavelength by this helical structure. For this reason, when the spiral axis is directed in the display surface direction, the light of a specific wavelength is reflected (planar state). Further, when a voltage is applied and the spiral axis is directed in a direction laying with respect to the display surface, the light is transmitted through the cell (focal conic state).

  This cholesteric liquid crystal has a feature that the state of the helical axis is maintained even when the application of voltage is stopped. That is, after the voltage is temporarily applied to drive the display of the cholesteric liquid crystal, the display is continued as it is even if the application of the voltage to the cholesteric liquid crystal is stopped. Therefore, the electronic shelf label 1 which can suppress power consumption can be comprised by using a cholesteric liquid crystal.

  Further, in the present embodiment, the display area of the display panel 16 is divided into two in the vertical direction, liquid crystal that selectively reflects green light is injected into the upper display area 161, and red is displayed in the lower display area 162. Liquid crystal that selectively reflects light is injected. The substrate on the back side of the liquid crystal is a black substrate for both the upper display area 161 and the lower display area 162. As a result, the upper display area 161 displays a green character or the like on a black background, and the lower display area 162 displays a red character or the like on a black background. In FIG. 4A, reference numeral 161a denotes a special price display area.

  Next, display driving performed for displaying on the display panel 16 of the electronic shelf label 1 in the present embodiment will be described. This display driving is performed by temporarily applying a voltage, and when the display driving is completed, the voltage application is stopped. The application and stop of the voltage is performed by the control by the control signal for the LCD power supply circuit 12 as described above.

  In the cholesteric liquid crystal used in the electronic shelf label 1, as described above, after standing for a long time in a fixed display state, when another image is displayed, the previous image remains without being completely erased. There is a problem that causes the phenomenon. This afterimage phenomenon occurs as the time for which it is left for a long time, and occurs in a shorter time as the ambient temperature increases. For this reason, this afterimage phenomenon countermeasure is indispensable for the display panel 16 of the electronic shelf label 1 in the present embodiment using the cholesteric liquid crystal. Therefore, the display drive for the display panel 16 of the electronic shelf label 1 includes a countermeasure against this afterimage phenomenon.

  That is, the above display drive is performed by a combination of the screen refresh drive performed first and the display drawing drive performed after the screen refresh drive. Among these, the display drawing drive is a drive in which the screen on the surface of the liquid crystal display device, which is performed to form a display image based on actual image data, is a state in which the dark state and the light state are mixed. The screen refresh drive is effective in preventing the above-mentioned afterimage phenomenon, and either focal conic drive, planar drive, or inverted image data drive is used.

  Of these, the focal conic driving is a driving in which the entire screen on the surface of the liquid crystal display device is in a focal conic state. Planar drive is a drive in which the entire screen is in a planar state. Inverted image data driving is performed using image data obtained by inverting the image data used for display drawing driving, and the screen is in a state in which light and darkness are completely reversed from the display by display drawing driving. Drive.

  Note that the screen refresh drive may be configured by combining at least two of focal conic drive, planar drive, and reverse image data drive.

  In the display drive for the display panel 16 of the electronic shelf label 1 in the present embodiment, the display drive performed by the combination of the screen refresh drive and the display drawing drive described above is required for the display panel 16 of the electronic shelf label 1. By performing at the time, the afterimage phenomenon can be prevented. Then, next, the display drive control processing for the display panel 16 of the electronic shelf label 1 will be specifically described.

  In the display drive control process described above, a stepwise temperature rank is determined in advance for the ambient temperature T of the electronic shelf label 1 detected by the temperature sensor 13, and a weighting coefficient corresponding to each temperature rank is determined. It is done. FIG. 5 is a table showing the relationship between the temperature rank of the ambient temperature and the weighting factor. That is, the weighting factor is 1 when the ambient temperature T is 0 ° C. or less, the weighting factor is 2 when the ambient temperature T exceeds 0 ° C. and 30 ° C. or less, and the ambient temperature T exceeds 30 ° C. and 60 ° C. The weighting factor is 4 if it is below, and the weighting factor is 8 if the ambient temperature T exceeds 60 ° C.

  The control IC 14 of the electronic shelf label 1 is a weighting coefficient corresponding to the temperature rank corresponding to the temperature detected by the temperature sensor 13 periodically at regular time intervals after the previous display drive as a display drive control process. Are accumulated to obtain a weighting factor sum which is a cumulative sum of the weighting factors. Then, when the obtained weight coefficient sum is equal to or greater than a predetermined determination reference value N described later, display driving is performed.

  In order to perform the display drive control process as described above, a counter C, a timer TM, and a flag F are provided on the software of the electronic shelf label 1. The counter C is used to determine when display driving is necessary to prevent the afterimage phenomenon. The timer TM is used to ensure the above-mentioned fixed time interval. The flag F is used to indicate that display driving has been performed. The flag F is normally in a reset state, and is set only immediately after display driving has been performed.

  Further, as described above, the ambient temperature of the electronic shelf label 1 is detected by the temperature sensor 13, and the detected ambient temperature of the electronic shelf label 1 is displayed as T. In addition, the RAM 143 which is a memory of the control IC 14 of the electronic shelf label 1 is used as a determination criterion for the count value of the counter C used to determine the time when display driving for preventing the afterimage phenomenon is necessary. A reference value N is stored in advance. The determination reference value N is determined so that the time when display driving for preventing the afterimage phenomenon is necessary is the optimum time. For example, 100 is used as the value of the determination reference value N.

  FIG. 6 and FIG. 7 are flowcharts showing display drive control processing for the display panel 16 of the electronic shelf label 1. Among these, the flowchart of FIG. 6 is a flowchart showing processing for determining a time when display driving is necessary to prevent the afterimage phenomenon, and the flowchart of FIG. 7 is a flowchart showing processing for performing display driving. . In the control IC 14 of the electronic shelf label 1, the processes shown in the two flowcharts of FIG. 6 and FIG. 7 are processed in parallel.

  First, it demonstrates based on the flowchart shown in FIG. In FIG. 6, first, the flag F is reset (S1), and the counter C is reset (S2). Next, the timer TM is reset (S3), and the timer TM is set with a time-up time and started (S4). The time-up time of the timer TM is set to such a value that the above-mentioned fixed time interval can be obtained. In general, the time-up time of the timer TM is about several hours.

  Next, it is checked whether or not the timer TM has expired (S5). If the timer TM has not expired, the predetermined time has not yet elapsed, so the flag F is set next. It is checked whether it has been done (S6). If the flag F is not set, display driving is not performed, so the process returns to S5, and the processes after S5 are repeated.

  If it is checked in S5 whether or not the timer TM has expired, if the timer TM has expired, the above-mentioned fixed time has elapsed. Then, next, the ambient temperature T of the electronic shelf label 1 is detected by the temperature sensor 13, and the detected ambient temperature T is compared with the above temperature rank (S7), and processing corresponding to the corresponding temperature rank is performed. Do.

  That is, when the ambient temperature T is 0 ° C. or less (S8), the weight coefficient 1 is added to the counter C (S9). When the ambient temperature T is 30 ° C. or less (S10), the weight coefficient 2 is added to the counter C (S11). When the ambient temperature T is 60 ° C. or less (S12), the weight coefficient 4 is added to the counter C (S13). Alternatively, when the ambient temperature T exceeds 60 ° C. (S12), the weighting coefficient 8 is added to the counter C (S14). When this process ends, the process returns to S3 and the processes after S3 are continued.

  By repeating this process, the counter C is counted up based on the ambient temperature of the electronic shelf label 1. In other words, when the ambient temperature of the electronic shelf label 1 is high, the count value accumulated in the counter C is increased compared to when the ambient temperature is low.

  Next, description will be made based on the flowchart shown in FIG. In FIG. 7, first, it is checked whether or not the electronic shelf label 1 has received display data from the shelf label server 2 (S21). If not received, the count value of the counter C is stored in the RAM 143 in advance. It is checked whether or not it is greater than the stored determination reference value N (S22). If the count value of the counter C is not equal to or greater than the determination reference value N (S22), the process returns to S21 and is repeated from the beginning.

  The electronic shelf label 1 receives display data from the shelf label server 2 in the check of whether or not the electronic shelf label 1 has received display data from the shelf label server 2 in S21. This is when the display starts on the panel 16 or when the display is changed. In addition, in the check of whether the count value of the counter C is equal to or greater than the determination reference value N in S22, the count value of the counter C is equal to or greater than the determination reference value N is an afterimage on the display panel 16 of the electronic shelf label 1. This is when display driving is required to prevent the phenomenon.

  Therefore, when the electronic shelf label 1 receives display data from the shelf label server 2 in the check of whether or not the electronic shelf label 1 has received display data from the shelf label server 2 in S21, or the counter C in S22 If it is checked whether the count value is equal to or greater than the determination reference value N and the count value of the counter C is equal to or greater than the determination reference value N, the process proceeds to S23.

  In S23, screen refresh driving is performed, then display drawing driving is performed (S24), flag F is further set (S25), and the process returns to S21 and is repeated from the beginning. The screen refresh drive in S23 can prevent an afterimage phenomenon on the display panel 16 of the electronic shelf label 1, and the display drawing drive in S24 forms a display image based on actual image data on the display panel 16. Can do.

  If the flag F is set in S25, whether or not the flag F in S6 of the flowchart showing the process for determining the time when display driving is necessary to prevent the afterimage phenomenon shown in FIG. 6 is set. In this check, the flag F is set. In this case, the process returns to S1 and the process is repeated from the beginning.

  That is, once the screen refresh drive and display drawing drive (ie, display drive) are performed, the counter C that determines the time when display drive is required to prevent the afterimage phenomenon is reset, and from the beginning. , Means counting again.

  Next, the display drive control process will be described with reference to Example 1 shown in FIG. 8 and Example 2 shown in FIG. In these examples, the time-up value set in the timer TM is 1 hour, and the determination reference value N is 50.

  First, Example 1 shown in FIG. 8 will be described. In Example 1, since display data is received when the power is turned on, display driving (screen refresh driving (S23) and display drawing driving (S24)) is performed when the power is turned on. C counts up. Since the count value of the counter C exceeds 50 13 hours after the power is turned on, display driving (screen refresh driving (S23) and display drawing driving (S24)) is performed 13 hours after the power is turned on. After this display driving is completed, the counter C is reset and the counter C starts counting up. Further, since the count value of the counter C exceeds 50 22 hours after the power is turned on, the display drive (screen refresh drive (S23) and display drawing drive (S24)) is performed 22 hours after the power is turned on. After the display drive is completed, the counter C is reset and the counter C starts counting up, and thereafter the processing is continued in the same manner.

  Next, Example 2 shown in FIG. 9 will be described. In Example 2, since display data is received when the power is turned on, display driving (screen refresh driving (S23) and display drawing driving (S24)) is performed when the power is turned on, and display driving is performed. After completion, the counter C starts counting up. Since display data is received again 10 hours after the power is turned on, display driving (screen refresh driving (S23) and display drawing driving (S24)) is performed at the time when the display data is received. After the end, the counter C is reset and the counter C starts counting up. Since the count value of the counter C exceeds 50 17 hours after the power is turned on, display driving (screen refresh driving (S23) and display drawing driving (S24)) is performed 17 hours after the power is turned on. After this display drive is completed, the counter C is reset and the counter C starts to be counted up. Thereafter, the processing is continued in the same manner.

  According to the electronic shelf label 1 in the present embodiment, the electronic shelf label 1 includes the temperature sensor 13 that detects the ambient temperature of the electronic shelf label 1 and the control IC 14 that controls display driving. . This control IC 14 is detected by the elapsed time and temperature sensor 13 that the count value of the counter C is equal to or greater than the determination reference value N after the previous display driving, in addition to the display start and display change. Display driving is performed when the time point at which a predetermined condition including temperature is satisfied is reached.

  Accordingly, since the optimum predetermined condition based on the ambient temperature of the electronic shelf label 1 can be set, the number of display driving operations can be minimized, and an increase in power consumption of the electronic shelf label 1 can be suppressed. However, it is possible to prevent the afterimage phenomenon.

  In addition, the time when the above predetermined condition is satisfied is earlier when the temperature detected by the temperature sensor 13 is higher than when the temperature is low, so that the optimal predetermined based on the ambient temperature of the electronic shelf label 1 is reached. Conditions can be set. Therefore, the number of times of display driving in the electronic shelf label 1 can be minimized, and an afterimage phenomenon can be prevented while suppressing an increase in power consumption of the electronic shelf label 1.

It is the schematic showing the whole structure of the electronic shelf label system using the electronic shelf label in this Embodiment. It is a functional block diagram of the shelf label server of the electronic shelf label system using the electronic shelf label in this Embodiment. It is a functional block diagram of the electronic shelf label in this Embodiment. (A), (b) is an external view of the electronic shelf label in this Embodiment. It is the table which showed the relationship between the temperature rank of the ambient temperature of the electronic shelf label in this Embodiment, and a weighting coefficient. It is the flowchart (the 1) which showed the display drive control process with respect to the display panel of the electronic shelf label in this Embodiment. It is the flowchart (the 2) which showed the display drive control process with respect to the display panel of the electronic shelf label in this Embodiment. It is the table which showed the content of Example 1 in this Embodiment. It is the table which showed the content of Example 2 in this Embodiment.

Explanation of symbols

1 Electronic shelf label 2 Shelf label server 3 Base station 4 Transceiver 6 Store server 7 POS terminal 8 Wireless LAN access point 9 Handy terminal 11 Battery 12 LCD power circuit 13 Temperature sensor 14 Control IC
DESCRIPTION OF SYMBOLS 15 Antenna 16 Display panel 17 COMMON driver 18 SEGMENT driver 21 Control part 22 Memory part 23 External storage part 24 Display part 25 Input part 26 Communication part 27 Power supply part 28 Bus line 100 Electronic shelf label system 141 CPU
142 ROM
143 RAM
144 RTC
145 A / D converter 146 RF circuit 147 I / O circuit 161 Upper display area 161a Special price display area 162 Lower display area 200 POS system

Claims (8)

A cholesteric liquid crystal having a memory property is used, and at least a display start and a display change are performed by a display drive performed by temporarily applying a voltage, and the display drive is a screen refresh drive performed earlier. , A liquid crystal display device in combination with a display drawing drive performed after the screen refresh drive,
Temperature detecting means for detecting the ambient temperature of the liquid crystal display device, and control means for controlling the display drive,
In addition to the display start and the display change, the control means satisfies a predetermined condition including an elapsed time since the previous display drive and a temperature detected by the temperature detection means. The liquid crystal display device is characterized in that the display driving is performed when the time point to be reached is reached.    The liquid crystal display device according to claim 1, wherein the time when the predetermined condition is satisfied is earlier when the temperature detected by the temperature detecting means is higher than when the temperature is low. For the temperature detected by the temperature detecting means, a stepwise temperature rank is determined in advance, and a weighting factor corresponding to each temperature rank is determined,
The control means integrates the weighting coefficient corresponding to the temperature rank corresponding to the temperature detected by the temperature detection means periodically at regular time intervals after the display driving performed last time, 3. The liquid crystal display according to claim 1, wherein a weighting factor total that is a cumulative sum of weighting factors is obtained, and the predetermined condition is satisfied and the display driving is performed when the weighting factor sum exceeds a predetermined number. apparatus.   The liquid crystal display device according to claim 3, wherein the weighting factor increases as the temperature rank corresponding to the weighting factor increases.   The liquid crystal display device according to claim 1, wherein the screen refresh driving is focal conic driving performed so that a focal conic state occurs.   The liquid crystal display device according to claim 1, wherein the screen refresh driving is planar driving performed so that a planar state occurs.   5. The liquid crystal display device according to claim 1, wherein the screen refresh drive is inverted image data drive performed using image data obtained by inverting image data used for the display drawing drive.   The screen refresh drive uses image data obtained by inverting the image data used for the focal drive, which is performed so as to generate the focal conic state, the planar drive which is performed so as to generate the planar state, or the display drawing drive. 5. The liquid crystal display device according to claim 1, wherein at least two of the reversed image data driving performed in combination are combined.

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