JP5131115B2 - Display system and display device - Google Patents

Description

  The present invention relates to a display system in which a memory-type display device and a data supply section for supplying display data to the display device are separated and connected between them by a communication path, and a display device used therein.

  In recent years, development of electronic paper has been actively promoted at companies and universities as a rewritable display device that can retain display contents even when the power is turned off. Various display methods such as an electrophoresis method, an electronic powder fluid method, a twist ball method, and a liquid crystal display have been proposed as display methods for electronic paper. Both types of electronic paper realize flexibility by using a flexible film substrate as a base. In addition, the electronic paper has a feature that it can hold a display state even when there is no power source and can be electrically rewritten, so that it can realize ultra-low power consumption electronic paper.

  Electronic paper is required to have a reflective display that is flexible to the above-mentioned paper and that is easy on the eyes and does not get tired. A promising method of electronic paper is a liquid crystal display element (LCD) using cholesteric liquid crystal, which is attracting attention because it is a reflective type and can display color. Cholesteric liquid crystal has excellent characteristics such as semi-permanent display retention (memory property), vivid color display, high contrast, and high resolution. Hereinafter, a cholesteric liquid crystal display element will be described as an example, but the disclosed technique is not limited thereto.

  When browsing digitized books, newspapers, comics, printed output from computers, etc., displaying these image data on electronic paper makes it possible to realize a display equivalent to that displayed on a normal liquid crystal. Then, the display on the electronic paper has an advantage that the power consumption can be suppressed as compared with the display on the liquid crystal. This is because the image data is not display data that can be rewritten several tens of times per second like a moving image, but display data that does not need to be rewritten for a certain period of time once displayed. A normal liquid crystal display device always applies voltage pulses even when displaying the same image, and consumes power. On the other hand, since electronic paper has a memory property, it is not necessary to rewrite when displaying the same image.

  A display device configured by electronic paper and a data supply unit that stores display data to be displayed on the electronic paper are separated, and the display data is supplied from the data supply unit to the electronic paper by communication. This improves the portability of the electronic paper. Thereby, it becomes possible to install electronic paper in various places. In particular, portability is greatly improved by performing communication of image data between the data supply unit and the electronic paper by a wireless method such as Bluetooth (registered trademark). When the wireless communication method is used, it is necessary to incorporate a power source in the display device in order to perform communication processing and display image rewriting processing. However, from the viewpoint of portability, the power source is required to be light and small.

  However, the lighter and smaller the power supply, the smaller the power supply capability, and the display device is required to be able to operate with a powerless power supply. Therefore, it is necessary to reduce the power consumption for a long time and to prevent a large current from flowing in a short time, that is, to reduce the maximum current.

  A drive unit for outputting an image in a separation type output system that separates an image output unit such as a printing device or a display device and an image data supply unit and communicates image data therebetween via Bluetooth (registered trademark) Then, it is possible to control the power supply to parts other than the drive part. Then, power is supplied to the drive unit only when an image is output. This stops unnecessary power supply to the drive unit that does not need to operate except during image output, thereby reducing power consumption.

  In a separate display system, it is known to reduce power consumption by setting a communication unit of a display device in a standby mode. Specifically, the power supply to the communication unit, the microprocessor for control, and other parts for outputting an image can be controlled. The communication unit receives a plurality of sets of image data at a time, and after the reception, the operation other than the minimum circuit necessary for sensing data reception is stopped and the standby mode is set. The rewriting process is performed in response to the timer activation by the processor. Thereby, the power consumption overhead due to the communication operation can be reduced.

JP 2003-163711 A JP 2006-30718 A International Publication WO2007 / 110949A1

  However, the above-described configuration for reducing the power consumption by setting the communication unit in the standby mode is to receive a plurality of sets of image data at a time, and a large capacity memory for storing these image data is provided in the display device. This creates another problem of miniaturization and low power consumption. In actual use, image data is often received one set at a time, and in such a case, the communication unit cannot be set to the standby mode.

  Further, in the above configuration, the communication unit is in the standby mode, and communication data can be sensed. Therefore, a reception operation is performed when data is communicated even in the standby mode, and the reception operation may be activated during the display rewriting process. In this case, a large current flows in a short period of time, and it becomes necessary to set the maximum current of the power source accordingly, resulting in a large power source.

  An object of the disclosed embodiment is to realize a display system and a display device that can operate even with a light and small power source with a simple configuration.

  A display system according to an embodiment includes a display device and a data supply unit that supplies display data to the display device, and the display system communicates display data from the data supply unit to the display device. Power display unit, a communication unit with the data supply unit, a display rewrite unit for rewriting the display of the display element, and a power supply control unit for controlling power supply to the communication unit and the display rewrite unit. The control unit stops the power supply to the communication unit during the rewrite period in which the display rewrite unit rewrites the display of the display element according to the display data supplied from the data supply unit, and the data supply unit displays the display during the rewrite period. Stop communication to the device.

  In the display system of the embodiment, power supply to the communication unit is stopped during the rewriting period for rewriting to display data, so that power consumption can be reduced, and in particular, power supply to the communication unit and other parts is not performed at the same time. Maximum current can be reduced. Since the data supply unit stops communication with the display device during the rewriting period, no problem occurs even if the communication unit of the display device is completely inactive.

  FIG. 1 is a block diagram illustrating a configuration of a display system according to the first embodiment.

  As shown in FIG. 1, the display system according to the first embodiment includes a display device 1 and a data supply unit 2, and the display device 1 and the data supply unit 2 are communicably connected by wireless communication. ing. Here, the Bluetooth (registered trademark) system is used for wireless communication, and image data compressed by the JPEG system is transmitted from the data supply unit 2 to the display device 1.

  The display device 1 includes an electronic paper 11, a display driving unit 12, a power supply control unit 13, an image processing unit 14, a memory 15, a temperature sensor 16, a memory rewriting time deriving unit 18, and a communication unit 18. Have. Although not shown, a control unit that controls the entire display device 1 is provided. The electronic paper 11 is a paper having flexibility. The portion excluding the electronic paper 11 of the display device 1 is also made thin and small, and the entire display device 1 is also in the form of a flexible paper.

  The data supply unit 2 includes a transmission data storage unit 21, a communication control unit 22, and a communication unit 23.

  The electronic paper 11 may be any memory-type display element that can hold an image displayed by writing processing for a long time without supplying power, but here, a cholesteric liquid crystal display element is used. The cholesteric liquid crystal display element will be described later. The display driving unit 12 drives the electronic paper 11 so as to perform display according to the image data. In the case of a cholesteric liquid crystal display element, the display drive unit 12 uses a general-purpose driver of a passive drive type.

  The power supply control unit 13 can independently control whether or not to supply power to each unit in the display device 11. In the case of electronic paper, a button battery or the like is used as a power source. Here, the power supply control unit 13 can independently control the power supplied to the display driving unit 12, the memory 15, the communication unit 18, the image processing unit 14, and the remaining part.

  The image processing unit 14 is constituted by, for example, a microprocessor or a DSP, processes the image data transmitted from the data supply unit 2 and stored in the memory 15, converts the image data to a format to be supplied to the display driving unit 12, and converts the image data. Image data is stored in the memory 15. The memory 15 stores the image data and the converted image data transmitted from the data supply unit 2. Further, the memory 15 also stores a characteristic value unique to the electronic paper 11 mounted on the display device 1. The part for storing the characteristic value is composed of a nonvolatile memory.

  The temperature sensor 16 detects the temperature of the electronic paper 11. Although the temperature detection location may be one location, the temperature of a plurality of locations may be detected and the average may be used as the detection temperature. The rewriting time deriving unit 18 derives a rewriting time required for rewriting the display image based on the characteristic value data stored in the memory 15, the temperature detected by the temperature sensor 16, and the image data transmitted from the data supply unit 2. The rewrite time deriving unit 18 is realized by a low-function microprocessor together with a control unit that performs overall control of the display device 1.

  The communication unit 18 of the display device 1 and the communication unit 23 of the data supply unit 2 communicate using the Bluetooth (registered trademark) system, and the communication unit 23 of the data supply unit 2 compresses the communication unit 18 of the display device 1 using the JPEG system. Sent image data. Note that it is also possible to transmit data from the communication unit 18 of the display device 1 to the communication unit 23 of the data supply unit 2.

  The transmission data storage unit 21 stores data to be transmitted to the display device 1 such as image data. The communication control unit 22 performs control to transmit the image data stored in the transmission data storage unit 21 from the communication unit 23.

  The data supply unit 2 is arranged near the display device 1 and is connected to the host computer by a wired method or a wireless method (for example, a telephone line). An image to be displayed is communicated from the host computer to the data supply unit 2. The transmission data storage unit 21 stores a large number of sets of image data, and may be supplied to the display device 1 and displayed in order at predetermined time intervals.

  Next, the display device 1 having the electronic paper 11 using cholesteric liquid crystal will be described in detail. In the following description, the prior art described in Patent Document 3 is referred to and incorporated.

  FIG. 2 is a diagram showing an overall configuration of a liquid crystal display device according to an embodiment using a dot matrix type display element 30 having a memory-type display material such as cholesteric liquid crystal. For example, the display element 30 has A4 size XGA specifications and has 1024 × 768 pixels. The display element 30 is used as the electronic paper 11.

  The power supply 31 outputs a voltage of 3V to 5V, for example. The booster 32 boosts the input voltage from the power supply 31 to 36V to 40V by a regulator such as a DC-DC converter. The voltage switching unit 33 generates various voltages by resistance division or the like. The voltage stabilizing unit 34 preferably uses an operational amplifier voltage follower circuit in order to stabilize various voltages supplied from the voltage switching unit 33. Although not shown, power is supplied from the power supply 31 not only to the boosting unit 32 but also to the image processing unit 14, the memory 15, the communication unit 18, and the like. It is possible to control whether or not.

  The original oscillation clock unit 35 generates a basic clock that is a basic operation. The frequency divider 36 divides the basic clock to generate various clocks necessary for the operation.

  The control circuit 37 generates a control signal based on the basic clock, various clocks, and image data, and supplies the control signal to the common driver 38 and the segment driver 39. The control circuit 37 is configured by a simple microprocessor (MCU) and controls each part of the display device 1. The control circuit 37 reads the temperature of the display element 30 detected by the temperature sensor 16 and derives the time required for rewriting from the detected temperature, the characteristic value of the display element 30 stored in the memory 15 and the image data to be rewritten. More specifically, the control circuit 37 displays the image processing time required for the conversion processing by the image processing unit 14 from the image data to be rewritten, the display element by the common driver 38 and the segment driver 39 from the converted image data, the detected temperature, and the characteristic value. The writing time required to write 30 images is derived. The sum of the image processing time and the writing time is the rewriting time.

  The memory 15 includes a dynamic memory unit such as DRAM or SRAM, and a non-volatile memory unit. The dynamic memory unit stores the image data received by the communication unit 18. The nonvolatile memory unit stores the characteristic value of the display element 30 input at the time of shipment.

  The image processing unit is composed of, for example, a microprocessor or a DSP, processes the image data supplied from the communication unit 19 stored in the memory 15, and converts the image data into a format to be supplied to the common driver 38 and the segment driver 39. . The converted image data is stored in the dynamic memory unit of the memory 15 and is supplied to the segment driver 39 during the writing process.

  From the above description, the electronic paper 11 of FIG. 1 corresponds to the display element 30 of FIG. 2, and the display driving unit 12 corresponds to the boosting unit 32, the voltage switching unit 33, the voltage stabilizing unit 34, the common driver 38, and the segment driver 39. The power supply control unit 13 corresponds to a part of the power supply 31 and the control circuit 37, and the rewrite time deriving unit 17 corresponds to a part of the control circuit 37.

  Next, rewrite time calculation processing will be described. The characteristic value of the display element stored in the nonvolatile part of the memory 15 is a voltage application time that the display driving part 12 applies to the electronic paper 11 during the writing process. For example, in the case of the cholesteric liquid crystal display element 30, the common driver 38 and the segment driver 39 apply a predetermined voltage (reset voltage: ± 36V) for a predetermined period in order to bring the liquid crystal into a planar state (white state). This application time differs for each display element. For example, there may be a case where a planar state is obtained if a reset voltage is applied for 50 ms, or a case where a planar state is not obtained unless 100 ms is applied. In addition, when a transition is made from a planar state to a state in which a planar state and a focal conic state are mixed (halftone state or black state), the relationship between the gradation value and the time for applying the writing voltage also varies depending on the display element. Further, there are various characteristic values such as the number of pixels of the display element 30 and the length of time during which no voltage is applied after the state transition. The memory 15 stores a characteristic value related to the image writing time among these.

  In the case of a cholesteric liquid crystal display element, an image can be rewritten in units of electrodes driven by a common driver 38. Therefore, the writing time differs depending on the size of the area to be rewritten. The writing time is expressed by the following formula.

Write time = Time to set the rewrite area in the planar state (reset time) + Time to change the rewrite area from the planar state to the planar state and the focal conic state (gradation write time) + No voltage application time In the planar state, a reset voltage is applied simultaneously to the entire rewrite area. Therefore, the reset time for putting the rewrite area in the planar state can be calculated from the above characteristic value.

  When the rewriting area is changed from the planar state to the planar state and the focal conic state, a scan pulse is applied to the area from the common driver 38, and a write voltage is applied from the segment driver 39 in synchronization with the application of the scan pulse. . Therefore, the time for which the rewrite area is in a state in which the planar state and the focal conic state are mixed (chairman write time) is represented by the number of rewrite lines × 1 line scan time. The scan time for one line can be calculated from the characteristic value as described above. In the case where a plurality of scans are performed in order to display a halftone, the total time of each scan is obtained.

  Depending on the display device, writing may be performed for each pixel. In this case, the time is calculated based on the number of pixels in the region to be rewritten. Furthermore, depending on the display element, the entire image may be rewritten even when a part of the image portion is rewritten. In this case, the size of the rewrite area does not affect the time, and the time is determined only by the characteristic value.

  The voltage non-application time is determined by the characteristic value.

  In the case of a cholesteric liquid crystal display element, the “reset time” and the “gradation writing time” vary depending on the temperature. Therefore, these times are corrected by the temperature of the display element 30 detected by the temperature sensor 16. For example, the memory 15 stores a plurality of characteristic values corresponding to the temperature, and the control circuit 37 (rewrite time deriving unit 17) reads the characteristic value corresponding to the detected temperature. The above calculation is performed to calculate the rewriting time.

  Since the performance of the image processing unit 14 hardly changes with temperature, it is possible to estimate the image processing time required to process the image data received by the image processing unit 14. For example, the image processing time is approximately proportional to the amount of image data, and may be determined according to the amount of image data.

  In any case, the same rewrite time needs to be derived under the same rewrite conditions.

  The rewriting time derived as described above is transmitted from the communication unit 18 of the display device 1 to the communication unit 23 of the data supply unit 2 before starting the processing of the image received by the image processing unit 14. The communication control unit 22 determines a communication disconnection time by adding a certain margin time to the transmitted rewriting time, and does not perform communication with the display device 1 during that time.

  On the other hand, in the display device 1, after the communication unit 18 transmits the rewriting time, the power supply control unit 13 controls the power supply 31 so as to stop the power supply to the communication unit 18. Further, the power supply control unit 13 performs control so that the power supply to the image processing unit 14 is started after the power supply to the communication unit 18 is stopped. When the processing in the image processing unit 14 ends, the power supply control unit 13 stops power supply to the image processing unit 14 and starts supplying power to the display driving unit 12 (common driver 38 and segment driver 39). Control to do. When the writing process to the electronic paper 11 (display element 30) is completed, the power supply control unit 13 displays the display drive unit 12 (boost unit 32, voltage switching unit 33, voltage stabilization unit 34, common driver 38, and segment driver 39). The power supply to the communication unit 18 is stopped and the power supply to the communication unit 18 is started. The communication unit 18 monitors the command for rewriting new image data from the data supply unit 2. At this time, the communication unit 18 is in a standby state (standby mode) for detecting only that communication is requested, and it is desirable to reduce power consumption.

  As described above, the communication unit 18 of the display device 1 is in a non-operating state in which the power supply is stopped and no signal is received from the data supply unit 2 until the rewriting process is completed after transmitting the rewriting time. become. If the communication unit 23 of the data supply unit 2 transmits a signal even though the communication unit 18 is not operating, the other party will be lost and normal communication operation cannot be performed thereafter. However, as described above, in the present embodiment, since the communication unit 23 of the data supply unit 2 does not transmit a communication signal to the communication unit 18 during the communication interruption time, no problem occurs.

  When the image data transmission destination of the data supply unit is a printer, the time until the output operation of the image data is completed due to a paper jam or the like is not constant, and the communication disconnection time cannot be set. On the other hand, in the case of a display device such as electronic paper, the rewriting time can be uniquely determined as described above. During the communication interruption time, the data supply unit stops the data communication, so that the power supplied to the communication unit of the display device can be stopped and the current supplied from the power source can be reduced.

  FIG. 3 is a flowchart showing the process of the display device 1 in the first embodiment, and FIG. 4 is a flowchart showing the process of the data supply unit 2 in the first embodiment. Hereinafter, processing of the display system of the first embodiment will be described.

  First, before starting the operation shown in FIG. 3 and FIG. 4, the display device 1 completes the exchange of the transmission / reception method determined by the Bluetooth (registered trademark) standard for communication with the data supply unit 2. It shall be. At this time, in the display device 1, power is supplied only to the communication unit 18.

  In step S1, processing for confirming whether there is a transmission request for image data is performed. If not, this step is repeated. If there is a transmission request, the processing proceeds to step S2.

  In step S2, processing for canceling the standby state and starting reception of image data is performed.

  In step S3, image data is received, and processing for storing the received image data in the memory 15 is performed.

  In step S4, it is determined whether the reception of the image data has been completed. If it has not been completed, step S3 is repeated, and when it is completed, the process proceeds to step S5.

  In step S <b> 5, the rewrite time deriving unit 17 reads the characteristic value of the electronic paper from the memory 15.

  In step S <b> 6, the rewrite time deriving unit 17 reads the temperature from the temperature sensor 16.

  In step S7, the number of lines in the rewrite area is derived from the image data received by the rewrite time deriving unit 17.

  In step S8, the rewrite time deriving unit 17 derives the reset time required for resetting the rewrite area and the time required for the writing process for one line at the current temperature.

  In step S9, the rewrite time deriving unit 17 calculates the value obtained by multiplying the write processing time for one line calculated in step S8 by the number of lines in the rewrite area (grayscale writing time), the reset time, and the voltage non-application time. Calculate the sum. This sum is the writing time required to display the received image data on the electronic paper.

  In step S10, the rewrite time deriving unit 17 calculates the image processing time required to expand the JPEG-compressed image from the received image data size.

  In step S11, the rewriting time deriving unit 17 calculates a rewriting time that is the sum of the writing time and the image processing time. The calculated value is transmitted to the data transmission unit 2 via the communication unit 18.

  In step S <b> 12, the power supply control unit 13 stops power supply to the communication unit 18.

  In step S <b> 13, the power supply control unit 13 starts power supply to the image processing unit 14.

  In step S <b> 14, the image processing unit 14 expands the JPEG-compressed image data stored in the memory 15.

  In step S <b> 15, the image processing unit 14 stores the developed data in the memory 15.

  In step S <b> 16, the power supply control unit 13 stops the power supply to the image processing unit 14.

  In step S <b> 17, the power supply control unit 13 starts power supply to the display drive unit 12 (common driver 38, segment driver 39, booster 32, voltage switching unit 33, voltage stabilization unit 34, etc.).

  In step S18, the display driving unit 12 (the boosting unit 32, the voltage switching unit 33, the voltage stabilizing unit 34, etc.) generates a reset voltage for putting the liquid crystal into the planar state.

  In step S19, the display driving unit 12 (common driver 38, segment driver 39) applies a reset voltage to the liquid crystal in the rewriting region to bring it into a planar state.

  In step S20, the display driving unit 12 (the boosting unit 32, the voltage switching unit 33, the voltage stabilizing unit 34, etc.) generates a writing voltage for setting the liquid crystal in a mixed state of the planar state and the focal conic state.

  In step S21, the display driving unit 12 (common driver 38, segment driver 39) applies a writing voltage to the liquid crystal in the rewriting area so as to be in a mixed state according to the pixel value.

  In step S <b> 22, the power supply control unit 13 stops the power supply to the display driving unit 12.

  In step S <b> 23, the power supply control unit 13 starts power supply to the communication unit 18.

  In step S24, the communication unit 18 enters a standby state. The process returns to step S1.

  Next, processing of the data supply unit 2 of the first embodiment will be described with reference to FIG.

  In step S31, the communication control unit 22 performs a process of confirming whether there is image data to be transmitted and displayed on the display device 1. If not, this step is repeated. If there is image data to be transmitted, the process proceeds to step S32. Proceed to

  In step S <b> 32, the communication unit 23 sends a transmission request to the display device 1. In response to this, the display device 1 performs steps S1 and S2.

  In step S <b> 33, the communication unit 23 transmits image data to the display device 1.

  In step S <b> 34, the communication unit 23 receives the rewrite time transmitted from the display device 1.

  In step S35, the communication control unit 22 sets a communication disconnection time by adding a certain margin to the received rewriting time, and sets a timer for the communication disconnection time. Further, the communication control unit 22 controls to stop communication from the communication unit 23 during the communication disconnection time.

  In step S36, the communication control unit 22 determines whether the communication disconnection time has elapsed, and continues this determination until the communication disconnection time ends. When the process ends, the process proceeds to step S37.

  In step S <b> 37, the communication control unit 22 controls to cancel communication from the communication unit 23.

  Even if data to be transmitted is generated during steps S35 and S36, the communication control unit 22 performs a process of holding the data until the communication of the communication unit 23 is canceled in step S37.

  In the operation of the first embodiment shown in the flowcharts of FIGS. 3 and 4, each time an image signal is received, the display device 1 calculates the rewrite time and transmits the calculated rewrite time to the data supply unit 2. It was. In the second embodiment, characteristic values of electronic paper are stored in the data supply unit 2, and temperature data of the electronic paper detected from the display device is transmitted to the data supply unit 2. Since the data supply unit 2 has image data, the rewrite time can be calculated based on the characteristic value and the temperature data.

  FIG. 5 is a diagram illustrating a configuration of the data supply unit 2 of the display system according to the second embodiment. As shown in FIG. 5, the data supply unit 2 of the second embodiment includes a characteristic value memory 24 and a rewrite time deriving unit 25 in addition to the configuration of the first embodiment. The characteristic value memory 24 stores characteristic values similar to those described in the first embodiment. The rewrite time deriving unit 25 has the same function as the rewrite time deriving unit 17 provided in the display device 1 of the first embodiment.

  In the display device 1 of the display system of the second embodiment, since it is necessary to perform the same calculation as in the first embodiment in order to determine the time for applying the voltage in the reset process and the gradation writing process, the first embodiment Similar to the embodiment, a rewrite time deriving unit 17 and a temperature sensor 16 are provided, and the memory 15 stores characteristic values. And it differs from 1st Embodiment that the communication part 18 transmits temperature data, without transmitting rewriting time.

  FIG. 6 is a flowchart illustrating processing in the display device 1 of the display system according to the second embodiment. FIG. 7 is a flowchart illustrating processing in the data supply unit 2 of the display system according to the second embodiment.

  Also in the second embodiment, before starting the processing shown in FIG. 6 and FIG. 7, an exchange regarding a transmission / reception method determined by the Bluetooth (registered trademark) standard between the display device 1 and the data supply unit 2. Shall be completed. First, processing in the display device 1 of the second embodiment will be described.

  In step S <b> 40, the rewrite time deriving unit 17 reads the characteristic value of the electronic paper from the memory 15 and transmits it to the data supply unit 2 via the communication unit 18 when exchanging the transmission / reception method. The rewrite time deriving unit 17 holds the characteristic value as it is.

  Steps S41 to S44 are the same as steps S1 to S4 of the first embodiment, and thus description thereof is omitted.

  In step S <b> 46, the rewrite time deriving unit 17 reads the temperature from the temperature sensor 16.

  In step S <b> 51, the rewriting time deriving unit 17 transmits the temperature data to the data supply unit 2 via the communication unit 18.

  In step S <b> 52, the power supply control unit 13 stops the power supply to the communication unit 18.

  In step S <b> 53, the power supply control unit 13 starts supplying power to the image processing unit 14.

  In step S <b> 54, the image processing unit 14 expands the JPEG-compressed image data stored in the memory 15.

  In step S55, the image processing unit 14 stores the developed data in the memory 15.

  In step S56, the power supply control unit 13 stops the power supply to the image processing unit 14.

  In step S57, the power supply control unit 13 starts supplying power to the display driving unit 12 (common driver 38, segment driver 39, boosting unit 32, voltage switching unit 33, voltage stabilization unit 34, etc.).

  In step S58, the display driving unit 12 (the boosting unit 32, the voltage switching unit 33, the voltage stabilizing unit 34, etc.) generates a reset voltage for bringing the liquid crystal into the planar state.

  In step S59, the display drive unit 12 (common driver 38, segment driver 39) applies a reset voltage to the liquid crystal in the rewriting region to bring it into a planar state.

  In step S60, the display driving unit 12 (the boosting unit 32, the voltage switching unit 33, the voltage stabilizing unit 34, etc.) generates a writing voltage for setting the liquid crystal in a mixed state of the planar state and the focal conic state.

  In step S61, the display driving unit 12 (the common driver 38 and the segment driver 39) applies a writing voltage to the liquid crystal in the rewriting area so as to be in a mixed state according to the pixel value.

  In step S <b> 62, the power supply control unit 13 stops the power supply to the display driving unit 12.

  In step S <b> 63, the power supply control unit 13 starts power supply to the communication unit 18.

  In step S64, the communication unit 18 enters a standby state. The process returns to step S41.

  Next, processing of the data supply unit 2 of the second embodiment will be described with reference to FIG.

  In step S70, the characteristic value memory 34 stores the transmitted characteristic value.

  In step S71, the communication control unit 22 performs a process of confirming whether there is image data to be transmitted and displayed on the display device 1. If not, this step is repeated. If there is image data to be transmitted, the process proceeds to step S72. Proceed to

  In step S <b> 72, the communication unit 23 sends a transmission request to the display device 1.

  In step S <b> 73, the communication unit 23 transmits image data to the display device 1.

  In step S74, the rewrite time deriving unit 25 calculates the rewrite time by the same method as in the first embodiment.

  In step S75, the communication control unit 22 sets a communication disconnection time by adding some margin to the calculated rewrite time, and sets a timer for the communication disconnection time.

  In step S76, the communication control unit 22 controls to stop communication from the communication unit 23 during the communication disconnection time.

  In step S77, the communication control unit 22 determines whether the communication disconnection time has elapsed, and continues this determination until the communication disconnection time ends. When the process ends, the process proceeds to step S78.

  In step S78, the communication control unit 22 performs control so as to cancel communication from the communication unit 23.

  As mentioned above, although the example using a cholesteric liquid crystal display device as electronic paper was demonstrated, this invention is not limited to this, If it is electronic paper, it is applicable.

FIG. 1 is a diagram illustrating an overall configuration of a display system according to the first embodiment. FIG. 2 is a diagram showing a schematic configuration of the cholesteric liquid crystal display device of the first embodiment. FIG. 3 is a flowchart illustrating processing of the display device of the display system according to the first embodiment. FIG. 4 is a flowchart illustrating processing of the data supply unit of the display system according to the first embodiment. FIG. 5 is a diagram illustrating a configuration of a data supply unit of the display system according to the second embodiment. FIG. 6 is a flowchart illustrating processing of the display device of the display system according to the second embodiment. FIG. 7 is a flowchart illustrating processing of the data supply unit of the display system according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Data supply part 11 Electronic paper 12 Display drive part 13 Power supply control part 14 Image processing part 15 Memory 16 Temperature sensor 17 Rewrite time deriving part 18 Communication part 21 Transmission data storage part 22 Communication control part 23 Communication part

Claims (6)

A display system comprising: a display device; and a data supply unit that supplies display data to the display device, wherein the display data is communicated from the data supply unit to the display device,
The display device includes a memory-type display element, a communication unit with the data supply unit, a display rewrite unit that rewrites the display of the display element, and a power source that controls power supply to the communication unit and the display rewrite unit. A supply control unit,
The power supply control unit stops power supply to the communication unit during a rewriting period in which the display rewriting unit rewrites the display of the display element according to display data supplied from the data supply unit,
The data supply unit stops communication with the display device during the rewriting period. The display device
A characteristic value memory for storing characteristic values related to rewriting of the display element;
A rewriting time deriving unit for deriving a rewriting time required for the display rewriting unit to rewrite the display of the display element to the supplied display data based on the characteristic value;
Before the rewriting period, the derived rewriting time is transmitted to the data supply unit,
The display system according to claim 1, wherein the data supply unit stops communication with the display device during the received rewrite time. The display device includes a temperature sensor that detects a temperature of the display element,
The rewriting time deriving unit derives a rewriting time required for the display rewriting unit to rewrite the display of the display element to the supplied display data based on the detected temperature in addition to the characteristic value. The display system according to claim 2. The data supply unit
A characteristic value memory for storing characteristic values related to rewriting of the display element;
A rewriting time deriving unit for deriving a rewriting time required for the display rewriting unit of the display element to rewrite the display data supplied with the display of the display element based on the characteristic value;
The display system according to claim 1, wherein the data supply unit stops communication with the display device during the rewriting time after the supply of display data is completed. The display device includes a temperature sensor that detects the temperature of the display element, and transmits the detected temperature to the data supply unit.
The rewriting time deriving unit of the data supply unit calculates a rewriting time required for the display rewriting unit to rewrite the display of the display element to the supplied display data based on the transmitted temperature in addition to the characteristic value. The display system according to claim 4, wherein the display system is derived. A memory-type display element, a communication section that receives display data from an external display data transmission section, a display rewrite section that rewrites the display of the display element, and a power supply to the display-side communication section and the display rewrite section. A power supply control unit to control,
A characteristic value memory for storing characteristic values related to rewriting of the display element;
A rewriting time deriving unit for deriving a rewriting time required for the display rewriting unit to rewrite the display of the display element to the supplied display data based on the characteristic value;
Before the rewriting period, the derived rewriting time is transmitted to the external display data transmission unit via the communication unit,
The display device, wherein the power supply control unit stops power supply to the communication unit during a rewriting period in which the display rewriting unit rewrites display data received by the display element.

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