JP2006259357A - Image display device and image writing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device and an image writing device that can write a desired image regardless of temperature, humidity, and illuminance. <P>SOLUTION: A wireless sensor 0 which detects a physical quantity (temperature, humidity, or illuminance) is provided in electronic paper 10. Then a control section 40 sends a radio wave from a transmission section 111 to the sensor. The sensor 0 once receiving the radio wave transmits a surface acoustic wave influenced by the physical quantity (temperature, humidity, or illuminance) as a radio wave signal to a reception section 112. The control section 40 analyzes the physical quantity in the electronic paper 10 on the basis of the radio wave signal that the reception section 112 receives and sets a voltage to be applied to the electronic paper 10. A driving pulse voltage generation section 36 applies the voltage to the electronic paper 10 under the control of the control section 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image display device and an image writing device, and more particularly to an image display device and an image writing device that perform image recording based on physical quantities in the image display device.

In recent years, computers, the Internet, and the like have been accelerating and electronic information has been increasing year by year. With the increase in electronic information, the consumption of paper for recording electronic information is also increasing. However, once the information is recorded, the paper cannot be reused by returning it to a blank paper while keeping the original form of the paper. Although it has become widespread that used paper is processed by recycling and recycled into writable paper, paper that has been used once is mostly discarded in a short time. Therefore, a recording medium that leads to reduction of paper consumption has been desired from the viewpoint of forest protection and environmental protection. Thus, as such a recording medium, optical writing electronic paper has been devised, in which electronic information can be instantaneously written and information can be rewritten any number of times (for example, Patent Document 1).
JP 2004-177473 A

  An image is written on the electronic paper by irradiating the electronic paper with an image and applying a voltage. The written image can be visually recognized by reflection of light such as sunlight or a fluorescent lamp. However, when writing an image, if the temperature and humidity in the electronic paper are not normal values, a desired image cannot be written. Further, in the electronic paper having a card configuration, a portion where an image is written is covered with a film material or the like, so that there is a difference between the external temperature and humidity and the temperature and humidity in the electronic paper. Therefore, even if it is determined that the conditions for writing to the electronic paper are appropriate based on the external temperature and humidity, the actual temperature and humidity in the electronic paper are different from the external environment. I was unable to do that. In addition, even when the illuminance at the time of writing an image varies, there is a case where the image cannot be written as planned. As described above, the conventional electronic paper is affected by temperature, humidity, and illuminance, and has a problem in that image writing cannot be performed according to the planned quality.

  The present invention has been made in view of such circumstances, and an object thereof is an image display device (electronic paper) capable of writing an image with a planned quality regardless of temperature, humidity, and illuminance, and image writing. To provide an apparatus (electronic paper writing apparatus).

  In order to solve the above problems, the present invention provides an image display medium and an image display medium provided inside the image display medium. When a predetermined radio wave signal is supplied from the outside, the image display medium is used as an energy source. Wireless measurement means that detects and outputs a radio signal having an attribute that reflects the detected physical quantity, and the image display medium includes a voltage application unit, and an image is externally received. There is provided an image display device which is an electronic paper on which an image is recorded by being irradiated and applied with a voltage in the voltage application unit.

  According to this image display device, the wireless measuring unit detects a physical quantity inside the image display device and outputs a radio signal having an attribute reflecting the physical quantity. Therefore, the physical quantity inside the image display device in the closed state can be detected.

  The physical quantity is at least one of temperature, humidity, and illuminance received by the image display medium from the outside. In addition, the wireless measurement unit includes an excitation unit that receives a radio wave to generate mechanical vibration, a mechanical vibration generated by the excitation unit is transmitted to generate a surface acoustic wave, and an attribute of the surface acoustic wave is a physical quantity And a transmission unit that converts the surface acoustic wave into an electric signal and outputs the signal as a radio wave signal. In this way, a surface acoustic wave whose attribute is changed by at least one physical quantity among temperature, humidity, and illuminance is output as a radio wave signal.

  Moreover, this invention is an image writing apparatus which writes an image in the image display apparatus in any one of Claim 1 to 3, Comprising: The image irradiation part which irradiates an image to the said image display apparatus, The said image irradiation part is the said When irradiating an image on the image display device, a voltage application unit that applies a voltage to the voltage application unit and a radio signal output from the wireless measurement unit are received, and the image display is performed based on the received radio signal An image comprising: a receiving unit that detects a physical quantity of a medium; and a control unit that controls at least one of an irradiation state of the image irradiation unit and an applied voltage of the voltage applying unit based on the physical quantity detected by the receiving unit. A writing device is provided.

  According to this image writing device, the physical quantity (temperature, humidity, illuminance) inside the image display device is analyzed from the radio wave signal output from the wireless measuring means, and the voltage applied to the electronic paper is controlled. Therefore, writing to the image display device can be performed by controlling the applied voltage regardless of the physical quantity inside the image display device.

Hereinafter, an electronic paper and an electronic paper writing apparatus for writing an image on the electronic paper according to the present invention will be described in detail with reference to the drawings.
[First embodiment]
(1) Structure of electronic paper FIG. 1 is a diagram illustrating a configuration of an electronic paper 10 according to the present embodiment.
The electronic paper 10 is configured by laminating a transparent substrate 18, a transparent electrode 19, and a display element layer 20 from below. Further, a photoconductive layer 21, a light absorption layer 22, a transparent electrode 23, and a transparent substrate 24 are laminated on the display element layer 20. Although the electrode 25 is shown as an integral body in FIG. 1, it is actually separated into two as shown in FIG. 2, and each of them is energized with the transparent electrode 19 and the transparent electrode 23. Further, the electronic paper 10 is configured to cover the entire surface by a surface layer portion 26 made of a material such as a film material. A wireless temperature sensor 0 is embedded in the surface layer portion 26. This temperature sensor 0 can detect the temperature in the electronic paper 10.

As the transparent substrate 18 and the transparent substrate 24, a known transparent substrate made of glass or plastic can be used as appropriate, and a flexible substrate of a polyester film film such as preethylene terephthalate can also be used. The thickness of the transparent substrate is preferably about 100 μm to 500 μm.
Moreover, as the transparent electrode 19 and the transparent electrode 23, an ITO (Indium-Tin-Oxide) electrode is suitable. The display element layer 20 is composed of capsulated cholesteric liquid crystal or the like. In the present embodiment, a case where cholesteric liquid crystal is used will be described.

  The photoconductive layer 21 is composed of, for example, an organic photoconductor having a dual CGL structure in which a charge generation layer (CGL) is provided on both the upper layer side and the lower layer side of a charge transport layer (CTL) made of a charge transport material. It is preferable. In addition, when the photoconductive layer 21 is configured by laminating at least a charge generation layer, a charge transport layer, and a charge generation layer in this order, an alternating voltage can be applied to the display element layer 20. A general liquid crystal material can be used as the display element layer, which is desirable.

  Here, FIG. 3 is an equivalent circuit for each pixel. As shown, the display element layer 20 is represented by a parallel circuit of a resistance component RLC and a capacitance component CLC, and the photoconductive layer 21 is formed of a resistance component ROPC and a static circuit. It is represented by a parallel circuit of capacitance component COPC. When an image is written on the electronic paper 10, light corresponding to the image is irradiated from below the electronic paper 10, as shown in FIG. In this state, when a voltage (pulse voltage) is applied between the transparent electrode 19 and the transparent electrode 23 via the electrode 25, a portion corresponding to each pixel of the photoconductive layer 21 corresponds to an image (in accordance with an irradiation light amount). A corresponding impedance change occurs. That is, in terms of an equivalent circuit, the value of the resistance component ROPC of the photoconductive layer 21 changes according to the amount of irradiation light for each pixel, thereby changing the partial pressure ratio between the photoconductive layer 21 and the display element layer 20. A difference in contrast according to the pressure ratio occurs in the display element layer 20. An image can be visually confirmed by the difference in contrast.

(2) Structure of Electronic Paper Writing Device FIG. 4 is a schematic diagram of an electronic paper writing device 30 that writes an image on the electronic paper 10. The electronic paper 10 is placed in close contact with the electronic paper writing device 30, but is displayed separately for the sake of convenience in order to make the explanation easy to understand. As shown in FIG. 4, the electronic paper writing device 30 includes a control unit 40 and an image irradiation unit 32 that irradiates the electronic paper 10 with an image.

  The image irradiation unit 32 generates a light pattern according to the image data input from the control unit 40, and irradiates the electronic paper 10 with the generated light pattern. The image irradiation unit 32 includes, for example, a two-dimensional array of liquid crystal display devices, CRT (Cathode Ray Tube) and FED (Field Emission Display), fluorescent display elements, plasma light emitting elements, electroluminescence light emitting elements, LED light emitting elements, and the like. The self-luminous display is used. In this embodiment, the case where the light emitting element which combined the LED array and the liquid crystal panel is used is shown.

  The electronic paper writing device 30 includes a drive pulse voltage generation unit 36 and a drive pulse voltage application unit 34. The drive pulse voltage generation unit 36 is connected to the control unit 40, detects a trigger signal (drive signal) for driving wave output input from the control unit 40, generates a drive pulse voltage, and applies a drive pulse voltage. The voltage is applied to the transparent electrode 19 and the transparent electrode 23 of the electronic paper 10 through the unit 34.

  In addition, the electronic paper writing device 30 includes a transmitting unit 111 and a receiving unit 112. The transmission unit 111 and the reception unit 112 are connected to the control unit 40, respectively. When the transmission unit 111 receives a radio transmission signal from the control unit 40, the transmission unit 111 transmits a radio signal toward the temperature sensor 0. Further, when receiving the radio signal from the temperature sensor 0, the receiving unit 112 transmits a radio wave reception signal including the radio signal to the control unit 40.

  The control unit 40 includes an input / output unit 41 such as an interface, a CPU (Central Processing Unit) 42, a ROM (Read Only Memory) 43, a RAM (Random Access Memory) 44, and the like. The CPU 42 controls each unit via the input / output unit 41. The ROM 43 includes a program for controlling the electronic paper writing device 30, a program for executing a calculation function and the like for calculating a temperature based on a result detected by the temperature sensor 0, and a drive pulse voltage based on the calculated temperature. A program for controlling the voltage generated by the generation unit 36 is stored. The RAM 44 is used as a work area when executing the program. In addition, the storage unit 45 stores a table (or an arithmetic expression) for calculating the temperature from the change in the frequency of the radio signal received from the reception unit 112.

The storage unit 45 stores control information INF45a. In the control information INF 45a, a value of an applied voltage with respect to the temperature inside the electronic paper 10 when an image is written on the electronic paper 10 is set.
Here, the optimum value of the voltage will be described in more detail with reference to FIG.
FIG. 5 is a diagram showing the relationship between the amount of light and the reflectance during recording on the electronic paper. Curves d1 and d2 shown in FIG. 5A are obtained when an image is written by applying the same voltage to each of the electronic papers under the conditions of the normal temperature t1 and the temperature t2 lower than the normal temperature. Reflectance is shown. As apparent from FIG. 5A, when an image is written at a temperature t2 lower than the normal temperature t1, the reflectance is lower than that at the temperature t1, regardless of the amount of irradiation light. For example, when the reflectance values when the light quantity is x1 are compared, the reflectance decreases from y2 to y1. If the reflectance is low, the contrast is lowered and the image becomes dark, which is not preferable.

  On the other hand, FIG. 5B shows that the reflectance of the amount of light reflected by the electronic paper changes by changing the voltage applied to the electronic paper under the same temperature condition. That is, when writing on electronic paper under a certain temperature condition, the reflectance is increased by increasing the voltage applied when writing. In the case of FIG. 5B, when the reflectance when the amount of light is x1 is compared, the reflectance increases from y1 to y2.

  The control information INF45a stored in the storage unit 45 stores an optimum applied voltage value corresponding to the temperature inside the electronic paper 10 based on the relationship shown in FIG. In the case of the present embodiment, it is stored by a table, but this may be stored by a mathematical expression.

  The control unit 40 is connected to an external device such as a personal computer, controls the image irradiation unit 32 based on image data input from the outside, performs image irradiation, and writes an image on the electronic paper 10. Do.

(3) Wireless Temperature Sensor (3-1) Structure of Temperature Sensor Here, the configuration and operation of the temperature sensor 0 will be described.
First, the basic configuration of the wireless temperature sensor 0 used in the present embodiment will be described.
As shown in FIG. 6, the wireless temperature sensor 0 includes a base substrate 1, a dielectric thin film 2 that is formed on the substrate 1 and propagates a surface acoustic wave (SAW), and a dielectric A pair of interdigital transducers (IDT) 3A and 3B, which are formed on the body thin film 2 and convert an electrical signal into a surface acoustic wave or a surface acoustic wave into an electrical signal, and the pair of combs Antennas 4A and 4B as transmission / reception units connected to one of the mold electrodes 3A and 3B via impedance matching units 5A and 5B and transmitting / receiving radio wave signals to / from an external transmission / reception unit, and a pair of comb electrodes 3A , 3B and ground electrodes 7A and 6B connected to the other side of the substrate 1 and a ground electrode 7 formed on the back surface of the substrate 1 and connected to the grounds 6A and 6B through through holes (not shown). Have
The frequency of the surface acoustic wave in the temperature sensor 0 is set by the shapes of the comb-shaped electrodes 3A and 3B and the impedance matching portions 5A and 5B. In general, the frequency of the surface acoustic wave generated on the dielectric thin film 2 is in the range of 400 to 800 MHz.

(3-2) Material of Temperature Sensor Next, the material of the members constituting the temperature sensor 0 will be described.
For use as a temperature sensor, LiNbO3 is used as the material of the dielectric thin film 2 shown in FIG. This LiNbO3 crystal is a material whose surface acoustic wave propagation speed changes sensitively to temperature changes, and its temperature coefficient is about 75 × 10 ⁻⁶ / ° C. This change in the propagation speed at the temperature changes the frequency of the surface acoustic wave. For example, in the experiment, a result is obtained in which the frequency changes by about 0.2 to 0.3% with respect to the center frequency f0 of the surface acoustic wave when the temperature changes by about 100 ° C.

  Here, since the antennas 4A and 4B, the impedance matching units 5A and 5B, and the comb-shaped electrodes 3A and 3B generate mechanical vibration of the center frequency f0 of the radio signal transmitted from the outside, the radio signal received by the receiving unit 112 Will be shifted by the change in frequency. The temperature sensor 0 obtains a result that the intensity of the received signal in the receiving unit 112 changes linearly according to the temperature change.

  The comb electrodes 3A and 3B, the antennas 4A and 4B, the impedance matching portions 5A and 5B, and the grounds 6A and 6B are integrally formed by a conductive pattern. As a material of this conductive pattern, metals such as Ti, Cr, Cu, W, Ni, Ta, Ga, In, Al, Pb, Pt, Au, and Ag, or Ti—Al, Al—Cu, Ti—N, An alloy such as Ni—Cr is preferably laminated in a single layer or a multilayer structure of two or more layers, and Au, Ti, W, Al, and Cu are particularly preferable as the metal. Moreover, it is preferable that the film thickness of this metal layer shall be 1 nm or more and less than 10 micrometers.

(3-3) Measurement Operation of Temperature Sensor Next, a basic measurement operation will be described. In the plan view of the temperature sensor 0 shown in FIG. 6A, for the sake of convenience, it is assumed that the signal moves from the left side to the right side of the drawing, but the signal flow is not actually directional. .

  The temperature sensor 0 exchanges radio signals with the transmitter 111 and with the receiver 112. The radio wave signal transmitted from the transmitter 111 is received by the antenna 4A, and the comb electrode 3A excites the dielectric thin film 2 by this signal to generate mechanical vibration. This mechanical vibration generates a surface acoustic wave on the surface of the dielectric thin film 2. The surface acoustic wave moves from the comb-shaped electrode 3A toward the comb-shaped electrode 3B, and the surface acoustic wave that has reached the comb-shaped electrode 3B is converted into an electric signal by the comb-shaped electrode 3B and passes through the antenna 4B. Sent. The receiving unit 112 receives a radio signal from the temperature sensor 0.

  The surface acoustic wave generated on the surface of the dielectric thin film 2 changes in amplitude, phase difference, frequency, etc. (attributes) due to a change in temperature applied to the dielectric thin film 2. The receiving unit 112 that has received the surface acoustic wave converts the radio wave signal into an electric signal and transmits it to the control unit 40. The control unit 40 can measure the temperature received by the temperature sensor 0 by analyzing the electrical signal.

(4) Operation of the First Embodiment Next, the operation of the first embodiment will be described with reference to FIGS. 4 and 7.
When the electronic paper 10 is set on the image irradiation unit 32 and the user gives an image writing instruction using an operation unit (not shown), the control unit 40 starts a processing routine shown in FIG.
As shown in FIG. 7, first, the controller 40 transmits a radio signal from the transmitter 111 (step SA2). Thereby, the temperature sensor 0 generates and outputs a radio wave having a frequency corresponding to the ambient temperature. When the reception unit 112 receives the radio wave transmitted from the temperature sensor 0 and a reception signal is output from the reception unit 112 to the control unit 40 (step SA4; YES), the control unit 40 is stored in the storage unit 45. The temperature measured by the temperature sensor 0 is obtained from the table (step SA6). Further, this result is stored in the RAM 44 (step SA8). And the control part 40 calculates | requires the applied voltage according to the temperature inside the electronic paper 10 which the temperature sensor 0 detected, and outputs it to the drive pulse voltage generation part 36 (step SA10). As a result, the drive pulse voltage generator 36 applies a voltage according to the internal temperature of the electronic paper 10 between the transparent electrodes 19 and 23. As described above, since the voltage to be applied can be changed according to the temperature condition inside the electronic paper 10, the optimum contrast can be obtained regardless of the temperature.

  As described above, according to the present embodiment, by providing the temperature sensor 0 inside the electronic paper 10, the temperature inside the electronic paper 10 can be detected, and the temperature outside the electronic paper 10 is used as a reference. Compared to the above, a more optimal voltage value can be set. Further, since the temperature sensor 0 is wireless, it is not necessary to provide a cable. Therefore, the electronic paper 10 can be carried freely without having to worry about the cable connection after the image has been written, without keeping the electronic paper 10 in a certain place.

[Second Embodiment]
In the first embodiment, a case where one temperature sensor (a temperature sensor corresponding to one frequency) is arranged inside the electronic paper 10 is shown, but a plurality of temperature sensors may be provided inside the electronic paper 10. Good. The description of the same configuration as that of the first embodiment is omitted.
(1) A plurality of temperature sensors A plurality of temperature sensors will be described with reference to FIG.
As shown in FIG. 8, the temperature sensor 0 ′ is formed with comb-shaped electrodes 3A-1, 3B-1,... 3A-4, 3B-4 having different shapes. In this temperature sensor 0 ′, surface acoustic waves corresponding to a plurality of frequencies are generated on the dielectric thin film 2 according to the frequency of the radio signal transmitted from the outside.

For example, the frequency of the surface acoustic wave set by the comb-shaped electrodes 3A-1 and 3B-1 and the impedance matching units 5A and 5B is set by f1, and the comb-shaped electrodes 3A-2 and 3B-2 and the impedance matching units 5A and 5B are set. The frequency of the surface acoustic wave to be generated is f2, the frequency of the surface acoustic waves set by the comb electrodes 3A-3 and 3B-3 and the impedance matching units 5A and 5B is f3, the comb electrodes 3A-4 and 3B-4 and The frequency of the surface acoustic wave set by the impedance matching units 5A and 5B is assumed to be f4.
In FIG. 8, the illustration of the ground and the ground electrode is omitted.

  Here, when a radio signal having a frequency f1 is transmitted from the external transmitter 111, the comb electrode 3A-1 corresponding to the frequency f1 generates mechanical vibrations in the comb electrode 3A, and the mechanical vibrations cause dielectrics. A surface acoustic wave is generated on the body thin film 2. This surface acoustic wave is transmitted to the comb-shaped electrode 3B-1. The attribute of the surface acoustic wave transmitted to the comb-shaped electrode 3B-1 changes under the influence of temperature. On the other hand, since the other comb-shaped electrodes 3A-2, 3B-2 to 3A-4, 3B-4 are not tuned to the frequency f1, generation of surface acoustic waves and transmission of radio signals based thereon are performed. Absent. That is, these comb-shaped electrodes 3A-2, 3B-2 to 3A-4, 3B-4 are set so as to be tuned to the frequencies f2, f3, and f4, respectively. When transmitted to the sensor 0 ', a surface acoustic wave is transmitted through a path of comb-shaped electrodes 3A-2 → 3B-2, and a radio wave signal corresponding to the surface acoustic wave is output via the antenna 4B.

Similarly, when a radio wave signal having a frequency f3 is transmitted to the temperature sensor 0 ′, a surface acoustic wave is transmitted through the path of the comb-shaped electrodes 3A-3 → 3B-3 and output via the antenna 4B. When the radio signal of f4 is transmitted to the temperature sensor 0 ′, the surface acoustic wave is transmitted through the path of the comb-shaped electrodes 3A-4 → 3B-4 and is output via the antenna 4B.
Therefore, if radio waves are transmitted to the temperature sensor 0 ′ in the order of the frequencies f1, f2, f3, and f4, response signals corresponding to these can be obtained. In this case, the change band of the signal output from the comb electrodes 3B-1, 3B-2, 3B-3, 3B-4 (output side) (the width of change due to temperature) should be set so as not to overlap. For example, even if the frequencies f1 to f4 are simultaneously output to the temperature sensor 0 ′, the four signals output as response signals can be separated and analyzed.

  Here, it is assumed that the temperature sensors 0-1, 0-2, 0-3, 0-4 are individually arranged in the four measurement objects a to d. Specifically, in the temperature sensor 0, since the frequency of the surface acoustic wave is set in the shape of the comb-shaped electrodes 3A and 3B, the temperature sensor 0-1 includes the comb of the temperature sensor 0 'shown in FIG. The mold electrodes 3A-1 and 3B-1 are formed, the temperature sensor 0-2 is formed with comb-shaped electrodes 3A-2 and 3B-2 of the temperature sensor 0 ', and the temperature sensor 0-3 is formed with the temperature sensor 0'. The comb electrodes 3A-3 and 3B-3 are formed, and the temperature sensor 0-4 is formed with the comb electrodes 3A-4 and 3B-4 of the temperature sensor 0 '. Thereby, the frequency of the surface acoustic wave is f1 for the temperature sensor 0-1, f2 for the temperature sensor 0-2, f3 for the temperature sensor 0-3, and f4 for the temperature sensor 0-4. That is, the temperature sensors 0-1 to 0-4 are specified by the frequencies f1 to f4 of the received radio signal.

The radio signal with the frequency f1 is measured by the temperature sensor 0-1 arranged at the measurement position a, and the radio signal with the frequency f2 is measured by the temperature sensor 0-2 arranged at the measurement position b. The signal can be measured by the temperature sensor 0-3 arranged at the measurement position c, and the radio wave signal of the frequency f4 can be measured by the temperature sensor 0-4 arranged at the measurement position d.
Such temperature sensors 0-1 to 0-4 are arranged at various locations inside the electronic paper 10, for example, at four corners. By arranging a plurality of temperature sensors in this way, it is possible to detect the temperature of the electronic paper 10 evenly as compared with the case where the temperature sensors are arranged at one place, and it is possible to apply a more optimal voltage. In the following description, the temperature sensors 0-1 to 0-4 are simply referred to as temperature sensors.

(2) Operation of Second Embodiment Next, the operation of the second embodiment will be described with reference to FIGS.
FIG. 9 is a block diagram of the temperature sensor, transmitter 111, receiver 112, and controller 40.
Here, in addition to the functions described above, the ROM 43 stores a BPF (band pass filter) function for extracting the vicinity of the set frequencies f1 to f4 in order to recognize the plurality of temperature sensors 0-1 to 0-4. .

  The operation of the control unit 40 is shown in FIG. As shown in FIG. 10, the control unit 40 transmits a radio wave signal from the transmission unit 111 (step SB2). At this time, as described above, the transmitter 111 transmits a radio wave that is a mixture of rectangular waves having frequencies f1, f2, f3, and f4 to the temperature sensor. When the reception unit 112 receives the radio wave transmitted from the temperature sensor and the radio reception signal is transmitted from the reception unit 112 to the control unit 40 (step SB4; YES), the control unit 40 performs a temperature measurement process (step SB4). SB6). By this temperature measurement process, the control unit 40 detects the temperatures of four locations inside the electronic paper 10. And the control part 40 calculates | requires an average value with respect to the temperature which the temperature sensors 0-1 to 0-4 detected, and specifies the temperature of the electronic paper 10 from an average value. Then, an applied voltage corresponding to the specified temperature is obtained and output to the drive pulse voltage generator 36 (step SB8).

The operation of the temperature measurement process will be described with reference to FIG.
In step SB4 shown in FIG. 10, the signal received by the control unit 40 from the receiving unit 112 is a radio wave signal in which different frequencies transmitted from the temperature sensor are mixed. First, the control unit 40 sets a counter (not shown) to “n = 0” (step SC2). The control unit 40 performs BPF processing for extracting the vicinity of the frequency f1 (step SC4), and calculates the temperature measured by the temperature sensor 0-1 from a table stored in the storage unit 45 in advance (step SC6). Further, this result is stored in the RAM 44 (step SC8).

Control unit 40 increments the counter to “n = n + 1” (step SC10). It is determined whether or not n is 4 or more (step SC12). In this determination, if the counter value is less than “4”, the measurement from each sensor is not completed, and thus the processing after step SC4 is continued.
When the above operation is performed and the counter value reaches “4”, it returns to the routine of FIG. 10 assuming that the measurement results for the four sensors have been calculated (step SC14).

  As described above, according to the present embodiment, it is possible to detect temperatures at a plurality of locations inside the electronic paper 10. For example, when the electronic paper 10 on which writing is performed has a relatively large size, a temperature difference occurs between both ends of the electronic paper 10. At that time, if the temperature sensor installed in the electronic paper 10 is one, even if the applied voltage to the vicinity of the installed temperature sensor is an optimal voltage, the applied voltage is not optimal in other places, As a result, there is a possibility that an image of the quality planned for the electronic paper 10 as a whole cannot be written. However, by providing a plurality of temperature sensors in the electronic paper 10, obtaining an average value or the like for the temperatures detected by those temperature sensors, and specifying the temperature of the electronic paper 10 from the average value, an optimum applied voltage can be obtained. The image can be obtained and the image can be written more reliably.

[Other embodiments]
(1)
The wireless sensor disposed inside the electronic paper 10 is not limited to a temperature sensor, and may be a humidity sensor and an illuminance sensor.
(1-1) Humidity Sensor In the first embodiment, the case where the image writing method changes depending on the temperature inside the electronic paper 10 is shown. However, the image writing method also changes depending on the humidity.
FIG. 12 is a diagram showing the relationship between the amount of light and the reflectance during recording on electronic paper. Curves d3 and d4 shown in FIG. 12A are an electronic paper in which an image is written by applying the same voltage to each of the electronic papers under conditions of normal humidity h1 and humidity h2 higher than normal humidity. The reflectance is shown. As is clear from FIG. 12A, when an image is written at a humidity h2 higher than the normal humidity h1, for example, when comparing the reflectance values when the amount of light is x1, the reflectance is y2 to y1. To drop.

  On the other hand, FIG. 12B shows that the reflectance of the amount of light reflected by the electronic paper changes by changing the voltage applied to the electronic paper under the same humidity condition. That is, when writing on electronic paper under certain humidity conditions, the reflectance is increased by increasing the voltage applied when writing. In the case of FIG. 12B, when the reflectance when the amount of light is x1 is compared, the reflectance increases from y1 to y2.

  Therefore, a case will be described in which a humidity sensor is provided in the electronic paper 10 and an image is written on the electronic paper 10 by changing the voltage applied based on the humidity detected by the humidity sensor.

When a humidity sensor is used instead of the temperature sensor 0 described above, LiTaO ₃ is used as the material of the dielectric thin film 2 shown in FIG. This LiTaO ₃ crystal is made of a material whose surface acoustic wave propagation velocity hardly changes with temperature change, and its temperature coefficient is about 18.0 × 10 ⁻⁶ / ° C. The temperature coefficient of the LiNbO ₃ crystal is as small as about 1/4, and the SAW change rate is about 0.005% with respect to a temperature change of 10 ° C.

A thin film of cellulose acetate is formed on the surface of LiTaO ₃ by spin coating at about 10 μm. This cellulose acetate has a water absorption property and has a property that the relative dielectric constant changes by about 50% between 10% and 70% RH (percent relative humidity). By forming a film having a dielectric constant on LiTaO _{3 in} this manner, for example, in an experiment, the humidity changes by 10% to 70%, so that the surface acoustic wave velocity changes by about 0.06%. Is obtained. Further, when the temperature change of the measurement object is significant, it can be corrected by using it together with the temperature sensor.
As described above, when a wireless sensor is used as the humidity sensor, it is detected from the experimental results that the frequency changes by about 0.06% with respect to the center frequency f0.

  Further, the shape and size of the comb-shaped electrodes 3A and 3B are made to function as a BPF that matches the center frequency f0 of the radio wave transmitted from the external transmitter (transmitter 111). The intensity of the received radio wave is shifted by frequency attenuation. This wireless sensor realizes a humidity sensor in which the intensity of the received signal in the receiving unit (receiving unit 112) linearly changes in accordance with a change in humidity.

Such a humidity sensor is provided inside the electronic paper 10 instead of the temperature sensor 0. Further, as a configuration of the control unit 40, the ROM 43 generates a drive pulse voltage generation unit based on the calculated humidity and a program for executing a calculation function and the like for calculating the humidity based on the result detected by the humidity sensor. A program for controlling the voltage to be stored is stored. In addition, in the control information INF 45 a stored in the storage unit 45, an applied voltage with respect to humidity inside the electronic paper 10 is set when an image is written on the electronic paper 10.
In the above configuration, the control unit 40 performs the processing shown in FIG. The physical quantity in step SA6 is humidity here.
Thus, by providing the humidity sensor inside the electronic paper 10 and controlling the voltage to be applied, the optimum contrast can be obtained regardless of the humidity.

(1-2) Plural humidity sensors A plurality of humidity sensors as described above may be provided inside the electronic paper 10. That is, the temperature sensors 0-1 to 0-4 shown in FIG. 9 are provided inside the electronic paper 10 instead of the humidity sensor. And the control part 40 performs the process shown in above-mentioned FIG. 10, FIG. The physical quantity in step SB6 in FIG. 10 and step SC6 in FIG. 11 is humidity here.
According to such a configuration, since the voltage can be applied based on the humidity of the entire electronic paper 10, it is possible to write an image more reliably than in the case where the voltage is applied based on the humidity at one location. .

(1-3) Illuminance Sensor In the above description, the case where the quality of the image recorded on the electronic paper 10 changes due to the temperature and humidity inside the electronic paper 10 has been described. The quality of the image also varies depending on the amount of exposure irradiated by.
FIG. 13 is a diagram showing the relationship between the amount of light and the reflectance during recording on electronic paper. Curves d5 and d6 shown in FIG. 13 show the reflectance when an image is written by applying a normal voltage and a voltage higher than the normal voltage. As is apparent from FIG. 13, when the image is written with an exposure amount L2 lower than the exposure amount L1 while driving at a normal voltage, the reflectance decreases from y1 to y2.

  On the other hand, by increasing the voltage applied when writing (corresponding to the curve d6), the reflectance increases. When the reflectance when the amount of light is L2 is compared, the reflectance increases from y2 to y1.

  Therefore, a case where an illuminance sensor is provided inside the electronic paper 10 and an image is written on the electronic paper 10 by changing a voltage applied based on the illuminance detected by the illuminance sensor will be described.

FIG. 14 shows the configuration of the illuminance sensor 100. The illuminance sensor 100 is obtained by forming an impedance converter and a photodiode on one of the comb electrodes of the temperature sensor 0 described above. In order to use this as an illuminance sensor, LiTaO ₃ is used as the material of the dielectric thin film 2 shown in FIG.

  When light having a certain illuminance (for example, 1000 lx) is applied to the photodiode 108, the impedance of the photodiode 108 changes in accordance with the amount of light, and this impedance change matches the impedance of the comb electrode 103B. 109 is transmitted to the comb-shaped electrode 103B. Here, the impedance change in the comb-shaped electrode 103B changes the reflection intensity when the SAW propagated from the comb-shaped electrode 103A on the input side is reflected by the comb-shaped electrode 103B. The comb electrode 103A receives the reflected SAW again and transmits it as an electromagnetic wave to the outside. In the wireless sensor configured in this way, it changes by about 0.1% with respect to the standard electric field strength.

  This wireless sensor realizes an illuminance sensor in which the intensity of a received signal in the receiving unit linearly changes in accordance with a change in light illuminance.

Such an illuminance sensor 100 is provided inside the electronic paper 10. Further, as a configuration of the control unit 40, the ROM 43 includes a program for executing a calculation function and the like for calculating illuminance based on the result detected by the illuminance sensor 100, and a drive pulse voltage generation unit based on the calculated illuminance. A program for controlling the voltage to be generated is stored. Further, in the INF 45 a stored in the storage unit 45, an applied voltage with respect to the illuminance received by the electronic paper 10 when an image is written on the electronic paper 10 is set.
In the above configuration, the control unit 40 performs the processing shown in FIG. Note that the physical quantity in step SA6 is illuminance here.
Thus, by providing the illuminance sensor 100 inside the electronic paper 10 and controlling the voltage to be applied, an optimum contrast can be obtained regardless of the illuminance.

(1-4) Plural illuminance sensors A plurality of illuminance sensors 100 as described above may be provided inside the electronic paper 10. That is, an illuminance sensor is provided inside the electronic paper 10 in place of the temperature sensors 0-1 to 0-4 described above. And the control part 40 performs the process shown in above-mentioned FIG. 10, FIG. Note that the physical quantity in step SB6 in FIG. 10 and step SC6 in FIG. 11 is illuminance here.
According to such a configuration, the voltage can be applied with reference to the illuminance received by the entire electronic paper 10, so that the image can be written more reliably than when the voltage is applied with reference to the illuminance at one location. Can do.

(2)
The material of each part of the wireless sensor (temperature sensor, humidity sensor, illuminance sensor) described above may be the following materials.
The material of the substrate 1 includes a single semiconductor such as Si, Ge, and diamond, glass, AlAs, AlSb, AIP, GaAs, GaSb, InP, InAs, InSb, AlGaP, AlLnP, AlGaAs, AlInAs, AlAsSb, GaInAs, GaInSb, and GaAsSb. III-V compound semiconductors such as InAsSb, II-VI compound semiconductors such as ZnS, ZnSe, ZnTe, CaSe, CdTe, HgSe, HgTe, and CdS, and Nb as a conductive or semiconductive single crystal substrate , La etc. doped SrTiO ₃ , Al doped ZnO, In ₂ O ₃ , RuO ₂ , BaPbO ₃ , SrRuO ₃ , YBa ₂ Cu ₂ O _7-X , SrVO ₃ , LaNiO ₃ , La _0.5 Sr _0.5 CoO _{3 , ZnGa 2 O 4, CdGa 2} O 4, MgTiO 4. Examples include oxides such as MgTi ₂ O ₄ or metals such as Pb, Pt, Al, Au, and Ag. From the viewpoint of compatibility with existing semiconductor processes and cost, materials such as Si, GaAs, and glass are used. It is preferable to use it.

The dielectric thin film _{2, SiO 2, SrTiO 3,} BaTiO 3, BaZrO 2, LaAlO 3, ZrO 2, Y 2 O 3 8% -ZrO 2, MGO, MgAl 2 O 4, LiNbO 3, LiTaO 3, AlVO _3, oxides such ZnO, as perovskite ABO ₃ type _{BaTiO 3, PbTiO 3, Pb 1} -X La X (Zr y Ti 1-y) 1-X / 4 O 3 (x, the value of y PZT, PLT, PLZT), Pb (Mg _0-3 Nb _2/3 ) O ₃ , KNbO _{3 and} other tetragonal, orthorhombic or pseudocubic materials, suspected ilmenite structures such as LiNbo ₃ , LiTaO ₃ etc. Sr _X Ba _{1 -X} Nb ₂ O ₆ , Pb _X Ba _X Nb ₂ O _6, etc. may be mentioned as representative ferroelectrics or tungsten bronze type. In addition, Bi ₄ Ti ₃ O ₁₂ , Pb ₂ KNb ₅ O ₁₅ , K ₃ Li ₂ Nb ₅ O ₁₅ , and the ferroelectric substitution dielectrics listed above are selected. Further, an ABO ₃ type perovskite oxide containing lead is preferably used. In particular, among these materials, materials such as LiNbO ₃ , LiTaO ₃ , and ZnO are more preferable because of remarkable changes in the surface velocity of the surface acoustic wave, the piezoelectric constant, and the like. The thickness of the dielectric thin film 2 is appropriately selected according to the purpose, but is usually set between 0.1 μm and 10 μm.

  The dielectric thin film 2 preferably has an epitaxial or unidirectional orientation from the viewpoint of the electromechanical coupling coefficient / piezoelectric coefficient of the comb-shaped electrode 3 or the dielectric loss of the antenna 4. Further, a thin film containing a group III-V semiconductor such as GaAS or carbon such as diamond may be formed on the dielectric thin film 2. Thereby, the surface velocity, the coupling coefficient, the piezoelectric constant, etc. of the surface acoustic wave can be improved.

(3)
In the above-described embodiment, when a plurality of wireless sensors (temperature sensor, humidity sensor, illuminance sensor) are used, the shape and size of the comb-shaped electrodes 3A and 3B are changed as a means for identifying each wireless sensor. The frequency of the surface acoustic wave generated in the body thin film is set individually and is identified by this frequency. The means for identifying the sensor is not limited to this, and it can also be realized by making the shape and size of the comb electrodes the same and making the separation distance d (see FIG. 6) between the comb electrodes different.
Specifically, the time of the surface acoustic wave generated on the dielectric thin film is different by making the separation distance between the comb electrodes different. Focusing on this point, the sensor may be identified by measuring the time from signal transmission of the transmitter to signal reception at the receiver.

(4)
In the above-described embodiment, the case where the temperature sensor, the humidity sensor, and the illuminance sensor are separately installed in the electronic paper 10 has been described. However, all or two or more types of sensors are installed, The applied voltage may be set from the physical quantity detected by the sensor.
Further, as an example of installing a plurality of sensors, in the above-described embodiment, the case where four sensors are installed has been described. However, the number of sensors is not limited to four. Dozens of sensors may be installed. The more applied sensors, the more appropriate applied voltage can be set.
(5)
In the above-described embodiment, when the temperature sensor 0 is used, the voltage applied by the control unit 40 is controlled based on the detected temperature. However, the exposure amount (LED light amount) irradiated by the image irradiation unit 32 is shown. ) May be controlled. Specifically, the LED light quantity decreases with the environmental temperature as shown in FIG. However, as shown in FIG. 15B, the exposure amount of the LED increases by increasing the drive current of the LED. Therefore, the controller 40 may control the LED drive current based on the temperature detected by the temperature sensor 0.

(6)
Further, the physical quantity detected by the wireless sensor may be used not only for writing an image on the electronic paper but also for checking the sealing degree of the electronic paper when the electronic paper is shipped. For example, the manufactured electronic paper is placed in a place where the humidity is higher than normal, and whether or not the electronic paper is manufactured with a normal sealing degree is checked from a humidity change detected by the wireless sensor. If it is not normally sealed, the humidity change is higher than when it is normally sealed. In this way, shipment of defective products can be prevented.

It is a figure which shows the structure of the electronic paper in 1st Embodiment of this invention. It is the figure which showed the transparent electrode in the same embodiment. It is the figure which showed the equivalent circuit schematic of the electronic paper in the same embodiment. It is the schematic which shows the electronic paper writing apparatus in the embodiment. It is the figure which showed the relationship between the light quantity which the electronic paper in the same embodiment light-receives, and a reflectance on the basis of temperature. It is a figure which shows the structure of the temperature sensor in the embodiment. It is the flowchart which showed the procedure which the control part in the embodiment performs. It is the figure which showed the structure of the temperature sensor in 2nd Embodiment of this invention. It is the block diagram which showed the structure of the temperature sensor in the same embodiment, and a control part. It is the flowchart which showed the procedure which the control part in the embodiment performs. It is the flowchart which showed the procedure of the physical quantity measurement process which the control part in the embodiment performs. It is the figure which showed the relationship between the light quantity which the electronic paper in other embodiment of this invention receives, and a reflectance on the basis of humidity. It is the figure which showed the relationship between the light quantity which the electronic paper in the same embodiment light-receives, and a reflectance on the basis of a voltage. It is the figure which showed the structure of the illumination intensity sensor in the embodiment. It is the figure which showed the relationship between environmental temperature and LED light quantity in the same embodiment.

Explanation of symbols

0 ... temperature sensor, 3A, 3B ... comb electrode, 4A, 4B ... antenna, 5A, 5B ... impedance matching unit, 6A, 6B ... ground, 10 ... electronic paper, 18 ... Transparent substrate, 19 ... Transparent electrode, 20 ... Display element layer, 21 ... Photoconductive layer, 22 ... Light absorption layer, 23 ... Transparent electrode, 24 ... Transparent substrate 30 ... electronic paper writing device, 111 ... sending unit, 112 ... receiving unit

Claims (4)

An image display medium;
When a predetermined radio signal is supplied from the outside provided inside the image display medium, the radio wave having an attribute that detects the physical quantity inside the image display medium using the signal as an energy source and reflects the detected physical quantity Wireless measuring means for generating and outputting signals,
The image display medium is an electronic paper that has a voltage application unit and records an image by irradiating an image from the outside and applying a voltage in the voltage application unit. Image display device.   The image display apparatus according to claim 1, wherein the physical quantity is at least one of temperature, humidity, and illuminance received by the image display medium from outside. The wireless measurement means includes an excitation unit that receives radio waves and generates mechanical vibrations;
A vibration medium unit in which mechanical vibration generated by the excitation unit is transmitted to generate a surface acoustic wave, and an attribute of the surface acoustic wave changes according to a physical quantity;
The image display apparatus according to claim 1, further comprising: a transmission unit that converts the surface acoustic wave into an electric signal and outputs the signal as a radio wave signal. An image writing device for writing an image on the image display device according to claim 1,
An image irradiation unit for irradiating the image display device with an image;
A voltage application unit that applies a voltage to the voltage application unit when the image irradiation unit irradiates the image display device with an image;
Receiving means for receiving a radio signal output from the wireless measuring means and detecting a physical quantity of the image display medium based on the received radio signal;
An image writing apparatus comprising: a control unit that controls at least one of an irradiation state of the image irradiation unit and an applied voltage of the voltage application unit based on a physical quantity detected by the reception unit.

Images