JP2005284148A - Device and method for electrochemical display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for electrochemical display that can suppress variation in display density (reflection factor) of write pixels and erasure pixels when cycles of image writing and erasure are repeated without making cycles of image rewriting long. <P>SOLUTION: This electrochemical display device is provided with a transparent electrode and a counter electrode which are arranged opposite each other and an electrolyte layer which is held between the transparent electrode and counter electrode and contains ions of metal, and is configure to write an image by applying a write voltage between the transparent electrode and counter electrode and depositing metal on the transparent electrode side, erase the image by applying an erasure voltage having the opposite polarity from the write voltage between the transparent electrode and counter electrode and dissolving the metal deposited on the transparent electrode side, and initialize the potential difference between the transparent electrode and counter electrode into a specified range before the write voltage is applied after the erasure voltage is applied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrochemical display device and an electrochemical display method based on the principle of performing display using electrochemical oxidation and reduction.

In recent years, with the spread of networks, documents that have been distributed as printed materials have been distributed as so-called electronic documents. Furthermore, books and magazines are often provided in the form of so-called electronic publishing. In order to view this information, the transparent electrode, which is the display-side electrode, and the counter electrode are arranged to face each other through a white colored electrolyte containing metal ions, and the image is written by depositing metal on the transparent electrode. An electrochemical display device has been proposed in which an image is erased by dissolving the deposited metal in an electrolyte (see, for example, Patent Document 1 and Patent Document 2). This makes it possible to increase the contrast and black density.
JP 2002-258327 A JP 2003-241227 A

  By the way, in the electrochemical display device as described above, the support substrate that supports the electrodes and other thin films that are used as necessary for mounting are often made of a resin material that is a dielectric. Since these resin materials have different dielectric constants ε and electrical conductivity σ due to differences in composition, when these resin materials are layered, the relaxation time (dielectric constant ε and electrical conductivity of each layer of the dielectric) It is considered that residual charges are generated between the layers due to the difference in the ratio of σ. In the electrochemical display device, since the resin materials are generally layered, it is considered that the residual charge as described above can be generated.

  The inventor of the present application actually created a prototype that simplified the above-described electrochemical display device, and between a transparent conductive film (hereinafter referred to as a transparent electrode) that is an electrode on the display side and a counter electrode facing it. It has been confirmed that when a pulse voltage is applied, a potential difference is generated between both electrodes after the pulse voltage is applied. This potential difference is considered to be caused by applying the pulse voltage between the electrodes to accumulate the above-described residual charges (or causing the above-described residual charge density distribution). Furthermore, the inventors of the present application have also confirmed that in the prototype described above, this potential difference does not disappear immediately but gradually decreases as time elapses.

  When such a transient phenomenon (hereinafter simply referred to as a transient) occurs, the following problem occurs. In the above electrochemical display device, when a pulse voltage for erasing an image is applied between both electrodes, the above transient continues for several seconds. However, if the next image writing / erasing cycle is started before the end of the transient, there is a problem that the display density of the image becomes lighter as the image writing / erasing cycle is repeated. Further, there is a problem that an image once written in a pixel becomes thinner as time passes. On the other hand, if the image is written / erased after waiting for the transient to end, the above problem does not occur. However, the image rewrite cycle takes a long time and cannot be put into practical use.

  The present invention has been made in view of such problems, and a first object of the present invention is to perform writing in a case where an image writing / erasing cycle is repeated without increasing the image rewriting cycle. An object of the present invention is to provide an electrochemical display device and an electrochemical display method capable of suppressing variations in display density (reflectance) of embedded pixels and erased pixels. A second object is to provide an electrochemical display device and an electrochemical display method capable of suppressing a change in display density (reflectance) of an image once displayed over a long period of time.

  The electrochemical display device of the present invention includes a transparent electrode and a counter electrode arranged so as to face each other, an electrolyte layer sandwiched between the transparent electrode and the counter electrode, and containing metal ions, and the transparent electrode and the counter electrode The write voltage is applied between the transparent electrode and the write control means for writing the image by depositing metal on the transparent electrode side, and the erase voltage is reversed to the write voltage between the transparent electrode and the counter electrode. By applying the polarity, the erasing control means for erasing the image by dissolving the metal deposited on the transparent electrode side, and between the transparent electrode and the counter electrode after applying the erasing voltage and before applying the writing voltage Initializing means for initializing the potential difference within a predetermined range. In the following description, “voltage” means “potential difference between ground as a reference and a certain point”, that is, “voltage based on ground”, and is referred to as “potential difference”. Sometimes it means "potential difference between two points (here, between both poles)".

  The electrochemical display method of the present invention is provided with a transparent electrode and a counter electrode arranged so as to face each other, and an electrolyte layer sandwiched between the transparent electrode and the counter electrode and containing metal ions. By applying a writing voltage between the electrodes, metal is deposited on the transparent electrode side to write an image, and an erasing voltage is applied between the transparent electrode and the counter electrode with a polarity opposite to the writing voltage. The metal deposited on the transparent electrode side is dissolved to erase the image, and after applying the erase voltage, the potential difference between the transparent electrode and the counter electrode is initially set within a predetermined range before applying the write voltage. It is made to become.

  In the electrochemical display device and the electrochemical display method of the present invention, a writing voltage is applied between the transparent electrode and the counter electrode, whereby a metal is deposited on the transparent electrode side to write an image. On the other hand, by applying an erasing voltage with a polarity opposite to that of the writing voltage between the transparent electrode and the counter electrode, the metal deposited on the transparent electrode side is dissolved to erase the image. Further, the potential difference between the transparent electrode and the counter electrode is initialized to a predetermined range after the erase voltage is applied and before the write voltage is applied. Initialization of potential difference means that transient of potential difference generated between both electrodes is forcibly terminated after erasing voltage is applied between both electrodes, and the potential difference between both electrodes falls within a predetermined range. Point to.

  According to the electrochemical display device and the electrochemical display method of the present invention, the potential difference between the transparent electrode and the counter electrode is initialized after the erase voltage is applied and before the write voltage is applied. An unstable transient state before writing can be resolved early. Therefore, fluctuations in display density (reflectance) of writing pixels and erasing pixels can be suppressed when the image writing / erasing cycle is repeated without increasing the image rewriting cycle. . In addition, a change in display density (reflectance) of an image once displayed can be suppressed over a long period of time without increasing the rewrite cycle of the image. That is, the display quality (cycle characteristics of write pixels and erase pixels, and memory characteristics of the display image) can be improved without extending the image rewrite cycle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a schematic configuration of an electrochemical display device and an electrochemical display method according to a first embodiment of the present invention. The electrochemical display device includes an electrochemical display element 10 having the structure shown in FIG. 2 and a display element driving unit 20 for driving the electrochemical display element 10. In the present embodiment, as described below, a passive matrix is used as a driving method of the electrochemical display device 10. FIG. 2 is a perspective view of the electrochemical display element 10.

  As shown in FIG. 2, the electrochemical display element 10 has a structure in which a first substrate 11 and a second substrate 12 are arranged to face each other with an electrolyte 13 (not shown) interposed therebetween. The transparent electrode 14 extends in a stripe shape on the surface of the first substrate 11 facing the second substrate 12, and the counter electrode 15 is disposed on the surface of the second substrate 12 facing the first substrate 11. Extends in a stripe shape, and the transparent electrode 14 and the counter electrode 15 are arranged to face each other so as to cross each other. These intersections constitute pixels.

  The first substrate 11 is made of a transparent material, for example, quartz glass. The second substrate 12 is made of, for example, quartz glass. The electrolyte 13 includes a solvent and a precipitation-dissolving material that precipitates and dissolves by an oxidation-reduction reaction. Examples of the solvent include a mixture of dimethyl sulfoxide and γ-butyrolactone. The precipitation-dissolving material is for enabling display of pixels by utilizing the change in color between the precipitated state and the dissolved state. Examples of the precipitation-dissolving material include metal ions that precipitate as a metal by reduction, specifically silver ions. The transparent electrode 14 deposits a metal to be displayed as a pixel, and is made of, for example, a transparent conductive film. Specifically, it is made of ITO (Indium Tin oxide) which is an oxide of tin (Sn) and indium (In). The counter electrode 15 is made of, for example, an electrochemically stable metal. Specifically, it is made of silver (Ag).

  The display element driving unit 20 includes a signal control unit 21, a transparent electrode driving unit 22, and a counter electrode driving unit 23. The signal control unit 21 is connected to the transparent electrode driving unit 22, and inputs the image data for one line 24 </ b> A and the synchronization timing signal 24 </ b> B to the transparent electrode driving unit 22. Further, the signal control unit 21 is also connected to the counter electrode driving unit 23, and a signal (hereinafter referred to as a phase setting signal) that sets the scanning signal 25A and which phase in one cycle of image writing / erasing. ) 25B and the synchronization timing signal 25C are input to the counter electrode drive unit 23. The above aspect setting signal corresponds to either the first, second, or third aspect at the time of writing as shown in FIG. 3, or the first or second aspect at the time of erasing. FIG. 3 conceptually shows a drive voltage waveform applied between the transparent electrode and the counter electrode in one cycle of image writing / erasing. Details thereof will be described later. The transparent electrode driving unit 22 and the counter electrode driving unit 23 correspond to a specific example of the writing control unit in the present embodiment. The transparent electrode driving unit 22 and the counter electrode driving unit 23 further correspond to specific examples of the erase control unit and the initialization unit in the present embodiment.

  The signal control unit 21 controls the transparent electrode driving unit 22 and the counter electrode driving unit 23 based on image signals and control signals received from the host computer.

  The transparent electrode drive unit 22 is for driving the transparent electrode 14 in accordance with the control from the signal control unit 21. The image data temporary storage unit 22A, the signal voltage pulse setting unit 22B, and the signal voltage pulse drive unit. 22C. The image data primary storage unit 22A is configured to temporarily store one line of image data received from the signal control unit 21. The signal voltage pulse setting unit 22B sets the magnitude and application time of the voltage pulse corresponding to one line of image data. The signal voltage pulse driver 22C applies a signal voltage pulse having a magnitude and an application time set by the signal voltage pulse setting unit 22B to each transparent electrode 14.

  The counter electrode driving unit 23 is for driving the counter electrode 15 in accordance with control from the signal control unit 21. The counter electrode selecting unit 23A, a selection voltage pulse setting unit 23B, and a selection voltage pulse driving unit 23C. And have. The counter electrode selector 23A selects a counter electrode to which a selection voltage is applied from a plurality of counter electrodes based on the scanning signal 25A. The selection voltage pulse setting unit 23B sets the magnitude and application time of the selection voltage pulse to be applied to the counter electrode selected by the counter electrode selection unit 23A based on the situation setting signal 25B. The selection voltage pulse drive unit 23C applies the selection voltage pulse having the magnitude and application time set by the selection voltage pulse setting unit 23B to the counter electrode 15.

  Next, the operation of the electrochemical display device configured as described above will be described. First, the operation principle of the electrochemical display element 10 will be described with reference to FIGS.

FIG. 4 shows the waveform of the applied voltage between the counter electrode 15 and the transparent electrode 14 when the potential of the counter electrode 15 is used as a reference. FIG. 5 shows a current-voltage characteristic (cyclic voltammetry diagram) when the triangular wave voltage shown in FIG. 4 is applied between the transparent electrode 14 and the counter electrode 15 with reference to the voltage of the counter electrode 15. It is. In FIG. 5, the counter electrode 15 is a silver (Ag) electrode, silver iodide (AgI), that is, silver ions (Ag ⁺ ) and iodine ions (I ⁻ ) are dissolved in the electrolyte, and iodide is further used as the supporting electrolyte. This is an example of characteristics when lithium (LiI) is dissolved together.

As shown in FIG. 5, when a voltage is applied from zero to a minus side between the transparent electrode 14 and the counter electrode 15 on the basis of the voltage of the counter electrode 15, silver does not precipitate for a while and the writing threshold is reached. Silver deposition on the transparent electrode 14 begins when the voltage (-Vth) is exceeded. Then, when the write threshold voltage (−Vth) is exceeded, a current accompanying the deposition starts to flow. Silver deposition exceeds the write voltage corresponding to the apex of the triangular wave voltage, continues even if the voltage gradually decreases, and continues even if the voltage drops below the previous write threshold voltage (−Vth). Silver deposition ends when the applied voltage drops to the holding voltage (-Vke). That is, once the write threshold voltage (−Vth) is exceeded and silver precipitation nuclei are formed on the surface on the transparent electrode side, silver deposition occurs even at a voltage lower than the write threshold voltage (−Vth). Occur. On the other hand, when a reverse polarity (plus) voltage is applied between the transparent electrode and the counter electrode, the dissolution of silver begins, and the silver that has precipitated when the erase threshold voltage Vith is reached disappears. When a higher voltage than this is applied, iodine is liberated and adheres to the electrode, and iodine ions (I ⁻ ) are oxidized electrochemically to become iodine (I ₂ ), which is colored yellow.

  Here, when driving a display device having the current-voltage characteristics (cyclic voltammetry diagram) as described above, the simplest is to apply a voltage exceeding the write threshold voltage (-Vth). It is conceivable that metal is deposited, the pixel is written, and a voltage not exceeding the erase threshold voltage Vith is applied to dissolve the metal to erase the pixel. On the other hand, in this embodiment, as described below, the pixel is written by applying the write voltage twice, and the pixel is erased by applying the erase voltage twice. I have to. Further, in the present embodiment, as described below, after applying the erase voltage twice, before applying the write voltage twice, the reset voltage is applied to initialize the potential difference between the electrodes. I have to.

  Next, the operation of the display element driving unit 20 will be described with reference to FIGS. 6 and 7.

  6 and FIG. 7 show that in a certain aspect (the first, second, or third aspect at the time of writing, or the first or second aspect at the time of erasure) The process which arises between the electrode drive part 22 and the counter electrode drive part 23 is represented along the time-axis. For convenience of explanation, the situation setting signal 25B is in the second situation at the time of writing and the second situation at the time of erasing (FIG. 6), the first and third aspects at the time of writing, and The case of the first situation at the time of erasure (FIG. 7) will be described separately.

  The case where the situation setting signal 25B is the second situation during writing and the second situation during erasing will be described. The signal control unit 21 first inputs the situation setting signal 25B to the counter electrode driving unit 23 (step S101). Next, the signal control unit 21 inputs the scanning signal 25A to the counter electrode driving unit 23 (step S102). The scanning signal 25 </ b> A here is a signal that means selecting a specific one of the plurality of counter electrodes. Based on the scanning signal 25A, the counter electrode selection unit 23A of the counter electrode driving unit 23 selects a counter electrode to which a selection voltage is applied from a plurality of counter electrodes (step S103). Based on the situation setting signal 25B, the voltage pulse setting unit 23B of the counter electrode driving unit 23 sets the magnitude and application time of the selection voltage pulse applied to the counter electrode set as described above (step S104s).

  The signal control unit 21 further inputs the image data for one line 24A to the transparent electrode driving unit 22 (step S105). The image data temporary storage unit 22A of the transparent electrode drive unit 22 temporarily stores the image data for one line 24A (step S106). The voltage pulse setting unit 22B of the transparent electrode driving unit 22 sets the magnitude and application time of the signal voltage pulse corresponding to one line of image data 24A temporarily stored by the image data temporary storage unit 22A (step S107).

  The signal control unit 21 inputs the synchronization timing signals 24B and 25C to the transparent electrode driving unit 22 and the counter electrode driving unit 23 in synchronization with each other (step S108). The signal voltage pulse drive unit 22C of the transparent electrode drive unit 22 applies the signal voltage pulse having the magnitude and application time set by the signal voltage pulse setting unit 22B to each transparent electrode 14 in synchronization with the synchronization timing signal 24C. (Step S109). The signal voltage pulse driving unit 23C of the counter electrode driving unit 23 causes the counter electrode setting unit 23A to output the signal voltage pulse having the magnitude and application time set by the signal voltage pulse setting unit 23B in synchronization with the synchronization timing signal 25C. Output to the set counter electrode 15 (step S110).

  By performing the above steps S101 to S110, the process for the first line of the screen is completed in the second aspect at the time of writing and the second aspect at the time of erasing. Subsequently, the steps for processing one line on the screen (steps S102 to S110) are repeated for a plurality of lines constituting one screen (step S111). Thereby, the processing in the second aspect at the time of writing and the second aspect at the time of erasing is completed.

  Next, the case where the above-described situation setting signal 25B is the first and third aspects at the time of writing and the first aspect at the time of erasing will be described. The signal control unit 21 first inputs the situation setting signal 25B to the counter electrode driving unit 23 (step S201). Next, the signal control unit 21 inputs the scanning signal 25A to the counter electrode driving unit 23 (step S202). The scanning signal 25A here is a signal which means selecting all the counter electrodes. Based on the scanning signal 25A, the counter electrode selection unit 23A of the counter electrode driving unit 23 selects a counter electrode to which a selection voltage is applied from a plurality of counter electrodes (step S203). Here, the counter electrode selector 23A selects all the counter electrodes. The voltage pulse setting unit 23B of the counter electrode driving unit 23 sets the magnitude and application time of the selection voltage pulse applied to the counter electrode set above based on the situation setting signal 25B (step S204).

  The signal control unit 21 inputs the synchronization timing signal 25C to the counter electrode driving unit 23 (Step S205). The selection voltage pulse driving unit 23C of the counter electrode driving unit 23 causes the counter electrode setting unit 23A to output the signal voltage pulse having the magnitude and application time set by the selection voltage pulse setting unit 23B in synchronization with the synchronization timing signal 25C. Output to the set counter electrode 15 (step S206). Here, the selection voltage pulse driving unit 23C outputs to all the counter electrodes simultaneously. The above “simultaneous” does not necessarily mean that the time is strictly the same.

  By performing steps S201 to S206 described above, the processes in the first and third aspects at the time of writing and the first aspect at the time of erasing are completed. In the first and third aspects at the time of writing and the first aspect at the time of erasing, instead of performing steps S201 to S206, the second aspect at the time of writing and the second aspect at the time of erasing. As described above, the step of processing one line of the screen (steps S102 to S110) may be repeated for a plurality of lines constituting one screen (step S111).

  Next, the operation of the electrochemical display element 10 will be described in detail with reference to FIGS. 3 and 8 to 14. FIG. 8 shows a state in which an image is written in the electrochemical display element 10. FIG. 9 shows an example of a drive voltage waveform at the time of writing. More specifically, FIG. 9 shows a voltage (signal voltage) applied to each transparent electrode 14 (C1, C2, C3... Cm) shown in FIG. 8 and each counter electrode 15 (R1, R2, R3... Rn). And a voltage applied to the pixels (C1, R1), (C1, R2), (C2, R2), (Cm, Rn), that is, between the transparent electrode 14 and the counter electrode 15 An example of a change with time of a total of three kinds of voltages (write voltage) applied between them is shown. FIG. 10 shows drive voltage waveforms at the time of writing in the comparative example. FIG. 11 shows a transient state when the potential difference is not initialized. FIG. 12 shows a transient state when the potential difference is initialized. FIG. 13 shows how the image is erased in the electrochemical display element 10. FIG. 14 shows an example of a driving voltage waveform at the time of erasing. More specifically, FIG. 14 shows a voltage (signal voltage) applied to each transparent electrode 14 (C1, C2, C3... Cm) shown in FIG. 13 and each counter electrode 15 (R1, R2, R3... Rn). And the voltage applied to the pixel (C1, R1), (C1, R2), (C2, R2), (Cm, Rn), that is, between the transparent electrode 14 and the counter electrode 15 This shows an example of a change with time of a total of three kinds of applied voltages (erase voltages).

  Hereinafter, the operation during writing will be described with reference to FIG. 3, FIG. 8, and FIG. As shown in FIGS. 3 and 9, three aspects are provided on the time axis. First, the first aspect is an aspect in which the potential difference is initialized and corresponds to a period of time Tr. The second aspect is an aspect in which metal precipitation nuclei are formed in pixels to be written in the entire screen (this is referred to as applying a first writing voltage), and corresponds to a period of time Ta. The pixel to be written refers to a pixel where the transparent electrode and the counter electrode selected when writing an image intersect. The third aspect is an aspect in which metal is further deposited on the previous pixel to be written and an image is displayed (this is referred to as applying a second writing voltage), and corresponds to a period of time Tw. It should be noted that the display is continued until the start of erasure after writing, which corresponds to a period of time Tm. Hereinafter, each aspect will be described in detail. Here, the writing target pixel refers to a pixel where the transparent electrode and the counter electrode selected when the image is written intersect.

  First, the operation for initializing the potential difference, which is the first aspect, will be described. Each transparent electrode 14 (C1, C2, C3... Cm) is grounded, the first signal voltage is set to the ground voltage, and the counter electrode drive unit 23 is a first selection smaller than the erase threshold voltage Vith. The voltage Vr is simultaneously output to each counter electrode 15 (R1, R2, R3... Rn) with the same polarity as that at the time of erasing described later. The output timing is preferably just before the voltage is applied in the second phase at the time of writing as shown in FIG. 9, but this embodiment is not limited to this, and the second timing at the time of erasing is not limited to this. After applying the voltage in the situation, it may be any time before the voltage is applied in the second situation at the time of writing. The above “simultaneous” does not necessarily mean that the time is strictly the same.

  For example, in the pixel (C2, R2), first, the ground voltage in each transparent electrode C2 and the first selection voltage Vr that is smaller than the erase threshold voltage Vith in the counter electrode R2 have the same polarity as in the later-described erase. Overlap. Due to these potential differences, a constant reset voltage Vr smaller than the erase threshold voltage Vith is applied. Thereby, the potential difference immediately before the application of the reset voltage can be made substantially equal to the potential difference at the transient convergence destination. At this time, it does not appear that some change has occurred on the screen. Further, although the reset voltage Vr is applied to all the pixels, even if a reset voltage Vr smaller than the erase threshold voltage Vith is applied from the above-described current-voltage characteristics (cyclic voltammetry diagram of FIG. 5). Anion oxidation does not occur.

  Next, the operation of applying the first write voltage, which is the second aspect, will be described. First, the transparent electrode driving unit 22 applies a voltage corresponding to image data for one line, for example, a second signal voltage (0, −Vwc, 0) to each transparent electrode 14 (C1, C2, C3... Cm). ... 0) is output at the same time. Here, there are locations where the signal voltage (−Vwc) is output and locations where it is not output. The locations where the signal voltage is output correspond to the pixel to be written. This means that it does not correspond to the target pixel. Then, the transparent electrode driving unit 22 sequentially outputs the second signal voltage corresponding to the image data for n lines constituting one screen. The second signal voltage (-Vwc) is a voltage having an absolute value smaller than the write threshold voltage (-Vth). On the other hand, the counter electrode driver 23 sequentially outputs the second selection voltage Vwr to each counter electrode 15 (R1, R2, R3... Rn) in synchronization with the signal voltage (−Vwc). Each of the second selection voltages Vwr is a voltage having an absolute value smaller than the write threshold voltage (−Vth).

  For example, in the pixel (C2, R2), the second signal voltage (−Vwc) at the transparent electrode C2 and the second selection voltage Vwr at the counter electrode R3 overlap. Based on these potential differences, a first write voltage (−Va = − (Vwc + Vwr)) equal to or higher than the write threshold voltage is applied between the transparent electrode and the counter electrode, and a metal precipitation nucleus is formed on the transparent electrode side. Is done. In the pixel (C2, R1), there is no period in which the second signal voltage (−Vwc) output from the transparent electrode C2 and the second selection voltage Vwr1 output from the counter electrode R1 overlap, and writing is performed. Only one of the second signal voltage (−Vwc) whose absolute value is lower than the threshold voltage (−Vth) or the second selection voltage Vwr1 is applied between the transparent electrode 14 and the counter electrode 15. is there. Therefore, no metal deposition occurs in the pixel (C2, R1).

  Finally, the operation of applying the second write voltage, which is the third aspect, will be described. First, each of the transparent electrodes 14 (C1, C2, C3... Cm) is grounded, and the third signal voltage is set to the ground voltage, and the counter electrode driving unit 23 uses the write threshold voltage (−Vth). A third selection voltage Vw having a small absolute value is simultaneously output to each counter electrode 15 (R1, R2, R3... Rn). Note that the term “simultaneously” does not necessarily mean that they are simultaneously strictly in time, but means that they are simultaneously in time to the extent that the user feels that the image has been displayed simultaneously on the entire screen. To do.

  For example, in the pixel (C2, R2), the third signal voltage (ground voltage) in the transparent electrode C2 and the third selection voltage Vw having an absolute value smaller than the write threshold voltage (-Vth) in the counter electrode R2 Overlap. Due to these potential differences, a second write voltage (−Vw) smaller than the write threshold voltage is applied to all the write target pixels, and the first write voltage (−Va) causes the first write voltage (−Va) to be applied onto the transparent electrode 14. Additional metal is deposited around the deposited nuclei of the deposited metal, and writing is completed. Note that the second write voltage (-Vw) is also applied to the pixel having no metal precipitation nuclei. However, from the current-voltage characteristics (cyclic voltammetry diagram) of FIG. In the absence of nuclei, metal deposition does not occur even when a second write voltage (-Vw) smaller than the write threshold voltage is applied.

  Since the image writing is performed as described above, the writing drive in the electrochemical display device of the present embodiment is excellent in the following points.

  In the present embodiment, as described above, the reset voltage is applied between both electrodes as means for initializing the potential difference. However, without initializing the potential difference, the next image write / It can be seen that when the erase cycle is started, the voltage immediately before the start of the image write / erase cycle increases as the write / erase cycle is repeated (FIGS. 10 and 11). On the other hand, when the potential difference is initialized as in the present embodiment, the image writing is not compared with the case where the next image writing / erasing cycle is started before the transient ends without initializing the potential difference. It can be seen that the potential difference just before starting the erase cycle is much lower and stable (FIG. 12). Further, it can be seen from FIG. 12 that by applying the reset voltage in the first aspect, the potential difference immediately before the application of the reset voltage is substantially equal to the potential difference at the transient convergence destination. Note that the potential difference at the transient convergence destination is determined by the structure / composition of the electrochemical display device, and is different when the structure / composition of the electrochemical display device is different. Therefore, the voltage at which the transient converges is not limited to that shown in FIG.

  As described above, in this embodiment, the reset voltage is applied and the potential difference between the transparent electrode and the counter electrode is initialized before the writing voltage is applied. A stable transient state can be resolved early. Therefore, fluctuations in display density (reflectance) of writing pixels and erasing pixels can be suppressed when the image writing / erasing cycle is repeated without increasing the image rewriting cycle. . In addition, a change in display density (reflectance) of an image once displayed can be suppressed over a long period of time without increasing the rewrite cycle of the image. That is, the display quality (cycle characteristics of write pixels and erase pixels, and memory characteristics of the display image) can be improved without extending the image rewrite cycle. In particular, when the write voltage is applied immediately after the erase voltage is applied, the above-described effect becomes even more remarkable by applying the reset voltage as in the present embodiment.

  In general, in an electrochemical display device, each pixel has a strong function mainly as a capacitor before metal deposition, and the resistance value and the threshold value between the electrodes decrease with the deposition. Yes. Therefore, if it is attempted to complete the metal deposition only by applying a single write voltage, when the pixels around the written pixel are written, the metal is further deposited on the already written pixel portion, which is unnecessary. Current flows, causing problems such as crosstalk and a decrease in contrast. On the other hand, if the two-stage write drive voltage waveform as in the present embodiment is used, it is possible to prevent the metal precipitation nuclei from becoming unnecessarily large in the first application of the first write voltage. Therefore, it is possible to effectively avoid the occurrence of crosstalk due to an unnecessary current flowing through the pixel on which the metal is deposited and the decrease in contrast.

  Further, if it is attempted to complete the metal deposition with only one write voltage, the deposition takes a long time for each pixel, and in particular, the display takes longer as the number of pixels increases. In contrast, in the present embodiment, when the first first write voltage is applied, a voltage is applied for each pixel for a short time to form only metal precipitation nuclei sequentially, and then the second second write voltage is applied. Since the voltage is applied to all the writing target pixels at the same time when the writing voltage is applied, the writing voltage is sequentially applied to each pixel once to complete the writing. Thus, the application time can be significantly shortened. That is, the time required for image display can be significantly shortened.

  Further, if metal deposition is to be completed only by applying a single write voltage, display is performed sequentially (from the upper left to the lower right) as the scanning lines (counter electrodes) are sequentially scanned. For this reason, a user feels unnatural how an image is displayed. On the other hand, in the present embodiment, the image is displayed on the entire screen all at once when the second write voltage is simultaneously applied to all the write target pixels. You can feel the situation naturally. Note that the term “simultaneously” does not necessarily mean that the time is exactly the same time, but means that the image is simultaneously timed to the extent that the user feels that the image has been erased simultaneously on the entire screen. .

  Next, the erase operation will be described with reference to FIGS.

  As shown in FIGS. 3 and 14, two aspects are provided on the time axis. First, the first phase is a phase in which most of the metal deposited on the transparent electrode side during writing (excluding the core portion) is dissolved (this is referred to as applying the first erase voltage), and the time Te Corresponds to the period of The second aspect is an aspect in which the metal precipitation nuclei slightly remaining on the transparent electrode side can be dissolved in a completely close state (this is called applying the second erasing voltage), and the time Ts It corresponds to a period. Hereinafter, each aspect will be described in detail.

  First, the operation of applying the first erase voltage, which is the first aspect, will be described. First, the transparent electrodes 14 (C1, C2, C3... Cm) are grounded, the fourth signal voltage is set to the ground voltage, and the counter electrode drive unit 23 has a first voltage smaller than the erase threshold voltage Vith. The selection voltage Ve of 4 is simultaneously output to each counter electrode 15 (R1, R2, R3... Rn) with the opposite polarity to that at the time of writing. Note that the term “simultaneously” does not necessarily mean that the images are simultaneously temporally exactly, but means that the images are simultaneously synchronized to the extent that the user feels that the entire image has been erased simultaneously. To do.

  For example, in the pixel (C2, R2), first, a fourth signal voltage (ground voltage) in each transparent electrode C2 and a fourth selection voltage Ve smaller than the erase threshold voltage Vith in the counter electrode R2 are written. Overlapping with reverse polarity. Due to these potential differences, a constant first erase voltage Ve smaller than the erase threshold voltage Vith is uniformly applied to all the pixels to be erased. Here, the erasure target pixel refers to a pixel where the transparent electrode and the counter electrode selected when erasing the image intersect. As a result, most of the deposited metal deposited on the transparent electrode during writing dissolves (except for the core portion). At this time, the user feels that the image has been erased simultaneously on the entire screen. The first erasing voltage Ve is applied also to a pixel having no metal precipitation nuclei, but when there is no metal precipitation nuclei from the above-described current-voltage characteristics (cyclic voltammetry diagram of FIG. 5). Does not oxidize anions even when an erase voltage smaller than the erase threshold voltage Vith is applied.

  Next, the operation of applying the second erase voltage, which is the second aspect, will be described. First, the transparent electrode driving unit applies a voltage corresponding to image erasure data for one line, for example, a fifth signal voltage (0, Vec, 0...) To each transparent electrode 14 (C 1, C 2, C 3... Cm). 0) is output simultaneously. Here, there are a portion where the fifth signal voltage Vec is output and a portion where it is not output. The portion where the fifth signal voltage Vec is not output corresponds to the erasure target pixel, and the portion where the fifth signal voltage Vec is not output is the erasure target. It means that it does not correspond to a pixel. The transparent electrode driver 22 sequentially outputs a fifth signal voltage corresponding to the image erasure data for n lines constituting one screen. Note that the fifth signal voltage Vec is smaller than the erase threshold voltage Vith. On the other hand, the counter electrode drive unit 23 sequentially outputs the fifth selection voltage (−Vern) to each counter electrode 15 (R1, R2, R3... Rn) in synchronization with the fifth signal voltage Vec. The absolute value of the fifth selection voltage (−Vern) is a voltage smaller than the erase threshold voltage Vith.

  For example, in the pixel (C2, R2), the fifth signal voltage Vec at the transparent electrode C2 and the fifth selection voltage (-Ver) at the counter electrode R2 overlap. Based on these potential differences, a second erasing voltage Vs (= Vec + Ver) equal to or higher than the erasing threshold voltage Vith is applied between the transparent electrode and the counter electrode to completely remove the metal precipitation nuclei slightly remaining on the transparent electrode side. It is also possible to dissolve in a close state. By applying such logic to all the erasure target pixels, the uniform fourth erasure voltage Vs is applied between the transparent electrode and the counter electrode in all the erasure target pixels, and slightly remains on the transparent electrode side. It is also possible to dissolve the deposited nuclei of the metal in a nearly complete state. In the pixel (C2, R1), there is no period in which the fifth signal voltage Vec output from the transparent electrode C2 and the fifth selection voltage (-Ver1) output from the counter electrode R1 overlap, and the erasing threshold is reached. Only one of the signal voltage Vec whose absolute value is lower than the voltage Vith or the fifth selection voltage (−Vwr1) is applied. Therefore, only a voltage having an absolute value lower than the erasing threshold voltage Vith is applied to the pixels other than the erasing target pixel, and no anion oxidation occurs in the pixels other than the erasing target pixel. In addition, since a voltage of Vith or higher is applied only for an extremely short time of time Tss, it is extremely rare that unwanted anion oxidation occurs after the remaining metal precipitation nuclei are dissolved. It is an important point.

  Since the image is erased as described above, the erase drive in the electrochemical display device of the present embodiment is excellent in the following points.

  It has been clarified from the experimental results so far that when an anionic oxidant is present in the vicinity of the electrode, the nucleation of the metal is inhibited. When writing (metal nucleation) is performed, the desired writing density cannot be reached, and the display becomes non-uniform. On the other hand, in the present embodiment, since the oxidation of anions hardly occurs as described above, the display is hardly uneven. Therefore, the display colors of the writing pixel and the erasing pixel are reflected. The cycle characteristics of the rate are very good.

  In the present embodiment, the first erase voltage is applied to all the pixels to be erased at the same time so that the user feels that the image has been erased simultaneously on the entire screen, so the image is erased. The user can feel the situation naturally. This “simultaneous” is synonymous with the above definition.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. In the first embodiment, a passive matrix is used as a driving method of the electrochemical display device. However, in the present embodiment, an active matrix is used instead. In the present embodiment, description of the same configuration, operation, action, and effect as those of the electrochemical display device of the first embodiment will be omitted as appropriate.

  FIG. 15 shows a schematic configuration of the electrochemical display device according to the present embodiment. The electrochemical display device includes an electrochemical display element 127 as shown in FIG. 16 and a display element driving unit 126 for driving the electrochemical display element 127. The display element driving unit 126 includes a signal control unit 121, a data line driving unit 122, a gate line driving unit 123, a source scanning line 124, a gate scanning line 125, and a pixel driving element 126. An intersection of gate scanning lines (address lines) 125 and source scanning lines (data lines) 124 wired in a matrix corresponds to one pixel. Note that the data line driving unit 122 and the gate line driving unit 123 correspond to a specific example of the writing control unit in this embodiment. The data line driving unit 122 and the gate line driving unit 123 further correspond to a specific example of the erase control unit and the initialization unit in the present embodiment.

  Each pixel is composed of an electrochemical display element 127 described later. In each pixel, for example, the transparent electrode 114 side is grounded (0 V), and the counter electrode 115 side is connected to the drain electrode of the pixel driving element 126. The gate of the pixel driving element 126 is connected to the gate scanning line 125, and the gate scanning line 125 is connected to the gate line driving unit 123. The source electrode of the pixel driving element 126 is connected to the source scanning line 124, and the source scanning line 124 is connected to the data line driving unit 122.

  As shown in FIG. 16, the electrochemical display element 127 has a structure in which a first substrate 111 and a second substrate 112 are arranged to face each other with an electrolyte 113 interposed therebetween. A transparent electrode 114 is formed on the entire surface of the first substrate 111 facing the second substrate 112, and a plurality of counter electrodes 115 are formed on the surface of the second substrate 112 facing the first substrate 111. Are formed in a grid pattern, and spacer beads 116 for maintaining a gap between the transparent electrode 114 and the counter electrode 115 are mixed in the electrolyte 113.

  Next, a method for driving the electrochemical display device will be described. The gate line driving unit 123 scans the plurality of gate scanning lines 125 from the top to the bottom by sequentially outputting the selection pulse in response to the output signal of the signal control unit 121. Thus, the gate line driving unit 123 operates in the same manner as the counter electrode driving unit 23 in the first embodiment. On the other hand, the data line driving unit 122 receives the output signal of the signal control unit 121 and outputs a data pulse, so that the data line driving unit 122 outputs the data pulse to the plurality of source scanning lines 124 in synchronization with the gate line driving unit 123. . That is, in this electrochemical display device, when image data from a recording medium or the like is sent to the signal control unit 121, a selection pulse is output from the gate line driving unit 123, and the data line driving unit 122 synchronizes with it. A data pulse is output. As described above, the data line driving unit 122 performs the same operation as the transparent electrode driving unit 22 in the first embodiment. Then, a pulse (reset voltage, write voltage, erase voltage) having a waveform as shown in FIG. 18 is selectively transmitted from the data line driver 122 to the pixel in which the gate and the source of the pixel drive element 126 are simultaneously turned on. Thus, image writing / erasing is performed.

  Since the image writing / erasing is performed as described above, the writing / erasing drive in the electrochemical display device of the present embodiment is excellent in the following points.

  By applying the reset voltage as in the present embodiment, the potential difference between the transparent electrode and the counter electrode is initialized before the writing voltage is applied. The transient state can be resolved early. Therefore, fluctuations in display density (reflectance) of writing pixels and erasing pixels can be suppressed when the image writing / erasing cycle is repeated without increasing the image rewriting cycle. . In addition, a change in display density (reflectance) of an image once displayed can be suppressed over a long period of time without increasing the rewrite cycle of the image. That is, display quality (cycle characteristics of write pixels and erase pixels, and memory characteristics of display images) can be improved without lengthening the image rewrite cycle. In particular, when the write voltage is applied immediately after the erase voltage is applied, the above-described effect becomes even more remarkable by applying the reset voltage as in the present embodiment.

  In addition, it has been clarified from the experimental results so far that when an anionic oxidant is present in the vicinity of the electrode, the nucleation of the metal is inhibited, and the oxidant is present in the vicinity of the electrode. If writing (metal nucleation) is performed in this state, the desired writing density cannot be reached and the display becomes non-uniform. In contrast, in this embodiment, since a voltage of Vith or higher is applied during erasing only for an extremely short time, oxidation of undesired anions generated after dissolving the remaining metal precipitation nuclei is performed. Hardly occurs. For this reason, the display hardly becomes uneven, and the cycle characteristics of the reflectance of the display color of the writing pixel and the erasing pixel are very excellent.

  Next, modifications common to the first embodiment and the second embodiment will be described.

  In addition to the above quartz glass, the first substrate 11 in FIG. 2 is, for example, a synthetic resin, specifically, an ester such as polyethylene naphthalate, polyethylene terephthalate or polycarbonate, a cellulose ester such as cellulose acetate, or a polyfluoride. Fluoropolymers such as vinylidene chloride or copolymers of polytetrafluoroethylene and hexafluoropropylene, polyethers such as polyoxymethylene, polyolefins such as polyacetal, polystyrene, polyethylene, polypropylene or methylpentene polymer, or You may comprise by polyimides, such as polyamide imide or polyether imide, or polyamide. These synthetic resins may be in the form of rigid substrates that do not bend easily, or may be film-like structures having flexibility.

  The second substrate 12 in FIG. 2 may be transparent or non-transparent, and may be made of white plate glass, ceramics, paper, or wood in addition to the above quartz glass. In addition, the synthetic resin described for the first substrate 11 may be used. When the counter electrode 15 has sufficient rigidity, the second substrate 12 may not be provided.

  As the solvent contained in the electrolyte 13 in FIG. 2, in addition to the mixture of dimethyl sulfoxide and γ-butyrolactone, for example, water, ethyl alcohol, isopropyl alcohol, propylene carbonate, dimethyl carbonate, ethylene carbonate, acetonitrile, sulfolane, Examples thereof include dimethoxyethane, ethyl alcohol, isopropyl alcohol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, γ-butyrolactone, γ-valerolactone, and mixtures thereof.

  As the precipitation-dissolving material contained in the electrolyte 13 in FIG. 2, in addition to the above-described silver ions, metal ions are not particularly limited. For example, bismuth ions, copper ions, silver ions, sodium ions, Lithium ion, iron ion, chromium ion, nickel ion or cadmium ion can be mentioned. Among them, particularly preferable metal ions are bismuth ions or silver ions, and more preferable are silver ions. Bismuth ions and silver ions can easily proceed with a reversible reaction and have a high degree of discoloration during precipitation. In particular, silver ions have an ionic valence of usually 1, so that the ionic valence is usually 3. This is because, compared with a certain bismuth ion, the amount of charge required to reduce one atom to a metal is one third. The metal ion is added to the solvent as a metal salt, for example. Examples of the metal salt include silver nitrate, silver borofluoride, silver halide, silver perchlorate, silver cyanide, and silver thiocyanide as long as they are silver salts. Any 1 type may be used for a metal salt, and 2 or more types may be mixed and used for it.

  The electrolyte 13 may also contain a supporting electrolyte salt, a colorant, and various additives as necessary.

  The supporting electrolyte salt is for increasing the ionic conductivity of the electrolyte so that the precipitation dissolution reaction of the precipitation dissolution material can be performed more effectively and stably. Examples of the supporting electrolyte salt include lithium salts such as LiCl, LiBr, LiI, LiBF4, LiClO4, LiPF6, and LiCF3 SO3, potassium salts such as KCl, KI, and KBr, or sodium salts such as NaCl, NaI, and NaBr. Or tetraalkyl quaternary ammonium salts such as tetraethylammonium borofluoride, tetraethylammonium perchlorate, tetrabutylammonium borofluoride, tetrabutylammonium perchlorate, or tetrabutylammonium halide salt. Any one of the supporting electrolyte salts may be used, or two or more of them may be mixed and used.

  The colorant is for improving contrast. Examples of the colorant include inorganic pigments and organic pigments, and these may be used alone or in combination. For example, when the color of the metal is black, such as silver, a white material with high concealability is preferable. As such a material, for example, inorganic particles such as titanium dioxide, calcium carbonate, silicon oxide, magnesium oxide or aluminum oxide can be used. Moreover, a pigment | dye can also be used. As the pigment, an oil-soluble dye is preferably used.

  The additive may be any one of a growth inhibitor, a stress suppressor, a brightener, a complexing agent, or a reducing agent in order to perform an electrochemical reaction, particularly a metal precipitation dissolution reaction reversibly and efficiently. It is preferable to contain seeds or a mixture of two or more kinds. As such an additive, an organic compound having a group having an oxygen atom (O) or a sulfur atom (S) is preferable. For example, thiourea, 1-allyl-2-thiourea, mercaptobenzimidazole, 2- Examples include mercaptobenzimidazole, coumarin, phthalic acid, succinic acid, salicylic acid, glycolic acid, dimethylamine borane, trimethylamine borane, tartaric acid, oxalic acid, and D-glucono-1,5-lactone.

  As a side reaction caused by anionic species may cause color development other than the desired color development, the additive can suppress side reactions caused by anionic species or decompose substances that have been generated as side reactions. It is preferable that any one kind or two or more kinds of a reducing agent or an oxidizing agent for mixing are included.

  As such a reducing agent, for example, an ascorbic acid compound or a trialkyl alcohol amine is preferable. Among these, a trialkyl alcohol amine species is preferable, and triethanolamine is preferable because long-term storage stability and high-temperature storage stability can be obtained.

  The electrolyte 13 may be a liquid so-called electrolytic solution composed of these liquid solvents, precipitation-dissolving materials, additives, and the like, but further includes a polymer compound that holds them, and is in a gel form. Also good. In the case of a gel, it may be composed of a single layer, but may be composed of a plurality of layers. In the case of a plurality of layers, the colorant need not be contained in the plurality of layers, but may be contained in at least one layer.

  Examples of the polymer compound include those having a repeating unit of alkylene oxide, alkyleneimine, alkylene sulfide in the main skeleton unit or the side chain unit or both, or a copolymer containing a plurality of these different units, Alternatively, a polymethyl methacrylate derivative, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, or a polycarbonate derivative is preferable. Any one of the polymer compounds may be used, or a mixture of two or more may be used.

  When the inorganic particles are included as a colorant, the thickness of the electrolyte 13 is preferably 20 μm to 200 μm, more preferably 30 μm to 120 μm, and even more preferably 30 μm to 50 μm. The thinner the electrode, the lower the resistance between the electrodes, and the reduction in color development / decoloration time and power consumption can be achieved. On the other hand, if it is too thin, the content of the colorant is reduced. This is because the mechanical strength is lowered and pinholes and cracks are also generated.

  The electrolyte 13 is produced, for example, by dissolving a precipitation-dissolving material in a solvent in which sulfoxide and a cyclic carboxylic acid ester are mixed, and then adding a supporting electrolyte salt, a colorant, and various additives as necessary. can do. Moreover, when setting it as a gel form, it can manufacture by mixing and drying this electrolyte solution and a high molecular compound. Alternatively, the electrolytic solution can be mixed with a monomer or oligomer that is a starting material for the polymer compound, and polymerized or crosslinked by a heating method or a UV irradiation method. In this case, a crosslinking aid or a photosensitizer may be used in combination in order to efficiently promote gelation.

  In addition to the above-mentioned ITO (Indium Tin oxide), the transparent electrode 14 in FIG. 2 is made of indium oxide (In2 O3), tin oxide (SnO2), ITO, indium oxide (In2 O3), or tin oxide (SnO2). ) Is preferably doped with tin or antimony (Sb). Moreover, you may comprise with magnesium oxide (MgO) or zinc oxide (ZnO).

  In addition to the above silver (Ag), the counter electrode 15 in FIG. 2 is an electrochemically stable metal, among which gold (Au), platinum (Pt), chromium (Cr), aluminum (Al), cobalt ( It is preferably composed of at least one selected from the group consisting of Co), palladium (Pd), and bismuth (Bi). Moreover, it is more preferable to use the same metal as the metal to be deposited because an electrochemically more stable electrode reaction can be realized. In addition, if the metal used for the main reaction can be sufficiently supplemented in advance or at any time, it may be composed of carbon. This is because the cost of the counter electrode 15 can be reduced by using carbon. Moreover, you may make it comprise with the same transparent conductive film as the transparent electrode 14. FIG.

[First embodiment]
The schematic configuration of the electrochemical display device according to the first embodiment of the present invention will be described below. This example relates to the first embodiment described above.

  FIG. 2 shows the configuration of the transparent electrode and the counter electrode used in the examples and comparative examples. The transparent electrode 14 was formed by forming an ITO film in a stripe shape on a quartz glass substrate having a thickness of 0.7 mm by a known method. The resistivity of this ITO film is about 7 ohm / □. The counter electrode 15 was formed by forming a silver film in a stripe shape on a quartz glass substrate having a thickness of 0.7 mm by a known method. The number of electrodes was 40, the electrode width was 0.3 mm, and the electrode pitch was 0.6 mm.

  As the electrolyte, 0.5 mol / l of silver iodide (AgI) as a precipitation-dissolving material and 0 as a supporting electrolyte salt in a solvent in which dimethylsulfoxide (DMSO) and γ-butyrolactone (γBr) were mixed at a ratio of 6: 4. .75 mol / l lithium iodide (LiI) is dissolved. To this electrolyte, a macromonomer TA140 (made by Daiichi Kogyo Seiyaku Co., Ltd.) composed of a trifunctional polytel group and titanium dioxide (TiO2) as a colorant are added at a weight ratio of 5: 1: 6. Evenly dispersed. Thereafter, a peroxide as a cross-linking material was added at a ratio of 1: 0.02-0.05 to the macromonomer TA140. As a gap forming material, a 50 μm true sphere was laid on the electrodes, both electrodes were overlapped, and the above electrolyte was injected into the space between both electrodes using a vacuum injection method. Then, after overlapping the end face with a desired member, this was heated at 70 to 100 degrees for several minutes to 10 minutes to carry out a crosslinking reaction.

  In this example, the electrochemical display element having the configuration shown in FIG. 2 was driven by the drive waveforms shown in FIG. 9 (writing) and FIG. 14 (erasing). In the drive voltage waveform at the time of writing, the time Ta required to form the metal precipitation nuclei by selectively applying the write voltage −Va (= − (Vwc + Vwr)) to the pixel to be written first is 800 msec, The time Ts required to apply the voltage Vw for further depositing metal to complete writing to the pixel to be written is 1200 msec, and the time Tsa required to address the first selection voltage Vwr for each line is 20 msec. . In the drive voltage waveform at the time of erasing, the time Te required to apply the erasing voltage Ve to the erasing target pixel first is 800 msec, and the voltage Vs (additionally dissolving the deposited metal remaining in the erasing target pixel selectively. = Vec + Ver) is set to 1200 msec, and the time Tss required to scan the fourth selection voltage Ver for each line is set to 20 msec.

  In addition, the other conditions of each Example are as follows. In Examples 1 to 4, in order to find the optimum conditions for initializing the potential difference, the rest time (Tp) is set to 0.7 sec, and the magnitude of the reset voltage (Vr) and the value of the application time (Tr) are set. Is changed as shown in the table below. Further, in Examples 5 to 6, the magnitude of the reset voltage is searched in order to find the optimum condition for initializing the potential difference when the image rewriting speed is further increased than that in the above example (rest time 0.0 sec). The values of (Vr) and application time (Tr) are changed as shown in the table below. Here, the pause time refers to the time from the time when image erasing is completed to the time when the application of the reset voltage (corresponding to the write voltage in the comparative example is not applied) is started. . The memory time refers to the time from the time when image writing is completed to the time when image erasing is started. The display memory time refers to the time until the reflectance of the pixel after writing increases by 5%. For example, immediately after the image is written, if the black reflectance is 10%, it indicates the time from that point to the point when the reflectance increases to 15%. This increase in reflectivity of 5% has a significance as a boundary line that a human recognizes that the display density of black has changed (lightened) in a visual experiment.

  In the comparative example, the electrochemical display element having the configuration shown in FIG. 2 was driven with the driving waveforms shown in FIG. 10 (writing) and FIG. 14 (erasing). In the drive voltage waveform at the time of writing, the time Ta required for forming the metal precipitation nuclei by first selectively applying the write voltage (−Va = − (Vwc + Vwr)) to the pixel to be written is 800 msec, The time Ts required to apply the voltage Vw for further depositing metal to complete writing to the pixel to be written is 1200 msec, and the time Tsa required to address the first selection voltage Vwr for each line is 20 msec. . Further, in the drive voltage waveform at the time of erasing, the time Te required to apply the erasing voltage Ve to the erasing target pixel first is 800 msec, and the voltage (Vs) for selectively dissolving the deposited metal remaining in the erasing target pixel selectively. = Vec + Ver) is set to 1200 msec, and the time Tss required to scan the fourth selection voltage Ver for each line is set to 20 msec.

  In addition, the other conditions of each comparative example are as follows. In Comparative Examples 1 to 3, the pause time is changed in order to investigate how the reduction of the pause time affects the reflectance of the display color and the display memory time under the condition that the reset voltage is not applied.

  From the result of the comparative example of FIG. 18, when the pause time is as long as 20 seconds and 5 seconds, the black and white reflectances are stable even after repeated writing / erasing cycles, but the pause time is 1 In the case of a short time, it can be seen that the reflectance of black and white changes rapidly with repeated writing / erasing cycles.

  Further, from the result of the comparative example of FIG. 19, even when the pause time is as long as 20 seconds and 5 seconds, the time (memory time) for holding the written image increases as the write / erase cycles are repeated. You can see that it is gradually decreasing. If the pause time is as short as 1 second, the number of times that the written image is retained (memory time) is rapidly reduced by simply repeating the write / erase cycle several times. It turns out that it becomes thin.

  From the above, it can be seen that when the pause time is shortened, the display quality (the cycle characteristics of the reflectance of the writing pixel and the erasing pixel and the memory property of the display image) is deteriorated. Therefore, in order to improve the display quality in the comparative example, it is necessary to extend the downtime.

  On the other hand, from the results of Examples 1 to 4 in FIG. 20, when the resting time was shortened to 0.7 seconds and the reset voltage was applied before writing, writing / erasing was performed under the conditions of Examples 1 and 2. It can be seen that the reflectance of black and white is stable even after repeated cycles. Further, from the results of Examples 5 to 6 in FIG. 20, when the rest time is further shortened to 0.0 seconds and the reset voltage is applied before writing, the cycle of writing / erasing is performed under the conditions of Example 5. It can be seen that the black and white reflectivities are stable even when superimposed. Therefore, even when the pause time is shortened, that is, when the image writing / erasing cycle is shortened, if the reset voltage is applied before writing under the conditions of Embodiments 1 and 2, the pause time is reduced. It can be seen that the cycle characteristics of the reflectance of the writing pixel and the erasing pixel are improved without increasing the length.

  Further, from the results of Examples 1 to 3 and 5 to 6 in FIG. 21, when the resting time is shortened and the reset voltage is applied before writing, the write / It can be seen that even if the erasing cycle is repeated, the time (memory time) for holding the written image is long enough for practical use. Further, it can be seen that the memory time is stable without decreasing as in the comparative example as the cycle of writing / erasing is repeated. Therefore, even when the pause time is shortened, that is, when the image writing / erasing cycle is shortened, if the reset voltage is applied before writing under the conditions of Embodiments 1 and 2, the pause time is lengthened. In spite of this, it can be seen that the cycle characteristics of the reflectance of the writing pixel and the erasing pixel are further improved than when the reset voltage is not applied and the pause time is long.

[Second Embodiment]
The schematic configuration of the electrochemical display device according to the second embodiment of the present invention will be described below. This example relates to the second embodiment described above.

  FIG. 15 shows the structure of the electrochemical display device used in Examples and Comparative Examples. As the transparent electrode 114, an ITO film was formed on the entire surface of the quartz glass substrate 111 by a known method. The counter electrode 115 was formed by depositing silver in a block shape on a quartz glass substrate 112 by a known method.

  The electrolyte 113 is 1.0 mol / l silver iodide (AgI) as a precipitated dissolved material in a solvent in which dimethyl sulfoxide (DMSO) and γ-butyrolactone (γBr) are mixed at a ratio of 6: 4, and a supporting electrolyte salt. 1.25 mol / l lithium iodide (LiI) is dissolved. To this electrolyte, a macromonomer TA140 (made by Daiichi Kogyo Seiyaku Co., Ltd.) composed of a trifunctional polytel group and titanium dioxide (TiO2) as a colorant are added at a weight ratio of 5: 1: 6. Evenly dispersed. Thereafter, a peroxide as a cross-linking material was added at a ratio of 1: 0.02-0.05 to the macromonomer TA140. As a gap forming material, a 50 μm true sphere was laid on the electrodes, both electrodes were overlapped, and the above electrolyte was injected into the space between both electrodes using a vacuum injection method. Then, after overlapping the end face with a desired member, this was heated at 70 to 100 degrees for several minutes to 10 minutes to carry out a crosslinking reaction.

  In this example, the electrochemical display device having the configuration shown in FIG. 15 was driven by the drive waveform shown in FIG. In the drive voltage waveform at the time of writing, a write voltage is selectively applied to the pixel to be written (10 cycles of a rectangular wave having a maximum value of −1.8 volts and an application time of 10 ms, and a minimum value of −0.8 volts and an application time of 10 ms). Was applied by precipitating a metal to perform writing. Further, in the drive voltage waveform at the time of erasing, by applying an erasing voltage (10 cycles of a rectangular wave with a maximum value +2.8 volts / application time 10 ms, a minimum value +1.0 volt / application time 20 ms) to the pixel to be erased. The metal was dissolved and erased.

  In addition, the other conditions of each Example are as follows. In Examples 1 to 8, in order to find an optimum condition for initializing the potential difference, the rest time (Tp) is set to 0.7 sec, and the magnitude of the reset voltage (Vr) and the value of the application time (Tr) are set. Is changed as shown in the table below.

  In the comparative example, in this example, the electrochemical display device having the configuration shown in FIG. 15 was driven by the drive waveform shown in FIG. 17 excluding the reset voltage. In the driving voltage waveform at the time of writing, a writing voltage is selectively applied to the writing target pixel (10 cycles of a rectangular wave in which minus 0.8 volts is applied for 10 ms and then minus 0.8 volts is applied for 10 ms). Was applied by precipitating a metal to perform writing. Further, in the drive voltage waveform at the time of erasing, by applying an erasing voltage (10 cycles of a rectangular wave that applies 1.0 volt for 20 ms after applying 2.6 volt for 10 ms) to the erasing target pixel. The metal was dissolved and erased.

  In addition, the other conditions of each comparative example are as follows. In Comparative Examples 1 to 5, the pause time is changed in order to examine how the reduction of the pause time affects the reflectance of the display color and the display memory time under the condition that the reset voltage is not applied.

  From the result of the comparative example of FIG. 22, when the pause time is as long as 4.7 seconds or more, the black and white reflectances are stable even after repeated writing / erasing cycles, but the pause time is 2 When it is as short as .7 seconds, it can be seen that the reflectance of white changes rapidly with repeated writing / erasing cycles.

  Further, from the result of the comparative example of FIG. 23, when the pause time is as short as 2.7 seconds, the time (memory time) for holding the written image decreases rapidly as the write / erase cycles are repeated. It can be seen that the image once written fades rapidly.

  From the above, it can be seen that when the pause time is shortened, the display quality (the cycle characteristics of the reflectance of the writing pixel and the erasing pixel and the memory property of the display image) is deteriorated. Therefore, in order to improve the display quality in the comparative example, it is necessary to extend the downtime.

  On the other hand, from the results of Examples 1 to 8 in FIG. 24, when the resting time was shortened to 0.7 seconds and the reset voltage was applied before writing, writing / erasing was performed under the conditions of Examples 3 and 4. It can be seen that the reflectance of black and white is stable even after repeated cycles. Therefore, even when the pause time is shortened, that is, when the image writing / erasing cycle is shortened, if the reset voltage is applied before writing under the conditions of Embodiments 3 and 4, the pause time is reduced. It can be seen that the cycle characteristics of the reflectance of the writing pixel and the erasing pixel are improved without increasing the length.

  Further, from the results of Examples 1 to 8 in FIG. 25, when the rest time is shortened and the reset voltage is applied before writing, the write / erase cycle is performed under the conditions of Examples 3 and 4. It can be seen that the time (memory time) for holding the written image is long enough for practical use even if it is superimposed. Further, it can be seen that the memory time is stable without decreasing as in the comparative example as the cycle of writing / erasing is repeated. Therefore, even when the pause time is shortened, that is, when the image writing / erasing cycle is shortened, if the reset voltage is applied before writing under the conditions of Embodiments 1 and 2, the pause time is lengthened. In spite of this, it can be seen that the cycle characteristics of the reflectance of the writing pixel and the erasing pixel are further improved than when the reset voltage is not applied and the pause time is long.

  Although the present invention has been described with reference to the two embodiments and the modifications thereof and the two examples, the present invention is not limited to these, and various modifications can be made.

  For example, in this embodiment and this example, the electrochemical display device having the configuration as shown in FIG. 1 or FIG. 15 is used. However, the electrochemical display device in the present invention is not limited to such a configuration. .

  In the first embodiment and the first example of the present invention, the write voltage and the erase voltage are applied between the electrodes in two steps as shown in FIG. The chemical display device is not limited to such a configuration. For example, a write voltage and an erase voltage may be applied between both electrodes once.

  In the second embodiment and the second example of the present invention, the writing voltage and the erasing voltage as shown in FIG. 17 are applied between both electrodes. It is not limited to such a configuration.

  In this embodiment and this example, the reset voltage is applied after the erase voltage is applied and before the write voltage is applied. However, the reset voltage may be applied immediately before the write voltage is applied. Most preferably, it may be just before the write voltage is applied. Further, there may be a time interval between the first aspect of writing to apply the reset voltage and the second aspect of applying the first writing voltage.

  In this embodiment and this example, as shown in FIG. 9, the reset voltage is applied to all the pixels at the same time. However, the electrochemical display device according to the present invention is limited to such a configuration. For example, the reset voltage may be applied to each pixel immediately before the write voltage is applied.

1 is a schematic configuration diagram of an electrochemical display device according to a first embodiment. It is a perspective view of the electrochemical display element which concerns on 1st Embodiment. It is a conceptual diagram of the drive voltage waveform of one cycle of writing and erasing according to the first embodiment. It is a wave form diagram which shows the triangular wave voltage applied in order to investigate an electric current-voltage characteristic. It is a characteristic view which shows an electric current-voltage characteristic. FIG. 2 is a flowchart showing operations in a second aspect at the time of writing and a second aspect at the time of erasing of the image display driving unit in FIG. 1. 6 is a flowchart showing operations in the first and third aspects at the time of writing and in the first aspect at the time of erasing of the image display driving unit in FIG. 1. It is the schematic showing a mode that an image is written in the electrochemical display element of FIG. It is a wave form diagram showing an example of the drive voltage waveform at the time of writing in a 1st embodiment. It is a wave form diagram showing the drive voltage waveform at the time of the write concerning the comparative example in a 1st embodiment. It is a wave form diagram showing the mode of a transient when a potential difference is not initialized. It is a wave form diagram showing the mode of a transient at the time of initializing a potential difference. It is the schematic showing a mode that an image is erase | eliminated in the electrochemical display element of FIG. It is a wave form diagram showing an example of the drive voltage waveform at the time of erasure concerning a 1st embodiment. It is a schematic block diagram of the electrochemical display apparatus which concerns on 2nd Embodiment. It is a perspective view of the electrochemical display element which concerns on 2nd Embodiment. It is a conceptual diagram of the drive voltage waveform of one cycle of writing / erasing according to the second embodiment. In Comparative Examples 1-3 which concern on 1st Embodiment, it is a characteristic view which shows the cycle characteristic of the write pixel and the erasure pixel when a drive voltage waveform is applied. In Comparative Examples 1-3 which concern on 1st Embodiment, it is a characteristic view which shows the memory property of a display image when a drive voltage waveform is applied. In Examples 1-6 which concern on 1st Embodiment, it is a characteristic view which shows the cycle characteristic of the write pixel and the erasure pixel when a drive voltage waveform is applied. In Examples 1-6 which concern on 1st Embodiment, it is a characteristic view which shows the memory property of a display image when a drive voltage waveform is applied. In Comparative Examples 1-3 which concern on 2nd Embodiment, it is a characteristic view which shows the cycle characteristic of the write pixel and the erasure pixel when a drive voltage waveform is applied. In Comparative Examples 1-3 which concern on 2nd Embodiment, it is a characteristic view which shows the memory property of a display image when a drive voltage waveform is applied. In Examples 1-6 which concern on 2nd Embodiment, it is a characteristic view which shows the cycle characteristic of the write pixel and the erasure pixel when a drive voltage waveform is applied. In Examples 1-6 which concern on 2nd Embodiment, it is a characteristic view which shows the memory property of a display image when a drive waveform is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electrochemical display element, 11 ... 1st board | substrate, 12 ... 2nd board | substrate, 13 ... Electrolyte, 14 ... Transparent electrode, 15 ... Counter electrode, 21 ... Signal control part, 22 ... Transparent electrode drive part, 22A ... Image data temporary storage unit, 22B ... signal voltage pulse setting unit, 22C ... signal voltage pulse drive unit, 23 ... counter electrode drive unit, 23A ... counter electrode selection unit, 23B ... selection voltage pulse setting unit, 23C ... selection voltage pulse drive 111: First substrate, 112: Second substrate, 113: Electrolyte, 114: Transparent electrode, 115: Counter electrode, 116 ... Spacer beads, 121 ... Signal control unit, 122 ... Data line driving unit, 123 ... Gate line driving unit, 124... Source scanning line, 125... Gate scanning line, 126... Pixel driving element, 127.

Claims (6)

An electrochemical display device that performs display by precipitation and dissolution of metal,
A transparent electrode and a counter electrode arranged to face each other;
An electrolyte layer sandwiched between the transparent electrode and the counter electrode and containing the metal ions;
A writing control means for writing an image by depositing metal on the transparent electrode side by applying a writing voltage between the transparent electrode and the counter electrode;
An erasing control means for erasing an image by dissolving a metal deposited on the transparent electrode side by applying an erasing voltage with a polarity opposite to the writing voltage between the transparent electrode and the counter electrode;
And an initializing means for initializing a potential difference between the transparent electrode and the counter electrode to a predetermined range after applying the erasing voltage and before applying the writing voltage. Display device. The transparent electrode and the counter electrode are each extended in plural so that the intersections of each constitute a pixel,
The write control means applies a first write voltage having a magnitude equal to or larger than the absolute value of the write threshold voltage between the transparent electrode corresponding to the pixel to be written and the counter electrode, and then writes the write voltage. Applying a second write voltage having a magnitude smaller than the absolute value of the threshold voltage;
The erasing control means uses a first erasing voltage having a magnitude smaller than an absolute value of an erasing threshold voltage between the transparent electrode corresponding to the erasing target pixel and the counter electrode as the second writing voltage. The second erase voltage having a magnitude equal to or larger than the absolute value of the erase threshold voltage after being applied with a reverse polarity is applied with a reverse polarity to the first write voltage. Electrochemical display device. The initialization unit performs initialization by applying a reset voltage having the same polarity as the second erase voltage between a transparent electrode and a counter electrode corresponding to all pixels. The electrochemical display device described in 1. A plurality of signal lines and a plurality of scanning lines extending so as to cross each other;
A pixel driving element provided at each intersection where the signal wiring and the scanning wiring intersect,
The transparent electrode and the counter electrode are arranged to face each other at each intersection so as to constitute a pixel, and connected to the pixel driving element at the corresponding intersection,
The writing control means drives the pixel driving element so that the writing voltage is applied between a transparent electrode corresponding to a pixel to be written and a counter electrode;
2. The electricity according to claim 1, wherein the erasing control unit drives the pixel driving element so that the erasing voltage is applied between a transparent electrode corresponding to an erasing target pixel and a counter electrode. Chemical display device. 5. The initialization according to claim 4, wherein the initialization unit performs initialization by applying a reset voltage having the same polarity as the erasing voltage between a transparent electrode and a counter electrode corresponding to all pixels. Electrochemical display device. An electrochemical display method for performing display by metal precipitation and dissolution,
A transparent electrode and a counter electrode disposed so as to face each other, and an electrolyte layer sandwiched between the transparent electrode and the counter electrode and containing the metal ions,
By applying a writing voltage between the transparent electrode and the counter electrode, a metal is deposited on the transparent electrode side to perform image writing,
By applying an erasing voltage with a polarity opposite to the writing voltage between the transparent electrode and the counter electrode, the metal deposited on the transparent electrode side is dissolved to erase the image,
An electrochemical display method comprising: initializing a potential difference between the transparent electrode and the counter electrode to a predetermined range after applying the erase voltage and before applying the write voltage.

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