JP2005266339A - Electrochemical display device and electrochemical display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical display device with an excellent cycle characteristic of a black reflectance by preventing image persistence and an electrochemical display method. <P>SOLUTION: In the electrochemical display device and in the electrochemical display method, a plurality of transparent electrodes and a plurality of counter electrodes disposed so as to make their mutual intersections constitute pixels and an electrolyte layer interposed between the transparent electrodes and the counter electrodes and containing a metal ion are arranged. To pixels to which a picture is to be written, the picture is written by applying a first writing voltage higher than an absolute value of a threshold writing voltage between the transparent electrodes and the counter electrodes and subsequently applying a second writing voltage lower than the absolute value of the threshold writing voltage between them so as to deposit a metal on the transparent electrode side. From pixels from which the picture is to be erased, the picture is erased by applying a first erasing voltage lower than an absolute value of a threshold erasing voltage between the transparent electrodes and the counter electrodes and subsequently applying a second erasing voltage higher than the absolute value of the threshold erasing voltage between them so as to dissolve the deposited metal on the transparent electrode side. <P>COPYRIGHT: (C)2005,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 browse these information, electrodes are placed opposite to each other via a white colored electrolyte containing metal ions, and the image is written by depositing metal on the display-side electrode, and the deposited metal is used as the electrolyte. For example, Patent Literature 1 proposes an electrochemical display device that erases an image by dissolving it in a glass. According to this, matrix driving is easy and contrast and black density can be increased.

  In the above-described electrochemical display device, display is generally performed by selectively depositing metal on each pixel using a threshold voltage at which metal is deposited. In this method, problems remain in terms of response speed, occurrence of crosstalk, and a decrease in contrast. An invention that solves these problems is proposed in Patent Document 2.

  In the above conventional electrochemical display device, it is common to apply an erase voltage to the entire screen at once. In such a conventional erasing method, when a voltage higher than a threshold voltage (hereinafter referred to as “erasing threshold voltage”) at which an anion dissolved in an electrolyte is oxidized during erasing is applied to the display-side electrode. Although the deposited metal can be dissolved quickly and the erasing time can be shortened, oxidation of the anion dissolved in the electrolyte also occurs, causing discoloration and deterioration of the material. .

  On the other hand, when erasing is performed by applying a voltage lower than the erasing threshold voltage so that anion oxidation does not occur, it takes a long time to erase the pixel on which the metal is deposited, and it takes a very long time to erase. There were drawbacks. In addition, when an erasing voltage lower than the erasing threshold voltage is applied, there is a possibility that a trace amount of metal may remain in the pixel on which the metal has been deposited. As a result, the pre-erase display appears and the so-called burn-in occurs.

Therefore, it is proposed in Patent Document 3 that erasing by applying a strong voltage higher than the erasing threshold voltage is as short as possible, and then erasing the deposited metal by applying a weak voltage lower than the erasing threshold voltage. ing. According to this, erasure can be performed at a higher speed than before, and the burn-in phenomenon in which the display before erasure appears when performing the next precipitation display after erasure can be alleviated.
JP 2002-258327 A JP 2003-337350 A JP 2003-337352 A

  However, the erasing method of the electrochemical display device proposed in Patent Document 3 described above has the following problems. That is, first, an erase voltage equal to or higher than the erase threshold voltage is applied to each erase target pixel. Thereafter, the deposited metal is dissolved by applying an erase voltage lower than the erase threshold voltage to all the pixels to be erased. In the driving voltage waveform at the time of erasing, when the first strong and short erasing voltage is applied, only a part of the deposited metal is dissolved, and then the erasing is completed by applying the erasing voltage to all the erasing target pixels. However, in this case, the metal deposited on the electrode surface may not be completely erased. In this case, burn-in occurs, which causes a problem that the cycle characteristics of the black reflectance are not sufficient. In addition, to the user, when the first strong and short erase voltage is applied, the display becomes thinner in order as the scanning line is scanned, and thereafter, the display is entirely erased by applying the erase voltage to all the pixels to be erased. appear. Therefore, there is a problem that the user visually feels that the display is erased visually, and that it takes a long time for the user to feel that the erase is completed.

  The present invention has been made in view of such problems, and a first object of the present invention is to provide an electrochemical display device and an electrochemical display method excellent in cycle characteristics of black reflectance by preventing burn-in. It is to provide. A second object of the present invention is to provide an electrochemical display device and an electrochemical display method capable of greatly reducing the time until the user feels that the erasure of an image has been completed. In addition to the second object, a third object of the present invention is to provide an electrochemical display device and an electrochemical display method that allow a user to naturally feel how an image is erased. .

  The first electrochemical display device of the present invention is sandwiched between a plurality of transparent electrodes and a plurality of counter electrodes arranged so as to intersect each other and the intersections constituting pixels, and between the transparent electrodes and the counter electrodes. After applying an electrolyte layer containing metal ions and a writing target pixel between the transparent electrode and the counter electrode, a first writing voltage having a magnitude greater than the absolute value of the writing threshold voltage is applied. A write control means for writing an image by depositing metal on the transparent electrode side by applying a second write voltage having a magnitude smaller than the absolute value of the write threshold voltage; and erasing The target pixel has a magnitude equal to or greater than the absolute value of the erase threshold voltage after applying a first erase voltage having a magnitude smaller than the absolute value of the erase threshold voltage between the transparent electrode and the counter electrode. By applying the second erase voltage, Dissolved metal deposited on the transparent electrode side and a deletion control means for erasing the image.

  The second electrochemical display device of the present invention is sandwiched between a plurality of transparent electrodes and a plurality of counter electrodes, which are arranged so that the crossing points constitute a pixel, and the transparent electrodes and the counter electrodes. The first erasing voltage is applied between the transparent electrode and the counter electrode simultaneously for the electrolyte layer containing metal ions and all the erasing target pixels, and then the second erasing voltage is sequentially applied to each erasing target pixel. And an erasing control means for erasing the image by dissolving the metal deposited on the transparent electrode side when applied.

  In the first electrochemical display method of the present invention, a plurality of transparent electrodes and a plurality of counter electrodes, which are arranged so as to intersect each other and constitute a pixel, are sandwiched between the transparent electrode and the counter electrode. An electrolyte layer containing metal ions is provided, and a first writing voltage having a magnitude equal to or larger than the absolute value of the writing threshold voltage is applied between the transparent electrode and the counter electrode for the writing target pixel. After that, by applying a second write voltage having a magnitude smaller than the absolute value of the write threshold voltage, metal is deposited on the transparent electrode side to write an image, After applying a first erase voltage having a magnitude smaller than the absolute value of the erase threshold voltage between the transparent electrode and the counter electrode, a second erase having a magnitude greater than the absolute value of the erase threshold voltage By applying voltage, transparent electrode side By dissolving the deposited metal is obtained so as to erase the image.

  In the second electrochemical display method of the present invention, a plurality of transparent electrodes and a plurality of counter electrodes, which are arranged so that the crossing points constitute a pixel, are sandwiched between the transparent electrode and the counter electrode. The first erasing voltage is applied between the transparent electrode and the counter electrode at the same time for all the erasing target pixels, and then the second erasing voltage is sequentially applied to each erasing target pixel. Is applied to dissolve the metal deposited on the transparent electrode side to erase the image.

  In the first electrochemical display device and the first electrochemical display method of the present invention, first, a first write voltage having a magnitude equal to or larger than the absolute value of the write threshold voltage is applied to the pixel to be written. The Thereby, for example, it is possible to form metal precipitation nuclei on the transparent electrode side. Thereafter, a second write voltage having a magnitude smaller than the absolute value of the write threshold voltage is applied to the write target pixel. Thereby, for example, it is also possible to write an image by further depositing metal on the transparent electrode side. Next, a first erase voltage having a magnitude smaller than the absolute value of the erase threshold voltage is applied to the erase target pixel. As a result, most of the metal deposited on the transparent electrode side is dissolved without anion oxidation. In this case, for example, the metal deposited on the transparent electrode side can be dissolved to a degree sufficient for the user to feel that the image has been erased. Thereafter, a second erase voltage having a magnitude equal to or larger than the absolute value of the erase threshold voltage is applied to the erase target pixel. Thereby, it is also possible to dissolve the metal precipitation nuclei slightly remaining on the transparent electrode side in a nearly complete state. Although the magnitude of the second erase voltage is larger than the absolute value of the erase threshold voltage, no voltage larger than the erase threshold voltage is applied to any pixel other than the erase target pixel, and therefore, the oxidation of anions hardly occurs.

  In the first electrochemical display device of the present invention, the application time of the second erase voltage applied to each individual pixel to be erased is shorter than the application time of the first erase voltage applied to all the pixels to be erased. In this case, since the time for applying a voltage equal to or higher than the erasing threshold voltage to the electrolyte is shortened, oxidation of the anion dissolved in the electrolyte can be suppressed for the erasing target pixel.

  In the second electrochemical display device and the second electrochemical display method of the present invention, first, the first erase voltage is applied simultaneously to all the pixels to be erased. Thereby, for example, it is possible to erase the image simultaneously on the entire screen. In addition, the above “simultaneous” does not necessarily mean that it is strictly simultaneously in time, but means that it is simultaneous in time to the extent that the user feels that the image has been erased simultaneously on the entire screen. To do. Thereafter, the second erasing voltage is sequentially applied to each erasing target pixel. Thereby, for example, it is possible to dissolve metal precipitation nuclei slightly remaining on the transparent electrode side in a state in which they are almost completely completed.

  According to the first electrochemical display device and the first electrochemical display method of the present invention, after applying the first erase voltage smaller than the erase threshold voltage, the second erase voltage equal to or higher than the erase threshold voltage is applied. Since it is applied, there is no image sticking and the cycle characteristics of black reflectance are very excellent.

  In addition, since the first erase voltage smaller than the erase threshold voltage is applied and then the second erase voltage higher than the erase threshold voltage is applied, the image is erased at high speed without causing deterioration of the screen display. The user can feel that it has been done.

  In addition, when the second erasing voltage equal to or higher than the erasing threshold voltage is made shorter than the application time of the first erasing voltage, the black reflectance cycle characteristics are further improved, and the display quality is further improved. To do.

  According to the second electrochemical display device and the second electrochemical display method of the present invention, the first erase voltage is simultaneously applied to all the pixels to be erased. It is also possible to make it feel.

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

  FIG. 1 shows a schematic configuration of an electrochemical display device according to an embodiment of the present invention. The electrochemical display device includes, for example, an electrochemical display element 10 and a peripheral circuit unit 20 for driving the electrochemical display element 10.

  FIG. 2 shows a schematic configuration of the electrochemical display element 10 shown in FIG. 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 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.

  The first substrate 11 in FIG. 2 is made of a transparent material, specifically, for example, quartz glass. The second substrate 12 in FIG. 2 is made of, for example, quartz glass. The electrolyte 13 in FIG. 2 includes, for example, 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 in FIG. 2 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 in FIG. 2 is made of an electrochemically stable metal, such as silver (Ag).

  As shown in FIG. 1, the peripheral circuit unit 20 includes a signal control unit 21, a transparent electrode drive circuit 22, and a counter electrode drive circuit 23. The signal control unit 21 is connected to the transparent electrode driving circuit 22 and the counter electrode driving circuit 23 via signal lines 24 and 25, respectively. The transparent electrode driving circuit 22 and the counter electrode driving circuit 23 are configured to selectively display each pixel of the electrochemical display element 10 based on a signal from the signal control unit 21. The transparent electrode driving circuit 22 and the counter electrode driving circuit 23 correspond to a specific example of the writing control means in the present invention. The transparent electrode driving circuit 22 and the counter electrode driving circuit 23 further correspond to a specific example of the erasing control means in the present invention.

  FIG. 4 shows current-voltage transient response characteristics when a triangular wave voltage as shown in FIG. 3 is applied between the transparent electrode and the counter electrode with reference to the voltage of the counter electrode. FIG. 4 is an example of characteristics when the counter electrode is a silver (Ag) electrode and silver ions and iodine ions are dissolved in the polymer electrolyte.

  The principle of FIG. 4 will be described. When a voltage is applied from zero to the negative side between the transparent electrode and the counter electrode as a reference, silver does not precipitate for a while, and when the write threshold voltage Vth is exceeded, the transparent electrode is transferred to the transparent electrode. Silver deposition begins. Then, when the write threshold voltage Vth is exceeded, a current accompanying 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 falls 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 precipitation occurs even at a voltage lower than the write threshold voltage Vth. On the other hand, when a reverse polarity (plus) voltage is applied between the transparent electrode and the counter electrode, dissolution of silver begins, and silver deposited 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, resulting in yellow coloration.

  When considering driving a display device that exhibits current-voltage transient response characteristics as described above, the simplest is to apply a voltage exceeding the write threshold voltage Vth to deposit metal and write the pixel. It is conceivable to erase the pixels by applying a voltage that does not exceed the erase threshold voltage Vith to dissolve the metal. This embodiment has a complicated operation in which the pixel is written by applying the write voltage twice and the pixel is erased by applying the erase voltage twice.

  Next, the operation of the electrochemical display device and the electrochemical display method configured as described above will be described. For simplification of description, a monochrome display with 3 × 3 pixels shown in FIG. 1 will be described as an example.

FIG. 5 shows an example of a drive voltage waveform at the time of writing in the embodiment of the present invention. In FIG. 5, the voltage applied to each transparent electrode C ₁ , C ₂ , C ₃ , the voltage applied to each counter electrode R ₁ , R ₂ , R ₃ , and the applied voltage of the pixel (C ₃ , R ₃ ), That is, the voltage applied between the transparent electrode and the counter electrode is shown.

At the time of display, first, the transparent electrode driving circuit simultaneously applies signal voltages (0, 0, Vwc) to the respective transparent electrodes (C ₁ , C ₂ , C ₃ ). Then, the counter electrode driving circuit sequentially applies the selection voltage Vwr to each counter electrode (R ₁ , R ₂ , R ₃ ). Here, the magnitudes of the signal voltage Vwc and the selection voltage Vwr are smaller than the absolute value of the write threshold voltage Vth. The signal voltage Vwc is output in synchronization with the output of the selection voltage Vwr.

Specifically, in the pixel (C ₃ , R ₃ ), the signal voltage Vwc of the transparent electrode C ₃ overlaps with the selection voltage Vwr of the counter electrode R ₃ , and as a result, the write threshold voltage is increased by these potential differences. A first write voltage Va (= Vwc−Vwr) having a magnitude greater than the absolute value is applied between the transparent electrode and the counter electrode, and metal precipitation nuclei are formed on the transparent electrode. On the other hand, in the pixel (C ₂ , R ₁ ), there is no period in which the signal voltage Vwc of the transparent electrode C ₂ and the selection voltage Vwr of the counter electrode R ₁ overlap, and the pixel (C ₂ , R ₁ ) has a magnitude lower than the absolute value of the write threshold voltage Vth. Either one of the signal voltage Vwc or the selection voltage Vwr is only applied between the transparent electrode and the counter electrode. Therefore, no metal deposition occurs.

Thereafter, each transparent electrode (C ₁ , C ₂ , C ₃ ) is grounded, and is smaller than the absolute value of the write threshold voltage Vth to each counter electrode (R ₁ , R ₂ , R ₃ ) by the counter electrode drive circuit. A selection voltage Vwr having a magnitude is applied simultaneously. As a result, the second write voltage Vw (= −Vwr) having a magnitude smaller than the absolute value of the write threshold voltage Vth is applied between the transparent electrode and the counter electrode due to these potential differences, and the previous write An additional metal is deposited around the deposition nucleus of the metal deposited on the transparent electrode side at the voltage Va, and an image is displayed (written). Here, the above "simultaneous" does not necessarily mean strictly simultaneously in time, but means that it is simultaneous in time to the extent that the user feels that images are displayed simultaneously on the entire screen. means. Note that the second write voltage Vw (= −Vwr) is also applied to a pixel having no metal precipitation nuclei, but the write threshold is determined by the current-voltage transient response characteristics of FIG. 4 described in detail above. Even if a second write voltage having a magnitude smaller than the absolute value of the voltage Vth is applied, metal deposition does not occur.

  Further, by making the application time Tas of the first write voltage Va shorter than the application time Tw of the second write voltage Vw, the number of scanning lines (the number of counter electrodes) is reduced by the reduction of the application time. ), The time Ta required for the formation of metal precipitation nuclei is shortened by the amount of time spent. The reason why such shortening is possible is that the first write voltage Va only needs to form metal precipitation nuclei on the transparent electrode side, so that it is not necessary to apply a voltage unnecessarily for a long time. . Since the second write voltage Vw is applied to all the write target pixels at the same time, the application time is much shorter than when applying a voltage to each write target pixel.

  Here, if it is attempted to complete the metal deposition with only one write voltage Va, the deposition takes a long time for each pixel, and in particular, the display takes longer as the number of pixels increases. 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.

  Further, if it is attempted to complete the deposition of metal with only one write voltage Va, the display is sequentially performed as the scanning lines (counter electrodes) are sequentially scanned. Therefore, the user not only visually feels that the image is displayed, but also takes a long time to feel that the display is completed.

  However, if the driving voltage waveform at the time of writing as in the present embodiment is applied, the above problem is solved.

  That is, in the present embodiment, after first applying the first write voltage Va having a magnitude equal to or larger than the absolute value of the write threshold voltage Vth, the magnitude is smaller than the absolute value of the write threshold voltage Vth. Since the second write voltage Vw having is applied, it is not necessary to unnecessarily increase the metal precipitation nuclei in the first application of the first write voltage Va. As a result, an unnecessary current does not flow to the pixel on which the metal is deposited, and crosstalk does not occur and contrast does not decrease.

  In the embodiment of the present invention, first the first write voltage Va equal to or higher than the write threshold voltage Vth is sequentially applied to each pixel, and then the write threshold voltage is applied to all write target pixels. Since the second write voltage Vw smaller than Vth is applied simultaneously, even if the write voltage is applied in two steps, the time required to display an image is very short. As a result, even if the number of pixels increases, not only the time for writing an image is very short, but also accurate precipitation display without crosstalk becomes possible. This “simultaneous” is synonymous with the above definition.

  Further, by applying the second write voltage Vw to all the write target pixels at the same time, the image is simultaneously displayed on the entire screen. This “simultaneous” is synonymous with the above definition. As a result, the user can naturally feel how the image is written.

FIG. 6 shows an example of a driving voltage waveform at the time of erasing in the embodiment of the present invention. In FIG. 6, the voltage applied to each transparent electrode (C ₁ , C ₂ , C ₃ ), the voltage applied to each counter electrode (R ₁ , R ₂ , R ₃ ), and the pixel (C ₃ , R ₃ ). Applied voltage, that is, the applied voltage between the transparent electrode and the counter electrode.

In erasing, first, each transparent electrode (C ₁ , C ₂ , C ₃ ) is grounded, and each counter electrode R ₁ , R ₂ , R ₃ has a polarity opposite to that at the time of writing by a counter electrode drive circuit. The selection voltage Ve having a magnitude smaller than the absolute value of the erase threshold voltage Vith is simultaneously applied. As a result, the first erase voltage Ve (= −Ver) having a magnitude smaller than the absolute value of the erase threshold voltage Vith is applied between the transparent electrode and the counter electrode due to these potential differences, and the previous write drive voltage. Most of the metal deposited on the transparent electrode is dissolved by applying the waveform. At this time, it appears to the user that the image has been erased. Here, the above "simultaneous" does not necessarily mean strictly simultaneously in time, but means that it is simultaneously in time to the extent that the user feels that the image has been erased simultaneously on the entire screen. means. Note that the first erase voltage Ve (= −Ver) is also applied to a pixel having no metal precipitation nuclei, but the erase threshold voltage of the current-voltage transient response characteristic of FIG. Even if the first erase voltage having a magnitude smaller than the absolute value is applied, the anion is not oxidized.

Thereafter, a signal voltage (0, 0, Vec) is simultaneously applied to each transparent electrode (C ₁ , C ₂ , C ₃ ) by the transparent electrode driving circuit. Then, a selection voltage Ver is sequentially applied to each counter electrode (R ₁ , R ₂ , R ₃ ) by the counter electrode drive circuit. Here, the magnitudes of the signal voltage Vec and the selection voltage Ver are smaller than the absolute value of the erase threshold voltage Vith. The signal voltage Vec is output in synchronization with the output of the selection voltage Ver.

Specifically, in the pixel (C ₃ , R ₃ ), the signal voltage Vec of the transparent electrode C ₃ and the fourth selection voltage Ver of the counter electrode R ₃ overlap, and as a result, the threshold voltage is erased by these potential differences. The second erase voltage Vs (= Vec-Ver) having a magnitude greater than the absolute value of the voltage Vith is applied, and the slight metal nuclei remaining on the transparent electrode are completely dissolved, thereby erasing the image. Complete. On the other hand, in the pixel (C ₂ , R ₁ ), there is no period in which the signal voltage Vec of the transparent electrode C ₂ and the selection voltage Ver of the counter electrode R ₁ overlap each other, and the pixel (C ₂ , R ₁ ) has a magnitude lower than the absolute value of the erase threshold voltage Vith. Only one of the signal voltage Vec and the selection voltage Ver is applied. Accordingly, only a voltage having a magnitude lower than the absolute value of 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.

  FIG. 7 shows a driving voltage waveform at the time of erasing proposed in Patent Document 3 as a comparative example. In this comparative example, the erase voltage Vs is first applied, and then the erase voltage Ve is applied.

  When the driving voltage waveform at the time of erasing as shown in FIG. 7 is used, the deposited metal is slightly dissolved by applying the first erasing voltage, and the deposited metal remaining on the electrode surface is dissolved by applying the next erasing voltage. However, the metal deposited on the electrode surface may not be completely erased. Therefore, the so-called burn-in problem has not been completely solved, and the black reflectance cycle characteristics are not sufficient. In addition, since the selection voltage is sequentially applied to each counter electrode in the first application of the erase voltage, the image becomes thinner as the counter electrode is sequentially scanned, and the entire image is erased by the subsequent application of the erase voltage. From the viewpoint of the user, this makes the image erasure feel visually unnatural and the erasure time also feels slow.

  However, if the driving voltage waveform at the time of erasing as shown in FIG. 6 used in this embodiment is applied, the above problem is solved.

  That is, in the present embodiment, since the first erase voltage Ve having a magnitude smaller than the absolute value of the erase threshold voltage Vith is first applied to the erase target pixel, it is transparent without causing anion oxidation. Most of the metal deposited on the electrode surface is dissolved. After that, since the second erase voltage Vs having a magnitude equal to or larger than the absolute value of the erase threshold voltage Vith is applied to the erase target pixel, it directly acts on the deposited metal slightly remaining on the transparent electrode surface. The remaining deposited metal is completely dissolved. Here, although the magnitude of the erase voltage Vs is larger than the absolute value of the erase threshold voltage Vith, a voltage larger than the absolute value of the erase threshold voltage Vith is not applied to the pixels other than the erase target pixel. Almost does not occur. As a result, no metal deposits remain on the electrode surface even after displaying and erasing the image many times, and there is almost no oxidation of the anion, so there is no burn-in and a black reflectance cycle. The characteristics are very good.

  In the present embodiment, since the first erase voltage Ve having a magnitude smaller than the absolute value of the erase threshold voltage Vith is first applied to the erase target pixel, the first erase voltage is applied after the first erase voltage is applied. Although a small amount of deposited metal remains on the electrode surface, the deposited metal does not remain so much that it is recognized by the user that the image remains unerased. After that, when a second erase voltage having a magnitude equal to or larger than the absolute value of the erase threshold voltage Vith is applied, even if this small amount of deposited metal is dissolved, the display on the screen is changed for the user. It does not appear to have occurred. As a result, the user feels that the erasure of the image has been completed when the first erasing voltage is applied, and can feel that the image has been erased at high speed without causing deterioration of the display device.

  The erase voltage Vs is a voltage having a magnitude exceeding the absolute value of the erase threshold voltage Vith, but a voltage having a magnitude exceeding the absolute value of the erase threshold voltage Vith is not applied to pixels other than the erase target pixel. Therefore, the oxidation of anions hardly occurs. Further, since the application time of the second erase voltage Vs having a magnitude exceeding the absolute value of the erase threshold voltage Vith is shorter than the application time of the first erase voltage Ve, an anion is also present in the pixel to be erased. Oxidation of is suppressed. As a result, it is less likely that metal precipitation nuclei are attached due to oxidation of anions and the display becomes non-uniform (the cycle characteristics of black reflectance deteriorate), so there is no more seizure, The black reflectance cycle characteristics are even better.

  In the embodiment of the present invention, the first erase voltage Ve is applied to all the erase target pixels at the same time, so that the image is erased simultaneously on the entire screen. As a result, the user can naturally feel how the image is erased. This “simultaneous” is synonymous with the above definition.

  In addition to the quartz glass, the first substrate 11 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. Fluorine polymers such as vinylidene or a copolymer of polytetrafluoroethylene and hexafluoropropylene, polyethers such as polyoxymethylene, polyolefins such as polyacetal, polystyrene, polyethylene, polypropylene or methylpentene polymer, or polyamide You may comprise by polyimide, such as imide or polyetherimide, 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 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 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, dimethoxyethane, Examples thereof include ethyl alcohol, isopropyl alcohol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, γ-butyrolactone, γ-valerolactone, and mixtures thereof.

  The deposition and dissolution material contained in the electrolyte 13 is not particularly limited as a metal ion in addition to the above silver ions. For example, bismuth ions, copper ions, silver ions, sodium ions, lithium ions, Iron ions, chromium ions, nickel ions or cadmium ions 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, LiBF ₄ , LiClO ₄ , LiPF _{6, and} LiCF ₃ SO ₃ , potassium salts such as KCl, KI, and KBr, or NaCl, NaI, or Sodium salts such as NaBr, or tetraalkyl quaternary ammonium salts such as tetraethylammonium borofluoride, tetraethylammonium perchlorate, tetrabutylammonium borofluoride, tetrabutylammonium perchlorate or tetrabutylammonium halide salt Can be mentioned. 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.

  Since there is a possibility that color development other than the desired color development may occur due to the side reaction caused by the anionic species, the additive may be any one of a reducing agent or an oxidizing agent for suppressing the side reaction caused by the anionic species. Or it is preferable that 2 or more types are mixed and contained.

  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.

The transparent electrode 14 is made of indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), ITO, indium oxide (In ₂ O ₃ ), or tin oxide in addition to the above-mentioned ITO (Indium Tin oxide). It is preferably composed of (SnO ₂ ) 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 is an electrochemically stable metal, among which gold (Au), platinum (Pt), chromium (Cr), aluminum (Al), cobalt (Co), It is preferably composed of at least one member selected from the group consisting of 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.

  In the write control means, the first and second write voltages are applied, but a third write voltage may be further applied. For example, in the write control means, after applying the first and second write voltages, a third write voltage having a magnitude equal to or larger than the absolute value of the write threshold voltage (−Vth) is applied. You may do it. In the erase control means, the first and second erase voltages are applied, but a third erase voltage may be further applied. For example, the erase control unit may apply a third erase voltage lower than the erase threshold voltage Vith.

[Example]
Below, schematic structure of the electrochemical display element which concerns on the Example of this invention is demonstrated. As shown in FIG. 8, the transparent electrode 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 counter electrode 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.

  The electrolyte was 0.5 mol / l silver iodide (AgI) as a precipitation-dissolved material in a solvent in which dimethylsulfoxide (DMSO) and γ-butyrolactone (γBr) were mixed at a ratio of 6: 4, and 0 as a supporting electrolyte salt. .75 mol / l lithium iodide (LiI) is dissolved. To this electrolyte, polyethylene oxide having a molecular weight of 200,000 as a polymer material and titanium dioxide (TiO2) as a colorant are added at a weight ratio of 1: 0.2: 1.2, and this is uniformly added. Dispersed. Thereafter, the cross-linking material was added to the polyethylene oxide in a weight ratio of 1: 0.02. After coating this on a transparent electrode at a thickness of 100 μm, the counter electrode was immediately bonded together and heated at 100 ° C. for 10 minutes to form a gelled polymer solid electrolyte between both electrodes. Here, if possible, the polymerization may be performed without adding a cross-linking material. Finally, the bonded end surfaces were sealed with an epoxy resin adhesive.

  The electrochemical display device manufactured in this way was driven by the driving waveforms shown in FIG. 5 (writing) and FIG. 6 (erasing). First, a time Te required to apply the same erase voltage Ve to all the pixels is 3000 msec, and a voltage Vs (= Ver−Vec) for selectively dissolving the deposited metal remaining in each pixel is selectively applied. The time Ts required for the scanning is 1200 msec, and the time Tss required for scanning the selection voltage Ver for each line is 30 msec.

  As a comparative example, the same electrochemical display element as described above was driven with the driving waveforms shown in FIG. 5 (writing) and FIG. 7 (erasing). First, a time Te required to apply the same erase voltage Ve to all the pixels is 3000 msec, and a voltage Vs (= Ver−Vec) for selectively dissolving the deposited metal remaining in each pixel is selectively applied. The time Ts required for the scanning is 1200 msec, and the time Tss required for scanning the selection voltage Ver for each line is 30 msec.

  FIG. 9 shows a change in reflectance when a drive waveform is applied in the example and the comparative example. In the embodiment, it can be confirmed that the image disappears simultaneously on the entire screen immediately after the first application of the first erase voltage. In this case, the screen returns to the original white state in about one second from the start of application of the first erase voltage. When applying a second erasing voltage in the latter half, when applying a strong erasing waveform for the purpose of completely dissolving a small amount of silver remaining on the transparent electrode, the reflectivity hardly changes. Can also be confirmed.

  In the comparative example, in the first application of the erasing voltage Vs, the selection voltage Ver is scanned in order from the first line, and it can be confirmed that the black silver is partially dissolved and the black becomes light accordingly. Furthermore, the application of the erase voltage Vs to each line only has the effect of thinning the display on the entire screen. By applying an erase voltage Ve lower than the latter anion oxidation voltage Vith to the entire screen, almost all black The silver melts and the screen returns to white. In this case, the screen returns to the original white state even if it takes about 2 seconds from the start of the erase waveform application. Although it is possible to speed up erasing somewhat by increasing the strength of the first erasing voltage Vs, it is difficult to completely dissolve black silver only by applying the erasing voltage Vs for a short time.

  In the comparative example, the erasing of the silver on the transparent electrode is not complete, so that burn-in occurs in several thousand cycles as the writing and erasing cycles are repeated. On the other hand, in the embodiment, since erasing can be performed completely, burn-in does not occur, and as a result, writing and erasing can be performed for 100,000 cycles or more.

  Summarizing the above results, the example has the effect that the cycle characteristic of the black reflectance is overwhelmingly superior. Further, the image erasing speed viewed from the user is overwhelmingly faster in the embodiment, and there is an effect that the image display is not deteriorated. In addition, the embodiment has an effect that an image can be overwhelmed naturally.

  The present invention has been described with reference to the embodiment and the examples. However, the present invention is not limited to this, and various modifications can be made.

  For example, in this embodiment, after sequentially applying the first write voltage between the transparent electrode and the counter electrode for each write target pixel, the second write voltage is simultaneously applied to all the write target pixels. And the first erase voltage is applied between the transparent electrode and the counter electrode at the same time for all the erase target pixels, and then the second erase voltage is sequentially applied to each erase target pixel. The write / erase voltage may be applied to the pixels at different intervals (timing).

  Further, the first erase voltage may be equal to or higher than the erase threshold voltage. Further, the second erase voltage may be smaller than the erase threshold voltage.

  The application time of the second erase voltage may be longer than the application time of the first erase voltage. Further, the application time of the first write voltage may be longer than the application time of the second write voltage.

It is a schematic block diagram of an electrochemical display apparatus. It is a schematic block diagram of the electrochemical display element 10 shown in FIG. 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. 2 shows an example of a driving voltage waveform at the time of writing according to the present embodiment. 6 shows an example of a driving voltage waveform at the time of erasing according to the present embodiment. 7 shows a drive voltage waveform at the time of erasing according to the cited example. The structure of the transparent electrode and counter electrode in an electrochemical display element is shown. In an Example and a comparative example, the change of a reflectance when a drive voltage waveform is applied is shown.

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 circuit, 23 ... Counter electrode drive circuit

Claims (11)

An electrochemical display device that displays an image by precipitation and dissolution of a metal,
A plurality of transparent electrodes and a plurality of counter electrodes arranged so as to intersect each other and the intersections constitute pixels,
An electrolyte layer sandwiched between the transparent electrode and the counter electrode and containing the metal ions;
For a pixel to be written, after applying a first write voltage having a magnitude equal to or greater than the absolute value of the write threshold voltage between the transparent electrode and the counter electrode, the absolute value of the write threshold voltage Write control means for writing an image by depositing the metal on the transparent electrode side by applying a second write voltage having a magnitude smaller than the value;
For a pixel to be erased, a first erase voltage having a magnitude smaller than the absolute value of the erase threshold voltage is applied between the transparent electrode and the counter electrode, and then the absolute value of the erase threshold voltage or higher is applied. An electrochemical display device comprising: erase control means for erasing an image by applying a second erase voltage having a magnitude to dissolve the metal deposited on the transparent electrode side. 2. The electricity according to claim 1, wherein the first erase voltage has a reverse polarity to the second write voltage, and the second erase voltage has a reverse polarity to the first write voltage. Chemical display device. 2. The electrochemical display device according to claim 1, wherein the erase control unit makes the application time of the second erase voltage shorter than the application time of the first erase voltage. The erasing control unit applies a first erasing voltage between the transparent electrode and the counter electrode simultaneously for all the erasing target pixels, and then sequentially applies a second erasing voltage to each erasing target pixel. 2. The electrochemical display device according to claim 1, wherein erasing is performed on the erasing target pixel. 2. The electrochemical display device according to claim 1, wherein the write control unit makes the application time of the first write voltage shorter than the application time of the second write voltage. The write control means sequentially applies the first write voltage between the transparent electrode and the counter electrode for each write target pixel, and then simultaneously applies the second write to all the write target pixels. The electrochemical display device according to claim 1, wherein a voltage is applied to perform writing on the pixel to be written. An electrochemical display device that displays an image by precipitation and dissolution of a metal,
A plurality of transparent electrodes and a plurality of counter electrodes arranged so as to intersect each other and the intersections constitute pixels,
An electrolyte layer sandwiched between the transparent electrode and the counter electrode and containing the metal ions;
The first erasing voltage is applied between the transparent electrode and the counter electrode at the same time for all the erasing target pixels, and then the second erasing voltage is sequentially applied to the individual erasing target pixels, whereby the transparent electrode side And an erasing control means for erasing the image by dissolving the metal deposited on the electrochemical display device. The electrochemical display device according to claim 7, wherein the erasing control unit makes the application time of the second erasing voltage shorter than the application time of the first erasing voltage. The erase control means makes the magnitude of the first erase voltage smaller than the absolute value of the erase threshold voltage, and makes the magnitude of the second erase voltage equal to or larger than the absolute value of the erase threshold voltage. The electrochemical display device according to claim 7. An electrochemical display method for displaying an image by precipitation and dissolution of a metal,
A plurality of transparent electrodes and a plurality of counter electrodes arranged so as to intersect with each other and constitute intersections, and an electrolyte layer sandwiched between the transparent electrodes and the counter electrodes and containing the metal ions Provided,
For a pixel to be written, after applying a first write voltage having a magnitude equal to or greater than the absolute value of the write threshold voltage between the transparent electrode and the counter electrode, the absolute value of the write threshold voltage By applying a second writing voltage having a magnitude smaller than the value, the metal is deposited on the transparent electrode side to write an image,
For a pixel to be erased, a first erase voltage having a magnitude smaller than the absolute value of the erase threshold voltage is applied between the transparent electrode and the counter electrode, and then the absolute value of the erase threshold voltage or higher is applied. An electrochemical display method comprising: applying a second erase voltage having a magnitude to dissolve the metal deposited on the transparent electrode side to erase an image. An electrochemical display method for displaying an image by precipitation and dissolution of a metal,
A plurality of transparent electrodes and a plurality of counter electrodes arranged so as to intersect with each other and constitute intersections, and an electrolyte layer sandwiched between the transparent electrodes and the counter electrodes and containing the metal ions Provided,
The first erasing voltage is applied between the transparent electrode and the counter electrode at the same time for all the erasing target pixels, and then the second erasing voltage is sequentially applied to the individual erasing target pixels, whereby the transparent electrode side An electrochemical display method comprising erasing an image by dissolving the metal deposited on the substrate.

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