JP2005189299A - Electrochemical display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical display device with which the redox reaction in an electrode on a counter electrode side can be stabilized and a sufficient display grade can be realized from the first cycle. <P>SOLUTION: An electrolyte 13 is arranged between a first electrode 14 consisting of ITO and a second electrode 15 consisting of platinum. The electrolyte 13 contains a silver ion as a first redox material which is deposited and dissolved by the redox reaction and a viologen derivative or styryl compound as a second redox material performing the reaction different from that of the first redox material. The redox reaction which makes a pair with the precipitation and dissolution of the silver ion is stably performed by the second redox material. The second redox material is not restricted to materials discolored by the redox reaction and may be any materials which are not discolored by the same. More particularly, the discoloring materials can increase a response speed and can enhance coloration efficiency with a smaller amount of injection charges and makes the delicate adjustment of black density and tint possible and are therefore desirable. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrochemical display device that displays image information by an electrochemical redox reaction.

  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. Conventionally, a CRT (Cathode-Ray Tube) or a liquid crystal display of a computer has been used to browse the information.

  However, it has been pointed out that these light-emitting displays are extremely fatigued for ergonomic reasons and cannot withstand long-time reading. In addition, there is a problem that the reading place is limited to the place where the computer is installed.

  Recently, some notebook computers can be used as portable displays due to the widespread use of notebook computers. However, these are mainly light-emitting devices using backlights, and are related to power consumption. Difficult to use for In addition, a reflective liquid crystal display has also been developed, which can be driven with low power consumption. However, the reflectance when the liquid crystal is not displayed (white display) is 30%, which is significantly more visible than the printed matter on paper. Poor and prone to fatigue, which also does not withstand prolonged reading.

  In order to solve these problems, recently, a display colored by moving colored particles between electrodes mainly by electrophoresis or rotating particles having dichroism in an electric field has been developed. is there. However, in this display, the gap between the particles absorbs light, resulting in poor contrast, and the practical writing speed (within 1 second) cannot be obtained unless the driving voltage is set to 100 V or higher. There is.

On the other hand, an electrochromic display (ECD) utilizing the change in color by applying a voltage has been developed. As such an electrochromic display device, for example, a device using tungsten oxide (WO ₃ ) that changes from transparent to blue when ions such as H ⁺ enter, or an organic material that develops color by oxidation or reduction is known. It has been. They are superior to the above-mentioned electrophoretic methods in terms of high contrast, but they are developed for dimming glass or watch displays that do not require black matrix quality and have no need for matrix drive. Therefore, at present, it is difficult to use for a matrix-driven display device such as a paper-like display or electronic paper. In addition, although the thing of a matrix drive (refer patent document 1) is also known, a drive element only comprises a part in combination with a liquid crystal display device.

  In addition, organic materials generally have poor light resistance, so when used in electronic paper that will continue to be exposed to light such as sunlight and room light, the organic material will fade and have a black density when used for a long time. The problem of deteriorating arises.

Therefore, the electrodes are arranged opposite to each other through a white colored electrolyte containing metal ions, and the image is written by depositing the metal on the display-side electrode, and the deposited metal is dissolved in the electrolyte. An electrodeposition type display device that performs erasing has been proposed (see, for example, Patent Document 2). According to this, matrix driving is easy and contrast and black density can be increased.
Japanese Examined Patent Publication No. 4-73764 JP 2002-258327 A

  However, even with this electrodeposition type display device, the characteristics, particularly the lifetime, are still insufficient. As the cause of the deterioration of the life, for example, when silver (Ag) is used as the metal to be deposited on the display side electrode and the counter electrode side is made of silver, the counter electrode accompanies the deposition of silver on the display side electrode. For example, silver is irreversibly dissolved from the side electrode. As a countermeasure against this, it is conceivable that the counter electrode is made of an insoluble material such as platinum (Pt). However, since the deposition of silver on the display side electrode is paired with the dissolution of silver on the counter electrode, the reaction becomes unstable if the counter electrode is made of a material that does not dissolve. There was a problem that the black density at the cycle was insufficient.

  The present invention has been made in view of such problems, and an object of the present invention is to stabilize the oxidation-reduction reaction at the electrode on the counter electrode side, and to realize an electric display capable of realizing a sufficient display quality from the first cycle. It is to provide a chemical display device.

  An electrochemical display device according to the present invention includes an electrolyte between a first electrode and a second electrode, and the electrolyte includes a first redox material that is precipitated and dissolved by a redox reaction, and the first redox material. And a second redox material exhibiting a redox reaction different from the first redox material. Here, examples of the first redox material include metal ions that precipitate as a metal by reduction. The second redox material is preferably a color changing material that changes color by the redox material. The second redox material is preferably an organic material. Specifically, examples of the second redox material include a viologen derivative or a styryl compound.

  In the electrochemical display device according to the present invention, the image is written when the first redox material is deposited, and the image is erased when the deposited first redox material is dissolved in the electrolyte. Further, the second redox material exhibits a redox reaction different from that of the first redox material accompanying the redox reaction of the first redox material.

  According to the electrochemical display device of the present invention, since the electrolyte includes the second redox material that performs a redox reaction different from that of the first redox material, the deposition of the first redox material and The oxidation-reduction reaction paired with dissolution can be stabilized, and sufficient display quality can be obtained from the first cycle. Moreover, since the electrode on the counter electrode side can be made of a material that does not dissolve, it is possible to prevent the life from deteriorating due to irreversible dissolution of the electrode on the counter electrode side and to prolong the life of the electrochemical display device.

  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. On the surface of the first substrate 11 facing the second substrate 12, a plurality of first electrodes 14 are arranged in a matrix corresponding to the pixels, and the second substrate 12 on the side facing the first substrate 11 is arranged. A second electrode 15 is formed on the entire surface. Further, a TFT (Thin Film Transistor) 16 is provided for each pixel on the surface of the first substrate 11 facing the second substrate 12, and the energization of the first electrode 14 is controlled by the TFT 16. It has become so. That is, this electrochemical display device has an active matrix type drive mechanism. Further, the side surfaces of the first substrate 11 and the second substrate 12 and the electrolyte 13 are sealed with a sealing member 17.

  The first substrate 11 is made of a transparent material, specifically, quartz glass or white plate glass. In addition, for example, synthetic resins, specifically, esters such as polyethylene naphthalate, polyethylene terephthalate or polycarbonate, cellulose esters such as cellulose acetate, or polyvinylidene fluoride or polytetrafluoroethylene and hexa Fluoropolymers such as copolymers with fluoropropylene, polyethers such as polyoxymethylene, polyolefins such as polyacetal, polystyrene, polyethylene, polypropylene or methylpentene polymer, or polyimides such as polyamideimide or polyetherimide Alternatively, it may be made of 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, for example, quartz glass, white plate glass, glass epoxy material, ceramics, paper, or wood. In addition, the synthetic resin described for the first substrate 11 may be used. In addition, when 2nd electrode 15 itself has sufficient rigidity, it can also be set as the structure which does not require the 2nd board | substrate 12. FIG.

  The electrolyte 13 includes, for example, a solvent, a first redox material that is deposited and dissolved by a redox reaction, and a second redox material that exhibits a redox reaction different from the first redox material. Yes. Thereby, in this electrochemical display device, the redox reaction paired with the precipitation and dissolution of the first redox material can be stably performed by the second redox material, which is sufficient from the first cycle. Display quality can be obtained.

  Examples of the solvent include hydrophilic ones such as water, ethyl alcohol, isopropyl alcohol or a mixture thereof, or propylene carbonate, dimethyl carbonate, ethylene carbonate, butyrolactone, acetonitrile, sulfolane, dimethoxyethane, ethyl alcohol, isopropyl alcohol. , Dimethylformamide, dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone or a mixture thereof, and the like.

  The first oxidation-reduction material is for enabling display of pixels by utilizing the change in color between the deposited state and the dissolved state. Examples of the first redox material include metal ions that precipitate as a metal by reduction. Although it does not specifically limit as metal ion, For example, bismuth ion, copper ion, silver ion, iron ion, chromium ion, nickel ion, or cadmium ion is 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 second redox material is for stabilizing the redox reaction paired with precipitation and dissolution of the first redox material. It is preferable that the second redox material has a redox potential close to the redox potential of the first redox material so that the redox reaction can be performed almost synchronously with the first redox material. . The second redox material is preferably an organic material. This is because it is not necessary to form a film, and can be easily added to the electrolyte 13, and the amount of addition can be easily adjusted, so that the manufacturing process is simplified.

  The second oxidation-reduction material is not limited to a color-changing material that changes color by the oxidation-reduction reaction as long as it can exhibit a stable reversible oxidation-reduction reaction in the electrolyte 13. A material may be used, but a color changing material is more preferable. By superimposing the color change due to the deposition of the first redox material and the color change of the color changing material, the response speed is increased as compared with the case of only the first redox material, or the coloring efficiency is increased with a small injection charge amount. Because it can.

  The color change of the color change material is not necessarily black. For example, by using a metal ion that changes to black as the first redox material and a color change material that changes to a color other than black, it is easy to finely adjust the black density or hue, and particularly easy to read character information. This is because the height can be increased. That is, conventionally, the black density adjustment requires complicated control of the injected charge amount, and the black hue can be adjusted by controlling the driving voltage or the like, but it is difficult to make a fine adjustment. On the other hand, in the present embodiment, for example, by using a color-changing material that changes color to blue together with silver ions that become black by precipitation, it is easy to display black with a subtle hue such as bluish black. It becomes possible.

  Further, as the color changing material, a material having a small injection charge amount necessary for obtaining a contrast suitable for clear display is preferable, and further, it is more preferable that the injection charge amount is smaller than that of the first redox material. This is because the response speed or coloring efficiency can be further increased.

  Specifically, examples of the color changing material include viologen derivatives such as bipyridinium salt compounds having a viologen structure, or 3,3-dimethyl-2- (P-dimethylaminostyryl) indolino [2,1-b] oxazoline (IRPDM). And styryl compounds. Moreover, the redox-type material which consists of these mixtures may be sufficient. Of these, viologen derivatives are preferred. This is because the injected charge amount is small and the coloring efficiency is excellent. Further, by changing the substituent, it can be changed into various colors such as blue, magenta, and green, and there are many color variations. For example, 1,1′-di-n-heptyl-4,4′-bipyridinium dibromide (hereinafter referred to as “heptylviologen”) is exemplified as one that changes to blue. 1,1′-di-n-ethyl-4,4′-bipyridinium dibromide (ethyl viologen) can be mentioned, and 1,1′-di-n-hexyl-4,4 is one that changes to magenta. And '-bipyridinium dibromide (hexyl viologen). The viologen derivative has a problem that the interaction between the molecules is strong because the colored species are radicals, and the undissolved residue is likely to occur. Therefore, in order to prevent crystallization of the molecule, the electrolyte 13 is cyclohexane together with the viologen derivative. It is preferable to include an inclusion compound such as dextrin.

  The content of the color-changing material may vary depending on the display quality such as the coloring efficiency of the color-changing material, the solubility in the electrolyte 13, and the required shade. For example, the higher the coloring efficiency, that is, the smaller the required injection charge amount, the smaller the content of the color changing material. Further, the amount of injected charge necessary as a whole may be reduced by increasing the content of the color-changing material having high coloring efficiency and decreasing the content of the first redox material.

  Examples of the non-discoloring material include ferrocene. In addition, as a 2nd oxidation reduction material, you may use 1 type (s) or 2 or more types among said color change material and non-color change material.

  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 chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), and hexafluorophosphorus. Lithium salt such as lithium acid lithium (LiPF ₆ ) or trifluoromethyl lithium sulfite (LiCF ₃ SO ₃ ), or potassium salt such as potassium chloride (KCl), potassium bromide (KBr), or potassium iodide (KI), or Sodium salt such as sodium chloride (NaCl), sodium bromide (NaBr) or sodium iodide (NaI), or tetraethylammonium tetrafluoroborate (N (C ₂ H ₅ ) ₄ LiBF ₄ ), tetraethyl perchlorate ammonium _{(N (C 2 H 5)} 4 ClO 4 , Tetrafluoroboric acid tetrabutylammonium _{(N (C 4 H 9)} 4 BF 4), tetrabutylammonium perchlorate _{(N (C 4 H 9)} 4 ClO 4) or tetra-alkyl quaternary such as tetrabutyl ammonium halide An ammonium salt is mentioned. The alkyl chain lengths of these tetraalkyl quaternary ammonium salts may be uneven. 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.

  In the case of inorganic particles, the content of the colorant is preferably 10% by mass to 80% by mass with respect to the electrolyte 13, more preferably 20% by mass to 70% by mass, and more preferably 30% by mass to 70% by mass. % Is more preferable. If the amount of the colorant is small, the desired coloration cannot be obtained. If the amount is large, the inorganic particles of the colorant aggregate to cause unevenness in whiteness (optical density), decrease in the amount of ions, and further the electrolyte. This is because the conductivity of 13 is lowered. That is, by including a colorant within this range, it is possible to realize a good colored state without causing these problems.

  On the other hand, in the case of a pigment, it may be about 10% by mass with respect to the electrolyte 13. This is because the coloring efficiency of the dye is much higher than that of the inorganic particles. Therefore, if the dye is electrochemically stable, the contrast can be improved even with a small amount.

  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, coumarin and 2-mercaptobenzimidazole are preferable because they can improve the reversibility of the metal precipitation dissolution reaction and can also provide excellent effects in long-term storage stability and high-temperature storage stability. Use is preferable because the effect is further increased.

  In addition, 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 is either a reducing agent or an oxidizing agent for suppressing the side reaction caused by the anionic species. It is preferable that 1 type or 2 types or more are mixed and contained. For example, when the electrolyte 13 contains a halide, the halide may be oxidized from an ionic state by a reaction shown in Chemical Formula 1, Chemical Formula 2, or Chemical Formula 3, depending on the potential.

括弧内の数値は水溶液における標準水素電極（ＮＨＥ）を基準電極とした標準電極電位である。

The numerical value in the parenthesis is the standard electrode potential with the standard hydrogen electrode (NHE) in the aqueous solution as the reference electrode.

括弧内の数値は水溶液における標準水素電極（ＮＨＥ）を基準電極とした標準電極電位である。

The numerical value in the parenthesis is the standard electrode potential with the standard hydrogen electrode (NHE) in the aqueous solution as the reference electrode.

括弧内の数値は水溶液における標準水素電極（ＮＨＥ）を基準電極とした標準電極電位である。

The numerical value in the parenthesis is the standard electrode potential with the standard hydrogen electrode (NHE) in the aqueous solution as the reference electrode.

  As such a reducing agent, for example, triethanolamine, which is a trialkyl alcohol amine species, is preferable because long-term storage stability and high-temperature storage stability can be obtained.

  Furthermore, as an additive, the thing for carrying out dispersion stabilization of the inorganic particle of a coloring agent may be included.

  The electrolyte 13 may be a so-called liquid electrolytic solution composed of such a liquid solvent, a precipitation-dissolving material, an additive, and the like, but further includes a polymer compound that holds them, and is in a gel form. It may be. 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 polyethylene oxide or polypropylene oxide having a skeleton structure represented by — (— C—C—O—) _n —, and a skeleton structure represented by — (— C—C—N—) _n —. Polyethyleneimine or polyethylene sulfide having a skeleton structure represented by — (— C—C—S—) _n — is preferable, and these skeleton structures may be branched with a main chain structure. Polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene chloride or polycarbonate is also preferable. Any one of the polymer compounds may be used, or a mixture of two or more may be used.

  The thickness of the electrolyte 13 is preferably 10 μm to 100 μm, more preferably 10 μm to 50 μm, when inorganic particles are included as a colorant. 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 it is not sufficient, and if it is less than 10 μm, the mechanical strength is lowered and pinholes and cracks are also generated.

  The electrolyte 13 is prepared by, for example, dissolving the first redox material and the second redox material in a solvent, and then adding a supporting electrolyte salt, a colorant, and various additives as necessary. Can be manufactured. Alternatively, if necessary, a supporting electrolyte salt, a colorant and various additives are added to the solvent, and then the first redox material and the second redox material are dissolved therein. Good. 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 1st electrode 14 deposits the metal displayed as a pixel, for example, is comprised by the transparent conductive film. Specifically, indium oxide (In ₂ O ₃ ) or tin oxide (SnO ₂ ) coated, ITO (Indium Tin Oxide), which is a mixture of indium oxide and tin oxide, or tin Or it is preferable to be comprised by what doped antimony (Sb) etc. Moreover, you may comprise with magnesium oxide (MgO) or zinc oxide (ZnO).

  The second electrode 15 is preferably made of an electrochemically stable metal, among which silver (Ag), platinum (Pt), chromium (Cr), aluminum (Al), cobalt (Co) and palladium. It is preferably composed of at least one member selected from the group consisting of (Pd). Or you may make it comprise with stainless steel. Further, if the metal used in the main reaction can be sufficiently supplemented in advance or as needed, it may be constituted by carbon. This is because the price of the second electrode 15 can be reduced by using carbon. Moreover, you may make it comprise with the same transparent conductive film as the 1st electrode 14. FIG.

  The sealing member 17 is comprised with the double-sided tape or the adhesive agent, for example. In addition, when the sealing member 17 is comprised with a double-sided tape, it can also serve as a spacer.

  As shown in FIG. 1, the peripheral circuit unit 20 includes a signal control unit 21, data line driving circuits 22 </ b> A and 22 </ b> B, and a gate line driving circuit 23. The signal control unit 21 is connected to the data line driving circuits 22A and 22B and the gate line driving circuit 23 via signal lines 24, 25 and 26, respectively. The data line drive circuits 22A and 22B and the gate line drive 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 electrochemical display device having such a configuration can be manufactured by, for example, the process shown in FIG.

  First, as shown in FIG. 3A, for example, a TFT 16 is formed on a first substrate 11 made of glass or the like by a known semiconductor manufacturing technique, and then the first electrode 14 made of ITO or the like is formed by vapor deposition or sputtering. Form. At this time, prior to the formation of the first electrode 14, a treatment for improving the binding property between the first substrate 11 and the first electrode 14 may be performed on the first substrate 11. Next, as shown in FIG. 3B, for example, the first substrate 11 is subjected to UV ozone treatment to perform cleaning and surface modification of the first substrate 11.

  As shown in FIG. 3C, the second electrode 15 made of platinum is formed on the second substrate 12 made of glass or the like by, for example, vapor deposition, sputtering, or plating. At this time, prior to forming the second electrode 15, the second substrate 12 and the second substrate 12 are formed such that the second electrode 15 is formed after forming a metal thin film different from the second electrode 15 on the second substrate 12 in advance. A treatment for improving the binding property with the electrode 15 may be performed. Further, the second electrode 15 made of carbon is formed on the second substrate 12 by converting the carbon into an ink using, for example, a resin and printing it on the second substrate 12 or by film formation by other dry process. Also good.

  Next, when the electrolyte 13 is in a gel form, as shown in FIG. 3D, for example, the electrolyte 13 is formed on the first substrate 11. After that, as shown in FIG. 3E, for example, the second substrate 12 is bonded to the first substrate 11 via the electrolyte 13 by a vacuum bonding method. At that time, the first electrode 14 and the second electrode 15 are arranged to face each other. Subsequently, as shown in FIG. 3F, for example, the side surfaces of the first substrate 11, the second substrate 12, and the electrolyte 13 are sealed with the sealing member 17, and the electrolyte 13 is heated as necessary. Alternatively, it is crosslinked by ultraviolet rays or the like. Finally, a peripheral circuit unit 20 is provided around the electrochemical display element 10. Thus, the electrochemical display device shown in FIG. 1 is completed.

  The electrochemical display device can also be manufactured by the process shown in FIG.

  First, after the TFT 16 and the first electrode 14 are sequentially formed on the first substrate 11 as in the previous manufacturing method, the UV ozone treatment is performed on the first substrate 11. In addition, the second electrode 15 is formed on the second substrate 12. After that, as shown in FIG. 4A, for example, the first substrate 11 and the second substrate 12 are arranged to face each other at a predetermined interval using the sealing member 17. Subsequently, as shown in FIG. 4B, for example, a fluid electrolyte 13 is injected from an injection port (not shown) by, for example, a vacuum injection method, and thereafter, as shown in FIG. 4C. For example, the inlet is sealed with an adhesive 31 or the like, and the electrolyte 13 is cross-linked by heat or ultraviolet rays as necessary. Finally, a peripheral circuit unit 20 is provided around the electrochemical display element 10. Thus, the electrochemical display device shown in FIG. 1 is completed.

  In this electrochemical display device, a predetermined voltage is applied between the first electrode 14 and the second electrode 15 by the peripheral circuit unit 20 based on the input image signal, and the first electrode 14 and the second electrode 15 are applied. The metal ions in the electrolyte 13 existing between the first electrode 14 move to the first electrode 14, the metal ions are reduced at the first electrode 14, the metal is deposited on the first electrode 14, and writing is performed. The deposited metal is recognized as an image through the first substrate 11. On the other hand, when a predetermined reverse voltage is applied between the first electrode 14 and the second electrode 15, the metal deposited on the first electrode 14 is oxidized and dissolved as metal ions in the electrolyte 13. Done. At that time, since the electrolyte 13 contains the metal ion as the first redox material and the second redox material, the redox reaction by the second redox material occurs along with the redox reaction of the metal ion. . Therefore, the oxidation-reduction reaction paired with the precipitation and dissolution of metal ions is performed stably, and sufficient display quality can be obtained from the first cycle.

  As described above, in the present embodiment, the electrolyte 13 includes the second redox material exhibiting a redox reaction different from that of the first redox material. Therefore, precipitation and dissolution of the first redox material are performed. The oxidation-reduction reaction paired with can be performed stably, and sufficient display quality can be obtained from the first cycle. Further, since the second electrode 15 can be made of platinum that does not dissolve, it is possible to prevent the deterioration of the lifetime due to the irreversible dissolution of the second electrode 15 and to prolong the lifetime of the electrochemical display device.

  In particular, if the second oxidation-reduction material is a color-changing material that changes color by oxidation-reduction reaction, the first oxidation-reduction material is superimposed by superimposing the color change caused by precipitation of the first oxidation-reduction material and the color change of the color-change material. The response speed can be increased as compared with the case of using only the reducing material, and the coloring efficiency can be increased with a small amount of injected charge. If a color-changing material that changes to a color other than black is used, fine adjustment of the black density or hue can be easily performed, and in particular, the readability of character information can be improved. In particular, if the second oxidation-reduction material is a viologen derivative, it is possible to express an abundant color with a small amount of injected charge, and therefore, it is possible to further easily adjust the black density or the hue.

  In the electrochemical display device according to the present embodiment, the electrochemical display element 10 may have a configuration other than that shown in FIG. For example, as shown in FIG. 5, the first electrode 14 is formed on the entire surface of the first substrate 11, a plurality of second electrodes 15 are formed in a matrix, and the TFTs correspond to the pixels on the second substrate 12. It is also possible to control the energization to the second electrode 15. In this case, the second electrode 15 is preferably formed so as to cover the entire TFT. In addition, an insulating layer (not shown) may be formed in a region excluding a portion facing the second electrode 15 of the first substrate 11. In FIG. 5, the electrolyte and TFT are omitted.

  In addition, as shown in FIG. 6, the first electrode 14 is formed in a stripe shape on the first substrate 11, the second electrode 15 is formed in a stripe shape on the second substrate 12, and the first electrode 14 and the second electrode 15 may be arranged to face each other so as to be orthogonal to each other. In FIG. 6, the electrolyte and the sealing member are omitted.

  Further, as shown in FIG. 7 as an example, the third electrode 18 made of silver or the like for accurately detecting the progress of the metal precipitation dissolution reaction without being affected by the first electrode 14 and the second electrode 15. May be provided. The driving of the electrochemical display element 10 can be accurately controlled by the third electrode 18 and the reliability can be improved. The third electrode 18 may be formed in an appropriate shape and an appropriate location according to the structure of the electrochemical display element 10, and may be formed by, for example, vapor deposition, sputtering, or plating.

  When the electrochemical display element 10 has a configuration other than that shown in FIG. 2, the configuration of the peripheral circuit unit 20 and the like may be appropriately changed according to the configuration of the electrochemical display element 10.

  Further, specific embodiments of the present invention will be described in detail.

(Example)
An electrochemical display device including the electrochemical display element 10 was produced. First, LiI, heptyl viologen, and AgI were respectively 750 mmol / l, 60 mmol / l in a solvent in which dimethyl sulfoxide (DMSO) and γ-butyrolactone (γBL) were mixed at a volume ratio of dimethyl sulfoxide: γ-butyrolactone = 3: 2. 1 and 500 mmol / l, and triethanolamine, coumarin, and 2-mercaptobenzimidazole were added to 67 mmol / l, 5 g / l, and 5 g / l to prepare an electrolytic solution. did.

  Next, the electrolyte solution and the polyether resin are mixed at a mass ratio of electrolyte solution: polyether resin = 5: 2, and further, titanium dioxide (IV) is added to the polyether resin at a mass ratio of 6 times that of the polyether resin. And uniformly dispersed with a homogenizer and a rotation / revolution mixer. Furthermore, an organic peroxide (“Perhexyl (registered trademark) ND” manufactured by NOF Corporation) as a polymerization initiator was added to this at a ratio of 2% by mass with respect to the polyether resin. A precursor solution was prepared by stirring.

  A first substrate 11 made of glass on which the first electrode 14 made of ITO is formed and a second substrate 12 made of glass on which the second electrode 15 made of platinum is formed are bonded to a double-sided tape having a thickness of 80 μm (Tesa Tape Co., Ltd.). Bonding was performed using a sealing member 17 made of “tesa (registered trademark) 4980”. The double-sided tape also served as a spacer between the first substrate 11 and the second substrate 12.

Subsequently, after the precursor solution is injected into the space between the first substrate 11 and the second substrate 12 by vacuum injection, the precursor solution is gelled by heating at 90 ° C. for 10 minutes in a thermostatic bath. The electrolyte 13 was formed. After that, the injection port and the end face of the bonding were sealed with an adhesive to produce the electrochemical display element 10. Finally, a peripheral circuit unit 20 was provided around the electrochemical display element 10. The conductivity of the obtained electrochemical display device was measured and found to be 18 × 10 ⁻⁴ S · cm ⁻¹ .

(Comparative example)
An electrochemical display device was fabricated in the same manner as in the Examples except that an electrolyte containing no heptyl viologen was used. The electrical conductivity of the obtained electrochemical display device of the comparative example was also measured and was 18 × 10 ⁻⁴ S · cm ⁻¹ , which was the same as that of the example.

  For the produced electrochemical display devices of Examples and Comparative Examples, the redox potential was examined by the cyclic voltammetry method. At that time, the potential sweep range was −1.2 V to +1.1 V, and the potential sweep speed was 50 mV / s. The cyclic voltammogram of the obtained example is shown in FIG. 8 and FIG. 9, and the cyclic voltammogram of the comparative example is shown in FIG. 10 and FIG. 9 is an enlarged view of a portion surrounded by a dotted line in FIG. 8, and FIG. 11 is an enlarged view of a portion surrounded by a dotted line in FIG.

  As can be seen from FIGS. 8 to 11, in the cyclic voltammograms of the examples, in addition to the peaks due to the reduction of silver, peaks due to the reduction of heptyl viologen were observed at about −0.6 V and about −1.0 V. This was not observed in the cyclic voltammogram of the comparative example. That is, if the electrolyte 13 contains silver ions as the first redox material and heptyl viologen that changes color due to the redox reaction as the second redox material, the color change of heptyl viologen and the precipitation of silver occur. It was found that it can be caused to overlap.

  In addition, with respect to the electrochemical display devices of Examples and Comparative Examples, the voltage was changed to −2.0 V, −2.4 V, and −2.8 V, respectively, and writing and erasing were performed, and driving characteristics and display characteristics were evaluated. Writing is performed by applying the above voltage for the time required to reach the required density (absolute reflectance 10%, optical density (optical density; OD) 1.0), while erasing is performed with the optical density in the initial state. An arbitrary voltage was applied for an arbitrary time in order to return to. One writing and one erasing were repeated 10 times, and a pause time until the optical density returned to the initial state was taken between each cycle. The optical density is measured by irradiating laser light having a wavelength of 670 nm from vertically above an electrochemical display device installed horizontally, and converting the intensity of reflected light received obliquely upward by 30 ° from incident light into optical density. Was determined by As the driving characteristics, the time (response time) until the required concentration was reached after voltage application was examined in the 10th cycle. Further, as display characteristics, the amount of charge required for the optical density to be 1.0 was examined. The results are shown in FIG.

  As can be seen from FIG. 12, in the example containing heptyl viologen, better results were obtained for both the response time and the required charge amount than the comparative example not containing heptyl viologen. That is, if the electrolyte 13 contains silver ions as the first redox material and heptyl viologen that changes color due to the redox reaction as the second redox material, the color change of heptyl viologen and the precipitation of silver occur. It has been found that, by superimposing, faster and darker display can be performed, high-speed response can be obtained, and the injected charge amount can be reduced.

  In the above embodiment, the viologen derivative has been described with a specific example. However, the above-described effects are considered to be attributable to the structure. Therefore, similar results can be obtained using other viologen derivatives. Moreover, although the said Example demonstrated the case where a gel-like electrolyte was used, the same result can be obtained even if it uses electrolyte solution.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the structure of the electrochemical display element has been described with a specific example, but other structures may be used. For example, although not shown, an electrolyte may be impregnated into a nonwoven fabric or a porous film. Further, a layer made of a material that can introduce and release ions or a layer made of a material that performs an oxidation-reduction reaction may be provided between the electrolyte 13 and the second electrode 15. In that case, the layer made of a material capable of introducing and releasing ions or the layer made of a material that performs a redox reaction preferably contains, for example, carbon (C).

  Furthermore, for example, the materials and thicknesses of the respective layers described in the above embodiments and examples, or the film formation method and film formation conditions are not limited, and other materials and thicknesses may be used. It is good also as a film | membrane method and film-forming conditions. For example, as the first redox material, a material other than metal ions may be used. Further, the first redox material may be changed to a color other than black. In this case, for example, by using a metal ion that changes color to a color other than black as the first redox material and a color change material that changes color to black as the second redox material, fine adjustment of the black density or hue is performed. You may make it perform. Furthermore, the colorant added to the electrolyte 13 may be other than white.

  In addition, in the above-described embodiments and examples, the case where the electrochemical display device has one electrochemical display element 10 has been described. However, a plurality of electrochemical display elements 10 may be arranged in a planar shape. . For example, each of the pixels of the three primary colors may be separated as one electrochemical display element 10.

  Furthermore, although cases have been described with the above embodiment and examples where the display area is divided into a plurality of pixels, the entire display area may constitute one pixel.

  In addition, in the above-described embodiment and examples, the case where black and white are displayed has been described. However, the electrochemical display device of the present invention can be applied to any of mono-color, multi-color, and full-color. .

  The electrochemical display device according to the present invention is particularly suitable for use in displaying character information such as an electronic book terminal, but can also be used for displaying symbols and images.

  Further, the electrochemical display device according to the present invention can be applied to an optical shutter or an optical communication device by utilizing a dimming function such as adjustment of reflected or transmitted light amount in addition to the use as a display device.

It is a block diagram showing the structure of the electrochemical display apparatus which concerns on one embodiment of this invention. It is a perspective view showing the structure of the electrochemical display element shown in FIG. It is sectional drawing showing the manufacturing process of the electrochemical display apparatus shown in FIG. It is sectional drawing showing the other manufacturing process of the electrochemical display apparatus shown in FIG. It is a perspective view showing the structure of the other electrochemical display element shown in FIG. It is a perspective view showing the structure of the other electrochemical display element shown in FIG. It is a perspective view showing the structure of the other electrochemical display element shown in FIG. It is a cyclic voltammogram showing the measurement result by the cyclic voltammetry method of the Example of this invention. It is a figure which expands and represents the part enclosed with the dotted line of the cyclic voltammogram shown in FIG. It is a cyclic voltammogram showing the measurement result by the cyclic voltammetry method of the comparative example of this invention. It is a figure which expands and represents the part enclosed with the dotted line of the cyclic voltammogram shown in FIG. It is a characteristic view showing the drive characteristic of an Example and a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electrochemical display element, 11 ... 1st board | substrate, 12 ... 2nd board | substrate, 13 ... Electrolyte, 14 ... 1st electrode, 15 ... 2nd electrode, 16 ... TFT, 17 ... Sealing member, 18 ... 3rd electrode , 20 ... Peripheral circuit part, 21 ... Signal control part, 22A, 22B ... Data line drive circuit, 23 ... Gate line drive circuit, 24, 25, 26 ... Signal line, 31 ... Adhesive.

Claims (10)

An electrochemical display device comprising an electrolyte between a first electrode and a second electrode,
The electrolyte includes a first redox material that is precipitated and dissolved by a redox reaction, and a second redox material that exhibits a redox reaction different from the first redox material. Chemical display device. The electrochemical display device according to claim 1, wherein the first redox material is a metal ion precipitated as a metal by reduction. The first oxidation-reduction material is at least one member selected from the group consisting of bismuth ions, copper ions, silver ions, iron ions, chromium ions, nickel ions, and cadmium ions. Electrochemical display device. 2. The electrochemical display device according to claim 1, wherein the second redox material is at least one of a color-changing material that changes color by a redox reaction and a non-color-changing material that does not change color by a redox reaction. The electrochemical display device according to claim 1, wherein the second redox material is an organic material. The electrochemical display device according to claim 1, wherein the second redox material is a viologen derivative or a styryl compound. The electrochemical display device according to claim 1, wherein the first electrode is a transparent electrode. _{2. The} electrochemical display device according to claim 1, wherein the first electrode is made of at least one of tin (IV) oxide (SnO ₂ ) and indium oxide (III) (In ₂ O ₃ ). The electrochemical display device according to claim 1, wherein the second electrode is a metal electrode. The electrochemical display device according to claim 1, wherein the second electrode is made of platinum (Pt) or stainless steel.

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