JP2010256603A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element of which corrosion of electrodes is little and a contrast holding ratio is not decreased even by repeated driving. <P>SOLUTION: The display element includes a pair of opposing electrodes (a display electrode and a counter electrode) and includes an electrolyte layer containing an organic solvent, a metallic salt compound, and a compound represented by general formula (1) between the pair of electrodes. The display element displays black and white when a voltage is applied. In the formula, A<SB>1</SB>is aliphatic, aryl, or heterocyclic group; n is an integer of 3-6; L is a bivalent linking group; X is alkyl, aryl, or heterocyclic group; and the plurality of L and X may be the same or different. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a novel electrochemical display element.

  In recent years, with the increase in the operating speed of personal computers, the spread of network infrastructure, the increase in capacity and price of data storage, information such as documents and images provided on printed paper on paper has become easier to use electronic information. Opportunities to obtain and browse electronic information are increasing more and more.

  As such electronic information browsing means, conventional liquid crystal displays and CRTs, and in recent years, light-emitting types such as organic EL displays are mainly used. Particularly, when electronic information is document information, it is relatively long time. It is necessary to pay close attention to this browsing means, and these actions are not necessarily human-friendly means. Generally, as a disadvantage of the light-emitting display, eyes flicker due to flickering, inconvenient to carry, reading posture is limited It is known that it is necessary to adjust the line of sight to a still screen, and that power consumption increases when read for a long time.

  As a display means to compensate for these drawbacks, a reflection type display having a so-called memory property that uses external light and does not consume power for image retention is known. However, it has sufficient performance for the following reasons. It's hard to say.

  That is, the method using a polarizing plate such as a reflective liquid crystal has a low reflectance of about 40%, which makes it difficult to display white, and it is difficult to say that many of the manufacturing methods used to manufacture the constituent members are simple. In addition, the polymer dispersed liquid crystal requires a high voltage and utilizes the difference in refractive index between organic substances, so that the resulting image has insufficient contrast. In addition, the polymer network type liquid crystal has problems such as a high driving voltage and a complicated TFT circuit required to improve the memory performance. In addition, a display element based on electrophoresis requires a high voltage of 10 V or more, and there is a concern about durability due to electrophoretic particle aggregation.

  As a display method for solving the drawbacks of each of the above-mentioned methods, an electrochromic display element (hereinafter abbreviated as EC method), an electrodeposition method (hereinafter abbreviated as ED method) using dissolution precipitation of metal or metal salt, etc. The electrochemical method is known. These systems have an advantage that they can be formed with a simple element configuration and can be driven at a low voltage of 3 V or less. The EC method enables full color display by selecting an electrochromic material, and the ED method has advantages such as excellent black and white contrast and black quality, and various methods have been disclosed (for example, patent documents). 1-3).

  However, the ED display element has a problem that the contrast gradually decreases by being repeatedly driven.

  On the other hand, there is a problem that the corrosion of the electrode occurs when trying to improve the decrease of the contrast retention ratio due to repeated driving with an additive, and there is a technology that makes it possible to prevent both the decrease of the contrast retention ratio during repeated driving and the prevention of electrode corrosion. It has been desired (for example, Patent Document 4).

U.S. Pat. No. 4,240,716 Japanese Patent No. 3428603 JP 2003-241227 A JP 2005-275227 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a display element in which the corrosion rate of the electrode is small and the contrast retention rate does not decrease even when repeatedly driven.

  The above object of the present invention is achieved by the following configurations.

  1. It has a pair of opposing electrodes (display electrode and counter electrode), has an electrolyte layer containing an organic solvent, a metal salt compound, and a compound represented by the following general formula (1) between the electrodes, and applies a voltage A display element which displays black and white by doing so.

(In the formula, A ₁ represents an aliphatic group, an aryl group or a heterocyclic group, n represents an integer of 3 to 6, L represents a divalent linking group, and X represents an alkyl group, an aryl group or a heterocyclic ring. A plurality of L and X may be the same or different.)
2. 2. The display element according to 1 above, wherein in the general formula (1), X is an alkyl group or a heterocyclic group.

  3. 3. The display element according to 1 or 2 above, which contains an auxiliary compound that can be oxidized and reduced.

  4). 4. The display element according to 3 above, wherein the auxiliary compound that can be oxidized and reduced is fixed to the display electrode and the counter electrode.

  According to the above means of the present invention, a display element in which the corrosion of the electrode is small and the contrast retention rate does not decrease even when it is repeatedly driven can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  In the present invention, the black display means a state in which the metal salt compound is reduced and the metal is deposited to give a black color, and the white display means that there is no metal precipitation and the metal salt compound is dissolved to exhibit a color. In other words, it refers to the state of white color due to white scatterers.

[Compound represented by the general formula (1)]
The feature of the present invention is that the compound represented by the general formula (1) is contained in the electrolyte, and the compound represented by the general formula (1) is obtained by repeatedly driving an ED display element. It has the effect of maintaining contrast. Further, side reactions on the electrode surface can be suppressed, and electrode corrosion caused by side reactions can be reduced.

In the general formula (1), A ₁ represents an aliphatic group, an aryl group, or a heterocyclic group.

  Examples of the aliphatic group include an alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, iso-pentyl group, 2-ethyl-hexyl group, octyl group, decyl group, etc.), cycloalkyl group ( For example, cyclohexyl group, cycloheptyl group, etc.), alkenyl group (for example, ethenyl-2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group) Etc.), cycloalkenyl groups (eg 1-cycloalkenyl group, 2-cycloalkenyl group etc.), alkynyl groups (eg ethynyl group, 1-propynyl group etc.) and the like.

  The aryl group is a monocyclic or condensed aryl group having 6 to 30 carbon atoms, preferably a monocyclic or condensed aryl group having 6 to 20 carbon atoms, and more preferably a phenyl group or a naphthyl group. An aliphatic group or an aryl group is preferable, an aliphatic group is more preferable, and an alkyl group is particularly preferable.

  Examples of the heterocyclic group include a pyridyl group, a pyrazinyl group, a pyrimidyl group, a benzothiazole group, a benzimidazole group, a thiadiazolyl group, a quinolyl group, and an isoquinolyl group.

  These aliphatic group, aryl group or heterocyclic group may have a substituent, and examples of the substituent include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an i-propyl group, a butyl group, t-butyl group, pentyl group, cyclopentyl group, hexyl group, cyclohexyl group, octyl group, dodecyl group, hydroxyethyl group, methoxyethyl group, trifluoromethyl group, benzyl group, etc.), aryl group (for example, phenyl group, naphthyl) Group), alkylcarbonamide group (for example, acetylamino group, propionylamino group, butyroylamino group, etc.), arylcarbonamide group (for example, benzoylamino group, etc.), alkylsulfonamide group (for example, methanesulfonylamino group) , An ethanesulfonylamino group, etc.), an arylsulfonamide group (for example, Benzenesulfonylamino group, toluenesulfonylamino group etc.), alkoxy group, aryloxy group (eg phenoxy etc.), alkylthio group (eg methylthio group, ethylthio group, butylthio group etc.), arylthio group (eg phenylthio group, tolylthio) Group), alkylcarbamoyl group (for example, methylcarbamoyl group, dimethylcarbamoyl group, ethylcarbamoyl group, diethylcarbamoyl group, dibutylcarbamoyl group, piperidylcarbamoyl group, morpholylcarbamoyl group, etc.), arylcarbamoyl group (for example, phenylcarbamoyl group) Methylphenylcarbamoyl group, ethylphenylcarbamoyl group, benzylphenylcarbamoyl group, etc.), carbamoyl group, alkylsulfamoyl group (for example, methylsulfamoyl group) Group, dimethylsulfamoyl group, ethylsulfamoyl group, diethylsulfamoyl group, dibutylsulfamoyl group, piperidylsulfamoyl group, morpholylsulfamoyl group, etc.), arylsulfamoyl group (for example, Phenylsulfamoyl group, methylphenylsulfamoyl group, ethylphenylsulfamoyl group, benzylphenylsulfamoyl group, etc.), sulfamoyl group, cyano group, alkylsulfonyl group (for example, methanesulfonyl group, ethanesulfonyl group, etc.) , Arylsulfonyl groups (for example, phenylsulfonyl group, 4-chlorophenylsulfonyl group, p-toluenesulfonyl group, etc.), alkoxycarbonyl groups (for example, methoxycarbonyl group, ethoxycarbonyl group, butoxycarbonyl group, etc.), aryloxycal Bonyl group (for example, phenoxycarbonyl), alkylcarbonyl group (for example, acetyl group, propionyl group, butyroyl group, etc.), arylcarbonyl group (for example, benzoyl group, alkylbenzoyl group, etc.), acyloxy group (for example, acetyloxy group) , Propionyloxy group, butyroyloxy group, etc.), carboxyl group, carbonyl group, sulfonyl group, amino group, hydroxy group, heterocyclic group (for example, oxazole group, thiazole ring, triazole ring, selenazole ring, tetrazole ring, oxadiazole ring) , Thiadiazole group, thiazine group, triazine group, benzoxazole group, benzthiazole group, indolenine group, benzselenazole group, naphthothiazole group, triazaindolizine group, diazaindolizine group, tetraazaine Lysine group). These substituents include those having a substituent, and may be further linked to each other to form a ring.

  n represents an integer of 3 to 6.

  L represents a divalent linking group. Although it does not specifically limit as such a bivalent coupling group, Specifically, an alkylene group, an arylene group, an aralkylene group, and an alkyleneoxy group are mentioned, As an alkylene group, a methylene group, ethylene group, n-propylene Group, n-butylene group and the like. Examples of the arylene group include a phenylene group, a naphthylene group, and a biphenylene group. Examples of the aralkylene group include a benzylene group and a phenethylene group. Examples of the alkyleneoxy group include an ethyleneoxy group, a propyleneoxy group, a polyethyleneoxy group, and a polypropyleneoxy group. The divalent linking group preferably has an ester bond, urea bond, urethane bond or amide bond in the structure, and more preferably has a structure containing an alkyleneoxy group. A plurality of L may be the same or different.

X represents an alkyl group, an aryl group or a heterocyclic group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an iso-pentyl group, a 2-ethyl-hexyl group, an octyl group, and a decyl group. The aryl group is, for example, a monocyclic or condensed aromatic group having 6 to 30 carbon atoms, preferably a monocyclic or condensed aromatic group having 6 to 20 carbon atoms, and more preferably a phenyl group or a naphthyl group. It is. Examples of the heterocyclic group include pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, oxazole, thiazole, oxadiazole, thiadiazole and the like. A plurality of X may be the same or different and are preferably an alkyl group or a heterocyclic group. The alkyl group may further have a substituent, and examples of the substituent include those having the same meaning as the substituent in A ₁ of the general formula (1). Preferred examples of the heterocyclic group include imidazole, 1,2,3-triazole, 1,2,4-triazole, and tetrazole.

  The compound represented by the general formula (1) in the present invention can be easily synthesized by methods that can be assumed by those skilled in the art.

  Although the specific example of a compound represented by General formula (1) based on this invention below is shown, it is not limited to these.

[Basic structure of display element]
In the display element of the present invention, the display portion is provided with a corresponding electrode (display electrode). The display electrode is provided with a transparent electrode such as an ITO electrode, and the other counter electrode is provided with a conductive electrode. Between the display electrode and the counter electrode, an electrolyte layer containing an organic solvent, a metal salt compound, a silver salt solvent and a compound represented by the general formula (1) according to the present invention is included, By applying positive and negative polarities, white display and black display can be switched reversibly.

〔substrate〕
The substrate that can be used in the present invention is preferably a transparent substrate. Examples of such a transparent substrate include polyester (for example, polyethylene terephthalate), polyimide, polymethyl methacrylate, polystyrene, polypropylene, polyethylene, and polyamide. Nylon, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyether sulfone, silicone resin, polyacetal resin, fluororesin, cellulose derivative, polyolefin and other polymer films, plate substrates, glass substrates and the like are preferably used. The transparent substrate used in the present invention refers to a substrate having a visible light transmittance of at least 50%.

  Further, as the counter substrate, for example, an opaque substrate such as an inorganic substrate such as a metal substrate or a ceramic substrate can be used.

〔electrode〕
(Display electrode)
Of the pair of opposed electrodes, the electrode (display electrode) located on the display side is preferably a transparent electrode. The transparent electrode is not particularly limited as long as it is transparent and conducts electricity. For example, Indium Tin Oxide (ITO: Indium Tin Oxide), Indium Zinc Oxide (IZO: Indium Zinc Oxide), Fluorine Doped Tin Oxide (FTO), Indium Oxide, Zinc Oxide, Platinum, Gold, Silver, Rhodium, Copper, Examples thereof include chromium, carbon, aluminum, silicon, amorphous silicon, and BSO (Bismuth Silicon Oxide). In addition, polythiophene, polypyrrole, polyaniline, polyacetylene, polyparaphenylene, polyselenophenylene, etc., and their modifying compounds can be used alone or in combination.

  Display electrodes include transparent conductive oxides such as Indium Tin Oxide (ITO: Indium Tin Oxide), Indium Zinc Oxide (IZO: Indium Zinc Oxide), Fluorine Doped Tin Oxide (FTO), Indium Oxide, Zinc Oxide, etc. It is preferable that it is an electrode.

  The surface resistance value is preferably 100Ω / □ or less, and more preferably 10Ω / □ or less. The thickness of the transparent electrode is not particularly limited, but is generally 0.1 to 20 μm.

  As one aspect of the transparent electrode, a nanoporous electrode having a nanoporous structure can be provided on the transparent electrode. This nanoporous electrode is substantially transparent when a display element is formed, and can carry an electroactive substance such as an electrochromic dye.

  The nanoporous structure as used in the present invention refers to a state in which an infinite number of nanometer-sized pores exist in a layer, and ionic species contained in the electrolyte can move within the nanoporous structure.

  As a method for forming such a nanoporous electrode, a dispersion containing fine particles constituting the nanoporous electrode is formed in layers by an inkjet method, a screen printing method, a blade coating method, etc., and then at a predetermined temperature. Method of making porous by heating, drying and firing, and method of making nanoporous by anodizing and photoelectrochemical etching after electrode layer is formed by sputtering method, CVD method, atmospheric pressure plasma method, etc. Etc. Also, the sol-gel method, Adv. Mater. It can also be formed by the method described in 2006, 18, 2980-2983.

The main components of the fine particles constituting the nanoporous electrode are metals such as Cu, Al, Pt, Ag, Pd and Au, metal oxides such as ITO, SnO ₂ , TiO ₂ and ZnO, carbon nanotubes, glassy carbon, It can be selected from carbon electrodes such as diamond-like carbon and nitrogen-containing carbon, and is preferably selected from metal oxides such as ITO, SnO ₂ , TiO ₂ , and ZnO.

  In order for the nanoporous electrode to have transparency, it is preferable to use fine particles having an average particle diameter of about 5 nm to 10 μm. As the shape of the fine particles, an arbitrary shape such as an indefinite shape, a needle shape, or a spherical shape can be used. The film thickness of the nanoporous electrode is preferably in the range of 0.1 to 10 μm, more preferably in the range of 0.25 to 5 μm.

(Counter electrode)
The counter electrode can be used without particular limitation as long as it conducts electricity.

  As a constituent material of the counter electrode, in addition to the same material as the transparent electrode, metals such as platinum, gold, silver, copper, aluminum, zinc, nickel, titanium, bismuth and alloys thereof, carbon, etc. have no transparency. A material can also be preferably used.

<Porous carbon electrode>
In the present invention, a porous carbon electrode can also be used. Examples of porous carbon electrodes that can be adsorbed and supported include graphite, non-graphitizable carbon, graphitizable carbon, composite carbon, and carbon compounds obtained by doping carbon with boron, nitrogen, phosphorus, etc. Can be mentioned. Examples of the shape of the carbon particles include mesophase microspheres and fibrous graphite. Mesophase spherules are obtained by firing coal tar pitch or the like at 350 to 500 ° C. When these spherules are further classified and graphitized by high temperature firing, a good porous carbon electrode is obtained. Further, fibrous graphite can be obtained from pitch-based, PAN-based, and vapor-grown fibers.

<Auxiliary electrode>
An auxiliary electrode can be attached to at least one of the pair of opposing electrodes according to the present invention. The auxiliary electrode is preferably made of a material having a lower electrical resistance than the main electrode portion. For example, metals such as platinum, gold, silver, copper, aluminum, zinc, nickel, titanium, and bismuth, and alloys thereof can be preferably used.

  The auxiliary electrode can be installed either between the main electrode portion and the substrate, or on the surface of the main electrode portion opposite to the substrate. In any case, it is only necessary that the auxiliary electrode is electrically connected to the main electrode portion.

  There are no particular restrictions on the arrangement pattern of the auxiliary electrodes. It can be suitably formed according to the required performance, such as a straight line, a mesh, or a circle. When the main electrode part is divided into a plurality of parts, the divided electrode parts may be connected to each other. However, in the case where the main electrode portion is a transparent electrode provided on the substrate on the display side, the auxiliary electrode is required to be provided with a shape and frequency that do not impair the visibility of the display element.

  As a method of forming the auxiliary electrode, a known method can be used. For example, a patterning method by photolithography, a printing method, an ink jet method, electrolytic plating or electroless plating, or a method of forming a pattern by exposing and developing using a silver salt photosensitive material may be used. Although the line width and the line interval of the auxiliary electrode pattern may be arbitrary values, it is necessary to increase the line width in order to increase the conductivity. On the other hand, when the auxiliary electrode is attached to the transparent electrode, the area coverage of the auxiliary electrode viewed from the display element observation side is preferably 30% or less, and more preferably 10% or less, from the viewpoint of visibility.

  Thus, the line width of the auxiliary electrode is preferably 1 μm or more and 100 μm or less from the viewpoint of transmittance and conductivity, and the line interval is preferably 50 μm to 1000 μm.

(Method of forming electrode)
A known method can be used to form the transparent electrode (display electrode) and the metal auxiliary electrode (counter electrode). For example, a method of depositing a mask on a substrate by sputtering or the like, a method of patterning by photolithography after forming the entire surface, and the like can be given. Electrodes can also be formed by electrolytic plating, electroless plating, printing methods, and ink jet methods.

  After forming an electrode pattern including a catalyst layer having a monomer polymerization ability on a substrate using an inkjet method, after polymerizing with the catalyst, a monomer component that can become a conductive polymer layer is added to polymerize the monomer component. Furthermore, a metal electrode pattern can be formed by performing metal plating such as silver on the conductive polymer layer, and the process can be greatly simplified since no photoresist or mask pattern is used. .

  When the electrode material is formed by a coating method, for example, a known method such as a dipping method, a spinner method, a spray method, a roll coater method, a flexographic printing method, a screen printing method, or the like can be used.

  Among the ink jet methods, the following electrostatic ink jet method can continuously print a high-viscosity liquid with high accuracy, and is preferably used for forming the transparent electrode and the metal auxiliary electrode according to the present invention. The viscosity of the ink is preferably 30 mPa · s or more, more preferably 100 mPa · s or more.

<Electrostatic inkjet method>
In the display element of the present invention, at least one of the transparent electrode of the composite electrode and the metal auxiliary electrode has a liquid discharge head having a nozzle with an internal diameter of 30 μm or less for discharging a charged liquid, and supplies a solution into the nozzle. It is one of the preferable embodiments that the liquid discharge device is provided with a supply unit that performs the discharge and a discharge voltage application unit that applies a discharge voltage to the solution in the nozzle. Furthermore, it is preferable that the solution in the nozzle is formed by using a discharge device provided with a convex meniscus forming means for forming a convexly raised state from the nozzle tip.

  Also provided is an operation control means for controlling the application of the drive voltage for driving the convex meniscus forming means and the application of the discharge voltage by the discharge voltage applying means, and this operation control means applies the discharge voltage by the discharge voltage applying means. It is also preferable to use a liquid ejection apparatus having a first ejection control unit that applies a driving voltage to the convex meniscus forming means when ejecting liquid droplets.

  In addition, an operation control unit that controls driving of the convex meniscus forming unit and voltage application by the discharge voltage applying unit is provided, and the operation control unit includes an operation for raising the solution by the convex meniscus forming unit, and application of the discharge voltage. Using a liquid ejection device that includes a second ejection control unit that performs the operation in synchronization with each other, and the operation control means includes: It is also a preferred form to use a liquid discharge apparatus having a liquid level stabilization control unit that performs operation control for drawing the liquid level inward.

  By producing an electrode pattern using such an electrostatic ink jet, an electrode having excellent on-demand properties, little waste material, and excellent dimensional accuracy can be advantageously obtained.

(Electronic insulation layer)
In the display element of the present invention, an electrical insulating layer can be provided.

  The electronic insulating layer applicable to the present invention may be a layer having both ionic conductivity and electronic insulating properties. For example, a solid electrolyte membrane in which a polymer or salt having a polar group is formed into a film, electronic insulating properties And a porous solid body having a low relative dielectric constant, such as a silicon-containing compound, and the like.

  As a method for forming a porous film, a sintering method (fusion method) (using fine pores formed between particles by partially fusing polymer fine particles or inorganic particles by adding a binder or the like), extraction method (After forming a constituent layer with a solvent-soluble organic substance or inorganic substance and a binder that does not dissolve in the solvent, the organic substance or inorganic substance is dissolved with the solvent to obtain pores), heating or degassing the polymer, etc. Well-known formation such as foaming method for foaming, phase change method for phase separation of polymer mixture by manipulating good solvent and poor solvent, radiation irradiation method for radiating various radiations to form pores The method can be used.

  Specifically, Japanese Patent Application Laid-Open Nos. 10-30181, 2003-107626, 7-95403, Japanese Patent Nos. 2635715, 2849523, 29987474, 3066426, 3464513, 3483644. , 3535942 and 306203, and the like.

〔Electrolytes〕
(Organic solvent)
An organic solvent is used for the electrolyte according to the present invention. The organic solvent preferably has a boiling point in the range of 120 to 300 ° C., for example, propylene carbonate, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, butylene carbonate, γ-butyl lactone, sulfolane, dimethyl sulfoxide, butyronitrile. , Propionitrile, acetonitrile, acetylacetone, 4-methyl-2-pentanone, 2-butanol, 1-butanol, 2-propanol, 1-propanol, acetic anhydride, ethyl acetate, ethyl propionate, dimethoxyethane, diethoxyfuran, Tetrahydrofuran, ethylene glycol, diethylene glycol, triethylene glycol monobutyl ether, tricresyl phosphate, 2 ethylhexyl phosphate Dioctyl phthalate, and di-octyl sebacate and the like.

(Metal salt compound)
A metal salt compound is used for the electrolyte according to the present invention. The metal salt compound according to the present invention may be any compound as long as it contains a metal species that can be dissolved and precipitated by driving the electrode on at least one electrode. Preferred metal species are silver, bismuth, copper, nickel, iron, chromium, zinc and the like, more preferably silver and bismuth, and particularly preferably silver.

<Silver salt compound>
The silver salt compound according to the present invention is silver or a compound containing silver in the chemical structure, such as silver oxide, silver sulfide, metallic silver, silver colloidal particles, silver halide, silver complex compound, silver ion and the like. There are no particular restrictions on the phase state species such as the solid state, the solubilized state in liquid, and the gas state, and the charged state species such as neutral, anionic, and cationic.

  The metal ion concentration contained in the electrolyte composition according to the present invention is preferably 0.2 mol / kg ≦ [Metal] ≦ 2.0 mol / kg. If the metal ion concentration is 0.2 mol / kg or more, a silver solution having a sufficient concentration can be obtained, and a desired driving speed can be obtained. If the metal ion concentration is 2 mol / kg or less, precipitation is prevented, and storage at low temperature is possible. The stability of the electrolyte is improved.

(Halogen ion, metal ion concentration ratio)
In the display element of the present invention, the molar concentration of halogen ions or halogen atoms contained in the electrolyte is [X] (mol / kg), and silver contained in the electrolyte or the total silver of the compound containing silver in the chemical structure. When the molar concentration is [Metal] (mol / kg), it is preferable to satisfy the condition defined by the following formula (1).

Formula (1): 0 ≦ [X] / [Metal] ≦ 0.1
In the present invention, the halogen atom means an iodine atom, a chlorine atom, a bromine atom, or a fluorine atom. When [X] / [Metal] is greater than 0.1, X ⁻ → X ₂ is generated during the oxidation-reduction reaction of the metal, and X ₂ easily cross-oxidizes with the deposited metal to dissolve the deposited metal. Therefore, the molar concentration of halogen atoms is preferably as low as possible relative to the molar concentration of metallic silver. In the present invention, 0 ≦ [X] / [Metal] ≦ 0.001 is more preferable. In the case of adding halogen ions, the halogen species preferably have a total molar concentration of [I] <[Br] <[Cl] <[F] from the viewpoint of improving memory properties.

  The electrolyte according to the present invention may further contain the following components.

(Supporting electrolyte)
As the supporting electrolyte used in the present invention, salts, acids, and alkalis that are usually used in the field of electrochemistry or the field of batteries can be used. The salt is not particularly limited, and for example, inorganic ion salts such as alkali metal salts and alkaline earth metal salts; quaternary ammonium salts; cyclic quaternary ammonium salts; quaternary phosphonium salts and the like can be used.

Specific examples of the salts include halogen ions, SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF Li salt, Na salt having a counter anion selected from ₆ ⁻ , AsF ₆ ⁻ , CH ₃ COO ⁻ , CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ K salt is mentioned.

Further, halogen ions, SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF ₆ ⁻ , AsF _{6 ^{-, CH 3 COO -, CH}} 3 (C 6 H 4) SO 3 -, and _{(C 2 F 5 SO 2)} 3 C - 4 quaternary ammonium salt having a counter anion selected from, specifically, (CH ₃ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ NF ₄ , (n-C ₄ H ₉ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (n- C ₄ H ₉ ) ₄ NClO ₄ , CH ₃ (C ₂ H ₅ ) ₃ NBF ₄ , (CH ₃ ) ₂ (C ₂ H ₅ ) ₂ NBF ₄ , (CH ₃ ) ₄ NSO ₃ CF ₃ , (C ₂ H ₅ ) ₄ NSO ₃ CF ₃ , (n-C ₄ H ₉ ) ₄ NSO ₃ CF ₃ ,

Etc.

Further, halogen ions, SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF ₆ ⁻ , AsF _{6 ^{-, CH 3 COO -, CH}} 3 (C 6 H 4) SO 3 -, and _{(C 2 F 5 SO 2)} 3 C - phosphonium salt having a counter anion selected from, specifically, _(CH 3) ₄ PBF ₄ , (C ₂ H ₅ ) ₄ PBF ₄ , (C ₃ H ₇ ) ₄ PBF ₄ , (C ₄ H ₉ ) ₄ PBF _{4 and the} like. Moreover, these mixtures can also be used suitably.

  As the supporting electrolyte according to the present invention, a quaternary ammonium salt is preferable, and a quaternary spiro ammonium salt is particularly preferable.

  The amount of the electrolyte salt used is arbitrary, but it is generally desirable that the electrolyte salt be present in the solvent at an upper limit of 20 M or less, preferably 10 M or less, more preferably 5 M or less, and the lower limit is usually 0. It is desirable that it be present at 0.01M or higher, preferably 0.05M or higher, more preferably 0.1M or higher.

(Silver salt solvent)
In the present invention, the electrolyte preferably contains a compound represented by the following general formula (G1) or general formula (G2) in order to promote dissolution and precipitation of metal salts (particularly silver salts).

  The compounds represented by the general formulas (G1) and (G2) are compounds that promote the solubilization of silver in the electrolyte in order to cause dissolution and precipitation of silver in the present invention. In general, in order to cause dissolution and precipitation of silver, it is necessary to solubilize silver in the electrolyte. For example, it causes a coordinate bond with silver or a weak covalent bond with silver. Compounds containing chemical structural species that interact with silver are useful. As the chemical structural species, halogen atoms, mercapto groups, carboxyl groups, imino groups and the like are known, but in the present invention, compounds containing thioether groups and mercaptoazoles are useful as silver solvents and It has a feature that it has little influence on coexisting compounds and high solubility in a solvent.

(Compound represented by General Formula (G1))
General Formula _{(G1) Rg 11 -S-Rg} 12
In the formula, Rg ₁₁ and Rg ₁₂ each represent a substituted or unsubstituted hydrocarbon group. Further, these hydrocarbon groups may contain one or more nitrogen atoms, oxygen atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and Rg ₁₁ and Rg ₁₂ may be linked to each other to form a cyclic structure. .

  Examples of groups that can be substituted for the hydrocarbon group include amino groups, guanidino groups, quaternary ammonium groups, hydroxyl groups, halogen compounds, carboxylic acid groups, carboxylate groups, amide groups, sulfinic acid groups, sulfonic acid groups, and sulfates. Groups, phosphonic acid groups, phosphate groups, nitro groups, cyano groups and the like.

  Hereinafter, specific examples of the compound represented by the general formula (G1) according to the present invention will be shown, but the present invention is not limited only to these exemplified compounds.

G1-1: CH ₃ SCH ₂ CH ₂ OH
G1-2: HOCH ₂ CH ₂ SCH ₂ CH ₂ OH
G1-3: HOCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OH
G1-4: HOCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OH
G1-5: HOCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂ OH
_{G1-6: HOCH 2 CH 2 OCH 2} CH 2 SCH 2 CH 2 SCH 2 CH 2 OCH 2 CH 2 OH
_{G1-7: H 3 CSCH 2 CH 2} COOH
G1-8: HOOCCH ₂ SCH ₂ COOH
G1-9: HOOCCH ₂ CH ₂ SCH ₂ CH ₂ COOH
G1-10: HOOCCH ₂ SCH ₂ CH ₂ SCH ₂ COOH
G1-11: HOOCCH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ COOH
G1-12: HOOCCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH (OH) CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ COOH
G1-13: HOOCCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH (OH) CH (OH) CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ COOH
G1-14: H ₃ CSCH ₂ CH ₂ CH ₂ NH ₂
G1-15: H ₂ NCH ₂ CH ₂ SCH ₂ CH ₂ NH ₂
G1-16: H ₂ NCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ NH _{2
G1-17: H 3 CSCH 2 CH 2} CH (NH 2) COOH
G1-18: H ₂ NCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ NH _{2
G1-19: H 2 NCH 2 CH 2} SCH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 SCH 2 CH 2 NH 2
G1-20: H ₂ NCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ NH ₂
G1-21: HOOC (NH ₂ ) CHCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ CH (NH ₂ ) COOH
G1-22: HOOC (NH ₂ ) CHCH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH (NH ₂ ) COOH
G1-23: HOOC (NH ₂ ) CHCH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH (NH ₂ ) COOH
_{G1-24: H 2 N (O =} ) CCH 2 SCH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 SCH 2 C (= O) NH 2
_{G1-25: H 2 N (O =} ) CCH 2 SCH 2 CH 2 SCH 2 C (O =) NH 2
_{G1-26: H 2 NHN (O =} ) CCH 2 SCH 2 CH 2 SCH 2 C (= O) NHNH 2
_{G1-27: H 3 C (O =} ) CNHCH 2 CH 2 SCH 2 CH 2 SCH 2 CH 2 NHC (O =) CH 3
_{G1-28: H 2 NO 2 SCH 2} CH 2 SCH 2 CH 2 SCH 2 CH 2 SO 2 NH 2
_{G1-29: NaO 3 SCH 2 CH 2} CH 2 SCH 2 CH 2 SCH 2 CH 2 CH 2 SO 3 Na
G1-30: H ₃ CSO ₂ NHCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ NHO ₂ SCH ₃
G1-31: H ₂ N (HN =) CSCH ₂ CH ₂ SC (NH) NH ₂ .2HBr
_{G1-32: H 2 N (HN =} ) CSCH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 SC (NH) NH 2 · 2HCl
_{G1-33: H 2 N (HN =} ) CNHCH 2 CH 2 SCH 2 CH 2 SCH 2 CH 2 NHC (NH) NH 2 · 2HBr
G1-34: [(CH ₃ ) ₃ NCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ N (CH ₃ ) ₃ ] 2 ⁺ · 2Cl ⁻

  Among the above-exemplified compounds, Exemplified Compound G1-2 is particularly preferable from the viewpoint that the objective effect of the present invention can be exhibited.

  (Compound represented by formula (G2))

In the formula, M represents a hydrogen atom, a metal atom or quaternary ammonium. Z represents an atomic group necessary for constituting a nitrogen-containing heterocyclic ring. n represents an integer of 0 to 5, Rg ₂₁ represents a substituent, and when n is 2 or more, each Rg ₂₁ may be the same or different, and may be connected to each other to form a condensed ring. It may be formed.

Examples of the metal atom represented by M in the general formula (G2) include Li, Na, K, Mg, Ca, Zn, and Ag. Examples of the quaternary ammonium include NH ₄ , N (CH ₃ ) ₄ , N (C ₄ H ₉ ) ₄ , N (CH ₃ ) ₃ C ₁₂ H ₂₅ , N (CH ₃ ) ₃ C ₁₆ H ₃₃ , N (CH ₃ ) ₃ CH ₂ C ₆ H _{5 and the} like It is done.

  Examples of the nitrogen-containing heterocycle having Z as a constituent in general formula (G2) include, for example, a tetrazole ring, a triazole ring, an imidazole ring, an oxadiazole ring, a thiadiazole ring, an indole ring, an oxazole ring, a benzoxazole ring, and a benzimidazole Ring, benzothiazole ring, benzoselenazole ring, naphthoxazole ring and the like.

The substituents represented by Rg ₂₁ of the general formula (G2), is not particularly limited, include, for example, substituents as described below.

  Halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom) Alkyl group (eg, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, octyl, dodecyl) , Hydroxyethyl, methoxyethyl, trifluoromethyl, benzyl, etc.), aryl groups (eg, phenyl, naphthyl, etc.), alkylcarbonamide groups (eg, acetylamino, propionylamino, butyroylamino, etc.), arylcarbonamide groups ( For example, benzoylamino etc.), alkylsulfonamide groups (eg methanesulfonylamino group, ethanesulfonylamino group etc.), arylsulfonamide groups (eg benzenesulfonylamino group, toluenesulfonylamino group etc.), Alkyloxy group (eg, phenoxy), alkylthio group (eg, methylthio, ethylthio, butylthio, etc.), arylthio group (eg, phenylthio group, tolylthio group, etc.), alkylcarbamoyl group (eg, methylcarbamoyl, dimethylcarbamoyl, ethylcarbamoyl, diethyl) Carbamoyl, dibutylcarbamoyl, piperidylcarbamoyl, morpholylcarbamoyl, etc.), arylcarbamoyl groups (eg, phenylcarbamoyl, methylphenylcarbamoyl, ethylphenylcarbamoyl, benzylphenylcarbamoyl, etc.), alkylsulfamoyl groups (eg, methylsulfamoyl, Dimethylsulfamoyl, ethylsulfamoyl, diethylsulfamoyl, dibutylsulfamoyl, piperidylsulfamoy , Morpholylsulfamoyl, etc.), arylsulfamoyl groups (eg, phenylsulfamoyl, methylphenylsulfamoyl, ethylphenylsulfamoyl, benzylphenylsulfamoyl, etc.), alkylsulfonyl groups (eg, methanesulfonyl) Group, ethanesulfonyl group, etc.), arylsulfonyl group (for example, phenylsulfonyl, 4-chlorophenylsulfonyl, p-toluenesulfonyl, etc.) alkoxycarbonyl group (for example, methoxycarbonyl, ethoxycarbonyl, butoxycarbonyl, etc.), aryloxycarbonyl group ( For example, phenoxycarbonyl etc.), alkylcarbonyl groups (eg acetyl, propionyl, butyroyl etc.), arylcarbonyl groups (eg benzoyl group, alkylbenzoyl groups etc.), acyl Ruoxy group (for example, acetyloxy, propionyloxy, butyroyloxy, etc.), heterocyclic group (for example, oxazole ring, thiazole ring, triazole ring, selenazole ring, tetrazole ring, oxadiazole ring, thiadiazole ring, thiazine ring, triazine ring, Benzoxazole ring, benzthiazole ring, indolenine ring, benzselenazole ring, naphthothiazole ring, triazaindolizine ring, diazaindolizine ring, tetraazaindolizine ring group). These substituents further include those having a substituent.

  Next, although the preferable specific example of a compound represented by general formula (G2) is shown, this invention is not limited to these compounds.

  Among the above-exemplified compounds, Exemplified Compounds G2-12, G2-18, and G2-20 are particularly preferable from the viewpoint that the object and effects of the present invention can be exhibited.

(Auxiliary compound (promoter) that can be redox)
In the display element of the present invention, for the purpose of promoting dissolution and precipitation of a metal salt compound (especially silver salt), an auxiliary compound (hereinafter referred to as “redox”) that can be exchanged with electrons by applying voltage to the electrode to be oxidized and reduced. , Referred to as a promoter) is preferably added. Particularly preferred are compounds that can be oxidized and reduced at an applied voltage of ± 3 V or less. For example, when an EC compound or metal salt compound is oxidized (or reduced) on the display electrode side, a high concentration can be obtained with a low driving voltage by using a reduction (or oxidation) reaction of the promoter on the counter electrode side. It becomes. The promoter may be one that does not change the optical density in the visible region (400 to 700 nm) as a result of the oxidation-reduction reaction, or one that changes, that is, the EC compound, or may be immobilized on the electrode. Although it may be added to the electrolyte, it is preferable that at least one promoter is immobilized on the counter electrode.

  The redox characteristics of the promoter can be confirmed using cyclic voltammetry or the like that sweeps the electrode potential linearly and measures the response current.

  Preferred promoters that can be used in the present invention include, for example, the following compounds.

1) N-oxyl derivatives typified by TEMPO, N-hydroxyphthalimide derivatives, hydroxamic acid derivatives, etc., compounds having an N—O bond 2) Allyloxy free radicals introduced with bulky substituents at the o-position, such as galvinoxyl 3) Ferrocene and other metallocene derivatives 4) Benzyl (diphenylethanedione) derivatives 5) Tetrazolium salts / formazan derivatives 6) Azine compounds such as phenazine, phenothiazine, phenoxazine, acridine 7) Pyridinium compounds such as viologen.

  In addition, hydrazyl free radical compounds such as benzoquinone derivatives, verdazyl, thiazyl free radical compounds, hydrazone derivatives, phenylenediamine derivatives, triallylamine derivatives, tetrathiafulvalene derivatives, tetracyanoquinodimethane derivatives, thianthrene derivatives, etc. can also be used as promoters. .

  In the display element of the present invention, promoters in the categories 1) and 3) are preferable, and metallocene derivatives are particularly preferable.

  A metallocene derivative is a general term for organometallic compounds having two cyclopentadienyl anions as ligands. The metal is not necessarily bicoordinate, and other ligands may be coordinated. A typical example is ferrocene. Ferrocene is preferred as a promoter according to the present invention because ferrocene undergoes one-electron oxidation at a potential as low as about 0.5 V with respect to a saturated calomel electrode (SCE) and exhibits extremely stable redox characteristics.

In order to the promoter is immobilized on the counter _{electrode, -CO 2 H, -P = O} (OH) 2, -OP = O (OH) 2, -SO 3 H or -Si (OR) ₃ (R represents an alkyl group) and the like, most preferably —Si (OR) ₃ . These groups are chemically bonded to the hydroxyl groups on the counter electrode and immobilized.

(White scattered matter)
In the display element of the present invention, it is preferable to contain a white scatterer from the viewpoint of further increasing the display contrast and white display reflectance, and a porous white scattering layer may be formed and present.

  The porous white scattering layer applicable to the present invention can be formed by applying and drying an aqueous mixture of an aqueous polymer and a white pigment that is substantially insoluble in the electrolyte solvent.

  In the present invention, “substantially not dissolved in an electrolyte solvent” is defined as a state in which the dissolved amount per kg of electrolyte solvent is 0 g or more and 10 g or less at a temperature of −20 ° C. to 120 ° C. The amount of dissolution can be determined by a known method such as a component determination method using a chromatogram or a gas chromatogram.

  In the present invention, examples of the water-based polymer that does not substantially dissolve in the electrolyte solvent include a water-soluble polymer and a polymer dispersed in the water-based solvent.

Examples of water-soluble compounds include proteins such as gelatin and gelatin derivatives, cellulose derivatives, natural compounds such as polysaccharides such as starch, gum arabic, dextran, pullulan and carrageenan, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, and acrylamide polymers. And synthetic polymer compounds such as derivatives thereof. As gelatin derivatives, acetylated gelatin, phthalated gelatin, polyvinyl alcohol derivatives as terminal alkyl group-modified polyvinyl alcohol, terminal mercapto group-modified polyvinyl alcohol, and cellulose derivatives include hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose and the like. It is done. Furthermore, Research Disclosure and those described in JP-A No. 64-13546, pages 71 to 75, U.S. Pat. No. 4,960,681, JP-A No. 62-245260, etc. Highly water-absorbing polymers, ie, homopolymers of vinyl monomers having —COOM or —SO ₃ M (M is a hydrogen atom or an alkali metal) or these vinyl monomers or other vinyl monomers (for example, sodium methacrylate, ammonium methacrylate) Copolymers with potassium acrylate, etc.) are also used. These binders can be used in combination of two or more.

  In the present invention, polyvinyl alcohol, polyethylene glycol, and polyvinylpyrrolidone compounds can be preferably used.

  Polymers dispersed in an aqueous solvent include latexes such as natural rubber latex, styrene butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, isoprene rubber, polyisocyanate, epoxy, acrylic, silicon, polyurethane, Examples thereof include a thermosetting resin in which urea, phenol, formaldehyde, epoxy-polyamide, melamine, alkyd resin, vinyl resin and the like are dispersed in an aqueous solvent. Of these polymers, it is preferable to use an aqueous polyurethane resin described in JP-A-10-76621.

  The average molecular weight of the water-based polymer according to the present invention is preferably in the range of 10,000 to 2,000,000, more preferably in the range of 30,000 to 500,000 in terms of weight average molecular weight.

  Examples of the white pigment applicable in the present invention include titanium dioxide (anatase type or rutile type), barium sulfate, calcium carbonate, aluminum oxide, zinc oxide, magnesium oxide and zinc hydroxide, magnesium hydroxide, magnesium phosphate, Magnesium hydrogen phosphate, alkaline earth metal salt, talc, kaolin, zeolite, acidic clay, glass, organic compounds such as polyethylene, polystyrene, acrylic resin, ionomer, ethylene-vinyl acetate copolymer resin, benzoguanamine resin, urea-formalin resin, A melamine-formalin resin, a polyamide resin, or the like may be used alone or in combination, or in a state having voids that change the refractive index in the particles.

In the present invention, titanium dioxide is preferably used among the above white particles. In particular, titanium dioxide surface-treated with an inorganic oxide (Al ₂ O ₃ , AlO (OH), SiO _2, etc.), and in addition to these surface treatments, Titanium dioxide subjected to organic treatment such as methylolethane, triethanolamine acetate, trimethylcyclosilane is more preferably used. Of these white particles, it is more preferable to use titanium oxide or zinc oxide from the viewpoint of preventing coloring at high temperature and the reflectance of the element due to the refractive index.

  In the present invention, the water mixture of the water-based compound and the white pigment is preferably in a form in which the white pigment is dispersed in water according to a known dispersion method. The mixing ratio of the aqueous compound / white pigment is preferably 1 to 0.01, more preferably 0.3 to 0.05 in terms of volume ratio.

  The thickness of the porous white scattering layer is preferably in the range of 5 to 50 μm, more preferably in the range of 10 to 30 μm.

  As the alcohol solvent, a compound having high solubility in water such as methanol, ethanol, isopropanol is preferably used, and the mixing ratio with the water / alcohol solvent is preferably in a range of 0.5 to 20 in terms of mass ratio. Preferably it is the range of 2-10.

(Solid electrolyte, gel electrolyte)
The electrolyte composition according to the present invention is not limited to a solution electrolyte composed of a solvent or an ionic liquid, but a highly viscous electrolyte or gel electrolyte containing a solid electrolyte or a polymer compound substantially free of a solvent ( Hereinafter, a gel electrolyte) can be used.

  Examples of the solid electrolyte and gel electrolyte applicable to the present invention include a solid electrolyte described in JP-A No. 2002-341387, a polymer solid electrolyte described in JP-A No. 2002-341387, and JP-A No. 2004-20928. A solid polymer electrolyte described in JP-A No. 2004-191945, a solid polymer electrolyte described in JP-A No. 2005-338204, and a polymer described in JP-A No. 2006-323022 Examples thereof include solid electrolytes, solid electrolytes described in JP-A No. 2007-141658, solid electrolytes described in JP-A No. 2007-163865, and gel electrolytes.

(Thickener added with electrolyte)
In the display element of the present invention, a thickener can be used for the electrolyte. For example, gelatin, gum arabic, poly (vinyl alcohol), hydroxyethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, poly ( Vinylpyrrolidone), poly (alkylene glycol), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (styrene-maleic anhydride), copoly ( Styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), poly (urethanes), phenoxy resins, poly (PVC Redene), poly (epoxide) s, poly (carbonates), poly (vinyl acetate), cellulose esters, poly (amides), hydrophobic transparent binders such as polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, polyester, Examples include polycarbonate, polyacrylic acid, polyurethane and the like.

  These thickeners may be used in combination of two or more. Moreover, the compound as described in pages 71-75 of Unexamined-Japanese-Patent No. 64-13546 can be mentioned. Among these, the compounds preferably used are polyvinyl alcohols, polyvinyl pyrrolidones, hydroxypropyl celluloses, polyalkylene glycols, polyvinyl acetals from the viewpoint of compatibility with various additives and improvement in dispersion stability of white particles. It is.

  In the display element of the present invention, polyethylene glycol having an average polymerization degree of 100 to 500 is preferable as a thickener, and it is preferably added in a range of 5 to 20% by mass ratio with respect to the organic solvent of the electrolyte layer.

[Other components of the display element]
In the display element of the present invention, a sealant, a columnar structure, and spacer particles can be used as necessary.

  The sealing agent is used to enclose the electrolyte so that it does not leak out. It is also called a sealing agent. Epoxy resin, urethane resin, acrylic resin, vinyl acetate resin, ene-thiol resin, silicon resin A curing type such as a thermosetting type, a photo-curing type, a moisture-curing type, or an anaerobic curing type such as a modified polymer resin can be used.

  Columnar structures provide strong self-holding (strength) between substrates, for example, cylindrical bodies, square pillars, elliptical pillars, trapezoidal pillars arranged in a predetermined pattern such as a lattice arrangement. A columnar structure such as a body can be mentioned. Alternatively, stripes arranged at predetermined intervals may be used. This columnar structure is not a random array, it can hold the substrate spacing appropriately, such as an evenly spaced array, an array where the distance gradually changes, and an array in which a predetermined layout pattern is repeated at a constant cycle. It is preferable that the sequence is considered so as not to hinder. If the ratio of the area occupied by the columnar structure in the display region of the display element is 1 to 40%, a practically sufficient strength as a display element can be obtained.

  A spacer may be provided between the pair of substrates to keep the gap between the substrates uniform. Examples of the spacer include a sphere made of resin or inorganic oxide. Further, a fixed spacer having a surface coated with a thermoplastic resin is also preferably used. In order to hold the gap between the substrates uniformly, only the columnar structure may be provided, but both the spacer and the columnar structure may be provided, or instead of the columnar structure, only the spacer is used as the space holding member. May be used. When the columnar structure is formed, the diameter of the spacer is equal to or less than the height, and preferably equal to the height. When the columnar structure is not formed, the spacer diameter corresponds to the cell gap thickness.

[Display element driving method]
The driving operation of the display element of the present invention may be simple matrix driving or active matrix driving. The simple matrix driving referred to in the present invention is a driving method in which current is sequentially applied to a circuit in which a positive line including a plurality of positive electrodes and a negative electrode line including a plurality of negative electrodes are opposed to each other in a vertical direction. Say that. By using simple matrix driving, there is an advantage that the circuit configuration and driving IC can be simplified and manufactured at low cost. The active matrix drive is a system in which scanning lines, data lines, and current supply lines are formed in a grid pattern, and are driven by TFT circuits provided in each grid pattern. Since switching can be performed for each pixel, there are merits such as gradation and a memory function. For example, a circuit described in FIG. 5 of Japanese Patent Application Laid-Open No. 2004-29327 can be used.

[Product application]
The display element of the present invention can be used in an electronic book field, an ID card field, a public field, a traffic field, a broadcast field, a payment field, a distribution logistics field, and the like. Specifically, keys for doors, student ID cards, employee ID cards, various membership cards, convenience store cards, department store cards, vending machine cards, gas station cards, subway and railway cards, bus cards, Cash cards, credit cards, highway cards, driver's licenses, hospital examination cards, electronic medical records, health insurance cards, Basic Resident Registers, passports, electronic books, etc.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<< Production of display element >>
[Production of display electrode]
(Production of electrode 1)
An ITO (Indium Tin Oxide) film having a thickness of 300 nm was formed on a 2 cm × 4 cm glass substrate having a thickness of 1.5 mm according to a sputtering method, and a transparent electrode (display electrode 1) was produced.

[Preparation of counter electrode]
(Preparation of electrode 2)
On the electrode 1 prepared above, the following titanium dioxide dispersion was screen-printed so that the average film thickness after drying was 20 μm, then dried at 50 ° C. for 30 minutes to evaporate the solvent, and then in an atmosphere at 85 ° C. The electrode 2 which formed the porous white scattering layer by drying for 1 hour was produced.

<Preparation of titanium dioxide dispersion>
After adding Kuraray Poval PVA235 (made by Kuraray Co., Ltd., polyvinyl alcohol resin) to a water / ethanol mixed solution so as to have a solid content concentration of 2% by mass and dissolving by heating, Titanium Dioxide CR-90 made by Ishihara Sangyo Co., Ltd. was added. A titanium dioxide dispersion was prepared by dispersing with an ultrasonic disperser so as to be 20% by mass.

(Preparation of electrode 3)
On electrode 1, ITO ink (X-490CN27, manufactured by Sumitomo Metal Mining Co., Ltd., average particle size: 20 nm) is mixed with zinc oxide particles (20 nm: manufactured by Wako Pure Chemical Industries, Ltd.) so as to be 15% by mass with respect to ITO particles. The mixture was stirred and applied by spin coating. After baking at 180 ° C. and drying, the sample was immersed in dilute nitric acid (diluted nitric acid having a specific gravity of 1.38 10 times), washed and dried. Further, 3% by mass of the following compound (A) (m: n = 6: 1, Mw: about 5000, Mw / Mn: 2.9) was added to anhydrous NMP, and the mixture was stirred for 1 hour at room temperature. Stir for hours. Thereafter, the substrate was dried and washed with methanol to prepare an electrode 3 in which (A) as an auxiliary compound was immobilized on the electrode through a silanol bond.

[Preparation of electrolyte]
(Preparation of electrolyte 1)
To 2.5 g of γ-butyrolactone, 0.025 g of the following SBP / PTS as a supporting electrolyte, 0.2 g of mercapto-1,2,4-triazole as a silver salt solvent, and 0.1 g of silver tosylate as a metal salt compound are dissolved by heating. Thereafter, the electrolyte 1 was prepared by cooling to room temperature.

(Preparation of electrolytes 2-7)
In the preparation of the electrolyte 1, electrolytes 2 to 7 were prepared in the same manner except that the comparative compound or the compound represented by the general formula (1) was added in the types and amounts shown in Table 1.

(Preparation of electrolyte 8)
After sequentially adding and dissolving 0.14 g of mercapto-1,2,4-triazole and 0.14 g of N-methylmercapto-1,2,4-triazole in 1.6 g of γ-butyrolactone, silver trifluoromethanesulfonate 0.14 g was added. After stirring and dissolving at room temperature, 0.1 g of polyethylene glycol 20,000 was added, and a solution prepared by dissolving 0.002 g of ferrocene and 0.02 g of lithium bistrifluorosulfonylimide in 0.2 g of γ-butyrolactone was added. An electrolyte 8 was prepared by adding 1.6 g of titanium dioxide having a particle size of 200 nm and vacuum degassing while stirring.

(Preparation of electrolytes 9 to 19)
In the preparation of the electrolyte 8, the electrolyte 9 was prepared in the same manner except that the comparative compound or the compound represented by the general formula (1) was added in the type and amount shown in Table 1 immediately before the addition of polyethylene glycol 20,000. ~ 19 were prepared.

[Production of display element]
(Preparation of display element 1)
After the periphery of the electrode 2 is edged with an olefin-based sealant containing 10% glass spherical beads having an average particle diameter of 40 μm as a volume fraction, the striped electrodes are orthogonal to each other between the electrodes 2 and 1. And then heated and pressed to produce an empty cell. The electrolyte 1 was vacuum-injected into the empty cell, and the injection port was sealed with an epoxy-based ultraviolet curable resin to produce a display element 1.

(Production of display elements 2 to 21)
In the production of the display element 1, display elements 2 to 21 were produced in the same manner except that the electrolyte 1 and the electrode 2 were changed to the combinations shown in Table 1.

<< Evaluation of display element >>
[Evaluation of contrast retention]
Connect both electrodes of the display element to both terminals of the constant voltage power source, apply a voltage of +1.5 V for 1 second, then apply a voltage of -1.5 V for 0.5 seconds as one cycle, and +1 The reflectance at a wavelength of 550 nm after application of .5V and the reflectance after application of -1.5V were measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing Co., Ltd., and the contrast was obtained to obtain CR ₁ (CR ₁ = (Reflectance after applying + 1.5V) / (Reflectivity after applying -1.5V)). After driving a total of 100 times under the same driving conditions, CR ₁₀₀ was determined by the same method, the contrast retention rate (%) was determined according to the following formula, and evaluated according to the following criteria.

Contrast retention (%) = CR ₁₀₀ / CR ₁ × 100
5: Contrast retention is 80% or more 4: Contrast retention is 65% or more and less than 80% 3: Contrast retention is less than 65% 2: Contrast change can be confirmed, but contrast retention is less than 65% 1: Contrast Cannot be observed visually.

(Evaluation of electrode corrosion)
The display element used for the evaluation of the stability of reflectance when repeatedly driven is disassembled, the display electrode is taken out, and the transmittance (T ₁₀₀ ) of ITO at 380 nm is measured using a spectrophotometer, The electrode corrosion rate was calculated according to the following formula using the transmittance (T ₁ ) of ITO before driving. The evaluation results are also shown in Table 1. It is presumed that the ITO electrode is corroded by repeated driving and the transmittance increases, and the smaller the electrode corrosion rate, the less the electrode corrosion and the better the stability.

Electrode corrosion rate (%) = (1−T ₁ / T ₁₀₀ ) × 100

  From the table, it was possible to provide a display device having an excellent electrode corrosion rate by using an electrolyte containing the compound according to the present invention. Furthermore, since the display element of the present invention is excellent in contrast retention, it has been clarified that it is excellent in repeated driving stability.

Claims (4)

It has a pair of opposing electrodes (display electrode and counter electrode), has an electrolyte layer containing an organic solvent, a metal salt compound, and a compound represented by the following general formula (1) between the electrodes, and applies a voltage A display element which displays black and white by doing so.

(In the formula, A ₁ represents an aliphatic group, an aryl group or a heterocyclic group, n represents an integer of 3 to 6, L represents a divalent linking group, and X represents an alkyl group, an aryl group or a heterocyclic ring. A plurality of L and X may be the same or different.)   The display element according to claim 1, wherein in the general formula (1), X is an alkyl group or a heterocyclic group.   The display element according to claim 1, further comprising an auxiliary compound that can be oxidized and reduced.   The display element according to claim 3, wherein the auxiliary compound that can be oxidized and reduced is fixed to the display electrode and the counter electrode.