WO2010140420A1 - Display element - Google Patents

Abstract

Disclosed is a display element which has high rewrite speed at low voltage and is stably driven repeatedly, and in which corrosion of an electrodes is reduced. Specifically disclosed is a display element which has an electrolyte layer between a pair of electrodes facing each other, and displays an image through application of a voltage. The display element is characterized in that the electrolyte layer contains a compound having a thioether chain and at least one carbonyl group, the thioether chain accounts for 30-99% by mass of the entire compound, and the compound as a whole does not contain a dissociative proton.

Description

Display element

The present invention relates to an electrochemical display element using a novel electrolyte layer composition.

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 a means for browsing such electronic information, conventional liquid crystal displays and CRTs, and in recent years, light-emitting types such as organic EL displays are mainly used. However, when the electronic information is document information, it is necessary to keep an eye on the browsing means for a relatively long time, and these actions are hardly human-friendly means.

In general, it has been pointed out that the disadvantages of light-emitting displays are flickering eyes, inconvenient to carry, limited reading posture, need to adjust the line of sight to a static screen, and increased power consumption when read for a long time. .

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

That is, the method using a polarizing plate such as a reflective liquid crystal has a difficulty in white display because the reflectance is as low as about 40%. In addition, since the polymer dispersed liquid crystal requires a high voltage and uses a difference in refractive index between organic substances, the contrast of an obtained image is not sufficient.

Also, the polymer network type liquid crystal has problems such as a high voltage and a complicated TFT circuit required to improve the memory performance. In addition, a display element using an electrophoresis method needs a high voltage of 10 V or more, and there is a concern about durability due to electrophoretic particle aggregation.

An electrodeposition method (hereinafter abbreviated as “ED method”) using dissolution precipitation of a metal or a metal salt is known as a display method that eliminates the drawbacks of each of the above-described methods. The ED method can be driven at a low voltage of 3 V or less, has advantages such as a simple cell configuration, excellent black-white contrast and black quality, and various methods have been disclosed (for example, Patent Document 1). To 3).

In addition, it is known that a mercaptoazole-based compound is used in the ED method, particularly in the ED method using a silver salt compound as a metal salt (see, for example, Patent Document 4). In Patent Document 5, it is known to use a thioether compound.

Patent Documents 4 and 5 show that a memory property is improved by containing a mercaptoazole compound or a thioether compound, but it is still not sufficient. Further, in an ED display element, the electrode is electrolyzed. Although it is considered that the electrode is easily corroded because it is in direct contact with the liquid, there is no mention of electrode corrosion prevention.

In order to improve the durability of the ED method in this way, it is considered to be an important issue to prevent the corrosion of the electrode. However, the corrosion of the electrode is not reduced without reducing other performances such as rewriting speed and repeated driving stability. An effective technique for preventing this problem has not yet been found, and improvement has been desired.

U.S. Pat. No. 4,240,716 Japanese Patent No. 3428603 JP 2003-241227 A Japanese Patent Laid-Open No. 2005-266652 JP 2009-98226 A

The present invention has been made in view of the above-described problems and circumstances, and a problem to be solved is to provide a display element that has a fast rewriting speed at a low voltage, a stable repetitive driving, and a little corrosion of electrodes.

The above object of the present invention can be achieved by the following configuration.

1. In a display element having an electrolyte layer between a pair of opposing electrodes and displaying an image by applying a voltage, the electrolyte layer is a compound having a thioether chain and at least one carbonyl group, and the entire compound A display element comprising: a compound having no dissociative protons.

2. 2. The display element according to 1 above, wherein the thioether chain occupies 30 to 99% by mass of the entire compound.

3. 3. The display element according to 1 or 2 above, wherein the compound is represented by the following general formula (1).

In the formula, X represents a sulfur atom or an oxygen atom, and at least one X in the compound is a sulfur atom. n and m represent an integer of 1 to 10, and a represents an integer of 1 to 50.

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ each represent a substituent that does not have a dissociable proton, one of which includes a carbonyl group. Further, they may be the same or different, and may be linked together to form a cyclic structure.

[] Represents a repeating unit, and when it is repeated, the atoms represented by X may be different from each other. In that case, R ₁ and R ₂ may be different from each other, and the integer represented by m may be different.

4). 4. The display device as described in 3 above, wherein R ₅ and R ₆ in the compound have a carbonyl group.

5. 5. The display element as described in 3 or 4 above, wherein n and m are 2 or 3.

6. 6. The display element according to any one of 3 to 5, wherein a is 2 or 3.

7. 7. The display element according to any one of 1 to 6, wherein the electrolyte layer contains an auxiliary compound that can be oxidized and reduced.

By means of the present invention, it is possible to provide a display element that has a high rewriting speed at a low voltage, a stable repetitive driving, and little electrode corrosion.

The display element of the present invention is a display element that has an electrolyte layer between a pair of opposed electrodes and displays an image by applying a voltage. The electrolyte layer is a compound having a thioether chain and at least one carbonyl group, the thioether chain accounting for 30 to 99% by mass of the entire compound, and the compound as a whole does not have a dissociable proton (Hereinafter abbreviated as the thioether compound of the present invention).

As an embodiment of the present invention, of a pair of opposing electrodes, an electrode positioned on the display side (hereinafter referred to as a display side electrode) is made of a transparent conductive oxide, and the electrolyte layer is the thioether compound of the present invention. In addition, it is preferable to further contain an auxiliary compound that can be oxidized and reduced.

Hereinafter, the present invention, its components, and the best mode and mode for carrying out the present invention will be described in detail.
<Thioether compound of the present invention>
The thioether compound of the present invention is a compound in the same category as the “metal salt solvent” used for promoting dissolution and precipitation of metal salts (particularly silver salts) in ED display elements. In particular, heterocyclic thiol compounds such as mercaptoazole are often used as the silver salt solvent, and the structural features are sulfur, which is said to interact with metal ions in the alkyl chain, compared to these known silver salt solvents. The point is that an atom is incorporated, and that at least one carbonyl group, which is also supposed to interact with a metal ion, is present and dissociable protons are excluded.

The thioether compound of the present invention is a compound having a thioether chain and at least one carbonyl group, the thioether chain occupying 30 to 99% by mass of the whole compound, and the compound as a whole does not have a dissociable proton It is.

As a result of the study by the present inventors, by using such a specific structure, the corrosive force of the compound itself can be suppressed, and a sulfur atom and a carbonyl group are arranged to increase the interaction force with the metal ion. As a result, the corrosion of the electrode was greatly suppressed, the stability during repeated driving was excellent, and the rewriting speed during low voltage driving was further improved. Although the detailed mechanism is unknown, it is speculated that the significant improvement in electrode corrosion is due to the elimination of dissociable protons from the system.

The thioether compound of the present invention preferably has a thioether chain represented by the general formula (1).

In the general formula (1), examples of the substituent represented by R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ include the following substituents as long as they do not have a dissociable proton. It is done.

A halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), 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.), alkoxy groups (eg, methoxy, ethoxy, propoxy, 2-propoxy, butoxy, t -Butoxy group, pentyloxy group, 2-ethylhexyloxy group, trifluoromethoxy group, etc.), dialkylamino group (eg, dimethylamino group, diethylamino group, dibutylamino group, etc.), diarylamino group (eg, diphenylamino group, Ditolylamino group Dimesitylamino group etc.), aryloxy group (eg phenoxy etc.), alkylthio group (eg methylthio, ethylthio, butylthio etc.), arylthio group (eg phenylthio group, tolylthio group etc.), dialkylcarbamoyl group (eg dimethylcarbamoyl, etc.) Diethylcarbamoyl, dibutylcarbamoyl, etc.), diarylcarbamoyl groups (eg, diphenylcarbamoyl, methylphenylcarbamoyl, ethylphenylcarbamoyl, benzylphenylcarbamoyl, etc.), dialkylsulfamoyl groups (eg, dimethylsulfamoyl, diethylsulfamoyl, dibutyl) Sulfamoyl, etc.), diarylsulfamoyl groups (eg, diphenylsulfamoyl, methylphenylsulfamoyl, ethylphenylsulfur) Moyl, benzylphenylsulfamoyl, etc.), alkylsulfonyl groups (eg, methanesulfonyl group, ethanesulfonyl group, etc.), arylsulfonyl groups (eg, phenylsulfonyl, 4-chlorophenylsulfonyl, p-toluenesulfonyl, etc.), alkoxycarbonyl groups (Eg, methoxycarbonyl, ethoxycarbonyl, butoxycarbonyl, etc.), aryloxycarbonyl groups (eg, phenoxycarbonyl, etc.), alkylcarbonyl groups (eg, acetyl, propionyl, butyroyl, etc.), arylcarbonyl groups (eg, benzoyl group, alkylbenzoyl) Group), dialkylaminocarbonyl group (eg, dimethylaminocarbonyl group, diethylaminocarbonyl group, etc.), diarylaminocarbonyl group (eg, diphenylamino group). Ruaminocarbonyl group, ditolylaminocarbonyl group, etc.), acyloxy group (eg, acetyloxy group, propionyloxy group, butyroyloxy group, etc.), carbonyl group, cyano group, or heterocyclic group (eg, 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, etc.), preferably halogen atom, alkyl group, alkoxy group, alkylthio group, acyl group, cyano group, more preferably alkyl group, alkoxy group. Group, al Thio group, a cyano group. These substituents may further have a substituent and may be linked to each other to form a condensed ring.

In the general formula (1), X represents a sulfur atom or an oxygen atom, and at least one X in the compound is a sulfur atom.

In general formula (1), a represents the number of repeating units. In order to have appropriate solubility, it is preferably 1 to 50, preferably 1 to 10. More preferably, it is 1-6.

[] Represents a repeating unit, and when a represents a number of 2 or more, a plurality of Xs are present, and in this case, Xs may be the same or different, and contain a sulfur atom. The larger the amount, the better. The integer represented by m may be the same or different.

In the above case, a plurality of R ₁ and R ₂ are also present, and in that case, they may be the same or different.

The content of the thioether chain of the present invention is 30 to 99% by mass of the whole compound. Preferably, the content is 33 to 85% by mass. Here, the content of the thioether chain refers to the mass% of the whole unit when the X of the unit represented by the general formula (1) is a sulfur atom with respect to the molecular weight of the whole compound.

For example, in exemplary compound A-1 below, the thioether chain has a molecular weight of 120 (SC ₂ H ₄ ) ₂ and the entire molecule is 266, so that it is calculated as 120/266 × 100 = 45 mass%.

Specific examples of the group having a dissociable proton that the thioether compound of the present invention does not have include a hydroxyl group, a sulfo group, a carboxyl group, a sulfato group, a —CONHSO ₂ — group (a sulfonylcarbamoyl group, a carbonylsulfuryl group). Famoyl group), —CONHCO— group (carbonylcarbamoyl group), —SO ₂ NHSO ₂ — group (sulfonylsulfamoyl group), sulfamoyl group, phosphato group, phosphono group, boronic acid group, phenolic hydroxyl group, etc. Depending on the pKa and the surrounding pH, a group capable of dissociating protons may be mentioned.

The thioether compound of the present invention does not have such a group having a dissociative proton as a whole molecule such as a thioether chain, a terminal group, and a linking group.

The thioether compound of the present invention has at least one carbonyl group. This carbonyl group is preferably present as a terminal group of the compound or as a substituent of the thioether chain or a linking group of the terminal group and the thioether chain. It is preferable that R ₅ and R ₆ have the carbonyl group.

The number of carbonyl groups is preferably 1 to 10, preferably 2 to 6 in one molecule. The terminal group is preferably a group having no dissociable proton such as an alkyl group, an alkenyl group, and an aryl group.

In the thioether compound of the present invention, the carbonyl group and the thioether chain are bonded directly or through a linking group. The linking group is preferably divalent to tetravalent. The linking group is a group that does not have a dissociable proton.

The use of the thioether compound of the present invention makes it possible to promote dissolution and precipitation of metal salts (particularly silver salts), that is, an improvement in rewriting speed during low-voltage driving is achieved. Furthermore, the electrode corrosion of the ITO electrode can be suppressed.

In general, in order to cause dissolution and precipitation of a metal, it is necessary to solubilize the metal in the electrolyte, for example, a metal that causes a coordinate bond with the metal and a weak covalent bond with the metal. It is considered that a compound containing a chemical structural species that interacts with is useful.

With particular attention to silver as a metal species, it is known that halogen atoms, mercapto groups, carboxyl groups, imino groups, and the like are chemical structural species that interact with silver. In the present invention, sulfur is present on the alkyl chain. A compound in which an atom (thioether chain) or a carbonyl group is substituted is useful as a silver solvent, has a feature that it has little influence on the coexisting compound and high solubility in the solvent.

The amount of the thioether compound used is generally 30 mol / L or less, preferably 20 mol / L or less, more preferably 10 mol / L or less as the upper limit in the solvent constituting the electrolyte layer. Desirably, the lower limit is usually 0.01 mol / L or more, preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more.

Preferred examples of the thioether compound of the present invention are shown below.

<Basic structure of display element>
In the display element of the present invention, a transparent electrode such as an ITO electrode is provided on the electrode 1 that is an electrode (display-side electrode) close to the display part among the pair of opposing electrodes, and the electrode 2 far from the other display part is provided. Are provided with conductive electrodes. Between the electrode 1 and the electrode 2, it has the electrolyte layer containing the organic solvent which concerns on this invention, a metal salt compound, the compound represented by General formula (1), etc., and positive / negative between at least a pair of opposing electrodes By applying a bipolar voltage, 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, silicon 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 transmittance for visible light 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 side transparent electrode)
Of the at least one pair of opposing electrodes, the electrode positioned on the display side (display side electrode) is preferably a transparent electrode.

The transparent electrode is not particularly limited as long as it is transparent and can conduct 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).

Also, polythiophene, polypyrrole, polyaniline, polyacetylene, polyparaphenylene, polyselenophenylene, etc., and their modifying compounds can be used alone or in combination.

As an electrode (display side electrode) positioned on the display side, Indium Tin Oxide (ITO: Indium Tin Oxide), Indium Zinc Oxide (IZO: Indium Zinc Oxide), Fluorine Doped Tin Oxide (FTO), Indium Oxide, An electrode made of a transparent conductive oxide such as zinc oxide is preferable.

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.

(Transparent porous electrode)
As one embodiment 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 ink jet method, a screen printing method, a blade coating method, etc., and then heated at a predetermined temperature. A method of making porous by drying, baking, a method of making nanoporous by anodizing or photoelectrochemical etching after forming an electrode layer by sputtering, CVD, atmospheric pressure plasma, etc. Is mentioned. 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, and diamond. It can be selected from carbon electrodes such as 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 be transparent, 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, those having an arbitrary shape such as an indefinite shape, a needle shape, and 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)
Of at least a pair of opposing electrodes, an electrode located on the opposite side of the display side with the electrolyte solution (hereinafter referred to as a counter electrode) is preferably a transparent electrode.

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

As the 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 their alloys, 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 as the counter electrode. 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 can be obtained by firing coal tar pitch or the like at 350 to 500 ° C., and further classifying these spherules and graphitizing by high-temperature firing can provide a good porous carbon electrode. In addition, fibrous graphite can be obtained from pitch-based, PAN-based, and vapor-grown fibers.

(Auxiliary electrode = grid electrode)
An auxiliary electrode can be attached to at least one of the at least one pair of electrodes according to the present invention.

The auxiliary electrode is preferably made of a material having a lower electrical resistance than the main electrode part. 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 is no particular limitation on the arrangement pattern of the auxiliary electrodes. It can be appropriately formed according to the required performance, such as linear, mesh, or circular. 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 for 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.

The line width and line spacing of the auxiliary electrode pattern may be arbitrary values, but it is necessary to increase the line width in order to increase the conductivity. On the other hand, when an auxiliary electrode is attached to the transparent electrode, from the viewpoint of visibility, 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.

Thus, from the viewpoint of transmittance and conductivity, the line width of the auxiliary electrode is preferably 1 μm or more and 100 μm or less, 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 and the metal auxiliary electrode. For example, a method of depositing a mask on a substrate by a sputtering method or the like, a method of patterning by a photolithography method after forming the entire surface, and the like can be given.

Also, electrodes can 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, a monomer component that is polymerized by the catalyst and becomes a conductive polymer layer after polymerization is added, It is also possible to form a metal electrode pattern by polymerizing and further performing metal plating such as silver on the conductive polymer layer, and the process is greatly reduced because no photoresist or mask pattern is used. It can be simplified.

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 is capable of continuously printing a highly viscous 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, and 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 having 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. Further, 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 state where the solution rises from the nozzle tip.

In addition, it comprises operation control means for controlling application of drive voltage for driving the convex meniscus forming means and application of discharge voltage by the discharge voltage application means, and this operation control means applies application of the discharge voltage by the discharge voltage application 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. A liquid discharge device having a second discharge control unit that synchronizes the liquid, and the operation control means includes a liquid level at the tip of the nozzle after the swell operation of the solution and the application of the discharge voltage. It is also a preferred form to use a liquid ejection apparatus having a liquid level stabilization control unit that performs operation control for drawing in the inside.

By producing an electrode pattern using such an electrostatic ink jet, it is advantageous that an electrode having excellent on-demand characteristics, little waste material, and excellent dimensional accuracy can be 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 (fusing method) (using fine pores formed between particles by partially fusing polymer fine particles or inorganic particles by adding a binder, etc.), extraction method ( After forming a constituent layer with a solvent-soluble organic or inorganic substance and a binder that does not dissolve in the solvent, the organic or inorganic substance is dissolved with the solvent to obtain pores), and the polymer is heated or degassed Known forming methods such as a foaming method in which foaming is performed, a phase change method in which a mixture of polymers is phase-separated by operating a good solvent and a poor solvent, and a radiation irradiation method in which pores are formed by radiating various types of radiation Can be used. Specifically, JP-A-10-30181, JP-A-2003-107626, JP-B-7-95403, JP-A-2635715, JP-A-2894523, JP-A-2987474, JP-A-3066426, and JP-A-3464513. No. 3,483,464, No. 3535942, No. 30622203, and the like.
<Electrolyte layer composition>
The electrolyte layer according to the present invention is characterized by containing the metal salt compound and the thioether compound of the present invention. The electrolyte layer composition other than the thioether compound of the present invention will be described in detail below.

[Organic solvent]
The organic solvent that can be used in the electrolyte layer composition according to the present invention 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, Riku registration Le phosphate, 2-ethylhexyl phosphate, dioctyl phthalate, and di-octyl sebacate and the like.

[Metal salt compounds]
The metal salt compound applicable to the display element of the present invention is a salt containing a metal species that can be dissolved and deposited by driving the counter electrode on at least one electrode on the counter electrode. It is preferable. Preferred metal species are silver, bismuth, copper, nickel, iron, chromium, zinc, etc., preferably silver and bismuth, and particularly preferred is silver.

The metal ion concentration contained in the electrolyte layer of 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 layer is improved.

[Silver salt compound]
As the silver salt compound that can be used in the present invention, silver or a compound containing silver in the chemical structure, for example, silver oxide, silver sulfide, metallic silver, silver colloidal particles, silver halide, silver complex compound, silver ion There are no particular restrictions on the phase state species such as the solid state, the solubilized state in liquid, the gas state, and the like, and the charged state species such as neutral, anionic, and cationic.

In the display element of the present invention, silver iodide, silver chloride, silver bromide, silver oxide, silver sulfide, silver citrate, silver acetate, silver behenate, silver p-toluenesulfonate, silver trifluoromethanesulfonate, mercapto It is preferable to use a known silver salt compound such as a silver salt with an acid or a silver complex with iminodiacetic acid. Among these, it is more preferable to use, as the silver salt, a compound that does not have a nitrogen atom having a coordination property with halogen, carboxylic acid, or silver, and for example, silver p-toluenesulfonate is particularly preferable.

[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 layer is [X] (mol / kg), and the molar concentration of metal ions contained in the electrolyte layer is [Metal] ( Mol / kg), it is preferable to satisfy the conditions defined by the following formula (1).

Formula (1)
0 ≦ [X] / [Metal] ≦ 0.01
The halogen atom as used in the field of this invention means an iodine atom, a chlorine atom, a bromine atom, and a fluorine atom. When [X] / [Metal] is larger than 0.01, X ⁻ → X ₂ is generated during the metal redox reaction, 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 case of adding a halogen ion, the halogen species preferably have a total molar concentration of [I] <[Br] <[Cl] <[F] from the viewpoint of improving memory properties.

The following components may be further used in combination with the electrolyte layer composition according to the present invention.

[Supporting electrolyte]
As the supporting electrolyte that can be used in the electrolyte layer composition according to 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 salts are 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 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 NBF 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
Furthermore, the following salts etc. are 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 - 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 lithium salt is preferable, and lithium trifluoromethanesulfonic acid imide is particularly preferable.

The amount of the supporting electrolyte used is arbitrary, but in general, the supporting electrolyte is present in the solvent as an upper limit of 20 mol / L or less, preferably 10 mol / L or less, more preferably 5 mol / L or less. The lower limit is usually 0.01 mol / L or more, preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more.

[Auxiliary compound that can be redox (promoter)]
In the display element of the present invention, an auxiliary compound that can be oxidized and reduced (hereinafter also referred to as a promoter) may be added for the purpose of promoting dissolution and precipitation of metal salts (particularly silver salts). 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 may be one that changes, that is, an electrochromic compound, and is immobilized on the electrode. Or may be added to the electrolyte layer.

Examples of preferred promoters that can be used in the present invention include the following compounds.
1) N-oxyl derivatives such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), N-hydroxyphthalimide derivatives, hydroxamic acid derivatives, etc., compounds having an N—O bond 2) Compounds having an allyloxy free radical with a bulky substituent introduced at the 0-position, such as galvinoxyl, etc. 3) Ferrocene, etc., metallocene derivatives 4) benzyl (diphenylethanedione) derivatives 5) tetrazolium salts / formazan derivatives 6) phenazine, phenothiazine, phenoxy Azine compounds such as sadin and 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 ferrocene derivatives are particularly preferable.

The amount of the auxiliary compound used is generally 20 mol / L or less, preferably 10 mol / L or less, more preferably 5 mol / L or less as the upper limit in the solvent constituting the electrolyte layer. Desirably, the lower limit is usually 0.001 mol / L or more, preferably 0.005 mol / L or more, and more preferably 0.01 mol / L or more.

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

The porous white scattering layer applicable to the present invention is formed by applying and drying an aqueous mixture of an aqueous polymer and a white pigment that does not substantially dissolve in the solvent of the electrolyte layer (hereinafter also referred to as electrolyte solvent). Can do.

The term “substantially insoluble in the electrolyte solvent” as used in the present invention is defined as a state where 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 is substantially insoluble 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, or cellulose derivatives, natural compounds such as starch, gum arabic, dextran, pullulan, and carrageenan polysaccharides, 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.

Further, Research Disclosure and those described on pages (71) to (75) of JP-A No. 64-13546, US Pat. No. 4,960,681, JP-A No. 62-245260, etc. Homopolymers of vinyl monomers having the described superabsorbent polymers, ie —COOM or —SO ₃ M (M is a hydrogen atom or an alkali metal), or between these vinyl monomers or other vinyl monomers (eg, sodium methacrylate, methacryl Copolymers with ammonium acid, 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, the water-based polyurethane resin described in JP-A-10-76621 is preferably used.

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.

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, acid 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, among the white particles, titanium dioxide is preferably used. In particular, titanium dioxide surface-treated with an inorganic oxide (Al ₂ O ₃ , AlO (OH), SiO _2, etc.), in addition to these surface treatments. Titanium dioxide that has been treated with an organic substance such as trimethylolethane, triethanolamine acetate, or trimethylcyclosilane is more preferably used.

Of these white particles, it is more preferable to use titanium oxide or zinc oxide from the viewpoint of coloring prevention at high temperature and the reflectance of the element due to the refractive index.

In the present invention, the water admixture 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 by volume, more preferably 0.3 to 0.05.

The film 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 the range of 0.5 to 20 in terms of mass ratio. More preferably, it is in the range of 2-10.

[Solid electrolyte, gel electrolyte]
The electrolyte that can be used in the display element of the present invention includes a solid electrolyte substantially free of solvent and a high-viscosity electrolyte or gel containing a polymer compound, in addition to a solution electrolyte composed of a solvent or an ionic liquid. Of the electrolyte (hereinafter, gel electrolyte).

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-2004-191945, a solid polymer electrolyte described in JP-A-2005-338204, and a polymer described in JP-A-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 to the electrolyte layer]
In the display element of the present invention, a thickener can be used in the electrolyte layer. For example, gelatin, gum arabic, poly (vinyl alcohol), hydroxyethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (Vinyl pyrrolidone), 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 (salt Vinylidene), 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. Further, compounds described on pages 71 to 75 of JP-A No. 64-13546 can be exemplified. Among these, the compounds preferably used are polyvinyl alcohols, polyvinyl pyrrolidones, hydroxypropyl celluloses, and polyalkylene glycols from the viewpoint of compatibility with various additives and improvement in dispersion stability of white particles.

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

Sealing agent is for sealing so that it does not leak to the outside and is also called sealing agent. Epoxy resin, urethane resin, acrylic resin, vinyl acetate resin, ene-thiol resin, silicon resin, modified resin A curing type such as a polymer resin, such as a thermosetting type, a photocurable type, a moisture curable type, and an anaerobic curable type can be used.

The columnar structure provides strong self-holding (strength) between the substrates, for example, a columnar body, a quadrangular columnar body, an elliptical columnar body, a trapezoidal array arranged in a predetermined pattern such as a lattice arrangement. A columnar structure such as a columnar body can be given.

Also, stripes arranged at a predetermined interval may be used. This columnar structure is not a random array, but can be properly maintained at intervals of the substrate, such as an evenly spaced array, an array in which the interval gradually changes, and an array in which a predetermined arrangement pattern is repeated at a constant period. The arrangement is preferably considered so as not to disturb the display.

If the ratio of the area occupied by the columnar structure to the display area 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 for uniformly maintaining a gap between the substrates. 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. The diameter of the spacer is equal to or less than the height of the columnar structure, preferably equal to the height. When the columnar structure is not formed, the diameter of the spacer corresponds to the thickness of the cell gap.

[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 in the present invention is a driving method in which a 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 drive, there is an advantage that the circuit configuration and drive 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 a TFT circuit provided in each grid pattern. Since switching can be performed for each pixel, there are advantages such as gradation and 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.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<< Production of display element >>
[Production of display-side electrode]
[Preparation of electrode 1]
A 300 nm-thick ITO (Indium Tin Oxide) film was formed on a 2 cm × 4 cm glass substrate having a thickness of 1.5 mm according to a sputtering method to obtain a transparent electrode (electrode 1).

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

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

(Preparation of electrolyte layer composition)
(Preparation of electrolyte layer composition 1)
In 2.5 g of γ-butyrolactone, 0.025 g of the following lithium trifluoromethanesulfonic acid imide as the supporting electrolyte, 0.1 g of silver trifluoromethanesulfonate as the metal salt compound, and 0.53 g of thioether exemplified compound A-1 of the present invention are dissolved. Thus, an electrolyte layer composition 1 was obtained.

(Preparation of electrolyte layer composition 2)
An electrolyte composition 2 was prepared in the same manner as the electrolyte layer composition 1 except that 0.004 g of ferrocene was added as a redox auxiliary compound.

(Preparation of electrolyte layer compositions 3 to 15)
The electrolyte layer composition 3 is the same as the electrolyte layer composition 2 except that the thioether exemplary compound A-1 of the present invention in the electrolyte layer composition 2 is changed to the types and amounts of the compounds shown in Table 1 below. ~ 15 were prepared.

Hereafter, the structure of the compound used for the comparative example is described.

[Production of display element]
(Preparation of display element 1)
After the periphery of the electrode 2 is edged with an olefin-based sealant containing glass spherical beads having an average particle diameter of 40 μm as a volume fraction of 10%, the striped electrodes are orthogonal to the electrodes 2 and 1 respectively. The cells were bonded together and further heated and pressed to produce an empty cell. The electrolyte layer composition 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 15)
Display elements 2 to 13 were produced in the same manner as in the production of the display element 1 except that the electrolyte composition 1 was changed to the electrolyte compositions 2 to 13.
<Evaluation of display element>
The display element was evaluated as follows. The evaluation was performed in an atmosphere of 23 ° C. and 55% RH.

[Evaluation of reflectance stability when driven repeatedly]
The driving stability was representatively evaluated by the reflectance stability, and the reflectance stability was evaluated by the contrast retention as follows.

An operation in which both electrodes of the display element are connected to both terminals of a constant voltage power source, a voltage of +1.5 V is applied for 1 second, and a voltage of −1.5 V is applied for 0.5 second is defined as one cycle. The reflectance at a wavelength of 550 nm after application of 5 V and the reflectance at a wavelength of 550 nm after application of −1.5 V were measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing, and the contrast was calculated from the following formula: CR ₁ It was.
Contrast: CR ₁ = (reflectance after + 1.5V application) / (reflectance after -1.5V application)
After driving a total of 1000 times under the same driving conditions, CR ₁₀₀₀ was determined by the same method, CR ₁ and CR ₁₀₀₀ were compared according to the following formula, and the contrast retention rate was evaluated in five stages.

Contrast retention ratio (%) = CR ₁₀₀₀ / CR ₁ × 1000
◎: Contrast retention is 80% or more ◎: Contrast retention is 65% or more and less than 80% ○: Contrast retention is less than 65% Δ: Contrast change can be confirmed but contrast retention is less than 65% ×: Contrast change 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 results are shown in Table 2.

It is presumed that the ITO electrode corrodes by repeated driving and the transmittance varies, and the smaller the electrode corrosion rate calculated from the transmittance, the less the electrode corrosion and the better the stability.

Electrode corrosion rate (%) = (1−T ₁ / T ₁₀₀₀ ) × 100
[Evaluation of rewriting speed]
Connect both electrodes of the display element to both terminals of the constant voltage power supply, control the upper limit of the current value to 10 mA per square centimeter, and apply a constant voltage of -1.5 V to the display side electrode for 1 second. Then, the reflectance at a wavelength of 550 nm when displayed in gray was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing Co., Ltd., and the obtained value was designated as R _BK1 . Here, the smaller the value of _RBK1, the faster the rewriting speed.

Table 2 shows the configuration and evaluation results of each display element obtained as described above.

As is apparent from the results shown in Table 2, the display elements 1 to 10 of the present invention are excellent in contrast retention when repeatedly driven by using the electrolyte composition containing the compound according to the present invention. The display element excellent in electrode corrosion could be provided.

Furthermore, it can be seen that the rewriting speed is high despite the fact that it can be driven at a voltage as low as ± 1.5V.

Claims (7)

In a display element having an electrolyte layer between a pair of opposed electrodes and displaying an image by applying a voltage, the electrolyte layer is a compound having a thioether chain and at least one carbonyl group, and the entire compound A display element comprising: a compound having no dissociative protons. 2. The display element according to claim 1, wherein the thioether chain occupies 30 to 99% by mass of the whole compound. The display element according to claim 1, wherein the compound is represented by the following general formula (1).
In the formula, X represents a sulfur atom or an oxygen atom, and at least one X in the compound is a sulfur atom. n and m represent an integer of 1 to 10, and a represents an integer of 1 to 50.
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ each represent a substituent that does not have a dissociable proton, one of which includes a carbonyl group. Further, they may be the same or different, and may be linked together to form a cyclic structure.
[] Represents a repeating unit, and when it is repeated, the atoms represented by X may be different from each other. In that case, R ₁ and R ₂ may be different from each other, and the integer represented by m may be different.

The display device according to claim 3, wherein R ₅ and R ₆ in the compound have a carbonyl group. 5. The display element according to claim 3, wherein n and m are 2 or 3. The display element according to any one of claims 3 to 5, wherein a is 2 or 3. The display element according to any one of claims 1 to 6, wherein the electrolyte layer contains an auxiliary compound that can be oxidized and reduced.