JP2010266592A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element which has a simple member constitution, is driven at a low voltage, hardly causes a reduction in rewriting speed upon the repeated drive, and is rewritable so many times. <P>SOLUTION: The display element contains, between a display electrode and a counter electrode opposed to the display electrode, an electrolyte composition containing a silver salt compound which dissolves and deposits by electrochemical oxidation-reduction reaction, and the display element is configured to display black and white with application of a voltage. A coating liquid containing an oxo-ammonium compound wherein a counter-anion is an anion-containing sulfonic acid polymer is applied on the counter electrode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display element, and more particularly to a novel electrochemical display element.

  In recent years, opportunities for obtaining and browsing information such as documents and images as simpler electronic information are increasing.

  As a means for browsing electronic information, various displays are mainly used. However, when the electronic information is a document, it is necessary to keep an eye on the display for a relatively long time. There are known disadvantages such as inconvenience or increased power consumption when read for a long time.

  As a display means to compensate for these drawbacks, a reflection type display that uses outside light and does not consume power for image retention and has a so-called “memory property” is known. It is hard to say that it has.

  That is, a method using a polarizing plate such as a reflective liquid crystal has a low reflectance of about 40%, and thus has a difficulty in white display. In addition, since the polymer dispersed liquid crystal requires a high voltage and uses the difference in refractive index between organic substances, the contrast of the obtained image is not sufficient. In addition, 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 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 eliminating the drawbacks of each of the above-described methods, an electrodeposition method (hereinafter, abbreviated as ED method) using dissolution precipitation of metal or metal salt is known. 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 and white contrast and black quality, and various methods have been disclosed (for example, Patent Documents 1 to 3). 5).

  In the ED system, a technique for immobilizing a redox polymer (for example, ferrocene polymer) on the counter electrode is important. (For example, refer to Patent Document 6) However, since the known ferrocene polymer is easily dissolved in the solvent contained in the electrolyte and easily detached from the electrode, the rewriting speed is greatly reduced when the element is driven repeatedly. In addition, it has a serious drawback that the number of rewrites is very small.

WO2004 / 068231 pamphlet WO2004 / 066773 pamphlet U.S. Pat. No. 4,240,716 Japanese Patent No. 3428603 JP 2007-72368 A JP 2008-111941 A

  The present invention has been made in view of the above problems, and its object is to have a simple member configuration, which can be driven at a low voltage, has almost no decrease in rewriting speed in repeated driving, and can be rewritten many times. It is providing the display element which is.

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

  1. A display that contains an electrolyte composition containing a silver salt compound that dissolves and precipitates by an electrochemical oxidation-reduction reaction between the display electrode and the counter electrode facing it, and displays black and white by applying a voltage. A display element, wherein a coating liquid containing an oxoammonium compound whose counter anion is a sulfonate anion-containing polymer is coated on the counter electrode.

  2. 2. The display element according to 1, wherein the sulfonate anion-containing polymer is a polystyrene sulfonate anion.

  3. 3. The display device according to 1 or 2, wherein the oxoammonium cation of the oxoammonium compound is represented by the following general formula (1) or (2).

(In the formula, R _{15 to} R ₁₈ each independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. X _{1 to} X ₅ each independently represent> CH ₂ ,> N ⁺ = O, or> N. ⁺ H-OH, R ₁₉ represents a hydrogen atom, a halogen atom or a substituent that can be substituted on three carbon atoms of a 6-membered ring, a plurality of R ₁₉ may be the same or different, and n is 0 to 0 Represents an integer of 3.)

  According to the present invention, it is possible to provide a display element that has a simple member configuration, can be driven at a low voltage, has almost no decrease in rewrite speed in repeated driving, and has a very large number of rewrites.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention 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 pair of opposed electrodes. The display electrode has a transparent electrode such as an ITO electrode, and the counter electrode has a conductive electrode coated with an oxoammonium compound (hereinafter abbreviated as an oxoammonium compound) in which the counter anion according to the present invention is a sulfonate anion-containing polymer. Is provided. Between the display electrode and the counter electrode, it has an electrolyte layer containing a silver salt compound and a white scattering layer. By applying positive and negative polarities between the counter electrodes, the white display and the black display can be reversible. Can be switched.

[Display electrode]
Of the counter electrodes, the electrode disposed 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.

  As an electrode arranged on the display side, transparent 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. An electrode made of a conductive 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 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, 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.

(Grid electrode: auxiliary electrode)
An auxiliary electrode can be attached to at least one of the display electrode and the counter electrode 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 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 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.

  The line width and line spacing of the auxiliary electrode pattern may be arbitrary values, but the line width needs to be increased 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.

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

[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.

Similarly to the display-side transparent electrode, a nanoporous electrode having a nanoporous structure can be provided on the counter electrode. 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. Particularly preferred is ITO.

As the counter electrode of the present invention, an electrode provided with a nanoporous TiO ₂ electrode or a nanoporous ITO electrode on an ITO electrode is preferable, and an electrode provided with a nanoporous ITO electrode is particularly preferable.

  Examples of the method for coating the counter electrode with the oxoammonium compound of the present invention include coating methods such as electrolytic polymerization, electrolytic deposition, dip, spin, and cast, and any method may be used.

<Oxoammonium compound>
[Sulfonic acid anion-containing polymer]
The sulfonate anion-containing polymer of the present invention refers to a polymer in which part or all of the sulfonate group in the sulfonate group-containing polymer is converted to a sulfonate anion. Conventionally known polymers are preferably used as the sulfonic acid group-containing polymer. As a specific example, the polymer unit contains about 50 to about 100% by mass, preferably about 80 to about 100% by mass, of one or more monomers selected from sulfonic acid group-containing monomers and salts thereof. Suitable examples of the sulfonic acid group-containing monomer include vinyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamidoethane sulfonic acid, 2-acrylamidopropane sulfonic acid, and 2-methacrylamide. Examples include propanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, allylsulfonic acid, methallylsulfonic acid, allyloxybenzenesulfonic acid, 2-hydroxy-3- (2-propenyloxy) propanesulfonic acid, and the like. It is done. The preferred weight average molecular weight of the sulfonate anion-containing polymer of the present invention is 10,000 or more and 5 million or less, and the preferred ratio of weight average molecular weight to number average molecular weight (hereinafter abbreviated as molecular weight distribution) is 1.5 or more and 4 0.5 or less, more preferably 100,000 or more and 3 million or less in weight average molecular weight, and 1.5 or more and 3.5 or less in molecular weight distribution, and particularly preferably 300,000 or more in weight average molecular weight. The molecular weight distribution is 1.5 or more and 2.5 or less. The molecular weight was calculated using polystyrene as a standard substance.

[Oxoammonium compounds]
The oxoammonium compound of the present invention is a compound having at least one oxoammonium group represented by the following formula (A1) in the molecule.

Formula (A1)> N ⁺ = O
[Polystyrene sulfonate anion]
As the polystyrene sulfonate anion of the present invention, one obtained by converting a part or all of the sulfonate group of a conventionally known polystyrene sulfonate into a sulfonate anion is preferably used. The preferred weight average molecular weight of polystyrene sulfonic acid is 10,000 or more and 50 million or less, and the preferred molecular weight distribution is 1.5 or more and 4.5 or less, more preferably 100,000 or more and 10 million or less in weight average molecular weight. Further, the molecular weight distribution is 1.5 or more and 2.5 or less, particularly preferably, the weight average molecular weight is 500,000 or more and 5 million or less, and the molecular weight distribution is 1.5 or more and 2.0 or less.

<Oxoammonium cation represented by the general formula (1)>
In General formula (1), R < ₁₅ > -R < ₁₈ > represents a hydrogen atom or a C1-C10 alkyl group each independently. Preferably, it is a hydrogen atom or a methyl group. Particularly preferred is a hydrogen atom. X _{1 to} X ₅ represent> CH ₂ >, N ⁺ ═O or> N ⁺ H—OH, and particularly X ₁ is preferably> N ⁺ ═O or> N ⁺ H—OH.

<Oxoammonium cation represented by the general formula (2)>
In the general formula (2), R ₁₉ represents a hydrogen atom, a halogen atom, or a substituent that can be substituted with three carbon atoms of a 6-membered ring. A plurality of R ₁₉ may be the same or different, and n represents an integer of 0 to 6, but specific examples of R ₁₉ include a hydrogen atom, a halogen atom (chlorine atom, bromine atom, fluorine atom, iodine atom). And an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 20 carbon atoms, an oxo group, a hydroxyl group, an alkoxy group, an aryloxy group, and an acyloxy group. Preferably, all of R ₁₉ are hydrogen atoms.

  Although the exemplary compound of the oxoammonium compound of this invention is shown below, this invention is not limited to these.

  The synthesis example of the oxoammonium compound of the present invention is shown below.

(Synthesis Example 1: Synthesis of Compound p1-1)
A solution prepared by dissolving 10 g (47 mmol) of polystyrene sulfonic acid (Mw = 1,500,000, Mw / Mn = 2.0) in 30 ml of pure water and 7.9 g (52 mmol) of azaadamantanoxy radical in 15 ml of methanol at room temperature. Slowly added. After stirring for 1 hour as it was, 100 ml of acetonitrile was slowly added dropwise to the reaction solution while stirring, and the produced polymer was filtered off and washed thoroughly with acetonitrile. The solvent was dried at 40 ° C. to obtain 16 g of the desired product p1-1. (Yield 89%, Mw = 15.3 million, Mw / Mn = 2.0)
(Synthesis Example 2: Synthesis of Compound p1-14)
10 g (43 mmol) of polyacrylamide t-butylsulfonic acid (Mw = 1.3 million, Mw / Mn = 3.0) is dissolved in 30 ml of pure water, and 7.9 g (47 mmol) of bisazaadamantanedioxy radical is dissolved in 15 ml of methanol. The dissolved solution was added slowly at room temperature. After stirring for 1 hour as it was, 100 ml of acetonitrile was slowly added dropwise to the reaction solution while stirring, and the produced polymer was filtered off and washed thoroughly with acetonitrile. The solvent was dried at 40 ° C. to obtain 15 g of the desired product p1-14. (Yield 84%, Mw = 13.3 million, Mw / Mn = 2.8)
(Synthesis Example 3: Synthesis of Compound p2-1)
A solution in which 10 g (47 mmol) of polystyrene sulfonic acid (Mw = 800,000, Mw / Mn = 2.0) was dissolved in 30 ml of pure water, and 8.1 g (52 mmol) of tetramethylpiperidineoxy radical was dissolved in 15 ml of methanol at room temperature. Slowly added. After stirring for 1 hour as it was, 80 ml of acetonitrile was slowly added dropwise to the reaction solution while stirring, and the produced polymer was separated by filtration and thoroughly washed with acetonitrile. The solvent was dried at 40 ° C. to obtain 17 g of the desired product p2-14. (Yield 94%, Mw = 779,000, Mw / Mn = 1.8)
(Synthesis Example 4: Synthesis of Compound p2-9)
10 g (39 mmol) of methallyloxybenzenesulfonic acid (Mw = 2.5 million, Mw / Mn = 2.5) was dissolved in 25 ml of pure water, and 6.7 g (43 mmol) of tetramethylpiperidineoxy radical was dissolved in 10 ml of methanol. The solution was added slowly at room temperature. After stirring for 1 hour as it was, 90 ml of acetonitrile was slowly added dropwise to the reaction solution while stirring, and the produced polymer was filtered off and washed thoroughly with acetonitrile. The solvent was dried at 40 ° C. to obtain 14 g of the desired product p2-9. (Yield 84%, Mw = 235.9 million, Mw / Mn = 2.6)
In addition, since the oxoammonium compound of the present invention uses the sulfonic acid of the sulfonate anion-containing polymer as a counter salt, the nitroxide radical causes disproportionation and becomes a 1: 1 mixture of oxoammonium cation type and aminoxy anion type. . Of course, in the case of the oxoammonium cation type, it is a cation type, and even in the case of the aminoxy anion type, the oxoammonium compound of the present invention is in any redox state since it receives two H ⁺ of sulfonic acid and becomes a cation type. Since a sulfonate anion (-)-containing polymer with low solubility to the electrolyte is always used as a counter salt and is preferably coated and fixed on the counter electrode, it is considered that the stability of repeated driving is excellent.

<Electrolyte composition>
[Organic solvent]
An organic solvent may be used in combination with 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.

[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. It is a generic term, and there are no particular limitations on the state species of the phase 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.

  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 A known silver salt compound such as a silver salt with an acid or a silver complex with iminodiacetic acid can be used. Among these, it is preferable to use, as a silver salt, a compound that does not have a nitrogen atom having coordination properties with halogen, carboxylic acid, or silver, and for example, silver p-toluenesulfonate is preferable.

  The metal ion concentration contained in the electrolyte 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 solution is improved.

[Halogen ion, silver 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
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 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.

[Metal salt solvent compound]
In the present invention, a silver salt solvent can be used to promote dissolution and precipitation of the silver salt. The silver salt solvent may be any compound that can solubilize silver in the electrolyte. For example, solubilize silver or a compound containing silver by coexisting with a compound containing a chemical structural species that interacts with silver, such as forming a coordinate bond with silver or forming a weak covalent bond with silver. It is common to use a means for converting to an object. As the chemical 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 is preferably used because it has little influence on the coexisting compound and high solubility in a solvent.

[Supporting electrolyte]
As the supporting electrolyte that can be used in the electrolyte composition of the present invention, salts, acids, and alkalis that are usually used in the field of electrochemistry or the field of batteries can be used.

  There are no particular limitations on the salts, 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 _{^{6 -, AsF 6 -, CH}} 3 COO -, CH 3 (C 6 H 4) SO 3 -, and _{(C 2 F 5 SO 2)} 3 C - Li salt having a counter anion selected from, Na salt or 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,

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.

  The supporting electrolyte of the present invention is preferably a quaternary ammonium salt, particularly preferably a quaternary spiro ammonium salt. The amount of the electrolyte salt used is arbitrary, but in general, the electrolyte salt 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.

[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 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 insoluble 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, 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. Furthermore, Research Disclosure and those described in pages (71) to (75) of JP-A No. 64-13546, US Pat. No. 4,960,681, JP-A No. 62-245260, etc. superabsorbent polymers described, namely -COOM or -SO 3 M _(M is a hydrogen atom or an alkali metal) homopolymer or a vinyl monomer together or with other vinyl monomers of the vinyl monomer having a (e.g., sodium methacrylate, 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, it is preferable to use an aqueous polyurethane resin described in JP-A-10-76621.

  The average molecular weight of the water-based polymer of 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 on a weight average basis.

  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, 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 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 the range of 0.5 to 20 by mass ratio, More preferably, it is the range of 2-10.

[Solid electrolyte, gel electrolyte]
The electrolyte according to the present invention is not only a solution electrolyte composed of a solvent or an ionic liquid, but also a high-viscosity electrolyte or gel electrolyte (hereinafter, referred to as a solid electrolyte or a polymer compound containing substantially no solvent). 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, 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 ratio with respect to the organic solvent of the electrolyte layer. .

(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 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), 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.

<Other components of the display element>
In the display element of the present invention, a substrate, a sealing agent, a columnar structure, spacer particles, an electrical insulating layer, and the like can be used.

〔substrate〕
The display electrode 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, Polymer films such as polyethylene, polyamide, nylon, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyether sulfone, silicon resin, polyacetal resin, fluororesin, cellulose derivatives, polyolefins, etc. are preferably used. It is done. 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 electrode substrate, for example, an opaque substrate such as an inorganic substrate such as a metal substrate or a ceramic substrate can be used.

[Sealant]
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.

[Columnar structure]
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. Alternatively, stripes arranged at predetermined intervals 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 in the display area of the display element is 1 to 40%, a practically sufficient strength as a display element can be obtained.

[spacer]
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 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 memory function. For example, a circuit described in FIG. 5 of JP-A-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. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Production of display element >>
(Preparation of electrolyte)
(Preparation of electrolyte 1)
In 2.5 g of γ-butyrolactone, 0.1 g of silver p-toluenesulfonate, 0.2 g of the compound (G1-3) and 0.025 g of spiro (1,1 ′)-bipyrrolidinium tosylate are dissolved to prepare an electrolytic solution 1 Got.

[Production of electrodes]
(Preparation of electrode 1) ITO electrode An ITO (Indium Tin Oxide) film having a thickness of 1.5 mm and a pitch of 145 μm and an electrode width of 130 μm is formed on a 2 cm × 4 cm glass substrate according to a known method. A transparent electrode (electrode 1) was obtained.

(Preparation of electrode 2) ITO-porous ITO
On electrode 1, ITO ink X-490CN27 (Sumitomo Metal Mining, 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, and mixed by stirring. The liquid was applied by spin coating. After baking at 180 ° C. and drying, it was immersed in diluted nitric acid (diluted nitric acid having a specific gravity of 1.38 10 times), then washed and dried to obtain an electrode 2 having a thickness of 0.4 μm.

(Preparation of electrode 3) Porous ITO + ferrocene polymer electrolytic deposition Using electrode 2, a platinum wire was used as a counter electrode, and a silver / silver ion electrode was used as a reference electrode. Ferrocene polymer (Fc polymer) was saturatedly dissolved in the electrolyte using 0.2 M / l n-tetrabutylammonium perchlorate-dichloromethane. In this solution, electrolytic deposition was performed at +1.0 V for 3 minutes. Thereafter, the substrate was dried and washed with methanol to obtain an electrode 3.

(Preparation of electrode 4) Porous ITO + polymer spin coat of the present invention ITO electrode X-490CN27 (Sumitomo Metal Mining, average particle size: 20 nm) on electrode 1 and zinc oxide particles (20 nm: manufactured by Wako Pure Chemical Industries) on ITO The mixture was mixed and stirred by spin coating so that 15% by mass of the particles and p1-1 of the present invention were 7% by mass with respect to the ITO particles. After baking at 180 ° C. and drying, the electrode 4 was immersed in dilute nitric acid (diluted nitric acid having a specific gravity of 1.38 10 times), then washed and dried to obtain an electrode 4 having a thickness of 0.45 μm.
(Production of electrodes 5 to 20)
Electrodes 5 to 20 were produced in the same manner except that p1-1 of the present invention in the electrode 4 was changed as shown in Table 1.

[Production of display element]
(Preparation of display element 1-1) ITO porous + TiO ₂ + electrolyte 1
On the periphery of the electrode 2 bordered with an olefin-based sealant containing 10% glass spherical bead spacers with an average particle diameter of 40 μm as a volume fraction, polyvinyl alcohol (average polymerization degree 3500, saponification degree 87% ) 20% by mass of Titanium Dioxide CR-90 manufactured by Ishihara Sangyo Co., Ltd. was added to 2% by mass of isopropanol solution, and the mixed liquid dispersed with an ultrasonic disperser was applied so that the film thickness after drying was 20 μm. Then, after drying at 15 ° C. for 30 minutes to evaporate the solvent, it was dried in an atmosphere at 45 ° C. for 1 hour. After spraying glass spherical bead-shaped spacers having an average particle diameter of 20 μm on the obtained titanium dioxide layer, the electrode 2 and the electrode 1 were bonded and heated and pressed to produce an empty cell. The electrolytic solution 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 1-1.

(Production of display elements 1-2 to 1-18)
Display elements 1-2 to 1-18 were produced in the same manner as the display element 1-1 except that the electrodes 3 of the display element 1-1 were changed as shown in Table 1.

<< Evaluation of display element >>
<< Evaluation 1: Evaluation of display elements 1-1 to 1-18 >>
[Evaluation of reflectance stability when driven repeatedly]
When both electrodes of the manufactured display element are connected to both terminals of a constant voltage power source, a voltage of +1.5 V is applied for 1.5 seconds, and then a voltage of -1.5 V is applied for 1 second to display gray The reflectance at a wavelength of 550 nm was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing. Under the same driving conditions, driving was performed 10 times in total, and the average value of the obtained reflectances was defined as R _ave1 . Under the same driving conditions, driving was performed 10 times in total, and the average value of the obtained reflectances was defined as R _ave1 . Further, after driving repeatedly 10,000 times, R _ave2 was obtained by the same method. R _BK1 = | R _ave1 −R _ave2 | was used as an index of the stability of the reflectance when the R _BK1 was repeatedly driven. Here, the smaller the value of R _BK1, the better the stability of the reflectance when it is repeatedly driven.

  Table 1 shows the evaluation results of the respective display elements obtained as described above.

[Evaluation of rewriting speed]
Connect both electrodes of the manufactured 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. Te measured by the spectral colorimeter CM-3700d wavelength 550nm reflectance manufactured by Konica Minolta sensing Inc. obtained while grayed, the obtained value was defined as _{R BK2.} Here, the smaller the value of R _BK2 is, the faster the black display rewriting speed is.

  Table 1 shows the configurations and evaluation results of the display elements obtained as described above.

  As is apparent from the results shown in Table 1, it can be seen that the display element of the present invention has less change in reflectance and change in rewriting speed when it is repeatedly driven than in comparison.

  According to the present invention, it is possible to provide a display element that has a simple member configuration, can be driven at a low voltage, has almost no decrease in rewrite speed in repeated driving, and has a very large number of rewrites.

Claims (3)

  A display that contains an electrolyte composition containing a silver salt compound that dissolves and precipitates by an electrochemical oxidation-reduction reaction between the display electrode and the counter electrode facing it, and displays black and white by applying a voltage. A display element, wherein a coating liquid containing an oxoammonium compound whose counter anion is a sulfonate anion-containing polymer is coated on the counter electrode.   The display element according to claim 1, wherein the sulfonate anion-containing polymer is a polystyrene sulfonate anion. The display device according to claim 1, wherein the oxoammonium cation of the oxoammonium compound is represented by the following general formula (1) or (2).

(In the formula, R _{15 to} R ₁₈ each independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. X _{1 to} X ₅ each independently represent> CH ₂ ,> N ⁺ = O, or> N. ⁺ H-OH, R ₁₉ represents a hydrogen atom, a halogen atom or a substituent that can be substituted on three carbon atoms of a 6-membered ring, a plurality of R ₁₉ may be the same or different, and n is 0 to 0 Represents an integer of 3.)