JP2011232488A - Display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly-durable electrochromic display element capable of multicolor display with uniform coloration and high rewriting speed.SOLUTION: A display element comprises, between a transparent substrate and a counter electrode, a plurality of display electrodes each being isolated by an insulation film and electrochromic layers covering the plural display electrodes and emitting different colors. An oxidation-reduction assistance compound is contained between the display electrode and the counter electrode.

Description

  The present invention relates to an electrochemical display element capable of multicolor display, and relates to a novel electrochemical display element having excellent durability and high rewriting speed.

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

  As a display means that compensates for these drawbacks, a reflection type display that uses external light and does not consume power for image retention (memory type) is known, but has sufficient performance for the following reasons. It's hard to say.

  That is, the method using a polarizing plate such as a reflective liquid crystal has a low reflectance of about 40% and is difficult to display white, and many of the production methods used for producing the constituent members are not easy. In addition, the polymer dispersed liquid crystal requires a high voltage and utilizes the difference in refractive index between organic substances, so that the resulting image has insufficient contrast. In addition, the polymer network type liquid crystal has problems such as a high voltage and a need for a complicated TFT circuit to improve the memory performance. In addition, a display element based on electrophoresis requires a high voltage of 10 V or more, and there is a concern about durability due to electrophoretic particle aggregation.

  As a display method for solving the disadvantages of each of the above-mentioned methods, there are an electrochromic display element (hereinafter abbreviated as EC method) and an electrodeposition method (hereinafter abbreviated as ED method) using dissolution precipitation of metal or metal salt. Are known. The EC method has the advantage of being capable of full-color display at a low voltage of 3V or less, a simple cell configuration, and excellent white quality. The ED method can also be driven at a low voltage of 3V or less and is a simple cell. There are advantages such as excellent constitution, black-to-white contrast and black quality, and various methods have been disclosed.

  Recently, an example has been disclosed in which a plurality of display electrodes and an electrochromic layer are provided separately between a transparent substrate and a counter electrode, thereby enabling multicolor display with simpler control (for example, patents). Reference 1).

  As a result of a detailed study of the technology disclosed in the above patent document by the present inventor, it has been found that the conventional technology has problems in durability and rewriting speed. As means for solving this, there are a method of adding a ferrocene compound as a redox buffer to an electrolyte as described in Patent Document 2, and a method using a radical polymer as described in Patent Document 3. As mentioned above, further improvements are required to meet the increasing demands of users in recent years.

  Patent Document 4 describes that an auxiliary compound is added to promote an electrochemical reaction of an electrochromic compound, and a full-color display is performed by arranging a monochromatic display element in a plane. Therefore, the color reproduction range is narrow and the color reproducibility is not sufficient.

  On the other hand, as a result of studies by the present inventors, when multicolor display is performed by laminating a plurality of display electrodes and an electrochromic layer in one display element as in Patent Document 1, coloring becomes uneven. It has been found that there is a problem that uneven coloring occurs.

JP 2009-163005 A Special table 2007-508587 gazette JP 2007-298713 A JP 2009-288409 A

  In general, in full-color display, it is possible to reproduce high color purity and widen the color reproduction range by laminating each color element such as a color film, rather than arranging each color element on a plane. I can do it.

  However, as a result of investigations by the present inventors, when the color forming elements are laminated as in Patent Document 1, if an attempt is made to color a plurality of electrochromic layers simultaneously, uneven coloring occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrochromic display element capable of multicolor display, which has excellent durability, high rewriting speed, and uniform coloring. It is.

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

  1. In a display element in which a plurality of display electrodes and an electrochromic layer that coats each display electrode and develops different colors are provided between a transparent substrate and a counter electrode, and the plurality of display electrodes are separated by an insulating film A display element comprising an oxidation-reduction auxiliary compound between the display electrode and the counter electrode.

  In the case of mixing colors by the subtractive color method, the color reproduction range is wider and the color reproducibility is better when the layers of different colors are formed by laminating different color pixels on a plane. However, it has been found that when the electrochromic layers are stacked and the adjacent electrochromic layers are colored simultaneously, the color development becomes unstable and the coloration becomes uneven. This is thought to be due to the fact that the current efficiency is lowered and the respective layers share the current, so that the oxidation and reduction of the electrochromic compound is biased.

  The oxidation-reduction auxiliary compound has a function of promoting the oxidation and reduction of the electrochromic compound, so that the current efficiency can be increased, the current corresponding to the applied voltage can be passed, the current is prevented from being biased, and the color development. Is considered to be uniform.

  2. 2. The display device according to 1 above, wherein the redox auxiliary compound is a radical compound or a metal complex compound.

  3. 2. The display element according to 1 above, wherein the redox auxiliary compound is a nitroxyl radical compound.

  4). 4. The display element according to 3 above, wherein the nitroxyl radical compound is a compound represented by the following general formula (1).

(Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom or an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a heterocyclic group which may have a substituent, Z ₁ represents a group of 4 or 5 atoms necessary for forming a cyclic structure, and R _{1 to} R ₄ and each atom constituting Z ₁ are connected to each other to form a cyclic structure. Z ₁ may further have a substituent.)
5). 2. The display element according to 1 above, wherein the redox auxiliary compound is metallocene.

  6). 6. The display element according to 5 above, wherein the metallocene is ferrocene.

  7). 7. The display element according to any one of 1 to 6, wherein the electrochromic layer is made of a semiconductor supporting an electrochromic compound.

  8). 8. The display element according to 7 above, wherein the electrochromic compound is chemically bonded to the metal oxide.

  9. 9. The display element according to any one of 1 to 8, wherein the insulating film is porous.

  10. 10. The display element according to any one of 1 to 9, wherein the insulating film is made of an inorganic material.

  According to the present invention, in an electrochromic display element capable of multicolor display, a display element having excellent durability, high rewriting speed, and uniform coloring can be provided.

Structure of electrochromic display element

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

  A display in which an electrolyte, a plurality of display electrodes, and an electrochromic layer that coats each display electrode and emits different colors are provided between the transparent substrate and the counter electrode, and the plurality of display electrodes are isolated by an insulating film In the device, the above problem could be achieved by a display device characterized in that the electrolyte contains an oxidation-reduction auxiliary compound.

  As a result of intensive studies in view of the above problems, the present inventor used an insulating film as an electrochromic layer that coats a plurality of display electrodes and each display electrode between the transparent substrate and the counter electrode and develops different colors. In the display element provided separately, by having an oxidation-reduction auxiliary compound between the transparent substrate and the counter electrode, it has been found that excellent durability, fast rewriting speed, and uniform colored display element can be realized, The present invention has been reached.

  An example of the present invention will be described with reference to FIG.

  A first display electrode 2, a first electrochromic layer 3, an insulating film 4, a second display electrode 5 and a second electrochromic layer 6 are provided on the transparent substrate 1. The counter electrode 7 is disposed with a gap therebetween.

  The counter electrode is provided on the substrate 8, and a white pigment layer 9 is provided on the counter electrode. An electrolyte 10 is filled between the transparent substrate 1 and the substrate 8, and the periphery of the transparent substrate 1 and the substrate 8 is sealed with a resin 11. The electrolyte also penetrates the first electrochromic layer and the second electrochromic layer, and exchanges electrons with the electrochromic compound.

  The first display electrode and the second display electrode are independently drawn out to the outside (not shown) and connected to a drive circuit (not shown).

<< Basic configuration of display element >>
In the display element of the present invention, the display section is provided with a plurality of display electrodes between the transparent substrate and the counter electrode. The display electrode is provided with a transparent electrode such as an ITO electrode, and the other counter electrode is provided with a conductive electrode. A preferred embodiment of the constituent layer between the transparent substrate and the counter electrode in the present invention will be described. Between the transparent substrate and the counter electrode, a first display electrode formed on the transparent substrate, a first electrochromic layer provided in contact with the first display electrode, and a first electrochromic layer, An insulating film provided in contact with the insulating film; a second display electrode provided in contact with the insulating film; and a second electrochromic layer provided in contact with the second display electrode.

  The first electrochromic layer preferably contains an electrolyte according to the present invention, a first electrochromic compound, and a semiconductor supporting the first electrochromic compound. By applying a voltage of both positive and negative polarity between the counter electrode and the first display electrode, reversibly switching between white and various colored states by coloring / decoloring reaction by oxidation / reduction of the first electrochromic dye. Can do. A semiconductor is used for conducting an oxidation-reduction reaction at high speed by transferring electrons from a display electrode to an electrochromic compound.

  Similarly to the first electrochromic layer, the second electrochromic layer preferably contains an electrolyte according to the present invention, a second electrochromic compound, and a semiconductor carrying the second electrochromic compound. . The second electrochromic compound develops a color different from that of the first electrochromic compound.

  In the present invention, it is also possible to display a full-color image by laminating three or more display electrodes and three or more electrochromic layers that emit different colors.

  In a preferred embodiment of the present invention, the electrochromic layer contains a metal salt that is reversibly dissolved and precipitated by an electrochemical redox reaction. In this embodiment, by applying a voltage of both positive and negative polarity between the counter electrodes, black-and-white display accompanying the dissolution and precipitation of the metal salt is performed, and this is combined with the coloring / decoloring reaction by oxidation / reduction of the electrochromic compound. It is possible to reversibly switch between black, white, and a colored state other than black.

  In a preferred embodiment of the present invention, the electrochromic compound is immobilized on the display electrode.

"electrode"
-Display electrode-
In the display element of the present invention, a transparent electrode is used as the display 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 order to form the electrode in this way, for example, an ITO film may be vapor-deposited on a transparent substrate by a sputtering method or the like, or an ITO film may be formed on the entire surface and then patterned by a photolithography method. 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.

-Semiconductor fine particles, semiconductor porous layer-
In order to immobilize an electrochromic dye (also referred to as EC dye) or the like in the electrochromic layer, it is preferable to contain semiconductor fine particles, and to form a semiconductor porous layer is one preferred form. In order to increase the surface area, the semiconductor porous layer has micropores capable of supporting an EC dye or the like on the surface and inside thereof. 1-5000 m < ² > / g is preferable and, as for the specific surface area of the said semiconductor porous layer, 10-2500 m < ² > / g is more preferable. Here, the specific surface area means the BET specific surface area obtained from the adsorption amount of nitrogen gas. If the specific surface area is too small, the adsorption amount of the EC dye cannot be increased, and the object of the present invention may not be achieved.

  The semiconductor fine particles are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a single semiconductor, an oxide semiconductor, a compound semiconductor, an organic semiconductor, a complex oxide semiconductor, or a mixture thereof. These may contain impurities as a dopant. There is no particular limitation on the form of the semiconductor, and it may be single crystal, polycrystal, amorphous, or a mixed form thereof.

  As the semiconductor fine particles, an oxide semiconductor is particularly preferable. An oxide semiconductor is a metal oxide having semiconductor properties, such as titanium oxide, zinc oxide, tin oxide, aluminum oxide, zirconium oxide, cerium oxide, silicon oxide, yttrium oxide, oxygen boron, magnesium oxide, Strontium titanate, potassium titanate, barium titanate, calcium titanate, calcium oxide, ferrite, hafnium oxide, tungsten oxide, iron oxide, copper oxide, nickel oxide, cobalt oxide, barium oxide, strontium oxide, vanadium oxide, aluminosilicate , Calcium phosphate, aluminosilicate and the like. These metal oxides may be used alone or in combination of two or more. From the viewpoint of electrical properties such as electrical conductivity and physical properties such as optical properties, it is selected from titanium oxide, zinc oxide, tin oxide, aluminum oxide, zirconium oxide, iron oxide, magnesium oxide, indium oxide, and tungsten oxide. When one kind or a mixture thereof is used, a multicolor display excellent in display switching speed is possible. In particular, when titanium oxide is used, multicolor display with a higher display switching speed is possible.

  The shape of the semiconductor fine particles is not particularly limited and can be appropriately selected according to the purpose. The shape may be any of a spherical shape, a nanotube shape, a rod shape, and a whisker shape, and two or more types having different shapes may be used. Fine particles can also be mixed. In the case of the spherical particles, the average particle size is preferably 0.1 to 1000 nm, and more preferably 1 to 100 nm. Two or more kinds of fine particles having different particle size distributions may be mixed. In the case of the rod-like particles, the aspect ratio is preferably 2 to 50000, and more preferably 5 to 25000.

  The semiconductor fine particles preferably carry an EC dye by a chemical bond. In an element capable of multicolor display, when an EC dye is supported by adsorption or the like, color separation is caused by the EC dye dissociating and acting on other display electrodes due to desorption or the like, resulting in color reproduction or color purity reduction. May decrease. In the case of chemical bonding with an EC dye, since the bond is stronger than that of adsorption or the like, color purity is not lowered or color mixing is unlikely to occur, and color reproducibility can be improved.

-Counter electrode-
In the display element of the present invention, a metal electrode or a carbon electrode is used as the counter electrode.

  As the metal electrode, for example, known metal species such as platinum, gold, silver, copper, aluminum, zinc, nickel, titanium, bismuth, and alloys thereof can be used. The metal electrode is preferably a metal having a work function close to the redox potential of silver in the electrolyte. Above all, silver or a silver electrode having a silver content of 80% or more is advantageous for maintaining the reduced state of silver. Excellent in preventing dirt. As an electrode manufacturing method, an existing method such as an evaporation method, a printing method, an ink jet method, a spin coating method, or a CVD method can be used.

  As the carbon electrode, a porous carbon electrode is preferable. 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.

<Redox auxiliary compound>
The oxidation-reduction auxiliary compound (also referred to as a mediator) according to the present invention functions as a mediator of an electrochromic reaction, and desirably has the same activity as that of the electrochromic reaction.

  In the presence of a mediator that causes electron transfer (oxidation) to the anode at a low potential, the mediator is first oxidized, and the substrate is oxidized by the oxidized mediator to obtain a product. The advantage is that it is possible to oxidize the substrate at an anodic potential lower than the oxidation potential of the substrate and that the oxidized mediator returns to the original mediator upon oxidation of the substrate. Is to act as Further, since oxidation at a low potential is possible, decomposition of the substrate and product can be suppressed.

  In the present invention, for example, when a compound that reversibly changes color by an electrochemical redox reaction is used as the substrate, the display element can be driven with a low driving voltage by coexisting a catalytic amount of an oxidation mediator. Thus, the durability of the display element is increased. Further, there are advantages such as an improvement in display switching speed and high color development efficiency. Similarly, the above effect can be obtained by a combination of a reducing mediator and a compound that reversibly discolors by an electrochemical redox reaction that produces a reduction color.

  With the redox auxiliary compound according to the present invention, the above effect can be obtained even in an electrochromic display element capable of multicolor display, and even when two or more colors are simultaneously developed, it acts as a mediator in a catalytic amount, An effect can be obtained.

  In the case where two or more colors are developed in one display element, if the density of the color to be developed becomes high, the current efficiency is lowered, and there is a case where the target density cannot be obtained or uneven coloring occurs. In the present invention, by using the redox auxiliary compound, there is an advantage that the current efficiency becomes constant regardless of the electrochromic compound and the density of the color to be developed, the color development is stabilized, and the uniformity is increased.

  The oxidation-reduction auxiliary compound according to the present invention may be contained in the electrolyte or may be immobilized on the electrode surface. Examples of the method of immobilizing on the electrode surface include a method of introducing a group that chemically or physically adsorbs with the electrode surface into the redox auxiliary compound, a method of polymerizing the redox auxiliary compound to form a thin film on the electrode surface, and the like. It is done.

  Hereinafter, the radical compound and metal complex according to the oxidation-reduction auxiliary compound in the present invention will be described.

[Radical compound]
In the present invention, the compound used as the redox auxiliary compound is preferably a radical compound, and more preferably a nitroxy radical compound.

  In this invention, it is one of the preferable aspects that the nitroxy radical compound which concerns on this invention is a compound represented by the said General formula (1).

  Hereinafter, the general formula (1) will be described.

In the general formula (1), R ₁ , R ₂ , R ₃ , and R ₄ are each independently a hydrogen atom or an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic ring that may have a substituent. Represents a group. Z ₁ represents an atomic group necessary for forming a cyclic structure, and preferably forms a 5-membered ring or a 6-membered ring. Z ₁ may further have a substituent, and these substituents are not particularly limited, and examples thereof include the following substituents. Alkyl groups (eg, methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl, hexyl, etc.), cycloalkyl groups (eg, cyclohexyl, cyclopentyl, etc.), alkenyl groups, cycloalkenyl groups , Alkynyl groups (for example, propargyl group), glycidyl groups, acrylate groups, methacrylate groups, aromatic groups (for example, phenyl group, naphthyl group, anthracenyl group, etc.), heterocyclic groups (for example, pyridyl group, thiazolyl group, oxazolyl group) Group, imidazolyl group, furyl group, pyrrolyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group, selenazolyl group, sriphoranyl group, piperidinyl group, pyrazolyl group, tetrazolyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, propyloxy) Group, pliers Oxy group, cyclopentyloxy group, hexyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, etc.) , Aryloxycarbonyl group (for example, phenyloxycarbonyl group), sulfonamide group (for example, methanesulfonamide group, ethanesulfonamide group, butanesulfonamide group, hexanesulfonamide group, cyclohexanesulfonamide group, benzenesulfonamide group ), Sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylamino) Sulfonyl group, phenylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), urethane group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, phenylureido group, 2-pyridylureido group, etc.), acyl Groups (eg, acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl, etc.), carbamoyl groups (eg, aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylamino) Carbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), acylamino group (for example, acetylamino group, benzoyla) Mino group, methylureido group, etc.), sulfonyl group (eg, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, phenylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (eg, amino group, Ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, anilino group, 2-pyridylamino group, etc.), halogen atom (eg chlorine atom, bromine atom, iodine atom etc.), cyano group, nitro group, sulfo group Carboxyl group, hydroxyl group, phosphono group (for example, phosphonoethyl group, phosphonopropyl group, phosphonooxyethyl group) and the like. Further, these groups may be further substituted with these groups.

R ₁ , R ₂ , R ₃ and R ₄ are each preferably a hydrogen atom or a C1-4 alkyl group, more preferably a hydrogen atom or a methyl group.

In addition, each atom constituting R _{1 to} R ₄ and Z ₁ may be linked to each other to form a cyclic structure. For example, a polycyclic structure such as an azanorbornene structure or an azaadamantane structure may be formed together with a nitrogen atom. Very good. In particular, an azaadamantane structure is a preferred embodiment.

  Specific examples of the nitroxyl radical represented by the general formula (1) are shown below, but the present invention is not limited to these exemplified compounds.

《Synthesis of nitroxy radical compound》
These compounds can be synthesized with reference to the method described in Tetrahedron letter 49 (2008) 48-52.

[Metal complex compounds]
In the present invention, the compound used as the oxidation-reduction auxiliary compound is one of the preferred embodiments that is a metal complex compound, and more preferably a metallocene. As the metallocene, ferrocene is particularly preferable.

  Specific examples of metallocene compounds that can be used in the present invention are shown below, but are not limited thereto.

<< Electrochromic compound (hereinafter referred to as EC compound or EC dye) >>
The EC compound is preferably a compound that exhibits a color developing or decoloring action by at least one of an electrochemical oxidation reaction and a reduction reaction and can form a chemical bond with the semiconductor porous layer. EC compounds include inorganic oxides such as tungsten oxide, iridium oxide, nickel oxide, cobalt oxide, vanadium oxide, molybdenum oxide, titanium oxide, indium oxide, chromium oxide, manganese oxide, Prussian blue, indium nitride, tin nitride, zirconium nitride chloride, etc. In addition to compounds, organometallic complexes, conductive polymer compounds, and organic dyes are known.

  Examples of the organometallic complex exhibiting EC characteristics include metal-bipyridyl complexes, metal phenanthroline complexes, metal-phthalocyanine complexes, rare earth diphthalocyanine complexes, and ferrocene dyes.

  Examples of the conductive polymer compound exhibiting EC characteristics include polypyrrole, polythiophene, polyisothianaphthene, polyaniline, polyphenylenediamine, polybenzidine, polyaminophenol, polyvinylcarbazole, polycarbazole, and derivatives thereof.

  In addition, a polymer material composed of a bisterpyridine derivative and a metal ion as described in, for example, JP-A-2007-112957 also exhibits EC characteristics.

  Organic dyes exhibiting EC characteristics include pyridinium compounds such as viologen, azine dyes such as phenothiazine, styryl dyes, anthraquinone dyes, pyrazoline dyes, fluorane dyes, donor / acceptor type compounds (for example, tetracyanoquinodis Methane, tetrathiafulvalene) and the like. In addition, compounds known as redox indicators and pH indicators can be used.

(Cf. Classification of EC compounds by color tone)
EC compounds are classified into the following three classes when classified in terms of color change.

  Class 1: EC compounds that change from one specific color to another by redox.

  Class 2: EC compounds that are substantially colorless in the oxidized state and exhibit a specific colored state that is the reduced state.

  Class 3: EC compounds that are substantially colorless in the reduced state and exhibit a particular colored state that is the oxidized state.

  In the display element of the present invention, the class 1 to class 3 EC compounds can be appropriately selected depending on the purpose and application.

[Class 1 EC compounds]
Class 1 EC compounds are EC compounds that change from a specific color to another color by oxidation-reduction, and are compounds that can display two or more colors in their possible oxidation states.

As compounds classified into class 1, for example, V ₂ O ₅ changes from orange to green by changing from an oxidized state to a reduced state, and similarly Rh ₂ O ₃ changes from yellow to dark green.

  Many of the organometallic complexes are classified as class 1, and ruthenium (II) bipyridine complexes, such as tris (5,5'-dicarboxylethyl-2,2'-bipyridine) ruthenium complexes, are between +2 and -4 valences, The color changes from orange to purple, blue, green blue, brown, red rust and red. Many of the rare earth diphthalocyanines also exhibit such multicolor characteristics. For example, in the case of lutetium diphthalocyanine, the color gradually changes from purple to blue, green, and red-orange according to oxidation.

  Many of the conductive polymers are also classified as class 1. For example, polythiophene changes from blue to red by changing from an oxidized state to a reduced state, and polypyrrole changes from brown to yellow. In addition, polyaniline or the like exhibits multi-color characteristics and changes from an amber color of an oxidation state to blue, green, and light yellow in order.

  EC compounds classified as class 1 have a merit that multicolor display is possible with a single compound, but on the other hand, they have a drawback that a state that can be said to be substantially colorless cannot be made.

[Class 2 EC compounds]
Class 2 EC compounds are compounds that are colorless or extremely light in an oxidized state and exhibit a specific colored state that is a reduced state.

Examples of the inorganic compounds classified as class 2 include the following compounds, each of which shows the color shown in parentheses in the reduced state. WO ₃ (blue), MnO ₃ (blue), Nb ₂ O ₅ (blue), TiO ₂ (blue) and the like.

  As an organometallic complex classified into class 2, for example, a tris (vasophenanthroline) iron (II) complex can be mentioned, which shows red in a reduced state.

  Examples of organic dyes classified as class 2 include compounds described in JP-A Nos. 62-71934 and 2006-71765, such as dimethyl terephthalate (red) and diethyl 4,4′-biphenylcarboxylate. (Yellow), 1,4-diacetylbenzene (cyan), or tetrazolium salt compounds described in JP-A-1-230026, JP-T-2000-504964, and the like.

  The most representative dyes classified into class 2 are pyridinium compounds such as viologen. Viologen compounds have the advantages of vivid display and color variations by changing the substituents, etc., so they are the most actively studied among organic dyes. ing. Color development is based on organic radicals generated by reduction.

  Examples of pyridinium-based compounds such as viologen include compounds described in the following patents, starting with JP 2000-506629 A.

  JP-A-5-70455, JP-A-5-170738, JP-A-2000-235198, JP-A-2001-114769, JP-A-2001-172293, JP-A-2001-181292, JP-A-2001-181293, Table 2001-510590, JP-A-2004-101729, JP-A-2006-154683, JP-T-2006-519222, JP-A-2007-31708, 2007-171817, 2007-219271, 2007-219272, JP-T JP 2007-279659, JP 2007-279570, JP 2007-279571, JP 2007-279572, and the like.

  Examples of pyridinium compounds such as viologen that can be used in the present invention are shown below, but are not limited thereto.

[Class 3 EC compounds]
Class 3 EC compounds are compounds that are colorless or extremely pale in the reduced state and exhibit a specific colored state that is an oxidized state.

  Examples of inorganic compounds classified as class 3 include iridium oxide (dark blue), Prussian blue (blue), and the like (each of which shows the color shown in parentheses in the oxidized state).

  There are few examples of conductive polymers classified into class 3, but for example, phenyl ether compounds described in JP-A-6-263846 can be mentioned.

  Many dyes are known as class 3 dyes, styryl dyes, azine dyes such as phenazine, phenothiazine, phenoxazine, and acridine, azole dyes such as imidazole, oxazole, and thiazole are preferable. .

  Examples of styryl dyes, azine dyes, and azole dyes that can be used in the present invention are shown below, but are not limited thereto.

[Chemical bonding group]
In the display device of the present invention, it is preferable that the EC compound has a chemical bonding group for chemically bonding with the metal oxide from the viewpoint of preventing color blur.

The chemical bonding group according to the present invention is preferably —COOH, —P—O (OH) ₂ , —OP═O (OH) ₂ and —Si (OR) ₃ (R represents an alkyl group).

<Insulating film>
The insulating film applicable to the present invention may be a layer having both ionic conductivity and electronic insulating properties, for example, a solid electrolyte film in which a polymer or salt having a polar group is formed into a film, an electronic insulating material Examples thereof include a highly porous membrane and a pseudo-solid electrolyte membrane supporting an electrolyte in its voids, a polymer porous membrane having voids, and a porous body of an inorganic material having a low relative dielectric constant such as a silicon-containing compound. Among these, a porous film is preferably used. Among them, from the viewpoint of ion conductivity and durability, the use of a porous film containing an inorganic material such as silica or alumina enables a display switching speed and stability. A display element with excellent properties can be provided.

  As a method for forming a porous film, a sintering method (fusion method) (using fine pores formed between particles by adding polymer fine particles or inorganic particles to a binder or the like and partially fusing them), an 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.

"Electrolytes"
“Electrolyte” generally refers to a substance that dissolves in a solvent such as water and exhibits ionic conductivity in a solution (hereinafter referred to as “electrolyte in a narrow sense”). In the description of the present invention, an electrolyte is defined as an electrolyte in a narrow sense. A mixture containing other metals, compounds and the like regardless of non-electrolytes is referred to as an electrolyte (also referred to as “broadly defined electrolyte” or electrolyte). Therefore, the electrolyte includes an electrolyte solvent.

[Electrolyte solvent]
In the present invention, an aprotic polar solvent is used as the electrolyte solvent. Examples of the aprotic polar solvent include dimethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, butyrolactan, diethyl ether, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, dioxolane, Methyldioxolane, acetonitrile, benzonitrile, nitrobenzene, N, N-dimethylformamide, N, N-diethylformamide, sulfooxide, dimethylsulfoxide, dimethylsulfone, tetramethylenesulfone, sulfolane, N-methyl-2-oxdorinoline and These mixtures can be used.

  The boiling point of the electrolyte solvent is not particularly limited, but it is preferably a high boiling point and preferably has a boiling point of 200 ° C. or higher from the viewpoint of preventing volatility and the reason for production.

  In the present invention, particularly preferably used solvents are compounds represented by the following general formulas (S1) and (S2).

[Compounds Represented by General Formulas (S1) and (S2)]
In the display element of the present invention, the electrolyte preferably contains a compound represented by the following general formula (S1) or (S2).

[Wherein L represents an oxygen atom or an alkylene group, and Rs ₁₁ to Rs ₁₄ each represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group or an alkoxy group. ]

[Wherein Rs ₂₁ and Rs ₂₂ each represents an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group or an alkoxy group. ]
First, the detail of the compound represented by general formula (S1) is demonstrated.

In the general formula (S1), L represents an oxygen atom or an alkylene group, and Rs ₁₁ to Rs ₁₄ each represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group, or an alkoxy group, These substituents may be further substituted with an arbitrary substituent.

  Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl, hexyl, octyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and the like as aryl groups. Examples of the cycloalkyl group such as phenyl group, naphthyl group and the like include, for example, a cyclopentyl group, cyclohexyl group and the like, an alkoxyalkyl group, for example, a β-methoxyethyl group, a γ-methoxypropyl group and the like, as an alkoxy group, Examples thereof include a methoxy group, an ethoxy group, a propyloxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, and a dodecyloxy group.

  Hereinafter, although the specific example of a compound represented by general formula (S1) is shown, in this invention, it is not limited only to these illustrated compounds.

  Subsequently, the detail of the compound represented by general formula (S2) is demonstrated.

In the general formula (S2), Rs ₂₁ and Rs ₂₂ each represents an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group, or an alkoxy group.

  Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl, hexyl, octyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and the like as aryl groups. Examples of the cycloalkyl group such as phenyl group, naphthyl group and the like include, for example, a cyclopentyl group, cyclohexyl group and the like, an alkoxyalkyl group, for example, a β-methoxyethyl group, a γ-methoxypropyl group and the like, as an alkoxy group, Examples thereof include a methoxy group, an ethoxy group, a propyloxy group, a pentyloxy group, a hexyloxy group, an octyloxy group, and a dodecyloxy group.

  Hereinafter, although the specific example of a compound represented by general formula (S2) is shown, in this invention, it is not limited only to these illustrated compounds.

  Of the compounds represented by the general formulas (S1) and (S2) exemplified above, the exemplary compounds (S1-1), (S1-2), and (S2-3) are particularly preferable.

  The compounds represented by the general formulas (S1) and (S2) are one type of electrolyte solvent. In the display element of the present invention, another solvent is used in combination as long as the object effects of the present invention are not impaired. be able to. Specifically, tetramethylurea, sulfolane, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, 2- (N-methyl) -2-pyrrolidinone, hexamethylphosphortriamide, N-methylpropionamide, N, N-dimethylacetamide, N-methylacetamide, N, N-dimethylformamide, N-methylformamide, butyronitrile, propionitrile, acetonitrile, acetylacetone, 4-methyl-2-pentanone, 2-butanol, 1-butanol, 2-propanol, 1-propanol, ethanol, methanol, acetic anhydride, ethyl acetate, ethyl propionate, dimethoxyethane, diethoxyfuran, tetrahydrofuran, ethylene glycol, diethylene glycol, triethylene glycol monobutyl Ether, water and the like. Among these solvents, it is preferable to include at least one solvent having a freezing point of −20 ° C. or lower and a boiling point of 120 ° C. or higher.

  Furthermore, as a solvent which can be used in the present invention, J.P. A. Riddick, W.M. B. Bunger, T.A. K. Sakano, “Organic Solvents”, 4th ed. , John Wiley & Sons (1986), Y. Marcus, “Ion Solvation”, John Wiley & Sons (1985), C.I. Reichardt, “Solvents and Solvent Effects in Chemistry”, 2nd ed. VCH (1988), G .; J. et al. Janz, R.A. P. T.A. Tomkins, “Nonqueous Electronics Handbook”, Vol. 1, Academic Press (1972).

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

  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 Examples include metal salts such as K salt.

Also, 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 ⁻ A quaternary ammonium salt having a counter anion selected from CH ₃ COO ⁻ , CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ , 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 ,

  Etc.

Also, 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 ⁻ , A phosphonium salt having a counter anion selected from CH ₃ COO ⁻ , CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ^— , specifically, (CH ₃ ) _{4 PBF 4, (C 2 H 5} ) 4 PBF 4, (C 3 H 7) 4 PBF 4, include _{(C 4 H 9) 4 PBF} 4 and the like. Moreover, these mixtures can also be used suitably.

As the supporting electrolyte of the present invention, a cyclic quaternary ammonium salt is preferable, and a quaternary spiro ammonium salt is particularly preferable. The _ClO ⁴ as counter anion ^{_{-, BF 4 -, CF 3}} SO 3 -, (C 2 F 5 SO 2) 2 N -, PF 6 - are preferable, and BF ₄ ^- is preferable.

  The amount of the electrolyte salt used is arbitrary, but in general, the electrolyte salt is desirably present in the solvent as an upper limit of 20 M or less, preferably 10 M or less, more preferably 5 M or less. It is desirable that it be present at 0.01M or more, preferably 0.05M or more, more preferably 0.1M or more.

  In the present invention, in addition to the electrolyte solvent and the supporting electrolyte, the following compounds may be added.

[Metal salt compounds]
The reproducibility of black can be improved by observing the image by the electrochromic layer according to the present invention by superimposing it with the electrodeposition image by the metal salt compound in the same cell.

  The metal salt compound is a salt containing a metal species that is contained in the electrolyte and can be dissolved and deposited by driving the electrode on at least one of the display electrode and the counter electrode. Any compound may be used as long as it is present. Preferred metal species are silver, bismuth, copper, nickel, iron, chromium, zinc and the like, particularly preferred are silver and bismuth, and silver is most preferred.

[Silver salt compound]
The silver salt compound is a generic name for 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 and the like. There are no particular limitations on the phase state species such as the solid state, the solubilized state in the liquid, the gas state, etc., and the charged state species such as neutral, anionic and cationic.

  The metal ion concentration contained in the electrolyte 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, metal ion concentration ratio]
In the display element using the silver salt compound, it is preferable to use a halogen ion or a halogen atom for the electrolyte, the molar concentration is [X] (mol / kg), and the silver or silver contained in the electrolyte is contained in the chemical structure. When the total molar concentration of silver of the contained compound is [Metal] (mol / kg), it is preferable that the condition defined by the following formula (1) is satisfied.

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 larger 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.

[Silver salt solvent]
In order to cause dissolution and precipitation of metal salts (particularly silver salts), it is preferable to contain a compound that promotes solubilization of silver in the electrolyte.

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

《White scattering material》
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 white scattering material is preferably a pigment.

  The porous white scattering layer applicable to the present invention can be formed by applying and drying a water mixture of a water-based polymer and a white pigment that is substantially insoluble in the electrolyte solvent, and can also form white scattering in the electrolyte. By adding a substance, the electrolyte solution between the counter electrode and the display electrode can have the function of a white scattering layer.

  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, zinc oxide, and zinc hydroxide are preferably used. In addition, titanium dioxide surface-treated with inorganic oxides (Al ₂ O ₃ , AlO (OH), SiO _2, etc.), in addition to these surface treatments, trimethylolethane, triethanolamine acetate, trimethylcyclosilane, etc. Titanium dioxide subjected to organic treatment can be 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.

  The white scattering layer preferably contains an aqueous polymer that does not substantially dissolve in the electrolyte solvent. Examples of the aqueous polymer include a water-soluble polymer and a polymer dispersed in an aqueous solvent.

Examples of the water-soluble polymer 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, polyvinyl pyrrolidone, acrylamide polymers, Examples thereof include synthetic polymer compounds such as derivatives thereof. Examples of gelatin derivatives include acetylated gelatin, phthalated gelatin, polyvinyl alcohol derivatives include 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. Two or more of these binders can be used in combination.

  In the present invention, gelatin and gelatin derivatives, or polyvinyl alcohol or derivatives thereof can be preferably used.

  Examples of the polymer dispersed in the aqueous solvent include natural rubber latex, styrene butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, isoprene rubber, and other latexes, polyisocyanate, epoxy, acrylic, silicone, and polyurethane. And thermosetting resins in which urea-based, phenol-based, formaldehyde-based, epoxy-polyamide-based, melamine-based, alkyd-based resin, vinyl-based 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.

  “Substantially insoluble in the electrolyte solvent” is defined as a state where the dissolved amount per kg of the 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 quantification method using a gas chromatogram.

  In the present invention, the water mixture of the water-based polymer and the white pigment is preferably in the 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.

  In the present invention, the medium for applying the water mixture of the water-based polymer and the white pigment may be at any position as long as it is on the component between the counter electrodes of the display element, but at least one electrode surface of the counter electrode It is preferable to apply on top. As a method for applying to a medium, for example, a coating method, a liquid spraying method, a spraying method via a gas phase, a method of flying droplets using vibration of a piezoelectric element, for example, a piezoelectric inkjet head, Examples thereof include a bubble jet (registered trademark) type ink jet head that causes droplets to fly using a thermal head that uses bumping, and a spray type that sprays liquid by air pressure or liquid pressure.

  The coating method can be appropriately selected from known coating methods. For example, an air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roller coater, transfer roller coater, curtain coater, double coater Examples include roller coaters, slide hopper coaters, gravure coaters, kiss roll coaters, bead coaters, cast coaters, spray coaters, calendar coaters, and extrusion coaters.

  The water mixture of the water-based polymer and the white pigment applied on the medium may be dried by any method as long as water can be evaporated. For example, heating from a heat source, a heating method using infrared light, a heating method using electromagnetic induction, and the like can be given. Further, water evaporation may be performed under reduced pressure.

  In the display element of the present invention, it is desirable to carry out a curing reaction of the water-based compound with a curing agent during or after applying and drying the water mixture described above.

  Examples of the hardener include, for example, U.S. Pat. No. 4,678,739, column 41, 4,791,042, JP-A-59-116655, 62-245261, and 61. No. 18842, 61-249054, 61-245153, JP-A-4-218044, and the like. More specifically, aldehyde hardeners (formaldehyde, etc.), aziridine hardeners, epoxy hardeners, vinyl sulfone hardeners (N, N'-ethylene-bis (vinylsulfonylacetamide) Ethane, etc.), N-methylol hardeners (dimethylolurea, etc.), boric acid, metaboric acid or polymer hardeners (compounds described in JP-A-62-234157). When gelatin is used as the aqueous compound, it is preferable to use a vinyl sulfone type hardener or a chlorotriazine type hardener alone or in combination. Moreover, when using polyvinyl alcohol, it is preferable to use boron-containing compounds such as boric acid and metaboric acid.

  These hardeners are used in an amount of 0.001 to 1 g, preferably 0.005 to 0.5 g, per 1 g of the aqueous compound. In addition, it is possible to perform heat treatment and humidity adjustment during the curing reaction in order to increase the film strength.

[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.

[Transparent substrate]
Examples of the transparent substrate that can be used in the present invention include polyolefins such as polyethylene and polypropylene, polycarbonates, cellulose acetate, polyethylene terephthalate, polyethylene dinaphthalene dicarboxylate, polyethylene naphthalates, polyvinyl chloride, polyimide, and polyvinyl. Synthetic plastic films such as acetals and polystyrene can also be preferably used. Syndiotactic polystyrenes are also preferred. These can be obtained, for example, by the methods described in JP-A Nos. 62-117708, 1-46912, and 1-178505. As these supports, those having resistance to curling due to heat treatment of Tg or less as in US Pat. No. 4,141,735 can be used. Further, the surface of these supports may be subjected to surface treatment for the purpose of improving the adhesion between the support and other constituent layers. In the present invention, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, and flame treatment can be used as the surface treatment. Furthermore, the support body described in pages 44 to 149 of publicly known technology No. 5 (issued by Aztec Co., Ltd. on March 22, 1991) can also be used. Furthermore, RDNo. 308119, page 1009, Product Licensing Index, Volume 92, P108, “Supports”, and the like. In addition, a glass substrate or an epoxy resin kneaded with glass can be used.

[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 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. 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.

  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 method for controlling the transparent state and the colored state of the display element of the present invention is preferably determined based on the redox potential of the electrochromic compound or redox auxiliary compound.

  In the present invention, since the first display electrode and the second display electrode are separated from each other by an insulating film, the potential of the first display electrode and the potential of the second display electrode with respect to the counter electrode are set. It can be controlled independently. As a result, the first electrochromic layer and the second electrochromic layer can be colored and decolored independently. According to the coloring / decoloring pattern of the first electrochromic layer and the second electrochromic layer, the coloring of only the first electrochromic layer, the coloring of only the second electrochromic layer, the first electrochromic layer and the first electrochromic layer Multicolor display such as color development of both electrochromic layers of 2 is possible.

  Furthermore, the black and white display accompanying the dissolution and precipitation of the metal salt can reversibly switch the colored state other than black, white, and black together with the coloring / decoloring reaction of the electrochromic compound. For example, in the case of a display element containing a silver compound, a colored state other than black is shown on the oxidation side, and a black state is shown on the reduction side. As an example of the control method in this case, the electrochromic compound is oxidized by applying a voltage nobler than the redox potential of the electrochromic compound to show a colored state other than black. The redox potential of the electrochromic compound and the silver compound The electrochromic compound is reduced to a white state by applying a voltage between the deposition overvoltages of the silver, and a silver voltage is deposited on the electrode by applying a lower voltage than the deposition overvoltage of the silver compound, indicating a black state, A method of dissolving and decoloring the deposited silver by applying a voltage between the oxidation potential of the silver and the oxidation-reduction potential of the electrochromic compound can be mentioned.

  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 there is particular notice, it represents "mass part" or "mass%".

Example 1
<Production of electrochromic particles>
First, 2-chromoethyltrichlorosilane, 4,4′-bipyridine, and 1-bromohexane were sequentially reacted with titanium oxide nanoparticles to produce electrochromic particles 1.

  Next, 2-bromoethyltrichlorosilane, 4,4′-bipyridine, and 2,4-dinitrochlorobenzene were sequentially reacted with the titanium oxide nanoparticles. Furthermore, the terminal was substituted with 4-cyanoaniline to produce electrochromic particles 2.

<Production of electrode>
(Production of electrode 1)
An ITO (Indium Tin Oxide) film having a pitch of 145 μm and an electrode width of 130 μm is formed on a glass substrate having a thickness of 1.5 mm and a size of 2 cm × 4 cm according to a known method, and is a transparent first display electrode An electrode (electrode 1) was obtained.

(Preparation of electrode 2)
A nickel electrode having an electrode thickness of 0.1 μm, a pitch of 145 μm, and an electrode interval of 130 μm is formed on a glass substrate having a thickness of 1.5 mm and a size of 2 cm × 4 cm by using a known method. And a gold-nickel counter electrode (electrode 2) having a depth of 0.05 μm replaced with gold from the electrode surface was obtained.

(Preparation of laminate 1)
On the electrode 1, the dispersion liquid of the electrochromic particle 1 was apply | coated by the spin coat method, and it was set as the 1st electrochromic layer. Subsequently, a silica nanoparticle dispersion (manufactured by C-I Kasei Co., Ltd.) was applied by a spin coating method to form an insulating film. Thereafter, an ITO fine particle dispersion (manufactured by Mitsubishi Materials Corporation) was applied by a spin coating method to form a second display electrode. Next, the dispersion liquid of the electrochromic particles 2 was applied by a spin coating method to form a second electrochromic layer.

  Thereafter, sintering was performed at 200 ° C. for 1 hour to obtain a laminate 1 including a plurality of display electrodes and an electrochromic layer.

(Preparation of laminate 2)
The dispersion liquid of the first electrochromic particles 1 was applied onto the electrode 1 at 120 dpi by an ink jet apparatus having a piezo-type head to form a first electrochromic layer. Subsequently, a silica nanoparticle dispersion (manufactured by Cii Kasei Co., Ltd.) was applied at 120 dpi with an ink jet apparatus to form an insulating film. Thereafter, an ITO fine particle dispersion (manufactured by Mitsubishi Materials Corporation) was applied at 120 dpi with an ink jet device to form a second display electrode. Next, the dispersion liquid of the 2nd electrochromic particle 2 was apply | coated by 120 dpi with the inkjet apparatus, and it was set as the 2nd electrochromic layer. In addition, dpi as used in the field of this invention represents the number of dots per 2.54 cm.

  Thereafter, sintering was performed at 200 ° C. for 1 hour to obtain a laminate 2 including a plurality of display electrodes and an electrochromic layer.

<Adjustment of electrolyte>
(Preparation of electrolytes 1 to 11)
In the composition shown in Table 1 below, titanium dioxide CR-90 made by Ishihara Sangyo Co., Ltd. was dispersed with an ultrasonic disperser in a solution obtained by adding a supporting electrolyte and a redox auxiliary compound to various solvents. Electrolytes 1 to 11 were prepared.

In the table,
DMSO represents dimethyl sulfoxide.

  SBP represents spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate.

Bu ₄ NClO ₄ represents (n-C ₄ H ₉ ) ₄ NClO ₄ .

<< Production of display element >>
(Preparation of display element 1-1)
The electrode 2 and the laminate 1 were bonded together via a 75 μm spacer, 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 1-15)
In the production of the display element 1-1, display elements 1-2 to 1-15 were obtained in the same manner except that the configurations of the electrolytic solution and the laminate were changed to the combinations described in Table 2.

<< Evaluation of display element >>
[Evaluation of reflectance stability (repeated resistance) when driven repeatedly]
The electrochromic display device of this example showed white in a state where no voltage was applied, and showed a high reflectance of about 60%. Next, when the electrode of the produced display element was connected to both terminals of the constant voltage power source and a voltage of 2.5 V was applied to the first display electrode with respect to the counter electrode, the color was developed in blue. Next, when a voltage of 2.5 V was applied to the second display electrode with respect to the counter electrode, the color was green. Further, when a voltage of 2.5 V was applied to the first display electrode and the second display electrode, the color was black. That is, an electrochromic display device capable of easily performing multicolor display is obtained by selecting a display electrode to which a voltage is applied between the first display electrode and the second display electrode.

Next, when a voltage of −2.5 V is applied to the first display electrode and the second display electrode for 1 second and then a voltage of +2.5 V is applied for 1 second with respect to the counter electrode for color display. The reflectance at the maximum absorption wavelength in the visible light region was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing. Driven a total of 10 times under similar driving conditions, the average value of the obtained reflectance was Rave3. Further, after driving repeatedly 10,000 times, Rave4 was obtained by the same method. ΔR _COLOR1 = | Rave3-Rave4 | was used as an index of the stability of the reflectance when ΔR _COLOR1 was repeatedly driven. Here, the smaller the value of ΔR _COLOR1 , the _better the stability of the reflectance when repeatedly driven, that is, the repeated durability.

[Evaluation of rewriting speed of colored display]
Both electrodes of the display element manufactured are connected to both terminals of the constant voltage power source, a low voltage of −2.5 V is applied to the first display electrode and the second display electrode for 3 seconds to display white, and then +2 The reflectance at the maximum absorption wavelength in the visible light region when a constant voltage of 0.5 V is applied for 0.5 seconds to display the color is measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing. The value obtained was _designated as R _COLOR1 . Here, the smaller the value of R _COLOR1, the faster the rewriting speed of the colored display.

[Evaluation of color uniformity]
The colored state when a voltage of −2.5 V is applied to the first display electrode and the second display electrode of the manufactured display element for 1 second and then a voltage of +2.5 V is applied for 1 second to cause color display. Evaluation was made visually by the following criteria.

○: Uniform color development state, no discoloration unevenness or density unevenness is observed Δ: Discoloration or density unevenness is recognized ×: Discoloration or density unevenness is remarkable Table 3 shows the evaluation results of each display element obtained as described above. Shown in

  As is clear from the results shown in Table 3, the display element satisfying the configuration of the present invention has improved reflectance stability, rewriting speed, and color uniformity when driven repeatedly compared to the comparative example. I understand that.

Example 2
The electrode and electrolyte described in Example 1 were used in Example 2 as well.

<Production of electrochromic particles>
First, the exemplary compound (V15) was reacted with titanium oxide nanoparticles to produce electrochromic particles 3.

  Next, the exemplary compound (V18) was reacted with the titanium oxide nanoparticles to produce electrochromic particles 4.

<Ink liquid adjustment>
First, the ink compound 1 was prepared by dissolving the exemplified compound (V15) in acetonitrile / ethanol so as to be 3 mmol / L.

  Next, the ink compound 2 was prepared by dissolving the exemplified compound (V18) in acetonitrile / ethanol so as to be 3 mmol / L.

<Production of laminate>
(Preparation of laminate 3)
On the electrode 1, the dispersion liquid of the electrochromic particle 3 was apply | coated by the spin coat method, and it was set as the 1st electrochromic layer. Subsequently, a silica nanoparticle dispersion (manufactured by C-I Kasei Co., Ltd.) was applied by a spin coating method to form an insulating film. Thereafter, an ITO fine particle dispersion (manufactured by Mitsubishi Materials Corporation) was applied by a spin coating method to form a second display electrode. Next, a dispersion of the electrochromic particles 4 was applied by a spin coating method to form a second electrochromic layer.

  Thereafter, sintering was performed at 200 ° C. for 1 hour to obtain a laminate 3 composed of a plurality of display electrodes and an electrochromic layer.

(Preparation of laminate 4)
The dispersion of the electrochromic particles 3 was applied onto the electrode 1 at 120 dpi using an inkjet apparatus having a piezo-type head to form a first electrochromic layer. Subsequently, a silica nanoparticle dispersion (manufactured by Cii Kasei Co., Ltd.) was applied at 120 dpi with an ink jet apparatus to form an insulating film. Thereafter, an ITO fine particle dispersion (manufactured by Mitsubishi Materials Corporation) was applied at 120 dpi with an ink jet device to form a second display electrode. Next, the dispersion liquid of the electrochromic particles 4 was applied at 120 dpi with an ink jet apparatus to form a second electrochromic layer.

  Thereafter, sintering was performed at 200 ° C. for 1 hour to obtain a laminate 4 including a plurality of display electrodes and an electrochromic layer.

(Preparation of laminate 5)
On the electrode 1, the ink liquid 1 was apply | coated by the spin coat method, and it was set as the 1st electrochromic layer. Subsequently, a silica nanoparticle dispersion (manufactured by C-I Kasei Co., Ltd.) was applied by a spin coating method to form an insulating film. Thereafter, an ITO fine particle dispersion (manufactured by Mitsubishi Materials Corporation) was applied by a spin coating method to form a second display electrode. Next, the dispersion liquid of the ink liquid 2 was applied by a spin coating method to form a second electrochromic layer.

  Thereafter, sintering was performed at 200 ° C. for 1 hour to obtain a laminate 5 including a plurality of display electrodes and an electrochromic layer.

<< Production of display element >>
(Preparation of display element 2-1)
The electrode 2 and the laminate 3 were bonded together via a 75 μm spacer 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 2-1.

(Preparation of display elements 2-2 to 2-18)
Display elements 2-2 to 2-18 were obtained in the same manner as in the manufacture of the display element 2-1, except that the configurations of the electrolyte solution and the laminate were changed to the configurations described in Table 4.

<< Evaluation of display element >>
[Evaluation of reflectance stability (repeated resistance) when driven repeatedly]
The electrochromic display device of this example showed white in a state where no voltage was applied, and showed a high reflectance of about 60%. Next, when a voltage of 1.5 V was applied to the first display electrode, a color was developed in yellow. Next, when a voltage of 1.5 V was applied to the second display electrode, magenta was developed. Further, when a voltage of 1.5 V was applied to the first display electrode and the second display electrode, the color was red. That is, an electrochromic display device capable of easily performing multicolor display is obtained by selecting a display electrode to which a voltage is applied between the first display electrode and the second display electrode.

Next, with the first display electrode and the second display electrode of the manufactured display element being applied to the negative electrode, a voltage of −1.5 V was applied for 1 second, and then a voltage of +1.5 V was applied for 1 second to cause color display. The reflectance at the maximum absorption wavelength in the visible light region was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing. Driven a total of 10 times under similar driving conditions, the average value of the obtained reflectance was Rave3. Further, after driving repeatedly 10,000 times, Rave4 was obtained by the same method. ΔR _COLOR1 = | Rave3-Rave4 | was used as an index of the stability of the reflectance when ΔR _COLOR1 was repeatedly driven. Here, the smaller the value of ΔR _COLOR1 , the _better the stability of the reflectance when repeatedly driven, that is, the repeated durability.

[Evaluation of rewriting speed of colored display]
Connect both electrodes of the display element to both terminals of the constant voltage power supply, apply a low voltage of -1.5 V to the display side electrode for 3 seconds to display white, and then apply a constant voltage of +1.5 V to 0 The reflectance at the maximum absorption wavelength in the visible light region when applied and colored for 5 seconds was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing, and the obtained value was _{designated as RCOLOR1} . . Here, the smaller the value of R _COLOR1, the faster the rewriting speed of the colored display.

[Evaluation of color uniformity]
A colored state when a voltage of −1.5 V is applied to the first display electrode and the second display electrode of the manufactured display element for 1 second and then a voltage of +1.5 V is applied for 1 second to cause color display. Was visually evaluated according to the following criteria.

○: Uniform color development state, no discoloration unevenness or density unevenness is observed Δ: Discoloration or density unevenness is recognized ×: Discoloration or density unevenness is remarkable Table 5 shows the evaluation results of each display element obtained as described above. Shown in

  As is clear from the results shown in Table 5, the display element satisfying the configuration of the present invention has improved reflectance stability, rewriting speed, and coloring uniformity when driven repeatedly compared to the comparative example. I understand that.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 1st display electrode 3 1st electrochromic layer 4 Insulating film 5 2nd display electrode 6 2nd electrochromic layer 7 Counter electrode 8 Substrate 9 White pigment layer 10 Electrolyte 11 Resin

Claims (10)

  A display in which an electrolyte, a plurality of display electrodes, and an electrochromic layer that coats each display electrode and emits different colors are provided between the transparent substrate and the counter electrode, and the plurality of display electrodes are isolated by an insulating film A display element, wherein the electrolyte contains an oxidation-reduction auxiliary compound.   The display element according to claim 1, wherein the redox auxiliary compound is a radical compound or a metal complex compound.   The display element according to claim 1, wherein the oxidation-reduction auxiliary compound is a nitroxyl radical compound. The display element according to claim 3, wherein the nitroxyl radical compound is a compound represented by the following general formula (1).

(Wherein R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom or an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a heterocyclic group which may have a substituent, Z ₁ represents a group of 4 or 5 atoms necessary for forming a cyclic structure, and R _{1 to} R ₄ and each atom constituting Z ₁ are connected to each other to form a cyclic structure. Z ₁ may further have a substituent.)   The display element according to claim 1, wherein the oxidation-reduction auxiliary compound is a metallocene.   The display element according to claim 5, wherein the metallocene is ferrocene.   The display element according to claim 1, wherein the electrochromic layer is made of a semiconductor carrying an electrochromic compound.   The display element according to claim 7, wherein the electrochromic compound is chemically bonded to the metal oxide.   The display element according to claim 1, wherein the insulating film is porous.   The display element according to claim 1, wherein the insulating film is made of an inorganic material.

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