JP2012128218A - Electrochromic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochromic display device which has high definition and has high element durability and display memory performance by a simple method.SOLUTION: The electrochromic display device includes: a display substrate 1 and a counter substrate 9 provided so as to face each other; a display electrode 2 provided on the display substrate 1; a plurality of pixel electrodes 8 provided on the counter substrate 9; an electrochromic layer 3 which is held between the display substrate 1 and the counter substrate 9 and is provided in contact with the display electrode 2; a charge holding layer 7 which is formed on the plurality of pixel electrodes 8 throughout the whole area of a formation region of the plurality of pixel electrodes 8; and a protective layer 6 which is provided on the charge holding layer 7 so as to cover the charge holding layer 7. An electrolytic solution 4 containing an electrolyte is filled between the display electrode 2 and the pixel electrodes 8, and the charge holding layer 7 contains a nickel oxide, and a surface resistance of a laminate structure comprising the charge holding layer 7 and the protective layer 6 is 1E+6 Ω/square or more.

Description

  The present invention relates to an electrochromic display device, and more particularly to an electrochromic display device capable of multicolor display.

  In recent years, there has been a growing need for electronic paper as an electronic medium replacing paper, and its development has been actively conducted. As means for realizing this display system, self-luminous display technologies such as a liquid crystal display and an organic EL display have been developed, and some products have been commercialized.

  On the other hand, a reflective display technology with low power consumption and less visual fatigue is promising as a display technology for next-generation electronic paper.

  As a reflective display technique, a reflective liquid crystal display technique using a cholesteric liquid crystal has been devised. However, this display technique uses selective reflection and a color filter, so the visibility is very poor, and it is far from “paper” in terms of saturation and color reproduction range.

Of the reflective display technologies, an electrochromic display technology made of an organic electrochromic material having both high color reproducibility and display memory properties has been attracting attention.
A phenomenon in which a redox reaction occurs reversibly and a color changes reversibly by applying a voltage is called electrochromism. An electrochromic display device is a display device that utilizes the coloring / decoloring (hereinafter referred to as color erasing) of an electrochromic compound that causes this electrochromic phenomenon. This electrochromic display device is a reflective display device, has a display memory property, and can be driven with a low voltage. Therefore, it is a potential candidate for display device technology for electronic paper applications, from material development to device design. R & D has been conducted extensively.

  However, problems remain in display memory performance and repeated durability due to decolorization of the electrochromic material due to reverse electron reaction at the pixel electrode and deactivation of the electrode itself due to oxidation / reduction reactions that occur on the surface of the pixel electrode. .

  Non-Patent Document 1 reports a technique for improving display memory performance by forming a capacitor by providing a charge retention layer on a pixel electrode. However, according to studies by the present inventors, it has been found that it is difficult to achieve both high-definition display and high display memory performance. That is, in order to achieve both, it is necessary to locally separate and form the charge retention layer on the pixel electrode, which leaves a demerit that complicated processes increase.

  Patent Document 2 discloses a technique for providing a semiconductor rectification layer having a stacked structure of a p-type and an n-type semiconductor on a pixel electrode and preventing a reverse electron reaction on the pixel electrode by using a rectification action. ing. However, according to the study by the present inventors, the diffusion of charges into the electrolyte is remarkable, and the display memory performance has a lot of room for improvement.

  Patent Documents 3 and 4 propose a technique for modifying the pixel electrode itself or the surface thereof with a nickel-containing material. In particular, Patent Document 4 proposes using nickel oxide as a pixel electrode. However, according to the study by the present inventors, nickel oxide itself undergoes a deoxygenation reaction in several times of color development and decoloration, and bubbles are generated in the electrolyte. There remains a problem with respect to device durability, in which the occurrence of the phenomenon occurs.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an electrochromic display device having both high-definition and high element durability and display memory properties by a simple method.

In order to solve the above problems, the electrochromic display device according to the present invention specifically has the technical features described in the following (1) to (5).
(1): A display substrate and a counter substrate provided to face each other, a display electrode provided on the display substrate, a plurality of pixel electrodes provided on the counter substrate, the display substrate and the counter substrate And an electrochromic layer provided in contact with the display electrode, a charge retention layer formed on the plurality of pixel electrodes over the entire surface of the plurality of pixel electrode formation regions, and the charge retention A protective layer provided on the layer so as to cover the charge retention layer, and having an electrolyte solution containing an electrolyte filled between the display electrode and the pixel electrode, and the charge retention The layer includes nickel oxide, and the laminated structure including the charge retention layer and the protective layer has a surface resistance of 1E + 6Ω / □ or more.
(2): A display substrate and a counter substrate that are provided to face each other, a plurality of display electrodes that are spaced apart from each other, and a plurality of electrodes that are provided on the counter substrate and that are opposed to the plurality of display electrodes. A plurality of electrochromic layers included in each of the plurality of display substrates, a charge retention layer formed on the plurality of pixel electrodes over the entire surface of the plurality of pixel electrode formation regions, and the charge And a protective layer provided on the holding layer so as to cover the charge holding layer, and includes an electrolyte filled between the display electrode closest to the display substrate and the pixel electrode. An electrochromic display comprising an electrolytic solution, wherein the charge retention layer includes nickel oxide, and a laminated structure including the charge retention layer and the protective layer has a surface resistance of 1E + 6Ω / □ or more. Equipment .
(3): The display substrate and the counter substrate that are provided to face each other, the plurality of display electrodes that are spaced apart from each other, the plurality of drive elements that are provided separately on the counter substrate, and the plurality of the plurality of display elements On the plurality of pixel electrodes, a plurality of pixel electrodes that are electrically connected to each other from the driving elements and face the plurality of display electrodes, a plurality of electrochromic layers that each of the plurality of display substrates has, A charge retention layer formed over the entire surface of the plurality of pixel electrode formation regions; and a protective layer provided on the charge retention layer so as to cover the charge retention layer; It has an electrolytic solution containing an electrolyte filled between the display electrode that is closest to the pixel electrode and the pixel electrode, and the charge holding layer contains nickel oxide, and consists of the charge holding layer and the protective layer The surface resistance of the laminated structure is 1 + Electrochromic display device characterized by 6 [Omega / □ at least.
(4) The electrochromic according to any one of (1) to (3), wherein the charge retention layer includes a plurality of nickel oxide layers and titanium oxide layers having different oxygen excess states. It is a display device.
(5): The charge retention layer is formed by laminating a nickel oxide layer having a high oxygen excess state, a titanium oxide layer, and a nickel oxide layer having a low oxygen excess state in this order from the pixel electrode side. (1) It is an electrochromic display device given in any 1 paragraph of (4).

  According to the present invention, it is possible to provide an electrochromic display device having both high-definition and high element durability and display memory properties by a simple method.

It is a schematic sectional drawing which shows the structure in one Embodiment of the electrochromic display apparatus which concerns on this invention. It is a schematic sectional drawing which shows the structure in other embodiment of the electrochromic display apparatus which concerns on this invention. It is a schematic sectional drawing which shows the structure in further another embodiment of the electrochromic display apparatus which concerns on this invention.

The electrochromic display device according to the present invention includes a display substrate 1 and a counter substrate 9 provided to face each other, a display electrode 2 provided on the display substrate 1, and a plurality of electrodes provided on the counter substrate 9. The plurality of pixel electrodes 9 are disposed on the plurality of pixel electrodes 9 and the electrochromic layer 3 sandwiched between the pixel electrode 8, the display substrate 1, and the counter substrate 9 and in contact with the display electrode 2. A charge retention layer 8 formed over the entire surface of the formation region; and a protective layer 7 provided on the charge retention layer 8 so as to cover the charge retention layer 8; A laminated structure having an electrolyte solution 4 containing an electrolyte filled between the pixel electrodes 8, the charge holding layer 7 containing nickel oxide, and the charge holding layer 7 and the protective layer 6. Surface resistance of 1E + 6Ω / □ or more And wherein the Rukoto.
Next, each component of the electrochromic display device of the present invention will be specifically described. However, the embodiment described below is a preferred embodiment in the present invention, and the scope of the present invention is not limited to these embodiments unless otherwise described in the following description. Absent.

FIG. 1 is a schematic diagram for explaining the configuration of the electrochromic display device of the present invention.
In the electrochromic display device, a display substrate 1 and a counter substrate 9 which are support substrates are provided on the outer side, and a display electrode 2 and a plurality of pixel electrodes 8 are formed on the inner surfaces thereof. An electrochromic layer 3 is formed adjacent to the display electrode 2, and the electrochromic layer 3 changes in color by a porous electrode layer made of conductive or semiconductive fine particles and an oxidation / reduction reaction carried on the fine particles. It consists of electrochromic molecules that cause On the plurality of pixel electrodes 8, a charge retention layer 7 is formed over the entire area where the pixel electrode 8 is formed. In FIG. 1, the display electrode 2 and the pixel electrode 8 are impregnated with an electrolytic solution 4 in which an electrolyte is dissolved, and further, a white reflective layer 5 is formed. The electrochromic display device is partitioned by a display substrate 1 and a counter substrate 9 facing each other and a plurality of partition walls 12 facing each other to form one cell. In addition, a well-known and usual material can be used for the partition 12.

<Display board 1>
The display substrate is not particularly limited as long as it is a transparent material, but a substrate such as a glass substrate or a plastic film is used. In addition, a transparent insulating layer, an antireflection layer, or the like may be coated on the front and back of the display substrate 1 in order to improve hermeticity, sealing property, and visibility.

<Counter substrate 9>
Since the counter substrate 9 does not need to be particularly transparent, a glass substrate, a plastic film, a silicon substrate, a metal substrate such as stainless steel, or a laminate of these is used.

<Display electrode 2>
The display electrode 2 is not particularly limited as long as it is a material having transparency and conductivity. The display electrode 2 is preferably made of a metal oxide such as indium oxide, zinc oxide, tin oxide, indium tin oxide, or indium zinc oxide. As a manufacturing method, a vacuum deposition method, a sputtering method, an ion plating method, or a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, as long as the material of the display electrode 2 can be formed by coating. Bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method, spray coating method, nozzle coating method, gravure printing method, screen printing method, flexographic printing method, offset printing method, inversion Various printing methods such as a printing method and an inkjet printing method can also be used.

<Pixel electrode 8>
The pixel electrode 8 is not particularly limited as long as it is a conductive material. As a material of the pixel electrode 8, a metal oxide such as indium oxide, zinc oxide, tin oxide, indium tin oxide, indium zinc oxide, or the like, a metal such as zinc or platinum, carbon, or a composite film thereof is used. Can be used. The pixel electrode 8 can be formed by a vacuum deposition method, a sputtering method, an ion rating method, or a spin coating method, a casting method, a micro gravure coating method, a gravure as long as the material of the pixel electrode 8 can be formed by coating. Coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method, spray coating method, nozzle coating method, gravure printing method, screen printing method, flexographic printing method, offset printing Various printing methods such as a printing method, a reverse printing method, and an inkjet printing method can also be used.

<Protective layer 6>
Nickel oxide contained in the charge retention layer 7 is reduced during the reduction reaction process of color development and decoloration of the electrochromic layer 3, and the retained oxygen is easily released. This is observed as generation of bubbles in the electrolytic solution and defects in the display image. In order to prevent the generation of bubbles, it is desirable that the nickel oxide layer included in the charge retention layer 7 is not in direct contact with the electrolytic solution.

The protective layer 6 is not particularly limited as long as it is a material that plays a role of preventing generation of bubbles in the electrolytic solution due to deoxygenation from nickel oxide contained in the charge retention layer 7, such as Al ₂ O ₃ or Various materials such as SiO ₂ or an insulator material containing them, zinc oxide, titanium oxide or a semiconductor material containing them, or an organic insulator material such as polyimide can be used. In particular, non-stoichiometric compounds can be obtained due to excess metal, and titanium oxide exhibiting n-type semiconductor characteristics is one of desirable materials from the viewpoint of the process.

  The thickness of the titanium oxide layer as the protective layer 6 is preferably 1 to 50 nm, more preferably 1 to 10 nm. The protective layer 6 can be formed by a vacuum deposition method, a sputtering method, an ion rating method, or a spin coating method, a casting method, a micro gravure coating method, a gravure as long as the material of the protective layer 6 can be applied and formed. Coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method, spray coating method, nozzle coating method, gravure printing method, screen printing method, flexographic printing method, offset printing Various printing methods such as a printing method, a reverse printing method, and an inkjet printing method can also be used. The protective layer 6 can be omitted when the nickel oxide layer included in the charge retention layer 7 is not in direct contact with the electrolytic solution.

<Charge retention layer 7>
It is desirable that the charge retention layer 7 formed on the pixel electrode 8 includes nickel oxide.
Nickel oxide is a kind of non-stoichiometric compound in which Ni can be in a +3 valence oxygen excess state in addition to +2 valence. It is known that this excess oxygen contributes to the electrical conduction of nickel oxide as a p-type semiconductor. It is known that nickel oxide takes in oxygen under a high temperature environment, and its conductivity is proportional to 1/4 of the oxygen partial pressure. In other words, a nickel oxide layer vacuum-deposited with a high oxygen partial pressure has a high carrier density that contributes to electric conduction, and conversely, a nickel oxide layer vacuum-deposited with a low oxygen partial pressure contributes to electric conduction. Carrier density to be reduced.

  Nickel oxide is also known as an electrochromic material capable of oxidative coloring, and is one of materials having a high reaction rate of oxidation / reduction reactions. It is known that nickel oxide is colored by oxidation from +2 valence to +3 valence.

  The charge retention layer 7 is preferably formed of a plurality of nickel oxide layers and titanium oxide layers having different oxygen excess states.

  A PN or NP junction composed of nickel oxide as a p-type semiconductor and titanium oxide as an n-type semiconductor is useful for preventing a reverse electron reaction on the pixel electrode 8. In order to prevent the reverse electron reaction, a structure that imparts charge rectification is desirable, and a PN or NP junction utilizing semiconductor characteristics, or a Schottky junction generated by joining these semiconductor and metal can be used.

Next, the display principle of the electrochromic display device of the present invention will be described in detail.
The display electrode 2 and the selected arbitrary pixel electrode 8 are electrically connected, and an arbitrary current is allowed to flow for a predetermined time, so that the selected one of the electrochromic layers 3 provided in contact with the display electrode 2 is selected. Color generation and decoloration can be caused in an area immediately above any pixel electrode 8. However, the electric charge accumulated in the pixel electrode 8 diffuses into the electrolytic solution through ions in the electrolytic solution, and color development occurs in the region of the electrochromic layer 3 immediately above the pixel electrode 8 that is not selected. This is observed as bleeding of the display image. In addition, the charge once diffused in the electrolyte solution returns to the pixel electrode 8 to cause a reverse electron reaction at the pixel electrode 8, resulting in poor display memory performance or reduction of the pixel electrode 8 itself. This may cause damage to the electrode due to, such as poor element durability.

  In the present invention, the charge retention layer 7 formed on the pixel electrode 8 is desirably formed of a plurality of nickel oxide layers and titanium oxide layers having different oxygen excess states. In other words, a nickel oxide layer having a low oxygen excess and capable of forming a thick film with reduced conductivity is desirable to prevent electric charges from diffusing into the electrolyte, and a p-type semiconductor is used to prevent a reverse electron reaction to the pixel electrode. A PN junction formed of a nickel oxide layer having excellent characteristics and a high oxygen excess state and a titanium oxide layer is advantageous.

  The thickness of the nickel oxide layer having a low oxygen-excess state, which plays a role of charge retention, is preferably a thick film in order to secure an oxidation / reduction reaction site for accumulating charges. Charge diffusion occurs in the nickel oxide layer. As a result, bleeding of the display image and deterioration of display memory properties occur. That is, the thickness of the nickel oxide layer needs to be designed so that the surface resistance of the laminated structure including the charge retention layer 7 and the protective layer 6 is 1E + 6Ω / □ or more. 500 nm is preferable, More preferably, it is 30-200 nm.

  A nickel oxide layer and a titanium oxide layer forming a PN junction for preventing a reverse electron reaction to the pixel electrode are formed by being sandwiched between the pixel electrode 8 and a nickel oxide layer having a low over-oxidation state that plays a role of charge retention. It is desirable. Each film thickness is preferably from 1 to 50 nm, more preferably from 1 to 10 nm, since the conductivity decreases as described above and bleeding of the display image occurs as described above.

  The charge retention layer 7 formed for the above reason is adjacent to the pixel electrode 8 in the order of a nickel oxide layer having a high oxygen excess and a PN layer formed from a titanium oxide layer, and a nickel oxide layer having a low oxygen excess. It is desirable to be laminated.

  One of the features of the present invention is that the surface resistance of the laminated structure including the charge retention layer 7 and the protective layer 6 is 1E + 6Ω / □ or more. Even if the charge retention layer 7 and the protective layer 6 are formed over the entire area where the plurality of pixel electrodes 8 are formed on the counter substrate 9, a high-definition display can be obtained without blurring of the display image. There is an advantage. This is because the step of patterning the charge retention layer 7 and the protective layer 6 can be omitted, and the current production equipment for thin film transistor (TFT) substrates such as liquid crystal and organic EL displays can be used as it is. Has the great advantage of becoming.

<Electrochromic layer 3>
The electrochromic layer 3 indicates a material containing an electrochromic material, and any of an inorganic electrochromic compound and an organic electrochromic compound may be used as the electrochromic material. In addition, a conductive polymer known to exhibit electrochromism can also be used. Examples of the inorganic electrochromic compound include tungsten oxide, molybdenum oxide, iridium oxide, and titanium oxide. Examples of the organic electrochromic compound include viologen, rare earth phthalocyanine, and styryl. Examples of the conductive polymer include polypyrrole, polythiophene, and polyaniline.

  Further, as the electrochromic layer 3 in the display element of the present invention, it is particularly desirable to use a structure in which an organic electrochromic compound is supported on conductive or semiconductive fine particles. Specifically, it is a structure in which fine particles having a particle size of about 5 nm to 50 nm are sintered on the electrode surface, and an organic electrochromic compound having a polar group such as phosphonic acid, carboxyl group, or silanol group is adsorbed on the surface of the fine particle. . In this structure, since electrons are efficiently injected into the organic electrochromic compound by utilizing the large surface effect of the fine particles, the structure responds faster than a conventional electrochromic display element. Furthermore, since a transparent film can be formed as a display layer by using fine particles, a high color density of the electrochromic dye can be obtained. Also, a plurality of types of organic electrochromic compounds can be supported on conductive or semiconductive fine particles.

  Specifically, polymer-based and dye-based electrochromic compounds include azobenzene, anthraquinone, diarylethene, dihydroprene, dipyridine, styryl, styryl spiropyran, spirooxazine, spirothiopyran, thioindigo, tetra Thiafulvalene, terephthalic acid, triphenylmethane, triphenylamine, naphthopyran, viologen, pyrazoline, phenazine, phenylenediamine, phenoxazine, phenothiazine, phthalocyanine, fluorane, fulgide, A low molecular organic electrochromic compound such as benzopyran or metallocene, or a conductive polymer compound such as polyaniline or polythiophene is used.

  In particular, a viologen compound or a dipyridine compound is preferably contained. These materials have a low color development / discoloration potential and exhibit good color values even in a plurality of display electrode configurations. Examples of the viologen type are described in Japanese Patent No. 3955641 and Japanese Patent Application Laid-Open No. 2007-171781, and examples of the dipyridine type are described in Japanese Patent Application Laid-Open No. 2007-171781 and Japanese Patent Application Laid-Open No. 2008-116718.

  On the other hand, inorganic electrochromic compounds such as titanium oxide, vanadium oxide, tungsten oxide, indium oxide, iridium oxide, nickel oxide, and Prussian blue are used as the metal complex-based and metal oxide-based electrochromic compounds.

  The conductive or semiconductive fine particles are not particularly limited, but a metal oxide is desirable. Materials include titanium oxide, zinc oxide, tin oxide, zirconium oxide, cerium oxide, yttrium oxide, oxygen boron, magnesium oxide, strontium titanate, potassium titanate, barium titanate, calcium titanate, calcium oxide, ferrite, oxide A metal oxide mainly composed of hafnium, tungsten oxide, iron oxide, copper oxide, nickel oxide, cobalt oxide, barium oxide, strontium oxide, vanadium oxide, aluminosilicate, calcium phosphate, aluminosilicate, or the like is used. Moreover, these metal oxides may be used independently and 2 or more types may be mixed and used. In view of physical properties such as electrical properties and optical properties such as electrical conductivity, a kind selected from titanium oxide, zinc oxide, tin oxide, zirconium oxide, iron oxide, magnesium oxide, indium oxide, tungsten oxide, Or when those mixtures are used, the multicolor display excellent in the response speed of color development / erasure is possible. In particular, when titanium oxide is used, multicolor display with a more excellent response speed of color development and decoloration is possible.

  The shape of the conductive or semiconductive fine particles is not particularly limited, but a shape having a large surface area per unit volume (hereinafter, specific surface area) is used in order to efficiently carry the electrochromic compound. For example, when the fine particle is an aggregate of nanoparticles, it has a large specific surface area, so that the electrochromic compound is more efficiently supported, and multicolor display with an excellent display contrast ratio of color development and decoloration is possible. .

<Electrolytic solution 4>
The electrolytic solution 4 is composed of an electrolyte and a solvent for dissolving the electrolyte. In addition, since the electrolyte solution 4 takes a layered form in the electrochromic display element, it may be referred to as an electrolyte solution layer or an electrolyte layer.
As the electrolyte material, for example, inorganic ion salts such as alkali metal salts and alkaline earth metal salts, quaternary ammonium salts, acids, and alkali supporting salts can be used. Specifically, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ COO, KCl, NaClO ₃ , NaCl, NaBF ₄ , NaSCN, KBF ₄ , Mg (ClO ₄ ) ₂ , Mg (BF ₄ ) ₂ etc. can be used. An ionic liquid can also be used. The ionic liquid may be any substance that is generally studied and reported. In particular, an organic ionic liquid has a molecular structure that exhibits a liquid in a wide temperature range including room temperature. Examples of molecular structures include cation components such as N, N-dimethylimidazole salt, N, N-methylethylimidazole salt, N, N-methylpropylimidazole salt, N, N-dimethylpyridinium salt, N, An aromatic salt such as a pyridinium derivative such as N-methylpropylpyridinium salt, or an aliphatic quaternary ammonium salt such as tetraalkylammonium such as trimethylpropylammonium salt, trimethylhexylammonium salt or triethylhexylammonium salt can be used. As the anion component, a compound containing fluorine is preferable in terms of stability in the atmosphere, and examples thereof include BF ₄ −, CF ₃ SO ₃ —, PF ₄ —, (CF ₃ SO ₂ ) ₂ N—, and the like. An ionic liquid formulated by a combination of these cationic components and anionic components can be used.

  Examples of solvents are propylene carbonate, acetonitrile, γ-butyrolactone, ethylene carbonate, sulfolane, dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, polyethylene glycol. Alcohols or a mixed solvent thereof can be used.

  Further, the electrolytic solution 4 does not need to be a low-viscosity liquid, and can take various forms such as a gel, a polymer cross-linking type, and a liquid crystal dispersion type.

<White reflective layer 5>
The white reflective layer 5 is for improving the white reflectance when the electrochromic display element is used as a reflective display device. The white reflective layer 5 can be produced by dispersing white pigment particles in the electrolytic solution or coating and forming a resin in which white pigment particles are dispersed. Examples of the material of the white pigment particles contained in the white reflective layer 5 include titanium oxide, aluminum oxide, zinc oxide, silica, cesium oxide, yttrium oxide, and the like.

<Drive element / drive device 11>
In the present invention, a plurality of driving elements and a circuit that electrically connects each driving element and the pixel electrode 8 function as the driving device 11. Examples of the driving device 11 include a segment driving device and a dot matrix driving device. The dot matrix driving device can be roughly divided into an active matrix driving device and a passive matrix driving device. The driving device 11 suitably used in the present invention is an active matrix driving device that can provide a plurality of display electrodes stacked on a display substrate without fine patterning.

<Other embodiments>
Another feature of the electrochromic display device of the present invention is that a plurality of display electrodes 2 and electrochromic layers 3 exist. With this configuration, color display can be performed. Details will be described with reference to FIG. However, FIG. 2 shows an example of the electrochromic display element of the present invention, and the electrochromic display element of the present invention is not limited to the configuration of FIG.

  As shown in FIG. 2, the electrochromic display device of the present invention has a display substrate 1 and a counter substrate 9 which are support substrates on the outside. The display substrate 1 includes a first display electrode 2a formed in contact with the display substrate 1, a first electrochromic layer 3a provided in contact with the first display electrode 2a, and a first electrochromic layer. An insulating layer 10 provided in contact with 3a, a second display electrode 2b provided in contact with the insulating layer 10, a second electrochromic layer 3c provided in contact with the second display electrode 2b, Have The display substrate 1 is a substrate for supporting the above laminated structure.

  The first and second electrochromic layers 3a and 3b are, as described above, a porous electrode made of conductive or semiconductive fine particles, and electrochromic molecules that are supported by the fine particles and exhibit a color change due to an oxidation-reduction reaction. It is desirable to consist of. On the plurality of pixel electrodes 8 formed on the counter substrate 9, the charge retention layer 7 is formed over the entire area where the pixel electrodes 8 are formed. In FIG. 2, the display electrode 2 and the pixel electrode 8 are impregnated with an electrolytic solution 4 in which an electrolyte is dissolved, and further, a white reflective layer 5 is formed.

  The first and second electrochromic layers 3a and 3b are preferably made of electrochromic molecules that exhibit different colors due to oxidation-reduction reactions. As a result, two-color display is possible. The electrochromic compounds provided on the plurality of display electrodes 2 are preferably all viologen-based or all dipyridine-based. By adopting a similar material structure, the color development / decoloration potential of each display electrode 2 can be made uniform, and the color development / erasure can be easily controlled with the same electrolyte. Similarly, by providing the third, fourth, display electrode 2 and electrochromic layer 3 through the insulating layer 10, multicolor display is possible.

  The insulating layer 10 is electrically insulated from the first display electrode 2a provided with the first electrochromic layer 3a and the second display electrode 2b provided with the second electrochromic layer 3b. It is intended to isolate. Since the first display electrode 2a and the second display electrode 2b independently control the potential with respect to the pixel electrode 8, the electric resistance between the display electrodes 2a and 2b is changed within the display electrode surfaces 2a and 2b. It must be formed larger than the electrical resistance. It is preferable that the resistance between the display electrodes 2a and 2b is at least 500 times the electric resistance in the display electrode surfaces 2a and 2b. The insulation between the display electrodes 2a and 2b can be controlled by the thickness of the electrochromic layer 3, but it is preferable to control by forming the insulating layer 10. Similarly, when the third, fourth, and display electrodes 2 and the electrochromic layer 3 are provided to be increased, the insulating layer 10 for compensating the insulation between the adjacent display electrodes 2 is inserted. It is desirable.

<Insulating layer 10>
The material of the insulating layer 10 is not particularly limited as long as it is porous. However, organic materials, inorganic materials, and composites thereof having high insulating properties, high durability, and excellent film formability are used. Is preferred.

  The porous film can be formed by a sintering method (using fine particles or inorganic particles that are partially fused by adding a binder or the like to make use of pores formed between the particles), an extraction method (which can be used as a solvent) After forming a constituent layer with a soluble organic or inorganic substance and a binder that does not dissolve in the solvent, the organic or inorganic substance is dissolved with the solvent to obtain pores), and the polymer is heated or degassed, etc. Use known forming methods such as foaming method, foaming method, 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 various radiations are radiated to form pores. Can do.

Specific examples include a polymer mixed particle film composed of inorganic nanostructured particles (SiO ₂ particles, Al ₂ O ₃ particles, etc.) and a polymer binder, a porous organic film (polyurethane resin, polyethylene resin), and a porous film. Examples include the formed inorganic insulating material film.
As this inorganic film, a material containing at least ZnS is preferable. ZnS has a feature that it can be deposited at high speed by sputtering without damaging the electrochromic layer or the like. Furthermore, ZnS—SiO ₂ , ZnS—SiC, ZnS—Si, ZnS—Ge, or the like can be used as a material containing ZnS as a main component. Here, the ZnS content is preferably about 50 to 90 mol% in order to maintain good crystallinity when the insulating layer is formed. Thus, particularly preferred _{materials, ZnS-SiO 2 (8/2)} , ZnS-SiO 2 (7/3), ZnS, ZnS-ZnO-In 2 O3-Ga 2 O 3 (60/23/10/7) It is.
By using such a material for the insulating layer 10, a good insulating effect can be obtained with a thin film, and a decrease in film strength (that is, peeling of the film) due to multilayering can be prevented.

  When ZnS or the like is formed by sputtering, ion permeability can be imparted to the inorganic insulating film by previously forming a porous particle film as an undercoat layer. In this case, the nanostructured semiconductor material described above can be used as a particulate film, but it is possible to form an insulating layer 10 having a two-layer structure by separately forming a porous particle film containing silica, alumina, or the like. It is preferable from the point. By making the insulating layer 10 into a porous film using such a technique, the electrolyte in the electrolytic solution 4 can penetrate into the insulating layer 10 and further to the display electrode 2. Movement of ionic charges in the liquid 4 is facilitated, and multicolor display excellent in response speed of color development and decoloration is possible. The film thickness of the insulating layer 10 is in the range of 20 to 1000 nm. When the film thickness is thinner than this range, it is difficult to obtain insulation. Further, when the film thickness is thicker than this range, the manufacturing cost increases, and the visibility tends to decrease due to coloring.

Next, the operation of multicolor display of electrochromic display according to the present invention will be described.
Since the electrochromic display has the above-described structure, multicolor display can be easily performed. That is, since the first display electrode 2a and the second display electrode 2b are provided separately via the insulating layer 10, any display electrode 2 and any one of the plurality of pixel electrodes are provided. The pixel electrode 8 is selected, electrically connected to each other, and an electric current is passed at a certain time, so that the electrode in contact with the selected display electrode 2 directly above the selected pixel electrode 8 is selected. The color-decoloring reaction occurs only in the chromic layer 3 region. That is, when one display electrode 2 out of the first and second display electrodes 2a and 2b and an arbitrary pixel electrode 8 out of the plurality of display electrodes 2 are selected, high-definition display in a single color is possible. When both the first and second display electrodes 2a and 2b and a plurality of arbitrary pixel electrodes 8 are selected, high-definition display with a mixed color of two colors is possible.

  Further, since the electrochromic display device of the present invention has a display memory property, the selection of the first and second display electrodes 2a and 2b and the selection of an arbitrary pixel electrode 8 out of a plurality are divided by time. High definition and multicolor display is possible. In other words, by selecting an arbitrary pixel electrode 8, a coloring region of the electrochromic layer 3 is selected two-dimensionally, and an arbitrary display electrode 2 is selected from the first and second display electrodes 2a and 2b. Thus, an arbitrary region of each electrochromic layer 3 can be colored and erased three-dimensionally.

<Examples 1-4 and Comparative Examples 1-5>
(Preparation of display electrode and electrochromic layer)
An ITO film having a thickness of about 100 nm was formed on a 40 mm × 40 mm glass substrate (display substrate) by a sputtering method in a 20 mm × 20 mm region and a lead portion to produce a display electrode. The electric resistance in the display electrode surface was about 200Ω. A titanium oxide fine particle dispersion (SP210 Showa Titanium) is spin-coated thereon, a titanium oxide particle film is formed by annealing at 120 ° C. for 15 minutes, and further, a viologen which is an electrochromic compound that develops a magenta color on it. A 1 wt% 2,2,3,3-tetrafluoropropanol solution of the compound was spin-coated, and an electrochromic layer composed of titanium oxide particles and an electrochromic compound was formed by annealing at 120 ° C. for 10 minutes.

(Preparation of pixel electrode, charge retention layer, protective layer)
An ITO film having a thickness of about 100 nm was formed on a 40 mm × 40 mm glass substrate (counter substrate) by sputtering, and then a pixel electrode having a 150 μm / 150 μm line / space and a lead-out portion were formed by photolithography. Subsequently, the following charge retention layer and protective layer were produced by sputtering over the entire surface of the counter substrate on which the pixel electrode was formed, excluding the lead portion. The oxygen flow rate ratio during nickel oxide film formation was 10% under high oxygen excess conditions and 4% under low oxygen excess conditions. Each film thickness is shown in parentheses.
In addition, the surface resistance of the charge retention layers of Examples 1 to 4 and Comparative Examples 1 and 4 was 1E + 6Ω / □ or more.

(Production of electrochromic display device)
Tetrabutylammonium perchlorate as the electrolyte, dimethyl sulfoxide and polyethylene glycol (molecular weight: 200) as the solvent, and UV curing adhesive (trade name: PTC10, manufactured by Jujo Chemical Co., Ltd.) in a weight ratio of 1.2: 5.4: 6 16 was prepared by adding 20 wt% of white titanium oxide particles (trade name: CR50, manufactured by Ishihara Sangyo Co., Ltd., average particle size: about 250 nm) to the solution mixed in Step No. 16, and applied to the counter substrate side. Then, UV light irradiation was cured from the opposite substrate side and bonded together to produce an electrochromic display device. The thickness of the electrolyte layer was set to 10 μm by mixing 0.2 wt% of bead spacers with the electrolyte layer.

(Color development test)
Color evaluation of the electrochromic display device produced above was performed.
Each pixel electrode was short-circuited, each pixel electrode was connected to the positive electrode, the display electrode was connected to the negative electrode, and a voltage of +6 V was applied for 500 msec using a constant voltage power source. Image blur was determined by visual observation immediately after voltage application to determine whether 150 μm lines / spaces reflecting pixel electrodes were separated and displayed on the electrochromic layer. ○ indicates that they are displayed separately, and x indicates that they are separated and not displayed due to bleeding.
Further, the display memory property was determined by visual observation whether or not a 150 μm line / space reflecting the pixel electrode was separately formed on the electrochromic layer after 10 minutes had passed immediately after voltage application. ○ indicates that the images are displayed separately, Δ indicates that the images are displayed separately with bleeding of the display image, and x indicates that they are displayed separately.
In addition, as the element durability, each pixel electrode is short-circuited, each pixel electrode is connected to the positive electrode, the display electrode is connected to the negative electrode, and a color development state after 500 times of a repeat test in which ± 1 mA is applied for 500 msec using a constant current power source Was visually determined. Bubble generation indicates that bubbles were generated during the repeated test.

  Table 2 summarizes image bleeding, display memory properties, and element durability of each of Examples 1 to 4 and Comparative Examples 1 to 5.

  From the above results, Example 3 showed the best characteristics. In Examples 1 to 4 and Comparative Examples 1, 4, and 5, it was possible to display an image without blurring immediately after the image was displayed. However, in Comparative Examples 1, 4 and 5, images could not be displayed due to the generation of bubbles or the deterioration of the pixel electrodes in repeated tests of several tens to several hundreds. In Examples 1, 2, and 4, bleeding occurs in the display image 5 to 9 minutes after image display, and the display memory property is slightly poor, but high definition and high element durability compared to Comparative Examples 1 to 5 It was a result of having.

(Threshold voltage for color development)
The voltage threshold evaluation of the color development / erasing of the electrochromic display device produced above was performed.
The electrochromic display devices of Examples 1 to 5 and Comparative Examples 1 to 5 were irradiated with halogen light, and the reflected light was measured with a spectrophotometer (Otsuka Electronics LCD5000). Light incidence was performed from the 30 degree direction, and the intensity of reflected light in the 90 degree direction was measured. Using the reflectance of a standard white plate (Yokogawa Electric Model 199002) as a reference, the reflectance before coloring of each of the electrochromic display devices produced above was about 40%.
Subsequently, each pixel electrode is short-circuited, each pixel electrode is connected to the positive electrode, the display electrode is connected to the negative electrode, voltage is swept from +6 V to −1 V / sec using a constant voltage power source, and the voltage at which the reflectance is reduced is expressed as a color development threshold Voltage was used. Further, once the electrochromic device was developed, voltage sweep was performed from -6 V at +1 V / sec, and the voltage at which the reflectance increased was defined as the decoloring threshold voltage.
Table 3 summarizes the color developing / erasing threshold voltages of the electrochromic display devices of Examples 1 to 4 and Comparative Examples 1 to 5.

  From the above results, the decoloring threshold voltage increased by 3 to 3.5 V in Example 3 in which the nickel oxide layer, the titanium oxide layer, and the nickel oxide layer in the low oxygen excess state were stacked. As a result, it is considered that the display memory performance was improved.

<Example 5 and Comparative Example 6>
(Preparation of display electrode and electrochromic layer)
An ITO film having a thickness of about 100 nm was formed on a 40 mm × 40 mm glass substrate (display substrate) by a sputtering method in a 20 mm × 20 mm region and a lead portion to produce a first display electrode. The electric resistance in the first display electrode surface was about 200Ω. A titanium oxide fine particle dispersion (SP210 Showa Titanium) is spin-coated thereon, a titanium oxide particle film is formed by annealing at 120 ° C. for 15 minutes, and further, a viologen which is an electrochromic compound that develops a magenta color on it. A 1 wt% 2,2,3,3-tetrafluoropropanol solution of the compound was spin-coated, and a first electrochromic layer composed of titanium oxide particles and an electrochromic compound was formed by annealing at 120 ° C. for 10 minutes.

Subsequently, an inorganic insulating layer of ZnS—SiO ₂ (8/2) was formed thereon with a thickness of 100 nm by a sputtering method. Further, an ITO film having a thickness of about 100 nm is formed on this by forming a 20 mm × 20 mm region in a portion overlapping with the ITO film formed by the first display electrode, and a partial lead-out portion different from the first display electrode is formed. Then, a second display electrode was produced. The resistance in the second electrode plane was about 200Ω. Further, the resistance between the first display electrode and the second display electrode was 40 MΩ or more, which was an insulating state.

  A titanium oxide fine particle dispersion (SP210 Showa Titanium) is spin-coated thereon, and a titanium oxide particle film is formed by annealing at 120 ° C. for 15 minutes. Further, a viologen compound that is an electrochromic compound that develops a yellow color thereon A second electrochromic layer composed of titanium oxide particles and an electrochromic compound was formed by spin-coating a 1 wt% solution of 2,2,3,3-tetrafluoropropanol and annealing at 120 ° C. for 10 minutes.

(Preparation of pixel electrode and charge retention layer)
An ITO film having a thickness of about 100 nm was formed on a 40 mm × 40 mm glass substrate (counter substrate) by sputtering, and then a pixel electrode having a 150 μm / 150 μm line / space and a lead-out portion were formed by photolithography. Subsequently, a nickel oxide layer (10 nm), a titanium oxide layer (10 nm), and a titanium oxide layer (10 nm) in a high oxygen excess condition than the counter substrate are formed by sputtering over the entire counter substrate on which the pixel electrode is formed, except for the lead portion. A nickel oxide layer (100 nm) and a titanium oxide layer (5 nm) under low oxygen excess conditions were sequentially formed, and the charge retention layer and protective layer of Example 5 were produced. The oxygen flow rate ratio during nickel oxide film formation was 10% under high oxygen excess conditions and 4% under low oxygen excess conditions. Each film thickness is shown in parentheses. Further, the surface resistance of the charge retention layer and the protective layer prepared in Example 5 was 1E + 6Ω / □ or more. Further, as Comparative Example 6, a counter substrate in which only the pixel electrode made of the ITO film was formed and the charge retention layer and the protective layer were not formed was also produced.

(Production of electrochromic display device)
Tetrabutylammonium perchlorate as the electrolyte, dimethyl sulfoxide and polyethylene glycol (molecular weight: 200) as the solvent, and UV curing adhesive (trade name: PTC10, manufactured by Jujo Chemical Co., Ltd.) in a weight ratio of 1.2: 5.4: 6 16 was prepared by adding 20 wt% of white titanium oxide particles (trade name: CR50, manufactured by Ishihara Sangyo Co., Ltd., average particle size: about 250 nm) to the solution mixed in Step No. 16, and applied to the counter substrate side. Then, UV light irradiation was cured from the opposite substrate side and bonded together to produce an electrochromic display device. The thickness of the electrolyte layer was set to 10 μm by mixing 0.2 wt% of bead spacers with the electrolyte layer.

(Color development test)
Color development evaluation of the electrochromic display device of Example 5 produced above was performed.
Two of the pixel electrodes were selected, the selected pixel electrode was connected to the positive electrode, the first display electrode was connected to the negative electrode, and a voltage of +6 V was applied for 100 msec using a constant voltage power source. Magenta-colored thin lines reflecting the shapes of the two selected pixel electrodes were observed in the first electrochromic layer. Subsequently, one of the previously selected pixel electrodes and another one that has not developed color are selected, the selected pixel electrode is connected to the positive electrode, the second display electrode is connected to the negative electrode, and a constant voltage is selected. A voltage of +6 V was applied for 100 msec using a power source. Yellow thin lines reflecting the selected two electrode shapes were observed in the second electrochromic layer. Among these, a red thin line, which is a subtractive color mixture of magenta and yellow, was observed immediately above the continuously selected pixel electrodes.
The color development of the electrochromic display device of Comparative Example 6 produced above was evaluated in the same manner as in Example 5. Immediately after the voltage application, as in Example 5, magenta, red, and yellow fine lines were observed.

Subsequently, the display memory properties of Example 5 and Comparative Example 6 10 minutes after the voltage application were visually evaluated.
In the electrochromic device of Example 5, magenta, red, and yellow fine lines were confirmed even after 10 minutes, whereas in Comparative Example 6, each fine line could not be confirmed after 10 minutes.

  Subsequently, repeated durability evaluation of the electrochromic display devices manufactured in Example 5 and Comparative Example 2 was performed. As in the color development test, two pixel electrodes are selected, the selected pixel electrode is connected to the positive electrode, the first display electrode is connected to the negative electrode, and +1 mA is supplied for 100 msec using a constant current power source. A magenta thin line was displayed on the electrochromic layer. Subsequently, one of the previously selected pixel electrodes and another one of the other uncolored portions are selected, the selected pixel electrode is connected to the positive electrode, the second display electrode is connected to the negative electrode, and a constant current is selected. Using a power source, +1 mA was allowed to flow for 100 milliseconds, and a yellow thin line was displayed on the second electrochromic layer. Thereafter, three pixel electrodes corresponding to the displayed thin lines were selected, the selected pixel electrodes were connected to the positive electrode, and the first and second display electrodes were short-circuited and connected to the negative electrode. Using a constant current power source, -1 mA was passed for 200 msec, and the magenta, red and yellow displays were erased. The above operation was performed 500 times, and the display of the magenta, red, and yellow thin lines after the operation was visually observed.

  The electrochromic device of Example 5 displayed magenta, red, and yellow thin lines that were comparable to the first time, whereas the electrochromic device of Comparative Example 6 displayed only very thin magenta, red, and yellow thin lines. Met. Further, the pixel electrode of the electrochromic device of Comparative Example 6 was discolored black.

<Example 6>
(Preparation of display electrode and electrochromic layer)
An ITO film having a thickness of about 100 nm was formed on a 90 mm × 90 mm glass substrate (display substrate) by a sputtering method in an 80 mm × 65 mm region and a lead portion to produce a first display electrode. The electric resistance in the first display electrode surface was about 200Ω. A titanium oxide fine particle dispersion (SP210 Showa Titanium) is spin-coated thereon, a titanium oxide particle film is formed by annealing at 120 ° C. for 15 minutes, and further, a viologen which is an electrochromic compound that develops a magenta color on it. A 1 wt% 2,2,3,3-tetrafluoropropanol solution of the compound was spin-coated, and a first electrochromic layer composed of titanium oxide particles and an electrochromic compound was formed by annealing at 120 ° C. for 10 minutes.

Subsequently, an inorganic insulating layer of ZnS—SiO ₂ (8/2) was formed thereon with a thickness of 100 nm by a sputtering method. Further, an ITO film having a thickness of about 100 nm is formed on the first display electrode in a region of 80 mm × 65 mm by a sputtering method, and a partial lead-out portion different from the first display electrode is formed. Then, a second display electrode was produced. The resistance in the second electrode plane was about 200Ω. Further, the resistance between the first display electrode and the second display electrode was 40 M or more, which was an insulating state.

  A titanium oxide fine particle dispersion (SP210 Showa Titanium) is spin-coated thereon, and a titanium oxide particle film is formed by annealing at 120 ° C. for 15 minutes. Further, a viologen compound that is an electrochromic compound that develops a yellow color thereon A second electrochromic layer composed of titanium oxide particles and an electrochromic compound was formed by spin-coating a 1 wt% solution of 2,2,3,3-tetrafluoropropanol and annealing at 120 ° C. for 10 minutes.

(Preparation of charge retention layer)
A sputtering method is used for a pixel electrode formation area of a low-temperature polysilicon TFT substrate (pixel electrode material: ITO, pixel electrode formation region 80 × 65 mm, 100 ppi, 2Tr1C configuration, current drive type) having a 4-inch diagonal active matrix. A nickel oxide layer (10 nm) under a high oxygen excess condition, a titanium oxide layer (10 nm), a nickel oxide layer (100 nm) under a low oxygen excess condition, and a titanium oxide layer (5 nm) are sequentially formed to form a charge retention layer and a protective layer. Was made. The oxygen flow rate ratio during nickel oxide film formation was 10% under high oxygen excess conditions and 4% under low oxygen excess conditions. Each film thickness is shown in parentheses. Moreover, the surface resistance of the charge retention layer and the protective layer prepared in Example 6 was 1E + 6Ω / □ or more.

(Production of electrochromic display device)
Tetrabutylammonium perchlorate as the electrolyte, dimethyl sulfoxide and polyethylene glycol (molecular weight: 200) as the solvent, and UV curing adhesive (trade name: PTC10, manufactured by Jujo Chemical Co., Ltd.) in a weight ratio of 1.2 to 5.4 to 6 pairs 16 was prepared by adding 20 wt% of white titanium oxide particles (trade name: CR50, manufactured by Ishihara Sangyo Co., Ltd., average particle diameter: about 250 nm) to the solution mixed in Step 16, and applied dropwise onto the TFT substrate (counter substrate) side. Thereafter, it was superposed on the display substrate, cured by UV light irradiation from the TFT substrate side, and bonded together to produce an electrochromic display device. The thickness of the electrolyte layer was set to 10 μm by mixing 0.2 wt% of bead spacers with the electrolyte layer.

(display)
The first display electrode was connected to a driving power source to display a still image. A magenta monochrome still image having a contrast ratio of 10: 1 was obtained by driving for about 1 second. Subsequently, the second display electrode was connected to a driving power source, and a still image display different from the previous one was performed. A still image composed of a subtractive mixture of magenta and yellow with a contrast ratio of 10: 1 was obtained by driving for about 1 second. This display image was not inferior to that immediately after display even after 5 minutes had passed since display.

DESCRIPTION OF SYMBOLS 1 Display substrate 2 Display electrode 3 Electrochromic layer 4 Electrolyte solution 5 White reflection layer 6 Protective layer 7 Charge retention layer 8 Pixel electrode 9 Opposite substrate 10 Insulating layer 11 Drive device

JP 2007-212493 A Japanese Patent Publication No. 02-036931 Japanese Patent No. 2730139

Displays Vol.25, p223-230, 2004

Claims (5)

A display substrate and a counter substrate provided opposite to each other;
Display electrodes provided on the display substrate;
A plurality of pixel electrodes provided on the counter substrate;
An electrochromic layer sandwiched between the display substrate and the counter substrate and provided in contact with the display electrode;
On the plurality of pixel electrodes, a charge retention layer formed over the entire surface of the plurality of pixel electrode formation regions;
A protective layer provided on the charge retention layer so as to cover the charge retention layer;
An electrolyte solution containing an electrolyte filled between the display electrode and the pixel electrode;
The charge retention layer comprises nickel oxide;
The electrochromic display device according to claim 1, wherein a surface structure of the multilayer structure including the charge retention layer and the protective layer is 1E + 6Ω / □ or more. A display substrate and a counter substrate provided opposite to each other;
A plurality of display electrodes spaced apart from each other;
A plurality of pixel electrodes provided on the counter substrate and opposed to the plurality of display electrodes;
A plurality of electrochromic layers of each of the plurality of display substrates;
On the plurality of pixel electrodes, a charge retention layer formed over the entire surface of the plurality of pixel electrode formation regions;
A protective layer provided on the charge retention layer so as to cover the charge retention layer;
An electrolyte containing an electrolyte that is filled between the display electrode closest to the display substrate and the pixel electrode;
The charge retention layer comprises nickel oxide;
The electrochromic display device according to claim 1, wherein a surface structure of the multilayer structure including the charge retention layer and the protective layer is 1E + 6Ω / □ or more. A display substrate and a counter substrate provided opposite to each other;
A plurality of display electrodes spaced apart from each other;
A plurality of driving elements separately provided on the counter substrate;
A plurality of pixel electrodes electrically connected by the plurality of driving elements, respectively, and facing the plurality of display electrodes;
A plurality of electrochromic layers of each of the plurality of display substrates;
On the plurality of pixel electrodes, a charge retention layer formed over the entire surface of the plurality of pixel electrode formation regions;
A protective layer provided on the charge retention layer so as to cover the charge retention layer;
An electrolyte containing an electrolyte that is filled between the display electrode closest to the display substrate and the pixel electrode;
The charge retention layer comprises nickel oxide;
The electrochromic display device according to claim 1, wherein a surface structure of the multilayer structure including the charge retention layer and the protective layer is 1E + 6Ω / □ or more.   4. The electrochromic display device according to claim 1, wherein the charge retention layer includes a plurality of nickel oxide layers and titanium oxide layers having different oxygen excess states. 5.   5. The charge retention layer is formed by laminating a nickel oxide layer having a high oxygen excess state, a titanium oxide layer, and a nickel oxide layer having a low oxygen excess state in this order from the pixel electrode side. The electrochromic display device according to any one of the above.

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