JP2007148230A - Electrochromic display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full-color electrochromic display element which has greatly improved memory characteristics and a full-color electrochromic display element which is easily made full-color and has greatly improved memory characteristics. <P>SOLUTION: The electrochromic display element is characterized in that electrode layers are formed on surfaces of at least one pair of opposite substrates, a porous film is formed of an insulating substance on at least one electrode layer, and an electrolyte containing electrochromic coloring matter is charged between the opposite substrates. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrochromic display element having greatly improved memory characteristics and a full color electrochromic display element that is easy to achieve full color and whose memory characteristics are greatly improved.

  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 increasingly increasing.

  As such electronic information browsing means, conventional liquid crystal displays and CRTs, and in recent years, light-emitting types such as organic EL displays are mainly used. Particularly, when electronic information is document information, it is relatively long time. It is necessary to pay close attention to this browsing means, and these actions are not necessarily human-friendly means. Generally, as a 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 to compensate 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 complicated TFT circuit required to improve the memory performance. In addition, a display element based on electrophoresis requires a high voltage of 10 V or more, and there is a concern about durability due to electrophoretic particle aggregation.

  On the other hand, an electrochromic display element (hereinafter, also referred to as an EC display element or simply a display element) can be driven at a low voltage of 3 V or less, but has a slow reaction speed, an insufficient image density as a display element, and the like. There was a problem.

In order to solve these problems, Patent Document 1 discloses a technique of forming a porous film with conductive nanoparticles and adsorbing a P or N type chromic material. Patent Document 2 discloses a first electrode + nanoporous film. Electrode + P or N type electrochromic agent (hereinafter also referred to as EC agent), second electrode + nanoporous + P or N type EC agent technology, Patent Document 3 states that EC agent + nanoporous nanometer in the first claim Crystal, viologen + phosphonoethyl in the second claim, TiO ₂ , 4 μm, 200 ° C., 12 hours heating to crystallize 7 nm to 12 nm in the examples, but the material combination of the present invention is not mentioned .

  Examples of semiconductor nanoporous layers are given in Patent Documents 3 to 10 and the like, but the porous film made of an insulating material of the present invention does not correspond to this.

  Patent Document 11 discloses that a conductor / semiconductor / insulator particle structure is used as an electrode using particles adsorbed with an EC agent. However, the obtained effect is different from that of the present invention.

  As an EC element, one in which an electrolyte solution showing an electrochromic reaction is filled between opposing supports is known. It is also known to use a porous layer as an electrode.

  In conventional methods, the porous layer is a conductive or semiconductive layer. Such a porous film has been reported to have an effect of promoting an electrochemical reaction.

However, when an appropriate voltage is applied, the reaction is promoted. However, when an overvoltage is applied or an energization time longer than necessary is passed, the reaction may go too far and the dye may not exhibit a reversible reaction. Furthermore, partial electrolytic concentration tends to occur, and color tone deterioration may easily occur.
European Patent No. 1,224,505 US Pat. No. 6,870,657 US Pat. No. 6,861,014 JP 2004-248242 A JP 2003-255400 A JP 2003-270670 A JP 2003-270671 A JP 2003-270672 A JP 2003-302659 A JP 2003-315839 A International Publication No. 04/066722 Pamphlet

  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 having greatly improved memory characteristics and a full color electrochromic display element that is easily made full-color and has greatly improved memory characteristics. That is.

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

  1. An electrochromic display element containing an electrochromic medium between at least a pair of substrates, wherein an electrode layer is applied to the inner surfaces of both substrates, and an insulating porous film is formed on at least one of the electrode layers An electrochromic display element.

  2. 2. The electrochromic display element according to 1, wherein the electrode layer on the side on which the insulating porous film is formed and the substrate are substantially transparent.

  3. 3. The electrochromic display element according to 1 or 2, wherein the insulating porous film is formed of metal oxide fine particles.

4). 4. The electrochromic display element according to 3, wherein the metal oxide fine particles are SiO ₂ or Al ₂ O ₃ .

  5. The electrochromic display element according to any one of claims 1 to 4, wherein the electrochromic medium includes at least an electrochromic agent and an electrolyte.

  6). 6. The electrochromic display element according to 5, wherein the electrochromic agent is adsorbed on an insulating porous film.

  According to the present invention, it is possible to provide an electrochromic display element with greatly improved memory characteristics and a full color electrochromic display element that is easy to achieve full color and with significantly improved memory characteristics.

  As a result of intensive studies, the present inventors have determined that the porous thin film using an insulating material does not play an electrical role while holding the electrochromic dye around the electrode. Has been found to reduce.

  Hereinafter, the present invention will be described in detail.

[Insulating porous membrane]
In the present invention, a porous film made of an insulating material is formed on at least one of the electrode layers. The insulating porous film according to the present invention may be a film 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, and electronic insulating properties. And a porous solid body having a low relative dielectric constant such as a silicon-containing compound, and the like.

  As a method for forming a porous film, there are a sintering method (fusion method. Polymer fine particles and inorganic particles are partially fused by adding a binder, etc., and pores formed between the particles are used), extraction method (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 a solvent to obtain pores), and the polymer is heated or degassed, etc. Known forming methods such as a foaming method for foaming, a phase change method for phase separation of a mixture of polymers by operating a good solvent and a poor solvent, and a radiation irradiation method for forming pores 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.

The porous film is preferably made of metal oxide fine particles. Particularly preferably used in the present invention are Al ₂ O ₃ and SiO ₂ . These films are particularly preferable because of their high transparency and resistance to electrolyte solvents.

As Al ₂ O ₃ particles, cubic and orthorhombic ones are known, but either is preferably used in the present invention. The SiO ₂ particles are particularly preferably amorphous particles.

  The particle shape is particularly preferably close to a true sphere. If the particle shapes are not uniform, there is a high possibility that electric field concentration will occur in the protrusions.

  The purity of each metal oxide is preferably sufficiently high, and a high purity such as 99% or more is particularly preferable.

The average particle diameter of the fine particles is preferably 1 nm to 5 μm, more preferably 10 to 50 nm. The specific surface area is preferably from ^{1 × 10 -3 ~1 × 10 2} m 2 / g by a simple BET method, more preferably from ^{1 × 10 -2 ~10m 2 / g} . The shape of the fine particles may be any shape such as indefinite shape, needle shape, or spherical shape.

  For the purpose of the present invention, the pore size of the porous membrane is required to sufficiently hold the electrochromic dye-containing liquid inside the porous membrane. At the same time, since the mechanical strength of the membrane is required, too large pores are not preferable.

  The film thickness of the porous film is not particularly defined according to the purpose, but is preferably about 30 μm or less. The lower limit is about 0.1 μm.

〔substrate〕
Examples of the 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 acetal. Synthetic plastic films such as polystyrene can also be preferably used. Syndiotactic polystyrenes are also preferred. These can be obtained, for example, by the methods described in JP-A-62-1117708, JP-A-1-46912, and 1-178505.

  Further, a metal substrate such as stainless steel, a paper support such as baryta paper and resin coated paper, and a support provided with a reflective layer on the plastic film, supported by JP-A-62-253195 (pages 29 to 31) The thing described as a body is mentioned. RDNo. 17643, page 28, ibid. No. 18716, page 647, right column to page 648, left column, and No. 307105, page 879 can also be preferably used. 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.

  When firing of the porous film is necessary, a glass substrate is preferably used. The opposing substrates may not be the same material.

  It is preferable that the substrate on the side where the porous film made of the insulating material is formed is substantially transparent. The term “substantially transparent” means that light in the visible region is sufficiently transmitted. Specifically, 70% or more of light in the visible region is transmitted.

[Electrochromic medium]
The electrochromic display element of the present invention contains an electrochromic medium between the electrodes. The electrochromic medium includes at least an electrochromic agent and an electrolyte. The state can be a liquid or a gel.

  Electrochromic media can be contained between the electrodes by various coating methods, screen printing methods, ink jet methods, sol-gel methods, etc. on the electrodes (preferably on the electrode on which the insulating porous film is formed). A method of forming a medium layer and then sealing it together with a counter electrode, or a method of injecting a predetermined distance between electrode substrates sealed in advance by a vacuum injection method, an atmospheric injection method, a meniscus method, etc. Can be selected from known methods.

  At that time, the electrochromic agent can be adsorbed on the insulating porous film in advance.

(Electrochromic agent)
The electrochromic agent used in the present invention is a compound that changes color by accepting electrons. An organic compound is particularly preferable. Various viologen compounds described in JP-A No. 2002-328401, dyes described in JP-T-2004-537743, and other known dyes can be used. When a leuco dye is used, a developer or a decolorizer may be used in combination as necessary.

(Electrolytes)
The electrolyte according to the present invention is not particularly limited as long as the electrochromic layer can be colored, decolored, changed in color, etc., but usually has an ionic conductivity of 1 × 10 ⁻⁷ S / cm or more at room temperature. What is shown is preferred. The electrolyte substance is not particularly limited, and a liquid system or a gelled liquid system that can fill the pores formed by the fine particles and the electrode substrate and the fine particles can be used.

  As said liquid system, what melt | dissolved supporting electrolytes, such as salts, acids, alkalis, etc. in the solvent can be used. The solvent is not particularly limited as long as it can dissolve the supporting electrolyte, but is preferably polar. Specifically, water, methanol, ethanol, propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane, acetonitrile, γ-butyrolactone, γ-valerolactone, sulfolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, acetonitrile, propiononitrile, glycerol Organic polar solvents such as talonitrile, adiponitrile, methoxyacetonitrile, dimethylacetamide, methyl pyrrolidinone, dimethyl sulfoxide, dioxolane, sulfolane, trimethyl phosphate, polyethylene glycol and the like are preferable, preferably propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane , Acetonitrile, γ-butyrolactone, sulfolane, dioxola , Dimethylformamide, dimethoxyethane, tetrahydrofuran, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethyl sulfoxide, dioxolane, sulfolane, trimethyl phosphate, organic polar solvents such as polyethylene glycol is desirable. These can be used alone or as a mixture in use.

The salt as the supporting electrolyte is not particularly limited, and examples thereof include inorganic ion salts such as various alkali metal salts and alkaline earth metal salts, quaternary ammonium salts, cyclic quaternary ammonium salts, and the like. Specifically, LiClO ₄ LiSCN, LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiPF ₆ , LiI, NaI, NaSCN, NaClO ₄ , NaBF ₄ , NaAsF ₆ , alkali metal salts of Na, K, etc. _{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 quaternary ammonium salts and cyclic quaternary ammonium salts such as or mixtures thereof as preferred.

  Acids as the supporting electrolyte are not particularly limited, and examples include inorganic acids and organic acids, and specific examples include sulfuric acid, hydrochloric acid, phosphoric acids, sulfonic acids, and carboxylic acids. The alkali as the supporting electrolyte is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.

  As the gelled liquid electrolyte, it is possible to use a viscous or gelled material by adding a polymer or a gelling agent to the liquid electrolyte. The polymer to be used is not particularly limited, and examples thereof include polyacrylonitrile, carboxymethyl cellulose, polyvinyl chloride, polyethylene oxide, polyurethane, polyacrylate, polymethacrylate, polyamide, polyacrylamide, cellulose, polyester, polypropylene oxide, and Nafion. . The gelling agent is not particularly limited, and examples thereof include oxyethylene methacrylate, oxyethylene acrylate, urethane acrylate, acrylamide, and agar.

(Thickener)
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 (vinyl) Pyrrolidone), poly (alkylene glycol), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (styrene-maleic anhydride), copoly (styrene) -Acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), poly (urethanes), phenoxy resins, poly ( Vinyl chloride Den), poly (epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, poly (amides), hydrophobic transparent binders such as polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, polyester, Examples include polycarbonate, polyacrylic acid, polyurethane and the like.

  These thickeners may be used in combination of two or more. Further, compounds described on pages 71 to 75 of JP-A No. 64-13546 can be exemplified. Among these, the compounds preferably used are polyvinyl alcohols, polyvinyl pyrrolidones, hydroxypropyl celluloses, and polyalkylene glycols from the viewpoint of compatibility with various additives and improvement in dispersion stability of white particles.

[Other additives]
Examples of the constituent layers of the display element of the present invention include auxiliary layers such as a protective layer, a filter layer, an antihalation layer, a crossover light cut layer, and a backing layer. Sensitizer, noble metal sensitizer, photosensitive dye, supersensitizer, coupler, high boiling point solvent, antifoggant, stabilizer, development inhibitor, bleach accelerator, fixing accelerator, color mixing inhibitor, formalin scavenger, Toning agents, hardeners, surfactants, thickeners, plasticizers, slip agents, UV absorbers, anti-irradiation dyes, filter light absorbing dyes, anti-bacterial agents, polymer latex, heavy metals, antistatic agents, matting agents Etc. can be contained as required.

  More specifically, these additives described above are described in detail in Research Disclosure (hereinafter abbreviated as RD), Volume 176 Item / 17643 (December 1978), Volume 184, Item / 18431 (August 1979), Volume 187. Item / 18716 (November 1979) and Volume 308 Item / 308119 (December 1989).

  The types of compounds and their descriptions shown in these three research disclosures are listed below.

Additive RD17643 RD18716 RD308119
Page Classification Page Classification Page Classification Chemical sensitizer 23 III 648 Upper right 96 III
Sensitizing dye 23 IV 648-649 996-8 IV
Desensitizing dye 23 IV 998 IV
Dye 25-26 VIII 649-650 1003 VIII
Development accelerator 29 XXI 648 Upper right Fog inhibitor, Stabilizer
24 IV 649 Upper right 1006-7 VI
Brightener 24 V 998 V
Hardener 26 X 651 Left 1004-5 X
Surfactant 26-7 XI 650 Right 1005-6 XI
Antistatic agent 27 XII 650 Right 1006-7 XIII
Plasticizer 27 XII 650 Right 1006 XII
Slipper 27 XII
Matting agent 28 XVI 650 Right 1008-9 XVI
Binder 26 XXII 1003-4 IX
Support 28 XVII 1009 XVII
〔substrate〕
Examples of the substrate that can be used in the display device of the present invention include polyolefins such as polyethylene and polypropylene, polycarbonates, cellulose acetate, polyethylene terephthalate, polyethylene dinaphthalene dicarboxylate, polyethylene naphthalates, polyvinyl chloride, and polyimide. Synthetic plastic films such as polyvinyl 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. Further, a metal substrate such as stainless steel, a paper support such as baryta paper and resin coated paper, and a support provided with a reflective layer on the plastic film, supported by JP-A-62-253195 (pages 29 to 31) The thing described as a body is mentioned. RDNo. 17643, page 28, ibid. No. 18716, page 647, right column to page 648, left column, and No. 307105, page 879 can also be preferably used. 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.

[Counter electrode]
In the EC display element of the present invention, it is preferable that at least one of the counter electrodes is a metal 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. Among them, 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.

  In the display element of the present invention, it is preferable that the electrode on the side where the porous film made of the insulating material is formed is substantially transparent. 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 manner, for example, an ITO film may be vapor-deposited on the 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.

  The gap between the electrodes varies depending on the dye used and the required rewriting speed and concentration, but can be set in the range of several tens to several hundreds of μm. Usually, it is about 20-500 micrometers.

[Bonded transparent conductive fine particle layer]
In the display element of the present invention, it is preferable that at least one of the counter electrodes has a layer containing transparent conductive fine particles by binding.

  As fine particles forming a layer containing transparent conductive fine particles, particles such as polymethyl methacrylate, cellulose, polycarbonate, titanium oxide, silicon oxide, zinc oxide, alumina, zeolite, and the like can be used. The conductive fine particles that can form the electrode film with the fine particles themselves include conductive fine particles such as Sn-doped indium oxide (ITO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide. In addition, fine particles in which the surface of the titanium oxide fine particles is coated with ITO, ATO, or FTO can be used. Here, the term “conductivity” as used herein refers to a powder resistance at a pressure of 10 MPa of 0.01 to 100 Ωcm, preferably 0.01 to 10 Ωcm.

In the present invention, the average particle size of the fine particles is preferably 5 nm to 10 μm, more preferably 20 nm to 1 μm. The specific surface area is preferably from ^{1 × 10 -3 ~1 × 10 2} m 2 / g by a simple BET method, more preferably from ^{1 × 10 -2 ~10m 2 / g} . The shape of the fine particles may be any shape such as indefinite shape, needle shape, or spherical shape.

  As the binding of the fine particles by the transparent conductive film, a sol-gel method can be employed. For example, Journal of the Ceramic Society of Japan, 102, 2, p200 (1994), Journal of Ceramic Industry Association 90, 4, p157, J . of Non-Cryst. Films of ITO and ATO can be formed by the method described in Solids, 82, 400 (1986). Moreover, a transparent conductive film can be formed by a sol-gel method using a sol liquid in which nonconductive fine particles such as PMMA spherical particles are dispersed, and a conductive film can be formed on the surface of these fine particles. Thus, the substantial surface area of the electrode can be increased by making the pores formed by the fine particles and the electrode substrate and the fine particles have the transparent conductive film as an outer shell.

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

  The sealing agent is for sealing so that the electrochromic medium does not leak to the outside, and is also called a sealing agent, epoxy resin, urethane resin, acrylic resin, vinyl acetate resin, ene-thiol resin, Curing types such as a thermosetting type, a photo-curing type, a moisture-curing type, and an anaerobic-curing type such as a silicone-based resin and a modified polymer resin 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 maintain an appropriate interval between the substrates, 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.

[Screen printing]
In the present invention, a sealant, a columnar structure, an electrode pattern and the like can be formed by a screen printing method. In the screen printing method, a screen on which a predetermined pattern is formed is placed on an electrode surface of a substrate, and a printing material (a composition for forming a columnar structure, such as a photocurable resin) is placed on the screen. Then, the squeegee is moved at a predetermined pressure, angle, and speed. Thereby, the printing material is transferred onto the substrate through the pattern of the screen. Next, the transferred material is heat-cured and dried. When the columnar structure is formed by the screen printing method, the resin material is not limited to a photocurable resin, and for example, a thermosetting resin such as an epoxy resin or an acrylic resin or a thermoplastic resin can also be used. As thermoplastic resins, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polymethacrylate resin, polyacrylate resin, polystyrene resin, polyamide resin, polyethylene resin, polypropylene resin, fluororesin, polyurethane resin , Polyacrylonitrile resin, polyvinyl ether resin, polyvinyl ketone resin, polyether resin, polyvinyl pyrrolidone resin, saturated polyester resin, polycarbonate resin, chlorinated polyether resin and the like. The resin material is preferably used in the form of a paste by dissolving the resin in an appropriate solvent.

  After the columnar structure or the like is formed on the substrate as described above, a spacer is provided on at least one of the substrates as desired, and the pair of substrates are overlapped with the electrode formation surfaces facing each other to form an empty cell. . A pair of stacked substrates is heated while being pressed from both sides, whereby the display cells are obtained. In order to obtain a display element, an electrolyte composition may be injected between substrates by a vacuum injection method or the like. Alternatively, when the substrates are bonded together, the electrolyte composition may be dropped on one substrate, and the liquid crystal composition may be sealed simultaneously with the bonding of the substrates.

[Display element driving method]
The display element of the present invention is characterized in that an electrochromic agent is colored during oxidation and an image is displayed by performing a driving operation of the counter electrode so as to be transparent during reduction.

  In the present invention, examples of the driving method of the electrochromic display device include the method described on pages 77 to 102 of “Electrochromic display” (published by 1991 Sangyo Tosho Co., Ltd.).

  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 advantages such as gradation and memory function. For example, a circuit described in FIG. 5 of JP-A-2004-29327 can be used. In the present invention, among the above-described driving operations, the active matrix driving is preferable from the viewpoint that the effects of the present invention can be expressed more.

  FIG. 1 illustrates an example of an electrochromic display element of the present invention.

[Product application]
The electrochromic display element of the present invention can be used in an electronic book field, an ID card-related field, a public-related field, a transportation-related field, a broadcasting-related field, a settlement-related field, a distribution logistics-related 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, health insurance cards, Basic Resident Registers, passports, electronic books, etc.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “%” in the examples represents “mass%”.

Example [Production of patterned electrode substrate]
A substrate on which an ITO film having a thickness of about 0.1 μm was formed on a glass having a thickness of 1.5 mm was etched to form an ITO electrode pattern having a pitch of 5 mm and a width of 4 mm.

[Preparation of porous membrane]
(Porous membrane 1: the present invention)
0.42 g of Al ₂ O ₃ (manufactured by Kanto Chemical Co., Nanotech 01176-13) and 0.25 g of polyethylene glycol (average molecular weight 500,000) are dispersed / dissolved in 5 g of propylene carbonate, and a wire bar is formed on the patterned electrode. The whole surface was applied using This was baked at 500 ° C. for 1 hour to obtain a porous membrane 1. The film thickness of the obtained porous membrane was 3.5 μm.

(Porous membrane 2: the present invention)
Disperse / dissolve 0.26 g of SiO ₂ (manufactured by Kanto Chemical Co., Nanotech 37848-23) and 0.25 g of polyethylene glycol (average molecular weight 500,000) in 5 g of propylene carbonate, and use a wire bar on the patterned electrode. The whole surface was applied. This was baked at 500 ° C. for 1 hour to obtain a porous membrane 2. The film thickness of the obtained porous membrane was 2.8 μm.

(Porous membrane 3: Comparative example)
A mixture of SnO ₂ doped with TiO ₂ and Sb (Ishihara Sangyo Co., Ltd., ET-300W) 0.59 g was dispersed in 5 g of propylene carbonate, and this was coated on the entire surface of the patterned electrode using a wire bar. This was baked at 500 ° C. for 1 hour to obtain a porous membrane 3. The resulting porous membrane had a thickness of 3.2 μm.

(Porous membrane 4: Comparative example)
SnO ₂ (manufactured by Kanto Chemical Co., Nanotech 37314-13) and polyethylene glycol (average molecular weight of 500,000) 0.17 g were dispersed in 5 g of propylene carbonate, and this was patterned on the entire surface using a wire bar on the patterned electrode. Applied. This was baked at 500 ° C. for 1 hour to obtain a porous film 4. The film thickness of the obtained porous membrane was 3.8 μm.

[Production of display element]
(Preparation of electrochromic medium)
0.05 mol / L lithium perchlorate and 0.05 mol / L ferrocene were dissolved in γ-butyrolactone. An electrochromic medium was obtained by dissolving bis- (2-phosphonoethyl) -4,4-bipyridinium dichloride in an amount corresponding to 0.2 mol / L as an electrochromic dye.

  Through a glass spacer (average particle diameter 20 μm), the glass with ITO on which no electrode pattern is formed and the glass substrate on which the porous films 1 to 4 are formed on the electrode surface are opposed to the ITO side. The electrochromic medium prepared above was overlapped and injected into the gap to seal the periphery, and display elements 1 to 4 were manufactured.

[Evaluation of display element]
(Drive experiment)
For each display element, the drive-reset was repeated while changing the voltage application time under the condition of constant drive voltage, and the change in reflectance at 500 nm was measured. The result is shown in FIG.

  From FIG. 2, the porous films 1 and 2 of the present invention obtained good results with no reduction in reaction rate and no dye burn-in. On the other hand, in the porous films 3 and 4 of the comparative example, the reaction rate decreased and the dye burn-in was also observed.

It is a figure which shows the example of the electrochromic display element of this invention. It is a figure which shows the reflectance change of a display element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating fine particle 2 Electrode layer 3 Conductive fine particle 4 Electrochromic medium 5 Seal 6 Substrate

Claims (6)

An electrochromic display element containing an electrochromic medium between at least a pair of substrates, wherein an electrode layer is applied to the inner surfaces of both substrates, and an insulating porous film is formed on at least one of the electrode layers An electrochromic display element. 2. The electrochromic display element according to claim 1, wherein the electrode layer and the substrate on the side on which the insulating porous film is formed are substantially transparent. The electrochromic display element according to claim 1, wherein the insulating porous film is formed of metal oxide fine particles. The electrochromic display element according to claim 3, wherein the metal oxide fine particles are SiO ₂ or Al ₂ O ₃ . The electrochromic display element according to claim 1, wherein the electrochromic medium includes at least an electrochromic agent and an electrolyte. The electrochromic display element according to claim 5, wherein the electrochromic agent is adsorbed on an insulating porous film.

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