JP2009042619A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element which can be manufactured at a low temperature and has durability. <P>SOLUTION: The display element having a transparent substrate having at least one transparent electrode on its surface, a substrate having at least one counter electrode on its surface arranged so that as to face the transparent electrode, and an electrolyte layer which contains at least an electrochromic compound between the electrodes. In this case, a porous layer is provided on the transparent electrode via a nonporous undercoat layer, and the nonporous undercoat layer contains partially at least the same substance as a substance which forms the porous layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display element that utilizes the coloring / decoloring reaction of an electrochromic compound.

  In recent years, with the increase in the operating speed of personal computers, the spread of network infrastructure, the increase in capacity and price of data storage, information such as documents and images provided on printed paper on paper has become easier to use electronic information. Opportunities to obtain and browse electronic information are increasing more and more.

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

  As a display means to compensate for these drawbacks, a reflection type display having a so-called memory property that uses external light and does not consume power for image retention is known. However, it 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, electrochromic display elements are known for applications such as light-control glass and anti-glare mirrors because they can be driven at a low voltage (approximately 3 V or less). In recent years, electrochromic devices comprising at least one electrode comprising a semiconductive nanostructured film modified by chemisorption of an electrically active compound are also known (see Patent Documents 1 and 2). .

  The electrochromic device of Patent Document 1 includes a redox chromophore chemisorbed on the surface of a nanostructured semiconductor electrode, and an electrically active compound that can be oxidized or reduced by a reversible method in the electrolyte. It has been dissolved.

  The electrochromic device of Patent Document 2 discloses a nanoporous nanocrystalline film comprising a conductive metal oxide on which an electrically active compound that is a redox promoter or redox chromophore is adsorbed.

  These devices are intended to improve switching speed by adsorbing an electrically active compound in a nanostructured film.

  However, in order to form a nanostructured film of these elements, it is necessary to perform a long time treatment at a high temperature of several hundred degrees, usually 400 ° C. or higher. For this reason, it is necessary to put a high-temperature and long-time treatment process into the production line, which is problematic in terms of productivity. Further, the substrate is limited to glass that is durable to high temperatures.

  On the other hand, the display element is required to be light and easy to carry. For that purpose, it is necessary to make the substrate a lightweight material such as a resin film. However, in the conventional technique, since a high temperature treatment is required, the resin film cannot be used.

  As a method for forming a porous layer at a low temperature, there is a method in which fine particles forming a porous layer are mixed with a small amount of a binder, applied and dried. In such a method, the drying temperature can be lower than 200 ° C.

However, it has been found that the porous layer thus provided has poor adhesion to the transparent electrode, and the porous layer peels off over time and repeated driving. The peeling of the porous layer causes problems such as a decrease in color density and uneven density of the display element.
International Publication No. 97/35227 JP 2003-511837 A

  The present invention has been made in view of the above problems, and an object thereof is to provide a display element that can be manufactured at a low temperature and has sufficient element durability.

  The above problem could be solved by the following configuration.

  1. A transparent substrate having at least one transparent electrode on its surface and a substrate having at least one counter electrode on its surface are arranged so that the transparent electrode and the counter electrode face each other, and at least an electrochromic compound is interposed between the electrodes In a display element having an electrolyte layer containing, a porous layer is provided on a transparent electrode via a non-porous undercoat layer, and the undercoat layer is made of the same material as that forming the porous layer. A display element containing at least a part.

  2. 2. The display element according to 1 above, wherein an electrochromic compound is adsorbed on the porous layer.

  3. 3. The display element according to 1 or 2 above, wherein the porous layer is a semiconductor porous layer containing at least one metal oxide.

  4). 4. The display element according to 3 above, wherein the metal oxide is selected from titanium oxide, tin oxide, and silicon oxide.

  5). The electrolyte layer contains a metal salt compound, and by driving between the electrodes, 1) color change due to oxidation and reduction reaction of the electrochromic compound, or 2) the metal salt on at least one of the counter electrodes (1) to (4), wherein a multicolor display of three or more colors is performed by black display, white display, and color display other than black using a reduction in color of the metal element contained in the compound and a color change caused by oxidative dissolution. The display element according to any one of the above.

  6). 6. The display element according to 5 above, wherein the metal salt compound is a silver salt compound.

  In addition to good durability of the element itself, a display element excellent in the stability of the color density during repeated driving, particularly the stability of the intermediate density could be obtained.

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

  As a result of intensive studies in view of the above problems, the present inventor has provided a porous layer on a transparent electrode via an undercoat layer, and the undercoat layer is made of the same substance as the substance forming the porous layer. By the display element containing the electrochromic compound characterized by containing at least a part thereof, the undercoat layer and the porous layer can be produced at a relatively low temperature of 200 ° C. or less, and when repeatedly used It has been found that a display element having excellent durability can be realized, and the present invention has been achieved.

  Details of the present invention will be described below.

  Each material used for the display element of this invention is demonstrated below.

(substrate)
As a substrate that can be used in the present invention, at least one of the substrates needs to be a transparent substrate having a transparent electrode on the surface in order to form a display element, and the other may be transparent or opaque. A substrate having on the surface thereof is used.

  Examples of the transparent substrate forming the transparent electrode include polyolefins such as polyethylene and polypropylene, polycarbonates, cellulose acetate, polyethylene terephthalate, polyethylene dinaphthalene dicarboxylate, polyethylene naphthalates, polyvinyl chloride, polyimide, and polyvinyl acetals. A synthetic plastic film 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 Nos. 62-117708, 1-46912, and 1-178505. In addition, a glass substrate, an epoxy resin kneaded with glass, or the like can be used.

  On the other hand, as a substrate having a counter electrode on the surface, in addition to the transparent substrate, a metal substrate such as stainless steel, a paper support such as baryta paper and resin coated paper, and a reflective layer are provided on the plastic film. Examples of the support include those described as a support in JP-A-62-253195 (pages 29 to 31). 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.

(Transparent electrode)
The transparent electrode is not particularly limited as long as it is transparent and conducts electricity. For example, Indium Tin Oxide (ITO: Indium Tin Oxide), Indium Zinc Oxide (IZO: Indium Zinc Oxide), Fluorine Doped Tin Oxide (FTO), Indium Oxide, Zinc Oxide, Platinum, Gold, Silver, Rhodium, Copper, Examples thereof include chromium, carbon, aluminum, silicon, amorphous silicon, and BSO (Bismuth Silicon Oxide). In 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.

(Counter electrode)
As the counter electrode according to the present invention, a metal electrode or a transparent electrode can be used. 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. 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.

(Porous layer)
The porous layer according to the present invention is a layer in which countless fine holes are formed, adsorbs an electrochromic compound, and does not inhibit the electrochemical reaction.

  The thickness of the layer needs to be a thickness capable of adsorbing a necessary amount of the electrochromic compound, but if it is too thick, the transparency is impaired and the contrast and resolution are lowered. In consideration of ensuring the transparency of the porous layer, the thickness of the porous layer is preferably 1 to 5 μm.

  Such a porous layer can be formed by various methods, but the most preferable method is a method using fine particles capable of adsorbing an electrochromic compound.

  Preferable fine particles are semiconductor metal oxides, and those in which the layer itself does not exhibit a specific color and is transparent to slightly white are particularly preferable. Examples of such semiconductor metal oxides include titanium oxide, silicon oxide, zinc oxide, tin oxide, and their dopes.

  In view of the adsorptivity of the electrochromic compound and the colorability of the porous layer itself, titanium oxide, tin oxide, and silicon oxide are preferably used.

  The average primary particle of the fine particles is preferably 5 to 100 nm, more preferably 20 to 80 nm. As the shape of the fine particles, an arbitrary shape such as an indefinite shape, a needle shape, a spherical shape, or the like is used.

  As one method for obtaining a porous layer using such fine particles, a sintering method is known, but the fine particles are welded at a high temperature of several hundred degrees to form the fine particles and the porous layer. Although adhesiveness to the substrate can be obtained, there are problems such as narrow selectivity of the substrate and difficulty in incorporating the baking process into the production line, which is not preferable.

  As a method for obtaining a porous layer at a relatively low temperature of 200 ° C. or lower, a sol-gel method, a coating method using a binder such as a binder, and the like are known. The adhesiveness to the transparent electrode is not strong, and when the electrochemical reaction of the electrochromic compound is repeated in the presence of the electrolyte solution, it peels off from the electrode, resulting in a decrease in contrast and resolution, and uneven coloring. .

(Underlayer)
In order to ensure adhesion between the porous layer and the transparent electrode, in the present invention, the following undercoat layer is provided between the porous layer and the transparent electrode.

  The undercoat layer in the present invention is non-porous, is provided between the transparent electrode and the porous layer, and contains at least a part of a substance that forms the porous layer.

  The undercoat layer is required to have transparency so as not to impair the color development performance of the display element, as well as adhesion to the transparent electrode. The thickness is not particularly limited as long as the object is achieved.

  Examples of a thin film forming method suitable for forming such a thin film include a vacuum deposition method, a sputtering method, an ion plating method, and a plasma CVD method. In terms of productivity, the sputtering method, the ion plate method, and the like. Ting method and plasma CVD method are suitable.

  Japanese Patent Application Laid-Open No. 2003-306769 discloses a method for forming a thin film on a substrate by applying plasma energy to a source gas under atmospheric pressure. However, such a method is also preferably used. it can.

(Electrochromic compound)
The electrochromic compound (hereinafter abbreviated as EC compound) used in the display element of the present invention is a phenomenon in which the property of optical absorption (color and light transmittance) of a substance reversibly changes due to electrochemical redox ( Any compound may be used as long as it is a compound exhibiting (electrochromism). Specific compounds include "Electrochromic display" (June 28, 1991, Sangyo Tosho Co., Ltd.) pp27-124, "Development of chromic materials" (November 15, 2000, CMC Corporation) pp81 The compound described in -95 etc. can be mentioned.

(Electrolyte layer)
The display element of the present invention has an electrolyte layer containing an electrolyte between the transparent electrode and the counter electrode.

  The “electrolyte” is generally a substance that ionizes into a cation and an anion when dissolved in a solvent. In the present invention, in addition to the electrolyte layer in which such an electrolyte is dissolved in a solvent, a molten salt or a solid electrolyte (solid electrolyte) having a property of moving ions inside can also be used as the electrolyte layer. It is.

[Electrolyte material]
Examples of the electrolyte that can be used in the display element of the present invention include the following compounds. KCl, KI, KBr, etc. as potassium compounds, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiCF ₃ SO ₃ etc. as lithium compounds, tetraethylammonium perchlorate, tetrabutylammonium perchlorate, tetraethylammonium borofluoride as tetraalkylammonium compounds And tetrabutylammonium borofluoride and tetrabutylammonium halide. Moreover, the molten salt electrolyte composition described in JP-A-2003-187881 paragraphs [0062] to [0081] can also be preferably used. Furthermore, a compound that becomes a redox pair such as I ⁻ / I ³⁻ , Br ⁻ / Br ³⁻ , and quinone / hydroquinone can be used.

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

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

[Thickener added with electrolyte]
In the display element of the present invention, a thickener can be used for the electrolyte. For example, gelatin, gum arabic, poly (vinyl alcohol), hydroxyethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, poly ( Vinylpyrrolidone), poly (alkylene glycol), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (styrene-maleic anhydride), copoly ( Styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), poly (urethanes), phenoxy resins, poly (PVC Redene), poly (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. Moreover, the compound as described in pages 71-75 of Unexamined-Japanese-Patent No. 64-13546 can be mentioned. Among these, the compounds preferably used are polyvinyl alcohols, polyvinyl pyrrolidones, hydroxypropyl celluloses, and polyalkylene glycols from the viewpoint of compatibility with various additives and improvement in dispersion stability of white particles.

[Other additives]
Examples of the constituent layers of the display element of the present invention include auxiliary layers such as a white scattering layer, a protective layer, a filter layer, an antihalation layer, a crossover light cut layer, and a backing layer. Among these auxiliary layers, Various additives such as chemical sensitizers, noble metal sensitizers, photosensitive dyes, supersensitizers, couplers, high boiling point solvents, antifoggants, stabilizers, development inhibitors in the following research disclosures, Bleaching accelerator, fixing accelerator, color mixing inhibitor, formalin scavenger, toning agent, hardener, surfactant, thickener, plasticizer, slip agent, ultraviolet absorber, irradiation prevention dye, filter light absorbing dye, Additives listed as antifungal agents, polymer latex, heavy metals, antistatic agents, matting agents, and the like can be included as necessary.

  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 25-6 VIII 649-650 1003 VIII
Development accelerator 29 XXI 648 Upper right Anti-fogging agent / 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
[Metal salt compounds]
The metal salt compound according to the present invention is any salt as long as it contains a metal species that can be subjected to oxidative dissolution / reduction deposition by driving the counter electrode on at least one electrode on the counter electrode. It may be a compound. Preferred metal species are silver, bismuth, copper, nickel, iron, chromium, zinc and the like, and particularly preferred are silver and bismuth.

[Silver salt compound]
Examples of the silver salt compound preferably used as the metal salt compound according to the present invention include silver or a compound containing silver in the chemical structure, such as silver oxide, silver sulfide, metallic silver, silver colloidal particles, silver halide, and silver complex. It is a generic term for compounds such as compounds and silver ions, and there are no particular limitations on the state species of the phase such as the solid state, the solubilized state in liquid and the gas state, and the charged state species such as neutral, anionic and cationic.

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

  The porous white scattering layer applicable to the present invention can be formed by applying and drying an aqueous mixture of an aqueous polymer and a white pigment that is substantially insoluble in the electrolyte solvent.

  Examples of the white pigment applicable in the present invention include titanium dioxide (anatase type or rutile type), barium sulfate, calcium carbonate, aluminum oxide, zinc oxide, magnesium oxide and zinc hydroxide, magnesium hydroxide, magnesium phosphate, Magnesium hydrogen phosphate, alkaline earth metal salt, talc, kaolin, zeolite, acidic clay, glass, organic compounds such as polyethylene, polystyrene, acrylic resin, ionomer, ethylene-vinyl acetate copolymer resin, benzoguanamine resin, urea-formalin resin, A melamine-formalin resin, a polyamide resin, or the like may be used alone or in combination, or in a state having voids that change the refractive index in the particles.

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

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

  Recently, a star-shaped titanium oxide has also been proposed. Such a titanium oxide particle has an effect that, due to its shape, uniform scattering at an incident angle occurs and the white scattering effect increases. It is also possible to use such titanium oxide.

  In the present invention, examples of the water-based polymer that does not substantially dissolve in the electrolyte solvent include a water-soluble polymer and a polymer dispersed in the water-based solvent.

Examples of water-soluble compounds include proteins such as gelatin and gelatin derivatives, cellulose derivatives, natural compounds such as polysaccharides such as starch, gum arabic, dextran, pullulan and carrageenan, polyvinyl alcohol, polyvinyl pyrrolidone, acrylamide polymers and their Examples include synthetic polymer compounds such as derivatives. As gelatin derivatives, acetylated gelatin, phthalated gelatin, polyvinyl alcohol derivatives as terminal alkyl group-modified polyvinyl alcohol, terminal mercapto group-modified polyvinyl alcohol, and cellulose derivatives include hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose and the like. It is done. Furthermore, Research Disclosure and those described in pages (71) to (75) of JP-A No. 64-13546, US Pat. No. 4,960,681, JP-A No. 62-245260, etc. superabsorbent polymers described, namely -COOM or -SO ₃ M (M is a hydrogen atom or an alkali metal) homopolymer or a vinyl monomer together or with other vinyl monomers of the vinyl monomer having a (e.g., sodium methacrylate, Copolymers with ammonium acid, potassium acrylate, etc.) are also used. Two or more of these binders can be used in combination.

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

  Polymers dispersed in an aqueous solvent include natural rubber latex, styrene butadiene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, isoprene rubber and other latexes, polyisocyanate, epoxy, acrylic, silicone, polyurethane, Examples thereof include a thermosetting resin in which urea, phenol, formaldehyde, epoxy-polyamide, melamine, alkyd resin, vinyl resin and the like are dispersed in an aqueous solvent. Of these polymers, it is preferable to use an aqueous polyurethane resin described in JP-A-10-76621.

  In the present invention, “substantially insoluble in an electrolyte solvent” is defined as a state in which the dissolved amount per kg of electrolyte solvent is 0 g or more and 10 g or less at a temperature of −20 ° C. to 120 ° C. The amount of dissolution can be determined by a known method such as a component determination method using a chromatogram or a gas chromatogram.

  In the present invention, the water mixture of the water-based compound and the white pigment is preferably in a form in which the white pigment is dispersed in water according to a known dispersion method. The mixing ratio of the aqueous compound / white pigment is preferably 1 to 0.01, more preferably 0.3 to 0.05 in terms of volume ratio.

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

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

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

  Porous as used in the present invention refers to the formation of a porous white scattering material by applying a water admixture of the water-based compound and the white pigment onto the electrode and drying it, and then the silver or silver is chemically treated on the scattering material. After supplying an electrolyte solution containing the compound contained in the structure, it can be sandwiched between opposing electrodes, giving a potential difference between the opposing electrodes, causing a silver dissolution precipitation reaction, and penetrating ions that can move between the electrodes Tell the state.

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

  Examples of the hardener used in the present invention include, for example, U.S. Pat. No. 4,678,739, column 41, 4,791,042, JP-A-59-116655, and 62-245261. No. 61-18942, 61-249054, 61-245153, JP-A-4-218044, and the like. More specifically, aldehyde hardeners (formaldehyde, etc.), aziridine hardeners, epoxy hardeners, vinyl sulfone hardeners (N, N'-ethylene-bis (vinylsulfonylacetamide) Ethane, etc.), N-methylol hardeners (dimethylolurea, etc.), boric acid, metaboric acid or polymer hardeners (compounds described in JP-A-62-234157). When gelatin is used as the aqueous compound, it is preferable to use a vinyl sulfone type hardener or a chlorotriazine type hardener alone or in combination. Moreover, when using polyvinyl alcohol, it is preferable to use boron-containing compounds such as boric acid and metaboric acid.

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

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

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

  The columnar structure provides strong self-holding (strength) between the substrates, for example, a columnar body, a quadrangular columnar body, an elliptical columnar body, a trapezoidal array arranged in a predetermined pattern such as a lattice arrangement. A columnar structure such as a columnar body can be given. Alternatively, stripes arranged at predetermined intervals may be used. This columnar structure is not a random array, but can 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.

[Configuration of full-color display element]
When performing full color display using the display element of the present invention,
1. A method of laminating electrochromic display elements that develop and erase colors in different colors such as yellow, magenta, cyan, red, green, blue, black,
2. A method of patterning a porous portion adsorbing an electrochromic compound that develops and decolors in different colors on a flat surface,
3. Examples include a method of adsorbing a plurality of types of electrochromic compounds that develop and decolor in different color tones in a porous layer between a pair of counter electrodes.

  In the case of 3, the electrochromic compound needs to have a threshold value. As a method of providing the threshold value, voltage or charge amount in the coloring or decoloring direction or voltage hysteresis in the coloring or decoloring direction is set for each dye. The method of changing to is mentioned.

[Display element driving method]
The active matrix drive according to the present invention is a method 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, the circuit described in FIG. ) 77-102.

[Product application]
The display element of the present invention can be used in an electronic book field, an ID card field, a public field, a traffic field, a broadcast field, a payment field, a distribution logistics field, and the like. Specifically, keys for doors, student ID cards, employee ID cards, various membership cards, convenience store cards, department store cards, vending machine cards, gas station cards, subway and railway cards, bus cards, Cash cards, credit cards, highway cards, driver's licenses, hospital examination cards, electronic medical records, health insurance cards, Basic Resident Registers, passports, electronic books, etc.

Example 1
(Production of electrode 1)
An ITO (Indium Tin Oxide) film was formed on a glass substrate having a thickness of 1.5 mm and a size of 2 cm × 4 cm according to a known method to obtain an electrode 1 as a transparent electrode.

(Preparation of electrode 2)
An ITO film was formed on a polyimide film having a thickness of 50 μm according to a known method to obtain an electrode 2 that was a transparent electrode.

(Preparation of electrode 3)
An FTO (fluorine-doped oxide) film was formed on a glass substrate having a thickness of 1.5 mm and a size of 2 cm × 4 cm according to a known method to obtain an electrode 3 that was a transparent electrode.

(Preparation of porous layer 1)
In an aqueous solution containing 2% by mass of polyvinyl alcohol (average molecular weight 30000), 20% by mass of titanium oxide having an average particle size of 25 nm was added and dispersed with an ultrasonic disperser to obtain titanium oxide dispersion 1.

  The dispersion 1 was applied on the electrode 1 so as to have a dry film thickness of 5 μm and dried at 120 ° C. for 30 minutes to obtain a porous layer 1.

(Preparation of porous layer 2)
An undercoat layer containing titanium oxide was provided on the electrode 1 under the following conditions.

Sputtering method: RF magnetron sputtering (depot up)
Titanium dioxide target diameter: φ2 inch (1 inch is 2.54 cm)
Substrate-target distance: 40 mm
Back pressure: 1.5 × 10 ⁻³ Pa
Sputtering pressure: 1.3 Pa Ar / O ₂ = 9/1
Output: 150W
The thickness of the obtained undercoat layer was about 30 nm.

  On this undercoat layer, the titanium oxide dispersion 1 was applied so as to have a dry film thickness of 5 μm and dried at 120 ° C. for 30 minutes to obtain a porous layer 2.

(Preparation of porous layer 3)
A porous layer 3 having a thickness of 5 μm was prepared in the same manner as the porous layer 2 except that the thickness of the undercoat layer was set to 70 nm.

(Preparation of porous layer 4)
A porous layer 4 having a thickness of 5 μm was produced in the same manner as the porous layer 2 except that the thickness of the undercoat layer was 120 nm.

(Preparation of porous layer 5)
The target was changed to a tin dioxide target, and an undercoat layer having a film thickness of 40 nm was obtained in the same manner as the porous layer 2. On this undercoat layer, the titanium oxide of the titanium oxide dispersion 1 was tin oxide (average particle diameter). The tin oxide dispersion changed to 20 nm) was applied and dried in the same manner to obtain a porous layer 5 having a thickness of 6 μm.

(Preparation of porous layer 6)
In accordance with Japanese Patent Application Laid-Open No. 2007-113043, an undercoat layer was formed under the following conditions.

<Mixed gas composition>
Discharge gas: Nitrogen gas 94.99 volume%
Thin film forming gas: tetraethoxysilane 0.01% by volume
Additive gas: Oxygen gas 5.0% by volume
<Film formation conditions>
1st electrode side Power supply type: A5
Frequency: 100kHz
Output density: 10 W / cm ²
Electrode temperature: 120 ° C
Second electrode side power supply type: B3
Frequency: 13.56 MHz
Output density: 10 W / cm ²
Electrode temperature: 90 ° C
The thickness of the obtained undercoat layer containing silicon oxide was 45 nm.

  A porous layer 6 having a film thickness of 5 μm was prepared in the same manner as the porous layer 2 except that the titanium oxide in the dispersion 1 was replaced with silicon dioxide (average particle size 15 nm).

(Preparation of porous layer 7)
A porous layer 7 was produced in the same manner as the porous layer 2 except that the electrode 3 was used instead of the electrode 1.

(Preparation of porous layer 8)
A porous layer 8 was produced in the same manner as the porous layer 2 except that the electrode 2 was used instead of the electrode 1.

(Preparation of porous layer 9)
On the undercoat layer produced in the same manner as the porous layer 6, a porous layer 9 was produced in the same manner as the porous layer 1 using the dispersion liquid 1.

(Synthesis of electrochromic compound EC-1)
Compound VIII obtained by synthesis according to Scheme 1 described in JP-A-2006-309216 was designated as EC-1.

(Adsorption of electrochromic compounds)
A 10 mmol / L ethanol solution of EC-1 was prepared, and porous layers 1 to 9 were respectively immersed in this for 4 hours, and then ethanol was evaporated to adsorb EC-1 to the porous layer.

(Preparation of electrolyte solution 1)
Electrolyte solution 1 was prepared by adding 40 mmol of ferrocene to propylene carbonate.

(Preparation of electrolyte solution 2)
In dimethyl sulfoxide, 4% by mass of bismuth chloride, 6% by mass of sodium iodide, 2% by mass of polyethylene glycol (average molecular weight 500,000) and 4% by mass of the following compound A-1 were dissolved to obtain an electrolytic solution 2. .

(Preparation of electrolyte solution 3)
Electrolyte solution 3 was obtained in the same manner except that bismuth chloride in electrolyte solution 2 was changed to silver iodide.

(Preparation of electrolyte solution 4)
Add 20% by mass of butyral resin with an average degree of polymerization of 1000 to γ-butyrolactone, heat and dissolve the butyral resin, and add 50% by mass of titanium dioxide surface-treated with lithium perchlorate and SiO ₂ , and ultrasonic dispersion The electrolyte solution 4 was prepared by dispersing with a machine. The electrolyte solution 4 has a viscosity of about 750 mPa · s at 25 ° C. and is in a gel form.

(Preparation of counter electrode 1)
A silver-palladium electrode having an electrode thickness of 0.8 μm was formed on a glass substrate having a thickness of 1.5 mm and a size of 2 cm × 4 cm by using a known method, and the counter electrode 1 was produced.

(Preparation of counter electrode 2)
A silver-palladium electrode having an electrode thickness of 0.8 μm was formed on a polyimide film having a thickness of 50 μm using a known method, and the counter electrode 2 was produced.

(Preparation of counter electrode 3)
Using a known method, a nickel electrode having an electrode thickness of 0.1 μm is formed on a glass substrate having a thickness of 1.5 mm and 2 cm × 4 cm, and the obtained electrode is further immersed in a displacement gold plating bath. A gold-nickel electrode (counter electrode 3) having a depth of 0.05 μm replaced with gold was obtained.

(Preparation of white scattering layers 1 to 3)
A white scattering layer coating solution in which titanium oxide (average particle size 32 nm) is added in an amount of 20% by mass in an aqueous solution containing 2% by mass of gelatin and dispersed with an ultrasonic disperser is applied to each of the counter electrodes 1 to 3 on a wire bar. Was applied so as to have a film thickness of about 100 μm, and then dried at 15 ° C. for 30 minutes and at 45 ° C. for 1 hour to prepare white scattering layers 1 to 3.

(Preparation of display element 1)
The peripheral portion of the white scattering layer 1 is bordered with an olefin-based sealant containing glass spherical beads having an average particle diameter of 40 μm and a volume fraction of 10%, and the inside is filled with the electrolyte solution 1, and EC-1 is formed thereon. The display element 1 was produced by covering and heating the porous layer 1 adsorbed with the heat so as to be inside.

(Production of display elements 2 to 7)
The display elements 2 to 7 are the same as the display element 1 except that the porous layer 1 on which the EC-1 of the display element 1 is adsorbed is replaced with the porous layers 2 to 7 on which the EC-1 is adsorbed. Was made.

(Preparation of display element 8)
The periphery of the white scattering layer 2 is bordered with an olefin-based sealant containing glass spherical beads having an average particle diameter of 40 μm and a volume fraction of 10%, and the inside is filled with the electrolyte solution 1, and EC-1 is formed thereon. The display element 8 was manufactured by covering and heating the porous layer 8 adsorbed with heat so as to be inside.

(Preparation of display element 9)
A display element 9 was produced in the same manner as the display element 2 except that the white scattering layer 2 was changed to the white scattering layer 3 and the electrolyte solution 1 was changed to the electrolyte solution 2.

(Preparation of display element 10)
A display element 10 was produced in the same manner as the display element 9 except that the electrolyte solution 2 was changed to the electrolyte solution 3.

(Preparation of display element 11)
A display element 11 was produced in the same manner as the display element 10 except that the porous layer 2 was changed to the porous layer 1.

(Preparation of display element 12)
A display element 12 was produced in the same manner as the display element 2 using the porous layer 9.

(Evaluation of display element)
For display elements 1 to 12, the stability of repeated driving was evaluated by the following method.

  Both electrodes of each display element are connected to both terminals of a constant voltage power source, a voltage of 1.2 V is applied for 0.5 seconds, and the reflectance of λmax in a colored state is measured by a spectrophotometer CM manufactured by Konica Minolta Sensing. It was measured at −3700 d and set as the initial reflectance Rmax0.

  A voltage of −1.2 V was applied to the colored element for 0.5 seconds, and the reflectance Rmin0 in the decolored state was measured.

  The application of 1.2 V for 0.5 seconds and the application of -1.2 V for 0.5 seconds were repeated at 1 second intervals, and the reflectance Rmax5000 in the colored state at 5000 times and the reflectance Rmin5000 in the decolored state were measured.

  As the contrast after 5000 times, the ratio of Rmax5000 and Rmin5000 = Rmax5000 / Rmin5000 was calculated.

  After driving 5,000 times, the unevenness of the display element in a state where +1.2 V was applied was visually evaluated. The level of display unevenness is evaluated in 7 levels. From the best, no unevenness (7), slightly unevenness (6), unevenness slightly (5), unevenness (4), unevenness (3), unevenness Inferior (2) and unevenness inferior (1) were used as indices of repeated stability. From a practical point of view, it is desirable that the level is at least the level (3).

  The results are shown in Table 1.

  As for the display elements 9 and 10, when the color of the display element was visually observed in the non-applied state and in the state where −1.5 V and +1.5 V were applied, all of the display elements were colorless, colored, and black-colored. Was presented.

Claims (6)

A transparent substrate having at least one transparent electrode on its surface and a substrate having at least one counter electrode on its surface are arranged so that the transparent electrode and the counter electrode face each other, and at least an electrochromic compound is interposed between the electrodes In a display element having an electrolyte layer containing, a porous layer is provided on a transparent electrode via a non-porous undercoat layer, and the undercoat layer is made of the same material as that forming the porous layer. A display element containing at least a part. The display element according to claim 1, wherein an electrochromic compound is adsorbed on the porous layer. The display element according to claim 1, wherein the porous layer is a semiconductor porous layer containing at least one metal oxide. The display element according to claim 3, wherein the metal oxide is selected from titanium oxide, tin oxide, and silicon oxide. The electrolyte layer contains a metal salt compound, and by driving between the electrodes, 1) color change due to oxidation and reduction reaction of the electrochromic compound, or 2) the metal salt on at least one of the counter electrodes 5. A multicolor display of three or more colors is performed by a black display, a white display, and a color display other than black using a color change caused by reduction precipitation and oxidation dissolution of a metal element contained in the compound. The display element according to any one of the above. The display element according to claim 5, wherein the metal salt compound is a silver salt compound.