JP2007322616A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element which has simple member constitution, can be driven with a low voltage, and has a high display contrast and white display reflectivity, the display element having high reflectivity of white display, a fast display speed, and small display unevenness. <P>SOLUTION: The display element has an electrolyte layer (3) containing silver or a compound containing silver in a chemical structure and a porous white scattering layer (4) between opposite electrodes and drives the opposite electrodes to dissolve and deposit silver, and is characterized in that the porous white scattering layer (4) has pores and L/D is ≥100, ≤2,000, where D represents internal diameters of the pores and L represents depths. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrochemical display element utilizing silver dissolution precipitation.

  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 disadvantage of the light-emitting display, eyes flicker due to flickering, inconvenient to carry, reading posture is limited It is known that it is necessary to adjust the line of sight to a still screen, and that power consumption increases when read for a long time.

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

  That is, the method using a polarizing plate such as a reflective liquid crystal has a low reflectance of about 40% and is difficult to display white, and many of the production methods used for producing the constituent members are not easy. In addition, the polymer dispersed liquid crystal requires a high voltage and utilizes the difference in refractive index between organic substances, so that the resulting image has insufficient contrast. In addition, the polymer network type liquid crystal has problems such as a high voltage and a 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. In addition, the electrochromic display element can be driven at a low voltage of 3 V or less, but the color quality of black or color (for example, yellow, magenta, cyan, blue, green, red, etc.) is not sufficient, and the memory There is a concern that a complicated film configuration such as a vapor deposition film is necessary for the display cell in order to ensure the property.

  As a display method that eliminates the drawbacks of each of the above-described methods, an electrodeposition (hereinafter abbreviated as ED) method that utilizes dissolution or precipitation of a metal or a metal salt is known. The ED method can be driven at a low voltage of 3 V or less, has advantages such as a simple cell configuration, excellent black-white contrast and black quality, and various methods have been disclosed (for example, Patent Document 1). -3)).

  As a result of examining the technologies disclosed in the above patent documents in detail, the present inventor has found that the reflectivity and display speed at the time of white display are insufficient to satisfy recent user needs in the prior art. For example, as a technique for controlling the reflectance during white display, the white scattering layer can be adjusted. However, if the thickness of the white scattering layer is reduced, the display speed is improved but light shielding is insufficient. When the white scattering layer is made thicker, the reflectance of the white scattering layer increases, but the reflectance of the white display increases, but the diffusion rate of the electrode reactant to the electrode slows down, resulting in a decrease in the display speed. Therefore, a technique capable of improving both the reflectance and display speed during white display has been desired.

Further, when displaying an image with a large number of halftones, gray display unevenness leads to a reduction in image quality. Therefore, a technique capable of suppressing display unevenness more than before has been desired.
U.S. Pat. No. 4,240,716 Japanese Patent No. 3428603 JP 2003-241227 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a display element that has a simple member configuration, can be driven at a low voltage, and has high display contrast and white display reflectance. It is an object of the present invention to provide a display element having a high display speed, a high display speed, and little display unevenness.

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

  1. A display element comprising an electrolyte layer containing silver or a compound containing silver in the chemical structure and a porous white scattering layer between the counter electrodes, and driving the counter electrode so as to cause dissolution and precipitation of silver In claim 1, wherein the porous white scattering layer has pores, and L / D is 100 or more and 2000 or less, where D is the inner diameter of the pores and L is the depth.

  2. 2. The display element according to 1 above, wherein the pores are arranged at an angle of 60 to 90 degrees with respect to the electrode.

  3. 3. The display element according to 1 or 2, wherein the pore is formed by a photoelectrochemical etching process.

  4). 4. The display element according to any one of items 1 to 3, wherein a main component of the porous white scattering layer is a metal oxide having an average particle size of 10 nm or more and 500 nm or less.

  5. 5. The display element as described in 4 above, wherein the metal oxide is titanium dioxide.

  6). 6. The display element according to any one of 1 to 5, wherein an average film thickness of the porous white scattering layer is 15 μm or more and 300 μm or less.

  7). The display element according to any one of 1 to 6, wherein the porous white scattering layer is fired at a temperature of 120 ° C. or higher.

  According to the present invention, a simple element configuration, a display element that can be driven at a low voltage, has a high display contrast, and a high white display reflectance, and has a high white display reflectance, a high display speed, and a small display unevenness. An element could be provided.

  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 contains an electrolyte layer containing silver or a compound containing silver in the chemical structure between the counter electrodes, and a porous white scattering layer. In a display element in which the counter electrode is driven so as to cause precipitation, the porous white scattering layer has pores, where the inner diameter of the pore is D and the depth is L, L / D The display element is characterized in that the display element is 100 or more and 2000 or less, can be driven with a simple member configuration, low voltage, and has high display contrast and high white display reflectance, and is provided with pores. When converting from black display to white display, a part of the silver image formed between the porous white scattering layer and the counter electrode at the time of black display is supplied with sufficient electrolyte through the pores, so Image loss can be achieved and the result , High reflectance of the white display, display speed, and it was possible to realize a display unevenness less display device.

  Details of the present invention will be described below.

  The display element of the present invention contains an electrolyte containing silver or a compound containing silver in the chemical structure between the counter electrodes, and is an ED type driving operation of the counter electrode so as to cause dissolution and precipitation of silver. It is a display element.

[Silver or a compound containing silver in the chemical structure]
Silver or a compound containing silver in the chemical structure according to the present invention is a general term for compounds such as silver oxide, silver sulfide, metallic silver, silver colloidal particles, silver halide, silver complex compounds, and silver ions. Phase state species such as solid state, solubilized state in liquid, and gas state, and charged state species such as neutral, anionic, and cationic are not particularly limited.

[Configuration of display element]
FIG. 1 is a schematic cross-sectional view showing an example of the basic configuration of the display element of the present invention.

  In FIG. 1, the ED display unit is provided with a pair of counter electrodes arranged at opposing positions. The electrode 1 which is one of the counter electrodes close to the ED display portion is provided with a transparent electrode such as an ITO electrode, and the other electrode 2 is provided with a metal electrode such as a silver electrode. An electrolyte 3 having silver or a compound containing silver in the chemical structure is supported between the electrode 1 and the electrode 2, and by applying positive and negative voltages between the counter electrodes, the electrode 1 and the electrode 2 are supported. A silver oxidation-reduction reaction is performed above, and the black state of the reduced silver image and the state of transparent silver ions in the oxidized state can be switched reversibly.

  In the display element of the present invention, a porous white layer in which metal oxide particles 5 are laminated on the electrode 2 on the non-display portion side of the pair of counter electrodes for the purpose of increasing display contrast and reflectance during white display. It has a scattering layer 4.

This porous white scattering layer 4 is an extremely effective means from the viewpoint of increasing the display contrast and the reflectance during white display. However, during black display, silver ions are reduced and silver is deposited on the surface of the electrode 1. On the surface of the electrode 2, the deposited silver is oxidized to produce silver ions, so that an electrochemical system is established. In addition, at the time of white display, the deposited silver is oxidized on the surface of the electrode 1 to produce silver ions. On the surface, silver ions are reduced and silver is deposited, so that an electrochemical system is established. For example, when metal oxide particles having a small particle size are used for the purpose of increasing the white display reflectance of the porous white scattering layer, the silver ions generated between the porous white scattering layer 4 and the electrode 2 in black display As a result, the space for diffusing from the surface of the electrode 2 to the electrode 1 side becomes extremely small, resulting in a slow black display speed. Further, at the time of white display, the diffusion of silver ions as a reactant on the surface of the electrode 2 becomes insufficient, resulting in a slow white display speed.
On the other hand, by using a metal oxide having a sufficient size, the space between the porous white scattering layer 4 and the electrode 2 can secure a sufficient volume, and the problem of migration of silver ions on the surface of the electrode 2 is solved. However, by using a metal oxide having a large particle diameter, the light shielding effect of the porous white scattering layer becomes insufficient, and the reflectance during white display cannot be obtained.

  In the present invention, for the purpose of solving the above trade-off, after forming the porous white scattering layer 4 with the metal oxide particles 5 having a relatively small particle diameter, the inner diameter is D and the depth is L. In this case, by forming the pores 6 having L / D of 100 or more and 2000 or less, it has sufficient display contrast and reflectivity during white display, and through this pore, sufficient ion diffusion during white display. By supplying the route, it is possible to sufficiently eliminate the deposited silver. In particular, the effect of the present invention is significant for display unevenness when a gray image is displayed.

(Porous white scattering layer)
The porous white scattering layer according to the present invention is preferably formed in a state of being laminated with metal oxide particles on the counter electrode.

  Such a porous white scattering layer generally includes a dispersion containing a dispersion solvent, a fluorescent whitening agent, a polymer compound, etc. as necessary together with a metal oxide, a wet coating method, an inkjet method, a printing method. Etc., and among them, a preferred method for forming the porous white scattering layer is a screen printing method.

  Examples of the particles constituting the porous white scattering layer according to the present invention include titanium dioxide (anatase type or rutile type), barium sulfate, calcium carbonate, aluminum oxide, zinc oxide, magnesium oxide, zinc hydroxide, and magnesium hydroxide. , Magnesium phosphate, magnesium hydrogen phosphate, alkaline earth metal salts, 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, melamine-formalin resin, polyamide resin and 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 above-mentioned particles, metal oxide particles having an average particle size of 10 nm or more and 500 nm or less can be preferably used. Among them, sufficient display contrast and whiteness, which are one of the object effects of the present invention, can be used. From the viewpoint of realizing a high reflectance at the time of display, titanium dioxide is more preferably used, and surface treatment is performed with an organic substance such as an inorganic oxide (Al ₂ O ₃ , AlO (OH), SiO _2, etc.) or a polyhydric alcohol. It is preferable to use titanium dioxide.

  The average film thickness of the porous white scattering layer according to the present invention is preferably 15 μm or more and 300 μm or less, more preferably 20 μm or more and 30 μm or less.

  Examples of the solvent for the dispersion forming the porous white scattering layer according to the present invention include water, toluene, xylene, ethanol, propanol, butanol, acetonitrile, acetylacetone, terpineol, butyl carbitol, and butyl carbitol acetate. be able to.

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

  In the present invention, the polymer compound is used by adding conductive powder such as tin oxide, gold, silver, cylinder, carbon, etc., and the mass ratio of the polymer compound is 0.01 to 10%. Is preferred.

  In the present invention, the medium to which the dispersion is applied may be at any position as long as it is on the component between the counter electrodes of the display element, but is preferably applied on at least one electrode surface of the counter electrode.

  The solvent of the dispersion applied on the electrode may be dried by any method as long as the solvent 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. The evaporation may be performed under reduced pressure.

  The term “porous” as used in the present invention means that after the dispersion is applied onto an electrode and dried to form a porous white scattering material, silver or a compound containing silver in the chemical structure is contained on the scattering material. It refers to a penetrating state in which an electrolytic solution is applied and then sandwiched between counter electrodes, and a potential difference is applied between the counter electrodes to cause a dissolution and precipitation reaction of silver, and the ionic species can move between the electrodes.

  In the display element of the present invention, it is desirable that the polymer compound is cured with a curing agent during or after the dispersion is applied and dried.

  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 polymer 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 polymer compound. In addition, it is possible to perform heat treatment and humidity adjustment during the curing reaction in order to increase the film strength.

  Moreover, in the display element of this invention, after forming the porous white scattering layer which concerns on this invention, performing a baking process at the temperature of 120 degreeC or more from a viewpoint which can form a stronger porous white scattering layer. preferable. The upper limit temperature cannot be defined unconditionally depending on the type of metal oxide used, but is generally 300 ° C. or lower.

〔pore〕
In the display element of the present invention, the porous white scattering layer has pores, and when the inside diameter of the pore is D and the depth is L, L / D is 100 or more and 2000 or less. L / D is preferably 500 or more and 2000 or less, and more preferably 1000 or more and 2000 or less.

  In the pores according to the present invention, the inner diameter D of the pores is not particularly limited as long as the L / D regulation condition is satisfied, but is preferably 10 nm or more and 500 nm or less. The depth L of the pore is not particularly limited as long as the above L / D conditions are satisfied, and is preferably 1 μm or more and 300 μm or less, but the function of the pore according to the present invention, that is, the electrode From the viewpoint of sufficiently supplying the electrolyte to the surface and surely dissolving the precipitated silver, the depth L of the pores is preferably penetrating from the surface of the porous white scattering layer to the electrode surface, and is therefore preferable. The depth L of the pores is 15 μm or more and 300 μm or less.

  Further, the application rate of the pores to the porous white scattering layer according to the present invention is a factor that greatly influences the achievement of the desired reflectance during white display and the disappearance effect of the precipitated silver. Setting a high pore rate increases the disappearance effect of the precipitated silver, while the reflectivity during white display by the metal oxide decreases. Conversely, if the pore rate is too low, sufficient white display is achieved. Although the reflectance can be obtained, the disappearance effect of the precipitated silver becomes insufficient. Therefore, the application rate of the pores to the porous white scattering layer according to the present invention is such that the area occupied by the pores per unit surface area of the porous white scattering layer is in the range of 1 to 20% by area. Moreover, it is preferable that the volume occupied by the pores per unit volume of the porous white scattering layer is in the range of 1% by volume to 20% by volume.

  In FIG. 1, the pores according to the present invention are formed on the condition perpendicular to the electrode, that is, at an angle of 90 degrees. However, in the present invention, the pore formation angle with respect to the electrode is shown. Is preferably in the range of 60 degrees or more and 90 degrees or less, more preferably 75 degrees or more and 90 degrees or less. The method for adjusting the formation angle of the pores according to the present invention can be achieved by appropriately adjusting the installation angle of a pore formation apparatus as described later at the time of pore formation.

  In the display element of the present invention, the pores according to the present invention are preferably formed by a photoelectrochemical etching method.

In the present invention, the photoelectrochemical etching method (also referred to as photoetching method) is a method in which a porous white scattering layer provided on an electrode is immersed in a solution, and light energy is applied in a state where an etching current is applied. For example, Journal of Electrochemical Society 134, pages 1038 to 1039 (1987) [J. Electrochem. Soc. Vol. 134 1038-1039 (1987)], R.M. L. Smith et al. (J. Appl. Phys., 71, R1, 1992), A.M. Lagoubi et al. (11th Photo-voltaic Solar Energy Conference, Montreux, 1992), 18th Solid-Surface Photochemistry Conference (announced on November 29, 1999), “Microstructure Control of TiO ₂ Surface by Photoelectrochemical Etching”, etc. Can be mentioned.

In the present invention, for example, a dispersion containing a metal oxide is formed on the non-display side electrode to a predetermined film thickness by a screen printing method, and then dried to form a porous white scattering layer. An electrode having a white white scattering layer is immersed in an acidic aqueous solution, an anodic polarization condition is an oxidation potential of +1.0 V (vs SCE: saturated calomel electrode), an ultrahigh pressure mercury lamp is used as a light irradiation light source, and the luminous flux is Condensing light and forming pores having a predetermined inner diameter D, depth L, and L / D under conditions of 1 C to 10 C / cm ² . At this time, the angle of an arbitrary pore can be obtained by appropriately setting the irradiation angle of the ultrahigh pressure mercury lamp to be irradiated.

(Electrolyte additive)
In the display element of the present invention, the electrolyte is composed of at least one compound represented by the following general formula (1) or (2) and a compound represented by the following general formula (3) or general formula (4). It is preferable to contain at least one kind.

In the general formula (1), L represents an oxygen atom or CH ₂ , and R _{1 to} R ₄ each represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group, or an alkoxy group.

In the general formula (2), R ₅ and R ₆ each represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group or an alkoxy group.

General formula (3)
R ₇ -S-R ₈
In the general formula (3), R ₇ and R ₈ each represent a substituted or unsubstituted hydrocarbon group. However, when a ring containing an S atom is formed, an aromatic group is not taken.

In the general formula (4), M represents a hydrogen atom, a metal atom or quaternary ammonium. Z represents a nitrogen-containing heterocyclic ring. n represents an integer of 0 to 5, and R ₉ represents a halogen atom, alkyl group, aryl group, alkylcarbonamide group, arylcarbonamide group, alkylsulfonamide group, arylsulfonamide group, alkoxy group, aryloxy group, alkylthio group. Group, arylthio group, alkylcarbamoyl group, arylcarbamoyl group, carbamoyl group, alkylsulfamoyl group, arylsulfamoyl group, sulfamoyl group, cyano group, alkylsulfonyl group, arylsulfonyl group, alkoxycarbonyl group, aryloxycarbonyl group Represents an alkylcarbonyl group, an arylcarbonyl group, an acyloxy group, a carboxyl group, a carbonyl group, a sulfonyl group, an amino group, a hydroxy group or a heterocyclic group, and when n is 2 or more, each R ₉ is the same. Or may be different from each other and may be linked to each other to form a condensed ring.

  First, the compound represented by the general formula (1) will be described.

In the general formula (1), L represents an oxygen atom or CH ₂ , and R _{1 to} R ₄ each represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group, or an alkoxy group.

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

  Hereinafter, although the specific example of a compound represented by General formula (1) is shown, in this invention, it is not limited only to these illustrated compounds.

  Next, the compound represented by the general formula (2) will be described.

In the general formula (2), R ₅ and R ₆ each represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a cycloalkyl group, an alkoxyalkyl group or an alkoxy group.

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

  Hereinafter, although the specific example of a compound represented by General formula (2) is shown, in this invention, it is not limited only to these illustrated compounds.

  Among the compounds represented by the general formula (1) and the general formula (2) exemplified above, the exemplary compounds (1-1), (1-2), and (2-3) are particularly preferable.

  The compounds represented by the general formulas (1) and (2) are one kind of electrolyte solvents. However, in the display element of the present invention, another solvent is used in combination as long as the object effects of the present invention are not impaired. be able to. Specifically, tetramethylurea, sulfolane, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, 2- (N-methyl) -2-pyrrolidinone, hexamethylphosphortriamide, N-methylpropionamide, N, N-dimethylacetamide, N-methylacetamide, N, N dimethylformamide, N-methylformamide, butyronitrile, propionitrile, acetonitrile, acetylacetone, 4-methyl-2-pentanone, 2-butanol, 1-butanol, 2 -Propanol, 1-propanol, ethanol, methanol, acetic anhydride, ethyl acetate, ethyl propionate, dimethoxyethane, diethoxyfuran, tetrahydrofuran, ethylene glycol, diethylene glycol, triethylene glycol 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). 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. T. et al. Tomkins, “Nonqueous Electronics Handbook”, Vol. 1, Academic Press (1972).

  In the present invention, the electrolyte solvent may be a single type or a mixture of solvents, but a mixed solvent containing ethylene carbonate is preferred. The addition amount of ethylene carbonate is preferably 10% by mass or more and 90% by mass or less of the total electrolyte solvent mass. A particularly preferable electrolyte solvent is a mixed solvent having a mass ratio of propylene carbonate / ethylene carbonate of 7/3 to 3/7. When the propylene carbonate ratio is larger than 7/3, the ionic conductivity is inferior and the response speed is lowered. When the propylene carbonate ratio is smaller than 3/7, the electrolyte tends to be deposited at a low temperature.

  In the display device of the present invention, it is preferable to use the compound represented by the general formula (3) or (4) together with the compound represented by the general formula (1) or (2).

In the general formula (3), R ₇ and R ₈ each represent a substituted or unsubstituted hydrocarbon group, and these include a linear group or a branched group. Further, these hydrocarbon groups may contain one or more nitrogen atoms, oxygen atoms, phosphorus atoms, sulfur atoms, and halogen atoms. However, when a ring containing an S atom is formed, an aromatic group is not taken.

  Examples of groups that can be substituted for the hydrocarbon group include amino groups, guanidino groups, quaternary ammonium groups, hydroxyl groups, halogen compounds, carboxylic acid groups, carboxylate groups, amide groups, sulfinic acid groups, sulfonic acid groups, and sulfates. Groups, phosphonic acid groups, phosphate groups, nitro groups, cyano groups and the like.

  Generally, in order to cause dissolution and precipitation of silver, it is necessary to solubilize silver in an electrolyte. For example, solubilize silver or a compound containing silver by coexisting with a compound containing a chemical structural species that interacts with silver, such as a coordinate bond with silver or a weak covalent bond with silver. It is common to use a means for converting to an object. As the chemical structural species, halogen atoms, mercapto groups, carboxyl groups, imino groups and the like are known, but in the present invention, the thioether group is also useful as a silver solvent and has little influence on the coexisting compound, It is characterized by high solubility in solvents.

  Hereinafter, although the specific example of a compound represented by General formula (3) is shown, in this invention, it is not limited only to these illustrated compounds.

3-1: CH ₃ SCH ₂ CH ₂ OH
3-2: HOCH ₂ CH ₂ SCH ₂ CH ₂ OH
3-3: HOCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OH
3-4: HOCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OH
3-5: HOCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂ OH
3-6: HOCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ OH
3-7: H ₃ CSCH ₂ CH ₂ COOH
3-8: HOOCCH ₂ SCH ₂ COOH
3-9: HOOCCH ₂ CH ₂ SCH ₂ CH ₂ COOH
3-10: HOOCCH ₂ SCH ₂ CH ₂ SCH ₂ COOH
3-11: HOOCCH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ COOH
3-12: HOOCCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH (OH) CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ COOH
_{3-13: HOOCCH 2 CH 2 SCH 2} CH 2 SCH 2 CH (OH) CH (OH) CH 2 SCH 2 CH 2 SCH 2 CH 2 COOH
3-14: H ₃ CSCH ₂ CH ₂ CH ₂ NH ₂
3-15: H ₂ NCH ₂ CH ₂ SCH ₂ CH ₂ NH ₂
3-16: H ₂ NCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ NH ₂
3-17: H ₃ CSCH ₂ CH ₂ CH (NH ₂ ) COOH
3-18: H ₂ NCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂
NH ₂
3-19: H ₂ NCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂
NH ₂
3-20: H ₂ NCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂
NH ₂
3-21: HOOC (NH ₂ ) CHCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ CH (NH ₂ ) COOH
3-22: HOOC (NH ₂ ) CHCH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ CH (NH ₂ ) COOH
3-23: HOOC (NH ₂ ) CHCH ₂ OCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ OCH ₂ CH (NH ₂ ) COOH
3-24: H ₂ N (═O) CCH ₂ SCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SCH ₂ C (═O) NH ₂
3-25: H ₂ N (O =) CCH ₂ SCH ₂ CH ₂ SCH ₂ C (O =) NH _{2
3-26: H 2 NHN (O =} ) CCH 2 SCH 2 CH 2 SCH 2 C (= O) NHNH 2
3-27: H ₃ C (O =) NHCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ NHC (O =) CH ₃
3-28: H ₂ NO ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ SO ₂ NH ₂
3-29: NaO ₃ SCH ₂ CH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ CH ₂ SO ₃ Na
3-30: H ₃ CSO ₂ NHCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ NHO ₂ SCH ₃
3-31: H ₂ N (NH) CSCH ₂ CH ₂ SC (NH) NH ₂ .2HBr
3-32: H ₂ N (NH) CSCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SC (NH) NH ₂ .2HCl
3-33: H ₂ N (NH) CNHCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ NHC (NH) NH ₂ .2HBr
3-34: [(CH ₃ ) ₃ NCH ₂ CH ₂ SCH ₂ CH ₂ SCH ₂ CH ₂ N (CH ₃ ) ₃ ] 2 ⁺ · 2Cl ⁻

  Among the above-exemplified compounds, Exemplified Compound 3-2 is particularly preferable from the viewpoint that the object and effects of the present invention can be exhibited.

  Next, the compound represented by formula (4) will be described.

In the general formula (4), M represents a hydrogen atom, a metal atom, or quaternary ammonium. Z represents a nitrogen-containing heterocyclic ring. n represents an integer of 0 to 5, and R ₉ represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkylcarbonamide group, an arylcarbonamide group, an alkylsulfonamide group, an arylsulfonamide group, an alkoxy group, an aryloxy group Group, alkylthio group, arylthio group, alkylcarbamoyl group, arylcarbamoyl group, carbamoyl group, alkylsulfamoyl group, arylsulfamoyl group, sulfamoyl group, cyano group, alkylsulfonyl group, arylsulfonyl group, alkoxycarbonyl group, aryl Represents an oxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group, an acyloxy group, a carboxyl group, a carbonyl group, a sulfonyl group, an amino group, a hydroxy group or a heterocyclic group, and when n is 2 or more, each R ₉ is They may be the same or different, and may be linked together to form a condensed ring.

Examples of the metal atom represented by M in the general formula (4) include Li, Na, K, Mg, Ca, Zn, and Ag. Examples of the quaternary ammonium include NH ₄ , N (CH ₃ ) ₄ , N (C ₄ H ₉ ) ₄ , N (CH ₃ ) ₃ C ₁₂ H ₂₅ , N (CH ₃ ) ₃ C ₁₆ H ₃₃ , N (CH ₃ ) ₃ CH ₂ C ₆ H _{5 and the} like It is done.

  Examples of the nitrogen-containing heterocycle represented by Z in the general formula (4) include a tetrazole ring, a triazole ring, an imidazole ring, an oxadiazole ring, a thiadiazole ring, an indole ring, an oxazole ring, a benzoxazole ring, and a benzimidazole ring. Benzothiazole ring, benzoselenazole ring, naphthoxazole ring and the like.

Examples of the halogen atom represented by R ₉ in the general formula (4) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include methyl, ethyl, propyl, i- Examples include propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, octyl, dodecyl, hydroxyethyl, methoxyethyl, trifluoromethyl, benzyl, etc. Examples of the aryl group include phenyl, naphthyl and the like. Examples of the alkylcarbonamide group include acetylamino, propionylamino, butyroylamino and the like. Examples of the arylcarbonamide group include benzoylamino and the like. Examples of the sulfonamide group include methanesulfonyl. Minosulfonyl, ethanesulfonylamino group and the like, arylsulfonamide groups include, for example, benzenesulfonylamino group, toluenesulfonylamino group and the like, and aryloxy groups include, for example, phenoxy and the like, alkylthio Examples of the group include each group such as methylthio, ethylthio, and butylthio. Examples of the arylthio group include phenylthio group and tolylthio group. Examples of the alkylcarbamoyl group include methylcarbamoyl, dimethylcarbamoyl, Examples include ethyl carbamoyl, diethyl carbamoyl, dibutyl carbamoyl, piperidyl carbamoyl, morpholyl carbamoyl and the like, and aryl carbamoyl groups include, for example, phenyl carbamoyl, methyl phenyl carbamoyl Examples include groups such as vamoyl, ethylphenylcarbamoyl, and benzylphenylcarbamoyl. Examples of the alkylsulfamoyl group include methylsulfamoyl, dimethylsulfamoyl, ethylsulfamoyl, diethylsulfamoyl, and dibutylsulfamoyl. Examples of each group include moyl, piperidylsulfamoyl, morpholylsulfamoyl, and arylsulfamoyl groups include, for example, phenylsulfamoyl, methylphenylsulfamoyl, ethylphenylsulfamoyl, benzylphenylsulfamoyl. Examples of the alkylsulfonyl group include a methanesulfonyl group and an ethanesulfonyl group. Examples of the arylsulfonyl group include phenylsulfonyl and 4-chlorophenylsulfonyl. Examples of each group include p-toluenesulfonyl and the like. Examples of the alkoxycarbonyl group include groups such as methoxycarbonyl, ethoxycarbonyl and butoxycarbonyl. Examples of the aryloxycarbonyl group include phenoxycarbonyl and the like. Examples of the alkylcarbonyl group include acetyl, propionyl, butyroyl, and the like. Examples of the arylcarbonyl group include a benzoyl group and an alkylbenzoyl group. Examples of the acyloxy group include acetyloxy. , Propionyloxy, butyroyloxy and the like, and examples of the heterocyclic group include oxazole ring, thiazole ring, triazole ring, selenazole ring, tetrazole ring, oxadiazole ring, thiadiazole ring, thiazol ring, and the like. Down ring, a triazine ring, a benzoxazole ring, benzothiazole ring, an indolenine ring, benzimidazole benzoselenazole ring, naphthothiazole ring, triazaindolizine ring, diaza indolizine ring, tetraazacyclododecane indolizine ring group, and the like. These substituents further include those having a substituent.

  Next, although the preferable specific example of a compound represented by General formula (4) is shown, this invention is not limited to these compounds.

  Among the above-exemplified compounds, Exemplified Compounds 4-12 and 4-18 are particularly preferable from the viewpoint that the object and effects of the present invention can be exhibited.

[Halogen ion, silver ion concentration ratio]
In the display element of the present invention, the molar concentration of halogen ions or halogen atoms contained in the electrolyte is [X] (mol / kg), and silver contained in the electrolyte or the total silver of the compound containing silver in the chemical structure. When the molar concentration is [Ag] (mol / kg), it is preferable to satisfy the condition defined by the following formula (1).

Formula (1)
0 ≦ [X] / [Ag] ≦ 0.01
The halogen atom as used in the field of this invention means an iodine atom, a chlorine atom, a bromine atom, and a fluorine atom. When [X] / [Ag] is larger than 0.01, X ⁻ → X ₂ is generated during the redox reaction of silver, and X ₂ easily cross-oxidizes with blackened silver to dissolve blackened silver. Therefore, the molar concentration of halogen atoms is preferably as low as possible relative to the molar concentration of silver. In the present invention, 0 ≦ [X] / [Ag] ≦ 0.001 is more preferable. In the case of adding halogen ions, the halogen species preferably have a total molar concentration of [I] <[Br] <[Cl] <[F] from the viewpoint of improving memory properties.

[Electrolyte-silver salt]
In the display device of the present invention, silver iodide, silver chloride, silver bromide, silver oxide, silver sulfide, silver citrate, silver acetate, silver behenate, silver p-toluenesulfonate, silver salt with mercapto, A known silver salt compound such as a silver complex with iminodiacetic acid can be used. Among these, it is preferable to use, as a silver salt, a compound that does not have a nitrogen atom having coordination properties with halogen, carboxylic acid, or silver, and for example, silver p-toluenesulfonate is preferable.

  The silver ion concentration contained in the electrolyte according to the present invention is preferably 0.2 mol / kg ≦ [Ag] ≦ 2.0 mol / kg. If the silver ion concentration is less than 0.2 mol / kg, it becomes a dilute silver solution, and the driving speed is delayed. If it is greater than 2 mol / kg, the solubility deteriorates, and precipitation tends to occur during low-temperature storage, which is disadvantageous. It is.

  In the display element of the present invention, various constituent layers can be provided as necessary in addition to the constituent elements described above.

[Porous electrode containing metal oxide]
In the display element of the present invention, a porous electrode containing a metal oxide can also be used.

  In the display element of the present invention, the surface of the counter electrode that is not on the image observation side is protected by a porous electrode containing a metal oxide, so that silver or silver on the surface that is not on the image observation side has a chemical structure. By finding that the oxidation-reduction reaction of the compound contained therein is carried out on or in the porous electrode containing the metal oxide, the choice of electrode types that are not on the image observation side is expanded and the durability is improved. Can be made.

  Examples of the metal oxide constituting the porous electrode according to the present invention include titanium oxide, silicon oxide, zinc oxide, tin oxide, Sn-doped indium oxide (ITO), antimony-doped tin oxide (ATO), and fluorine-doped tin oxide. (FTO), aluminum-doped zinc oxide and the like, or a mixture thereof.

The porous electrode is formed by binding or contacting a plurality of fine particles of the metal oxide. The average particle diameter of the metal oxide fine particles is preferably 5 nm to 10 μm, more preferably 20 nm to 1 μm. The specific surface area of the metal oxide fine particles is preferably ^{1 × 10 -3 ~1 × 10 2} m 2 / g by a simple BET method, more preferably at 1 × 10 ^-2 ~10m ² / g . In addition, the metal oxide fine particles may have any shape such as an indefinite shape, a needle shape, a spherical shape, or the like.

  As a method for forming or binding metal oxide fine particles, a known sol-gel method or sintering method can be employed. For example, 1) Journal of the Ceramic Society of Japan, 102, 2, p200 (1994), 2 ) Ceramics Association Journal 90, 4, p157, 3) J. of Non-Cryst. Solids, 82, 400 (1986) and the like. In addition, a method of obtaining a porous electrode by dispersing titanium oxide dendrimer particles produced by a vapor phase method on a solution and coating the solution on a substrate and drying at a temperature of about 120 to 150 ° C. to remove the solvent is used. You can also. The metal oxide fine particles are preferably bound, and preferably have a resistance of 0.1 g or more, preferably 1 g or more with a continuous load type surface property measuring instrument (for example, a scratch tester).

  Porous as used in the present invention refers to a penetrating state in which a porous electrode is disposed, a potential difference is applied between the counter electrodes, and a silver dissolution and precipitation reaction can occur, and the ionic species can move within the porous electrode. Say.

(Electronic insulation layer)
In the display element of the present invention, an electrical insulating layer can be provided.

  The electronic insulating layer applicable to the present invention may be a layer having both ionic conductivity and electronic insulating properties. For example, a solid electrolyte membrane in which a polymer or salt having a polar group is formed into a film, electronic insulating properties And a porous solid material having a low relative dielectric constant, such as a silicon-containing compound, and the like.

  As a method for forming a porous film, a sintering method (fusing method) (using fine pores formed between particles by partially fusing polymer fine particles or inorganic particles by adding a binder, etc.), extraction method ( After forming a constituent layer with a solvent-soluble organic substance or inorganic substance and a binder that does not dissolve in the solvent, the organic substance or inorganic substance is dissolved with the solvent to obtain pores), and the polymer is heated or degassed Known forming methods such as foaming method for foaming, phase change method for phase separation of polymer mixture by manipulating good solvent and poor solvent, radiation irradiation method for radiating various radiations to form pores, etc. 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.

[Electrolyte material]
In the display element of the present invention, when the electrolyte is a liquid, the following compounds can be included in the electrolyte. 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.

  Further, when the supporting electrolyte is a solid, the following compounds exhibiting electron conductivity and ion conductivity can be contained in the electrolyte.

Vinyl fluoride polymer containing perfluorosulfonic acid, polythiophene, polyaniline, polypyrrole, triphenylamines, polyvinylcarbazoles, polymethylphenylsilanes, Cu ₂ S, Ag ₂ S, Cu ₂ Se, AgCrSe _2, etc. F-containing compounds such as chalcogenide, CaF ₂ , PbF ₂ , SrF ₂ , LaF ₃ , TlSn ₂ F ₅ , CeF ₃ , Li salts such as Li ₂ SO ₄ , Li ₄ SiO ₄ , Li ₃ PO ₄ , ZrO ₂ , CaO _{, Cd 2 O 3, HfO 2} , Y2O 3, Nb 2 O 5, WO 3, Bi 2 O 3, AgBr, AgI, CuCl, CuBr, CuBr, CuI, LiI, LiBr, LiCl, LiAlCl 4, LiAlF 4, AgSBr _{, C 5 H 5 NHAg 5 I} 6, Rb 4 Cu 16 I 7 Cl 13, Rb 3 Cu 7 Cl 10, LiN, Li 5 NI 2 Compounds such as li ₆ NBr _3, and the like.

  Moreover, a gel electrolyte can also be used as the supporting electrolyte. When the electrolyte is non-aqueous, the oil gelling agents described in paragraphs [0057] to [0059] of JP-A No. 11-185836 can be used.

[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 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 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
〔Layer structure〕
The constituent layers between the counter electrodes of the display element of the present invention will be further described.

As a constituent layer according to the display element of the present invention, a constituent layer containing a hole transport material can be provided. Examples of hole transport materials include aromatic amines, triphenylene derivatives, oligothiophene compounds, polypyrroles, polyacetylene derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polythiophene derivatives, polyaniline derivatives, polytoluidine derivatives, CuI, CuSCN CuInSe ₂ , Cu (In, Ga) Se, CuGaSe ₂ , Cu ₂ O, CuS, CuGaS ₂ , CuInS ₂ , CuAlSe ₂ , GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O ₃ Etc.

〔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 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 29-31) 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.

〔electrode〕
In the 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. Above all, silver or a silver electrode having a silver content of 80% or more is advantageous for maintaining the reduced state of silver. Excellent in preventing dirt. As an electrode manufacturing method, an existing method such as an evaporation method, a printing method, an ink jet method, a spin coating method, or a CVD method can be used.

  In the display element of the present invention, it is preferable that at least one of the counter electrodes is a transparent electrode. The transparent electrode is not particularly limited as long as it is transparent and conducts electricity. For example, Indium Tin Oxide (ITO: Indium Tin Oxide), Indium Zinc Oxide (IZO: Indium Zinc Oxide), Fluorine Doped Tin Oxide (FTO), Indium Oxide, Zinc Oxide, Platinum, Gold, Silver, Rhodium, Copper, Examples thereof include chromium, carbon, aluminum, silicon, amorphous silicon, and BSO (Bismuth Silicon Oxide). In 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.

[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 be properly maintained at intervals of the substrate, such as an evenly spaced array, an array in which the interval gradually changes, and an array in which a predetermined arrangement pattern is repeated at a constant period. The arrangement is preferably considered so as not to disturb the display. If the ratio of the area occupied by the columnar structure in the display area of the display element is 1 to 40%, a practically sufficient strength as a display element can be obtained.

  A spacer may be provided between the pair of substrates for uniformly maintaining a gap between the substrates. Examples of the spacer include a sphere made of resin or inorganic oxide. Further, a fixed spacer having a surface coated with a thermoplastic resin is also preferably used. In order to hold the gap between the substrates uniformly, only the columnar structure may be provided, but both the spacer and the columnar structure may be provided, or instead of the columnar structure, only the spacer is used as the space holding member. May be used. The diameter of the spacer is equal to or less than the height of the columnar structure, preferably equal to the height. When the columnar structure is not formed, the diameter of the spacer corresponds to the thickness of the cell gap.

[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.

[Driving method of display element]
In the display element of the present invention, it is preferable to perform a driving operation in which silver black is precipitated by applying a voltage equal to or higher than the precipitation overvoltage, and silver black is continuously precipitated by applying a voltage lower than the precipitation overvoltage. By performing this driving operation, the writing energy can be reduced, the driving circuit load can be reduced, and the writing speed as a screen can be improved. It is generally known that overvoltage exists in electrode reactions in the electrochemical field. For example, overvoltage is described in detail on page 121 of “Introduction to Chemistry of Electron Transfer—Introduction to Electrochemistry” (published by Asakura Shoten in 1996). Since the display element of the present invention can also be regarded as an electrode reaction between the electrode and silver in the electrolyte, it can be easily understood that overvoltage exists even in silver dissolution precipitation. Since the magnitude of the overvoltage is governed by the exchange current density, it is possible to continue silver black precipitation by applying a voltage equal to or lower than the precipitation overvoltage after the formation of silver black as in the present invention. However, it is estimated that electron injection can be easily performed with little extra electric energy.

  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.

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

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<< Production of each component material >>
(Preparation of electrolyte 1)
In 2.5 g of dimethyl sulfoxide, 90 mg of sodium iodide and 75 mg of silver iodide were added and completely dissolved to obtain an electrolytic solution 1.

(Preparation of Dispersion 1)
Dispersion 1 was obtained by dispersing 20% by mass of titanium oxide having an average particle size of 300 nm in an aqueous solution containing 2% by mass of polyvinyl alcohol (average molecular weight 30000) using an ultrasonic disperser.

(Preparation of Dispersion 2)
Dispersion 2 was obtained by dispersing 20% by mass of titanium oxide having an average particle size of 20 nm in an aqueous solution containing 2% by mass of polyvinyl alcohol (average molecular weight 30000) using an ultrasonic disperser.

(Production of electrode 1)
An ITO film having a pitch of 145 μm and an electrode width of 130 μm was formed on a glass substrate having a thickness of 1.5 mm and a size of 2 cm × 4 cm to obtain a transparent electrode (electrode 1).

(Preparation of electrode 2)
A silver-palladium electrode (electrode 2) having an electrode thickness of 0.8 μm, a pitch of 145 μm, and an electrode interval of 130 μm is formed on a glass substrate having a thickness of 1.5 mm and a size of 2 cm × 4 cm by using a known method. Got.

(Preparation of electrode 3)
On the electrode 2, the dispersion 1 was screen-printed so that the average film thickness after drying was 20 μm, then dried at 50 ° C. for 30 minutes to evaporate the solvent, and then 1 in an atmosphere at 85 ° C. The porous white scattering layer was formed by drying for a time, and this was used as the electrode 3.

(Preparation of electrode 4)
On the electrode 2, the dispersion 1 was screen-printed so that the average film thickness after drying was 10 μm, then dried at 50 ° C. for 30 minutes to evaporate the solvent, and then 1 in an atmosphere at 85 ° C. A porous white scattering layer was formed by drying for a period of time, and this was used as the electrode 4.

(Preparation of electrode 5)
On the electrode 2, the dispersion 2 was screen-printed so that the average film thickness after drying was 20 μm, and then dried at 50 ° C. for 30 minutes to evaporate the solvent. The porous white scattering layer was formed by drying for a period of time, and this was used as the electrode 5.

(Preparation of electrode 6)
The produced electrode 5 is subjected to anodic polarization in an acidic aqueous solution at +1.0 V (vs SCE), and a photoetching amount of 10 C / cm ² at an angle of 90 degrees with respect to the electrode 5 using an ultrahigh pressure mercury lamp. Then, pores were formed under the conditions of an inner diameter D of 250 nm, a depth of 20 μm, L / D = 80, and an area ratio of pores of 15 area%.

(Preparation of electrode 7)
The produced electrode 5 is subjected to anodic polarization in an acidic aqueous solution at +1.0 V (vs SCE), and a photoetching amount of 1 C / cm ² at an angle of 90 degrees with respect to the electrode 5 using an ultrahigh pressure mercury lamp. Then, pores were formed under the conditions of an inner diameter D of 20 nm, a depth of 1.6 μm, L / D = 80, and an area ratio of pores of 7.5 area%.

(Preparation of electrode 8)
The produced electrode 5 is subjected to anodic polarization in an acidic aqueous solution at +1.0 V (vs SCE), and a photoetching amount of 3 C / cm ² at an angle of 90 degrees with respect to the electrode 5 using an ultrahigh pressure mercury lamp. Then, pores were formed under the conditions of an inner diameter D of 20 nm, a depth of 10 μm, L / D = 500, and an area ratio of pores of 7.5 area%.

(Preparation of electrode 9)
The produced electrode 3 is subjected to anodic polarization in an acidic aqueous solution at +1.0 V (vs SCE), and a photoetching amount of 10 C / cm ² at an angle of 90 degrees with respect to the electrode 3 using an ultrahigh pressure mercury lamp. The pores were formed under the conditions of an inner diameter D of 100 nm, a depth of 20 μm, L / D = 200, and an area ratio of pores of 12.5 area%.

(Production of electrode 10)
The dispersion 2 was screen-printed on the electrode 2 so that the average film thickness after drying was 10 μm, and then dried at 50 ° C. for 30 minutes to evaporate the solvent. An electrode prepared by drying for a period of time to form a porous white scattering layer was anodic polarized in an acidic aqueous solution at an angle of 90 degrees with respect to the electrode 3 using an ultrahigh pressure mercury lamp at +1.0 V (vs SCE). in treated until the optical etching amount of 5C / cm ^2, the inner diameter D is 100 nm, the depth 10 [mu] m, and form pores in L / D = 100, the area ratio 12.5 area% of the pore conditions, This was designated as an electrode 10.

(Preparation of electrode 11)
The produced electrode 5 is subjected to anodic polarization in an acidic aqueous solution at +1.0 V (vs SCE), and a photoetching amount of 10 C / cm ² at an angle of 90 degrees with respect to the electrode 5 using an ultrahigh pressure mercury lamp. The pores were formed under the conditions of an inner diameter D of 20 nm, a depth of 20 μm, L / D = 1000, and a pore area ratio of 7.5 area%.

(Preparation of electrode 12)
An electrode 12 was produced in the same manner as in the production of the electrode 11 except that the irradiation angle of the ultrahigh pressure mercury lamp to the electrode 5 was changed to 55 degrees.

(Preparation of electrode 13)
After the electrode 11 was produced, a baking treatment for 1 hour was performed in an atmosphere at 250 ° C., and this was used as an electrode 13.

(Preparation of electrode 14)
The produced electrode 5 is subjected to anodic polarization in an acidic aqueous solution at +1.0 V (vs SCE), and a photoetching amount of 10 C / cm ² at an angle of 90 degrees with respect to the electrode 5 using an ultrahigh pressure mercury lamp. Then, pores were formed under the conditions of an inner diameter D of 8 nm, a depth of 20 μm, L / D = 2500, and an area ratio of pores of 7.5 area%. In the production of the electrode 14, pore formation was performed under the above conditions, but stable pores could not be formed.

<< Production of display element >>
[Production of Display Element 1]
After the electrode 3 and the electrode 1 were bonded together, the empty cell was produced by heating and pressing. The electrolytic solution 1 was vacuum-injected into the empty cell, and the injection port was sealed with an epoxy-based ultraviolet curable resin to produce the display element 1.

[Production of display elements 2 to 12]
In the production of the display element 1, display elements 2 to 12 were obtained in the same manner except that the electrode 3 was changed to electrodes 4 to 14, respectively.

<< Measurement and performance evaluation of display element characteristics >>
About each produced said display element, the measurement of the characteristic value and performance evaluation were performed in accordance with the following method. However, since the display element 14 could not form stable pores, it was excluded from the evaluation.

(Evaluation of pore: ratio of pore depth / pore diameter, measurement of orientation of pore with respect to electrode)
Obtain images of 10 arbitrary locations of the porous white scattering layer with an electron microscope VE-9800 manufactured by Keyence Corporation, and calculate the ratio of the pore depth / pore diameter at each location and the average value of the inclination of the pore with respect to the electrode. did.

(Evaluation of display element: measurement of reflectance during white display)
A voltage of 1.5 V was applied to each of the display devices prepared above for 3 seconds to display white, and the reflectance at 550 nm was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing. The measured reflectance and R _W, was the R _W as an index of the reflectance of the white display.

(Evaluation of display element: Evaluation of display speed)
A voltage of 1.5 V is applied to each of the display devices prepared above for 3 seconds to display white, then a voltage of −1.5 V is applied for 0.5 seconds to display gray, and a reflectance at 550 nm. Was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing. The measured reflectance was _RGlay, and _RGlay was used as an indicator of display speed. Here, it is assumed that the display speed is higher as R _Glay is lower.

(Evaluation of display element: Evaluation of display unevenness resistance)
A voltage of 1.5 V is applied to each of the display devices prepared above for 3 seconds to display white, then a voltage of −1.5 V is applied for 0.5 seconds to display gray, and any display element can be displayed. The reflectance at 550 nm at two locations was measured with a spectrocolorimeter CM-3700d manufactured by Konica Minolta Sensing Co., and the difference in reflectance was calculated. The calculated difference in reflectance was _ΔRGlay, and _RGlay was used as an indicator of display unevenness resistance. Here, it is assumed that the smaller the ΔR _Glay is, the less display unevenness is.

  The results obtained as described above are shown in Table 1.

  As is clear from the results shown in Table 1, in the case of the display elements 1 and 2 in which the porous white scattering layer is composed of titanium oxide having an average particle size of 300 nm, it is impossible to achieve both white reflectance and display speed. I understand. This is because when the average thickness of the porous white scattering layer is high, the light shielding is sufficient and the white display reflectivity is improved, but the diffusion of reactants and products to the electrode is limited, so the display speed is high. In the display element 2, if the porous white scattering layer is thin, diffusion of reactants and products from the electrode surface is promoted, so that the display speed is improved. This is because the reflectance of white display is lowered due to insufficient.

  Further, in the case of the display element 3 in which the porous white scattering layer is composed of titanium oxide having an average particle diameter of 20 nm, a certain degree of improvement in white reflectance is observed, but if the average particle diameter of titanium oxide is small, the porous element is porous. The porosity of the white-white scattering layer is reduced, and the diffusion of the reactants and products is restricted, so that the display speed and display unevenness resistance are reduced.

  On the other hand, the display element having a porous white scattering layer having a pore depth / pore diameter ratio of 10 or more according to the present invention has both white reflectance and display speed and further improved display unevenness. In particular, it can be seen that when the ratio of the pore depth / pore diameter is 1000 or more and the orientation of the pores with respect to the electrode is 60 degrees or more, the improvement in the display speed is large.

  This is because, by taking the shape and arrangement of the pores of the present invention, the reactant and product are smoothly diffused, thereby improving the display speed and further leading to suppression of display unevenness. . It can be seen that the above effect is further enhanced when the porous white scattering layer is fired at a temperature of 250 ° C.

It is a schematic sectional drawing which shows an example of the basic composition of the display element of this invention.

Explanation of symbols

1, 2 Electrode 3 Electrolyte 4 Porous white scattering layer 5 Metal oxide particle 6 Pore D Pore inner diameter L Pore depth

Claims (7)

A display element comprising an electrolyte layer containing silver or a compound containing silver in the chemical structure and a porous white scattering layer between the counter electrodes, and driving the counter electrode so as to cause dissolution and precipitation of silver In claim 1, wherein the porous white scattering layer has pores, and L / D is 100 or more and 2000 or less, where D is the inner diameter of the pores and L is the depth. The display element according to claim 1, wherein the pores are arranged at an angle of 60 to 90 degrees with respect to the electrode. The display element according to claim 1, wherein the pores are formed by a photoelectrochemical etching process. 4. The display element according to claim 1, wherein a main component of the porous white scattering layer is a metal oxide having an average particle diameter of 10 nm or more and 500 nm or less. The display element according to claim 4, wherein the metal oxide is titanium dioxide. The display element according to any one of claims 1 to 5, wherein an average film thickness of the porous white scattering layer is 15 µm or more and 300 µm or less. The display element according to claim 1, wherein the porous white scattering layer is baked at a temperature of 120 ° C. or higher.

Images