JP2007121418A - Electrochromic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochromic device having very high color purity, capable of accurate color control and capable of sharp and clear full-color image display. <P>SOLUTION: In the electrochromic device, a pair of electrode structures 11, 12 in which at least transparent electrodes 2, 7 are formed on supporting substrates 1, 6 are disposed while holding an electrolyte layer 5 in such a way that the transparent electrodes 2, 7 face each other, and a porous electrode 4 on which an organic EC dye comprising a bipyridine compound of a dimerized structure is adsorbed is formed on at least one of the transparent electrodes 2, 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrochromic device excellent in response speed, color development efficiency, display color purity, capable of forming a clear and sharp image, and excellent in repeated durability.

In recent years, there has been an increasing demand for display dye materials that are bright and excellent in color purity, consume less power, and can be easily applied to full color display.
Conventionally, light-emitting elements such as CRT, LCD, PDP, ELD and the like have a feature of being bright and easy to see, and many techniques have been proposed.
However, since the various light-emitting elements are used in such a way that the user looks directly at the light emission, there is a problem that visual fatigue occurs when viewed for a long time.
In addition, mobile devices such as mobile phones are often used outdoors, and there is also a problem that the visibility is deteriorated by canceling light emission under sunlight.
In addition, LCD is a technology that is particularly in demand among light-emitting elements, and is used in various display applications such as large and small. However, LCD has a narrow viewing angle and is not easy to view. Compared to the light emitting element, there is a problem to be improved.

By the way, regarding the reflective display element, various technologies have been proposed due to an increase in demand for electronic paper.
For example, a reflective LCD or an electrophoretic method can be used.
Conventionally, as the reflective LCD, a GH type liquid crystal system using a dichroic dye, a cholesteric liquid crystal, and the like are known. These methods have the advantage of lower power consumption because they do not use a backlight compared to conventional light emitting LCDs, but they have a viewing angle dependency and low light reflection efficiency. There is a problem that the screen will inevitably become dark.
On the other hand, the electrophoresis method is a method that utilizes a phenomenon in which charged particles dispersed in a solvent move by an electric field, and has the advantage of low power consumption and no viewing angle dependency. However, in the case of performing full color, it is necessary to apply a juxtaposed mixing method using a color filter, so that there is a problem that the reflectance is lowered and the screen is inevitably darkened.

Conventionally, an electrochromic (hereinafter abbreviated as EC) element is used for a light control mirror of an automobile, a timepiece or the like.
The light emitted from this EC element does not require a polarizing plate, has no viewing angle dependency, has a light receiving type, has excellent visibility, has a simple structure and can be easily enlarged, and has a variety of color tones depending on the selection of materials. It has the advantage that it is possible to emit light.
When such an EC element is used, a subtractive color mixture of cyan (C), magenta (M), and yellow (Y) can be applied, and the C, M, and Y coloring layers are stacked. Thus, full color display can be realized.
Further, black can be displayed by mixing C, M, and Y, and white can be displayed by making each pigment transparent with the color of each pigment being decolored and making the background color white.

  On the other hand, when the red, red, green, and blue dyes are applied and the R, G, and B color layers are stacked, white / black display is easy. There is an arbitrary neutral color display. Further, when R, G, and B are arranged in the same plane, white display is easy, but black display and arbitrary intermediate color display cannot be performed.

Recently, as a display device using an EC element, a proposal has been made regarding a display device having a structure in which a semiconductor nanoporous layer is provided on at least one of a pair of transparent electrodes and an EC dye is supported on the semiconductor nanoporous layer. (For example, refer to Patent Documents 1 and 2.)
Since this display device can form an open circuit and can stop the display state only by blocking the movement of electrons between the electrodes and maintaining the oxidation-reduction state, power for maintaining the display image is unnecessary, and power consumption is extremely high. It is particularly excellent in that it is low.

JP 2003-248242 A JP 2003-270670 A

By the way, the above-mentioned conventional known documents are not premised on performing full-color display, and have disclosed EC dyes that develop color in cyan (C), magenta (M), and yellow (Y) necessary for full-color display. There wasn't.
In addition, these display devices have a problem that color purity is low and it is difficult to display a precise and clear color image.

  In addition, a non-patent document (Display 20 (1999) 137) discloses a technique for forming a purple color by forming a dimer with the compounds represented by the following formulas (2) and (3). Yes. In the formula, X is halogen.

However, although it can be said that it is possible to color the blue to magenta color by aggregating the molecules of the compounds of the above formulas (2) and (3), it is possible to stably aggregate and overlap these molecules. It is extremely difficult to control from a practical viewpoint.
Furthermore, since the amount of dimer formed of the compounds of the above formulas (2) and (3) changes depending on the device fabrication conditions and the adsorption density of the dye compound to the electrode, a stable color spectrum can be obtained. It had a problem that it was not possible.
In addition, when a display device manufactured using these is operated repeatedly many times, the dimer formation amount changes, the shape of the color development spectrum changes, and there is a problem that it is practically inferior in terms of durability. It was.

  Therefore, in the present invention, in view of the problems of the EC element proposed in the past as described above, a proposal is made regarding an organic electrochromic dye that can contribute to full color, particularly capable of magenta color development. It was decided to provide an electrochromic device having high purity, capable of forming a clear image, having low dependency on the amount of dye adsorbed to the electrode, and excellent in repeated durability.

  In the present invention, a pair of electrode structures in which at least transparent electrodes are formed on a support substrate are disposed with an electrolyte layer sandwiched between the transparent electrodes so that the transparent electrodes face each other, and the pair of transparent structures A porous electrode to which at least a bipyridine compound represented by the following general formula (1) is adsorbed is formed on at least one of the electrodes, and a voltage is applied to the pair of electrode structures. Thus, an electrochromic device is provided that performs reversible color erasing of magenta.

However, in the general formula (1), a and b are integers satisfying a × b = 4, and X ^b− represents an appropriate b-valent anion.
Y _{1 to} Y ₄ and Z _{1 to} Z ₄ are hydrogen atoms, or aliphatic hydrocarbon groups, ether groups, acyl groups, halogen groups or cyano groups, ester groups, hydroxy groups, amino groups, amide groups, aromatics Represents a group hydrocarbon group, and at least one of Y _{1 to} Y ₄ and Z _{1 to} Z ₄ is an adsorbing group for adsorbing to the porous electrode.

  According to the present invention, an electrochromic device having excellent response speed and color development efficiency, high color purity, capable of precise image control, and capable of stably forming a clear color display many times was obtained. .

Hereinafter, the electrochromic device of the present invention and a display method using the same will be specifically described with reference to the drawings.
However, the present invention is not limited to the following examples, and a conventionally known configuration can be added as appropriate, and does not depart from the gist of the present invention.

FIG. 1 shows a schematic sectional view of an example of the electrochromic device of the present invention.
The electrochromic device 10 includes a display electrode structure 11 having a configuration in which a transparent electrode 2 and a porous electrode 4 on which an organic EC dye 3 made of a bipyridine compound described later is supported are provided on a support substrate 1, and a support substrate. 6, a counter electrode structure 12 having a configuration including a transparent electrode 7 and a porous electrode 8 is disposed so as to face each other with an electrolyte layer 5 interposed therebetween.
In FIG. 1, porous electrodes 4 and 8 are formed on both of the opposing transparent electrodes 2 and 7, but the present invention is not limited to this configuration, and only one electrode is necessary if necessary. It is good also as a structure in which the porous electrode was formed. Hereinafter, the components will be sequentially described.

The support substrates 1 and 6 are preferably made of a material having excellent heat resistance and high dimensional stability in the planar direction. Specifically, glass materials and transparent resins can be applied, but the present invention is not limited thereto. Absent.
Examples of the transparent resin include polyethylene terephthalate, polyethylene naphthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, and polystyrene.

The transparent electrodes 2 and 7 are formed by laminating a transparent electrode layer on a predetermined transparent substrate.
Examples of the material for forming the transparent electrode layer include a mixture of In ₂ O ₃ and SnO ₂ , a so-called ITO film, and a film coated with SnO ₂ or In ₂ O ₃ .
Further, Sn, Sb, F, or the like may be doped into the ITO film or a film coated with SnO ₂ or In ₂ O ₃ , and other MgO, ZnO, or the like can be applied.

The porous electrodes 4 and 8 are made of a material having a large surface area in order to enhance the dye-supporting function described later. For example, those having a porous shape, a lot shape, a wire shape or the like having fine pores on the surface and inside are preferable.
As the material of the porous electrodes 4 and 8, for example, a metal, an intrinsic semiconductor, an oxide semiconductor, a composite oxide semiconductor, an organic semiconductor, carbon, or the like can be applied.
Examples of the metal include Au, Ag, Pt, and Cu. Examples of the intrinsic semiconductor include Si, Ge, and Te. Examples of the oxide semiconductor include TiO ₂ , SnO ₂ , Fe ₂ O ₃ , SrTiO ₃ , WO ₃ , ZnO, ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , V ₂ O ₅ , In ₂ O ₃ , Examples thereof include CdO, MnO, CoO, TiSrO ₃ , KTiO ₃ , Cu ₂ O, sodium titanate, barium titanate, and potassium niobate. Examples of the complex oxide semiconductor include SnO ₂ —ZnO, Nb ₂ O ₅ —SrTiO ₃ , Nb ₂ O ₅ —Ta ₂ O ₅ , Nb ₂ O ₅ —ZrO ₂ , Nb ₂ O ₅ —TiO _2. , Ti—SnO ₂ , Zr—SnO ₂ , Sb—SnO ₂ , Bi—SnO ₂ , In—SnO _2, etc., and particularly TiO ₂ , SnO ₂ , Sb—SnO ₂ , and In—SnO ₂ are suitable. . Examples of the organic semiconductor include polythiophene, polypyrrole, polyacetylene, polyphenylene vinylene, and polyphenylene sulfide.

Next, the organic EC dye 3 will be described.
The organic EC dye 3 is assumed to be carried on the surface of the porous electrode 4 and inside the fine pores. In the present invention, the organic EC dye 3 is particularly a dimeric bipyridine compound represented by the following general formula (1) And

However, in the above general formula (1), a and b are integers satisfying a × b = 4, and X ^b− represents an appropriate b-valent anion. Fluorine ion, chlorine ion, bromine ion, iodine ion, perchlorate ion, periodate ion, hexafluorophosphate ion, hexafluoroantimonate ion, hexafluorostannate ion, phosphate ion, boron fluoride Inorganic acid ions such as hydrocyanic acid ions and tetrafluoroboric acid ions, thiocyanate ions, benzenesulfonate ions, naphthalenesulfonate ions, naphthalene disulfonate ions, p-toluenesulfonate ions, alkylsulfonate ions, benzenecarboxylic acids It is selected from organic acid ions such as ions, alkyl carboxylate ions, trihaloalkyl carboxylate ions, alkyl sulfate ions, trihaloalkyl sulfate ions, nicotinate ions, and tetracyanoquinodimethane ions.

Y _{1 to} Y ₄ and Z _{1 to} Z ₄ are a hydrogen atom, an aliphatic hydrocarbon group, an ether group, an acyl group, a halogen group, a cyano group, an ester group, a hydroxy group, an amino group, an amide group, and an aromatic hydrocarbon. Any one of the groups is represented, and at least one of Y ₁ to Y ₄ and Z _{1 to} Z ₄ is an adsorption group for adsorbing to the porous electrode.
Examples of the adsorbing group for adsorbing to the porous electrode include acidic groups such as a carboxyl group, a sulfonic acid group, and a phosphonic acid group, an amino group, a metal alkoxide, and a metal halide.

The bipyridine compound of the organic EC dye represented by the general formula (1) is different from the dye compounds (general formulas (2) and (3)) applied in the conventional technique described above, and the fragrances at both ends in the molecule. Since the bipyridine structure is dimerized by the ring, stable magenta color development can be easily realized.
In this general formula (1), it is expressed as tetravalent, but when magenta color development is performed, a divalent radical state is obtained by a reduction reaction. This compound can be stabilized in this divalent state, and it was confirmed that it is extremely excellent as an organic EC dye for magenta color development.
Specific examples [Chemical Formula 5] to [Chemical Formula 13] of the bipyridine compound represented by the general formula (1) are shown below.

Examples of the method of supporting the organic EC dye composed of the bipyridine compound on the porous electrode 4 include a method of adsorbing on the surface of the porous electrode and a method of chemically bonding the surface of the porous electrode and the organic EC dye. Conventionally known techniques can be applied.
Specifically, a dry process such as a vacuum deposition method, a coating method such as spin coating, an electric field deposition method, an electric field polymerization method, a natural adsorption method immersed in a solution of a compound to be supported, and the like can be appropriately selected. A method of chemically bonding an organic EC dye to the porous electrode surface is suitable.

As a natural adsorption method, a method in which a transparent substrate on which a porous electrode 4 that has been previously dried is formed is immersed in a solution in which a predetermined organic EC dye is dissolved, or a predetermined organic EC dye is dissolved. The method of apply | coating a solution to the porous electrode 4 is mentioned.
In order to spontaneously adsorb the organic EC dye on the porous electrode 4, it is necessary to introduce an adsorptive functional group into the chemical structure of the organic EC dye. This adsorptive functional group is appropriately selected according to the material of the porous electrode to be adsorbed. For example, when the porous electrode 4 is composed of an oxide semiconductor, it is included in the chemical structure of the organic EC dye. It is preferable to introduce an adsorptive functional group such as a phosphonic acid group, a sulfonic acid group, a carboxyl group, a hydroxy group, or an amino group.
The adsorptive functional group may be introduced directly into the skeleton of the organic EC dye or via another predetermined functional group. Among the above, when introducing an adsorbing group through a predetermined functional group, a method of introducing the adsorbing group through a functional group such as an alkyl group, a phenyl group, an ester, an amide group or the like is preferable.
Examples of the solvent for dissolving the organic EC dye include water, alcohol, acetonitrile, propionitrile, halogenated hydrocarbons, ethers, dimethyl sulfoxide, N, N-dimethylformamide, N-methylpyrrolidone, esters, Carbonates, ketones, hydrocarbons and the like can be applied. These may be used singly or may be used in combination as appropriate.

Further, when the organic EC dye is chemically bonded to the surface of the porous electrode 4, a predetermined functional group may be interposed between the surface of the porous electrode 4 and the organic EC dye skeleton. For example, functional groups such as alkyl groups, phenyl groups, esters, and amides are suitable.
Further, after the surface of the porous electrode 4 is modified with a silane coupling agent or the like, an organic EC dye may be chemically bonded and formed.

Although FIG. 1 shows an example in which the organic EC dye 3 is supported only on the porous electrode 4 on the display electrode structure 11 side, the electrochromic device of the present invention is not limited to this configuration. .
In other words, the porous electrode 8 on the counter electrode structure 12 side may be configured to carry a predetermined organic EC dye. In this case, it is necessary to select materials so that the coloring reaction and the decoloring reaction occur according to the reverse reaction of the oxidation reaction and the reduction reaction, respectively.
For example, when the bipyridine dye supported on the porous electrode 4 becomes a radical state by the reduction reaction and develops color, the porous electrode 8 has the same color tone as the bipyridine dye supported on the porous electrode 4 in a steady state. An organic EC dye that is decolorized by an oxidation reaction is selected.
As described above, by adopting a configuration in which the organic EC dye is supported in both the electrode structures 11 and 12, in the finally obtained electrochromic device, the color development can be clarified and the sharpness of the image can be improved. .

The electrolyte layer 5 has a configuration in which a supporting electrolyte is dissolved in a solvent.
Examples of the supporting electrolyte include lithium salts such as LiCl, LiBr, LiI, LiBF ₄ , LiClO ₄ , LiPF ₆ , and LiCF ₃ SO ₃ , potassium salts such as KCl, KI, and KBr, and NaCl, NaI, NaBr, and the like. And tetraalkylammonium salts such as tetraethylammonium borofluoride, tetraethylammonium perchlorate, tetrabutylammonium borofluoride, tetrabutylammonium perchlorate, and tetrabutylammonium halide.
A known redox compound may be added to the electrolyte layer 5 as necessary. As the redox substance, for example, a ferrocene derivative, a tetracyanoquinodimethane derivative, a benzoquinone derivative, a phenylenediamine derivative, or the like can be applied.
As the solvent, a solvent that dissolves the supporting electrolyte and does not dissolve the organic EC dye described above is selected.
For example, it is appropriately selected from water, acetonitrile, dimethylformamide, propylene carbonate, dimethyl sulfoxide, propylene carbonate and the like.

Further, a so-called matrix material may be applied to the electrolyte layer 5.
Matrix material can be appropriately selected depending on the purpose, for example, skeletal unit _{respectively, - (CC-O) n} -, - (CC (CH 3) -O) n -, - (CC-N ) _n- , or-(C-C-S) _n- , for example, polyethylene oxide, polypropylene oxide, polyethyleneimine, and polyethylene sulfide.
In addition, you may have a branched structure suitably by making these into a principal chain structure. Polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene chloride, polycarbonate, and the like are also suitable.

The electrolyte layer 5 may be a polymer solid electrolyte layer.
In this case, it is preferable to add a predetermined plasticizer to the polymer of the matrix material.
As the plasticizer, when the matrix polymer is hydrophilic, water, ethyl alcohol, isopropyl alcohol, and a mixture thereof are preferable. When the matrix polymer is hydrophobic, propylene carbonate, dimethyl carbonate, ethylene carbonate, γ- Preferred are butyrolactone, acetonitrile, sulfolane, dimethoxyethane, ethyl alcohol, isopropyl alcohol, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, n-methylpyrrolidone, and mixtures thereof.

Next, a display method using the electrochromic device 10 described above will be described.
In the electrochromic device 10 of FIG. 1, the surface of the porous electrode 4 carries a bipyridine compound represented by the general formula (1), which is an organic EC dye that does not absorb in the visible region in a steady state.
A predetermined lead wire is connected to the pair of electrode structures 11 and 12 constituting the electrochromic device 10 to constitute a display device.
When a predetermined voltage is applied through a predetermined lead wire, electrons are exchanged between the porous electrode 4 and the organic EC dye material carried on the porous electrode 4, and an electrochemical reduction reaction occurs in the organic EC dye, and magenta. Color develops.

Note that the electrochromic device of the present invention is not limited to the configuration shown in FIG. 1, and may be configured as a device capable of multicolor display.
That is, an electrode structure having the same structure as the electrochromic structure shown in FIG. 1 and having a porous electrode supported by a material that develops yellow (Y) or cyan (C) as an organic EC dye is laminated. As a result, a full color display electrochromic device capable of reversibly performing a combination of a plurality of colors and the color generation / deletion display thereof can be obtained.

  Next, specific examples of the electrochromic device of the present invention and comparative examples will be described.

(Preparation of display electrode structure)
On a support substrate 1 made of glass having a thickness of 1.1 mm, a 15 Ω / □ FTO film (transparent electrode 2) was formed in a plane.
Next, polyethylene glycol was dissolved at a rate of 5% by weight in a slurry in which 15% by weight of titanium oxide having a primary particle diameter of 20 nm was dispersed in an aqueous hydrochloric acid solution having a pH of about 1.0 to prepare a coating material. This paint was applied on the FTO film by a squeegee method.
Next, an FTO substrate on which a titanium oxide porous electrode 4 having a film thickness of 3 μm is formed by performing a drying process at 80 ° C. for 15 minutes on a hot plate, further sintering at 500 ° C. for 1 hour in an electric furnace. Obtained.

(Adsorption of organic EC dye to porous electrode)
The FTO substrate on which the porous electrode 4 made of the titanium oxide film is formed is immersed in a 0.02M aqueous solution of a bipyridine compound for 1 hour, 6 hours or 24 hours, and a dye (organic EC dye film) is placed on the titanium oxide electrode. Adsorbed.
Thereafter, the substrate was washed with an ethanol solution and dried.

(Preparation of counter electrode structure)
On a support substrate 6 made of glass having a thickness of 1.1 mm, a 15Ω / □ FTO film (transparent electrode 7) was formed in a plane.
Next, polyethylene glycol was dissolved at a ratio of 5% by weight in a slurry in which 20% by weight of antimony-doped tin oxide having a primary particle diameter of 20 nm was dispersed in an acidic aqueous solution to prepare a paint. This paint was applied on the FTO film by a squeegee method.
Next, FTO in which an antimony-doped tin oxide porous electrode 8 having a film thickness of 7 μm was formed by performing a drying treatment at 80 ° C. for 15 minutes on a hot plate and further sintering at 500 ° C. for 1 hour in an electric furnace. A substrate was obtained.

(Preparation of solution for electrolyte layer)
As the electrolyte layer 5 forming solution, a solution obtained by dissolving 0.1 mol / L of lithium perchlorate in gamma-butyrolacron, dehydrating and degassing was applied.

(Lamination of electrode structure)
Adhesion of display electrode structure (substrate with dye-adsorbed titanium oxide porous electrode) and counter electrode structure (substrate with antimony-doped tin oxide porous electrode) produced as described above to a thermoplastic film having a thickness of 50 μm Using an agent, bonding was performed at 90 ° C.
At this time, an injection port was formed in a part so that the electrolyte solution could be injected by a process described later.

(Injection of electrolyte solution)
The electrolytic solution was injected from the injection port.
Thereafter, the injection port was sealed with an epoxy-based thermosetting resin, thereby completing an electrochromic device including electrode structures facing each other with the electrolyte layer sandwiched therebetween.
In accordance with the manufacturing process of the electrochromic device described above, different organic EC dyes supported on the porous electrode were applied to prepare sample cells of the following examples and comparative examples.

(Synthesis of organic EC dye compound: [Chemical Formula 5])
To 40 ml of chloroform, 0.03 mol of 3,4-dimethylbenzoic acid, 0.062 mol of N-bromosuccinimide and 0.001 mol of benzoyl peroxide were added and reacted at 100 ° C. for 3 hours. The white powder obtained by removing the solvent under reduced pressure was thoroughly washed with diethyl ether and pure water and dried to obtain 3,4-bis (bromomethyl) benzoic acid.
1H-NMR (DMSO) δ: 13.20 (1H, s), 8.06 (1H, s), 7.88 (1H, d, J = 7.8Hz), 7.61 (1H, d, J = 8.0Hz),
4.89 (4H, d, J = 13.9Hz).
0.05 mol of 4,4′-bipyridine was dissolved in 50 ml of acetonitrile and refluxed. Thereto was added dropwise 40 ml of acetonitrile in which 0.02 mol of 1,2-bis (bromomethyl) benzene was dissolved. After 2 hours, the precipitated solid was collected by filtration and washed with acetonitrile to obtain 1,1 ″-[1,2-phenylene-bis (methylene)] bis-4,4′-bipyridinium-dibromide.
1H-NMR (D20) δ: 8.63 (4H, d, J = 5.6Hz), 8.40 (4H, d, J = 2.7Hz), 8.08 (4H, d, J = 5.6Hz),
7.65 (4H, d, J = 18.5Hz), 7.49 (4H, d, J = 3.4Hz), 5.97 (4H, s).
The two compounds obtained by the above method were dissolved in 0.01 mol each in 40 ml of a mixed solvent of IPA / water = 1: 1 and refluxed for 24 hours. The precipitated solid was collected by filtration and recrystallized from MeOH to obtain an organic EC dye ([Chemical Formula 5]).
1H-NMR (D20) δ: 9.18-9.09 (3H, m), 8.27 (8H, m), 8.07 (2H, m), 7.95 (2H, m), 7.82-7.77 (8H, m),
6.24-5.91 (8H, m).
The compounds shown in the above [Chemical 6] to [Chemical 13] can also be synthesized by the same procedure as in the above [Chemical 5].

〔Example〕
As the organic EC dye, the compound of [Chemical Formula 5] synthesized as described above was applied and adsorbed to the porous electrode constituting the display electrode structure to produce an electrochromic device.
When a voltage of -1.5 V was applied between the display electrode and the counter electrode of this electrochromic device, a bright magenta color was immediately exhibited. The response speed of the display change was about 180 ms.
Further, when 0.5 V was applied between the electrodes, it became transparent again immediately. The response speed of the display change was about 60 ms.
The immersion time of the display electrode in the organic EC dye solution was changed to 1 hour, 6 hours, and 24 hours, and the measurement was performed for the color density when -1.5 V was applied between the display electrode and the counter electrode. As a result, the spectral shape did not change as shown in the visible absorption spectrum of FIG.
As shown in FIG. 2, the color density tends to increase when the immersion time in the organic EC dye solution is long, but even if the immersion time is set to a short time of about 1 hour, it is practically sufficient. A color density was obtained.
Further, a visible absorption spectrum before and after applying -1.5 V and 0.5 V alternately 1 million times at 1 Hz between the display electrode and the counter electrode of the electrochromic device in this example was measured. The result is shown in FIG. According to this, even after the voltage application was repeated 1 million times, almost no change in the initial state and spectrum shape was observed.
As is apparent from FIGS. 2 and 3, according to the electrochromic device of the present invention, the absorption wavelength width was narrow, and vivid magenta color development / decoloration could be performed reversibly.
Further, by applying the bipyridine compound having the structure represented by the general formula (1), which is peculiar to the present invention, as an organic EC dye, a practically sufficient color density can be obtained even if the amount of adsorption to the electrode is small. Furthermore, even when the color-decoloring operation is repeated many times, an extremely stable magenta color image display can be realized.

[Comparative Example 1]
As the organic EC dye, the compound represented by the general formula (2) was applied. In this case, X ⁻ in the general formula (2) is Cl ⁻ .
This was adsorbed to the porous electrode 4 constituting the display electrode structure 11 of the electrochromic device shown in FIG.
When a voltage of −1.5 V was applied between the display electrode and the counter electrode of this electrochromic device, a purple color was exhibited. The response speed of the display change was about 180 ms.
Further, when a voltage of 0.5 V was applied between the display electrode and the counter electrode, the color immediately disappeared again and became transparent. The response speed of the display change was about 60 ms.
The color density when the voltage of −1.5 V is applied between the display electrode and the counter electrode by changing the immersion time of the display electrode in the organic EC dye solution to 1 hour, 6 hours, and 24 hours, respectively. As a result of the measurement, as shown in the visible absorption spectrum of FIG. 4, a change in color density was observed depending on the immersion time, and the spectrum shape was changed.
As shown in FIG. 4, the absorption wavelength width is broad and inferior to the case of the above embodiment in that sharp color display is performed. Further, it was found that the absorption wavelength was shifted depending on the immersion time in the organic EC dye solution, and stable color development could not be obtained.
Further, a visible absorption spectrum before and after applying -1.5 V and 0.5 V alternately 1 million times at 1 Hz between the display electrode and the counter electrode of the electrochromic device in this example was measured. The result is shown in FIG.
According to this, it was confirmed that after the voltage application was repeated 1 million times, the spectrum shape clearly changed from the initial state, and the color development state became unstable after many uses.
As is apparent from FIGS. 4 and 5, when the compound represented by the general formula (2) was applied as the organic EC dye, a purple color was exhibited, but the magenta color required for full color display was not obtained. .
In addition, when the adsorption density of the dye to the porous electrode is small, the color density is reduced as compared with the above examples, and the color density is greatly decreased by many operations, and stable display cannot be performed.

[Comparative Example 2]
As the organic EC dye, the compound represented by the general formula (3) was applied. In this case, X ⁻ in the general formula (3) is Cl ⁻ .
This was adsorbed to the porous electrode 4 constituting the display electrode structure 11 of the electrochromic device shown in FIG.
When −1.5 V was applied between the display electrode and the counter electrode of this electrochromic device, magenta to purple color was exhibited. The response speed of the display change was about 180 ms. Further, when 0.5 V was applied between the electrodes, the color disappeared immediately and became transparent. The response speed of the display change was about 60 ms.
The color density when the voltage of −1.5 V is applied between the display electrode and the counter electrode by changing the immersion time of the display electrode in the organic EC dye solution to 1 hour, 6 hours, and 24 hours, respectively. As a result of the measurement, as shown in the visible absorption spectrum of FIG. 6, a change in color density was observed depending on the immersion time, and the spectrum shape was changed.
As shown in FIG. 6, it is inferior to the above embodiment in that the absorption wavelength width is broad and sharp color display is performed. It was also found that the absorption wavelength was shifted depending on the immersion time in the organic EC dye solution, and stable color development could not be obtained.
Further, the visible absorption spectrum before and after applying -1.5 V and 0.5 V alternately 1 million times at 1 Hz between the display electrode and the counter electrode of the electrochromic device in this example was measured, and the result is shown in FIG. Shown in
According to this, it was confirmed that after the voltage application was repeated 1 million times, the spectrum shape clearly changed from the initial state, and the color development state became unstable after many uses.
As apparent from FIGS. 6 and 7, when the compound represented by the general formula (3) was applied as the organic EC dye, magenta to purple color was exhibited. However, the clear magenta color required for full color display was obtained. It was not obtained.
In addition, when the adsorption density of the dye to the porous electrode is small, the color density is reduced as compared with the above examples, and the color density is greatly decreased by many operations, and stable display cannot be performed.

  As is apparent from the above, according to the present invention, the dimerized bipyridine compound represented by the general formula (1) is applied as the organic EC dye supported on the porous electrode constituting the electrode structure. Thus, it was possible to provide a magenta color electrochromic device that is extremely excellent in response and has a sharp color tone and can perform stable reversible color development.

1 shows a schematic cross-sectional view of an example of an electrochromic device of the present invention. The result of having measured the visible absorption spectrum of the apparatus of an Example is shown. The result of having measured the visible absorption spectrum change of the apparatus of an Example is shown. The result of having measured the visible absorption spectrum of the apparatus of the comparative example 1 is shown. The result of having measured the visible absorption spectrum change of the apparatus of the comparative example 1 is shown. The result of having measured the visible absorption spectrum of the apparatus of the comparative example 2 is shown. The result of having measured the visible absorption spectrum change of the apparatus of the comparative example 2 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,6 ... Support substrate, 2 ... Transparent electrode, 3 ... Organic EC pigment | dye, 4,8 ... Porous electrode, 5 ... Electrolyte layer, 10 ... Electrochromic device, 11 ... Display electrode structure , 12 ... Counter electrode structure

Claims (2)

A pair of electrode structures on which at least a transparent electrode is formed on a support substrate are disposed so as to sandwich an electrolyte layer so that the transparent electrodes face each other,
A porous electrode on which at least a bipyridine compound represented by the following general formula (1) is adsorbed is formed on at least one of the pair of transparent electrodes,
An electrochromic device, wherein a voltage is applied to the pair of electrode structures to reversibly magenta color.

However, in the general formula (1), a and b are integers satisfying a × b = 4, and X ^b− represents an appropriate b-valent anion.
Y _{1 to} Y ₄ and Z _{1 to} Z ₄ are hydrogen atoms, or aliphatic hydrocarbon groups, ether groups, acyl groups, halogen groups or cyano groups, ester groups, hydroxy groups, amino groups, amide groups, aromatics Represents a group hydrocarbon group, and at least one of Y _{1 to} Y ₄ and Z _{1 to} Z ₄ is an adsorbing group for adsorbing to the porous electrode. 2. The electrochromic device according to claim 1, wherein the porous electrode is made of a metal, a semiconductor material, or a conductive polymer having a mesoporous shape, a particle shape, a lot shape, or a wire shape.

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