JP2019095811A - Driving method of electrochromic device - Google Patents

Abstract

To provide a driving method that can suppress de-coloring residue without deteriorating an electrochromic device which has an oxidizing or reducing electrochromic material on surfaces of both electrodes.SOLUTION: A driving method of an electrochromic device comprising a first and a second electrode 11, 13, an electrolyte 15, and a first and a second electrochromic layer 21, 22 performs a step to alternately apply voltage V3, which has a reverse polarity to that of voltage V2 and has a smaller absolute value than the V2, and voltage V4, which has the same polarity as that of threshold voltage V1 and is lower than the voltage V1, the voltage applied between two electrodes being defined as the voltage V2 being the voltage more than or equal to threshold voltage V1 which is required for an electrochromic compound or an electrochromic composition in at least one of the first electrochromic layer 21 and the second electrochromic layer 22 to cause color change.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of driving an electrochromic device.

  The phenomenon in which the redox reaction occurs reversibly and the color changes reversibly by applying a voltage is called electrochromism. Electrochromism is generally formed between two opposing electrodes, and the redox reaction occurs in a configuration in which the ion-conductive electrolyte layer is filled between the electrodes. When a reduction reaction occurs in the vicinity of one of the two opposing electrodes, an oxidation reaction that is a reverse reaction occurs in the vicinity of the other electrode. The electrochromic element utilizes this electrochromism, and many studies have been made to date that applications derived from the characteristics of electrochromism can be realized.

  In order to obtain a transparent display device in such an electrochromic device, it is necessary to be made of a material having a colorless and transparent state. Examples of such materials include viologen compounds which are in a transparent state in the neutral state and exhibit an electrochromic phenomenon in which color is developed in the reduced state. In combination with the viologen compound, titanium oxide is preferably used. Among these, it is known that high optical density and high contrast ratio can be maintained by using titanium oxide particles as support particles of the electrochromic compound in the laminated structure.

In order to obtain a higher optical density and a high contrast ratio, it is also possible to make an electrochromic device having an oxidizing or reducing electrochromic material on the surfaces of both electrodes.
However, since the oxidation-reduction reaction rates at the two electrodes are different, charge imbalance occurs at the two electrodes as the color formation drive and the color elimination drive are performed, and as a result, a slight color is developed even when the color elimination drive is performed (color elimination The rest) is likely to occur.

On the other hand, various studies have been made on a driving method for causing an electrochromic device (electrochromic element) to react from a colored state to a decolored state.
Patent Documents 1 to 3 propose a method of intermittently and repeatedly applying a decoloring pulse that outputs a constant current for a fixed time.
However, when the electrochromic is colored or decolored at a high speed, if the driving method is to apply a constant current, the resistance of the electrochromic device changes, and the applied voltage also changes. When the changed voltage is increased, the electrochromic device is degraded. In addition, when the voltage is limited, it becomes difficult for the current to flow, so that there is a problem that the response of color development or decolorization of the electrochromic is significantly reduced.

In Patent Documents 4 to 6, driving methods are proposed in which coloring and decoloring are performed by applying a decoloring voltage of reverse polarity larger than the coloring voltage for a short time.
However, when a reverse decoloring voltage larger than the coloring voltage is applied, the decoloring residue is eliminated but the deterioration of the electrochromic device is accelerated.

In Patent Document 7, the potential is alternately changed between the potential of a value obtained by adding an appropriate value to the absolute value of the potential at which the redox reaction occurs during color development, and the potential of a value obtained by subtracting the appropriate value from the absolute value. A driving method has been proposed in which a natural waveform is applied and a natural potential is applied at the time of decoloring driving.
However, there is no effect on the decoloring residue which can not be erased by the natural potential, such as the decoloring residue due to the charge imbalance of the electrochromic device having the oxidizing or reducing electrochromic material on both electrode surfaces.

In patent document 8, a symmetrical high frequency voltage (sine wave, square wave, triangular wave) of kHz to MHz order is controlled at the peak value, frequency and number of pulses to display the electrochromic display body, and the current direction limiting element is There has been proposed a method of adjusting the gradation by applying the voltage to the electrochromic display via the above.
However, in addition to the fact that the frequency is too high in view of the response speed of general electrochromic devices, there is no specific description related to the control method of the current direction, and a very sensitive current even if possible. There is a big problem that the cost becomes very high because it needs to be detected.

In Patent Document 9, a plurality of pulses having a level in the color removal direction is applied as an initialization pulse in the initialization driving process before a predetermined color development state is generated, and at least one of the bottom levels of the plurality of pulses is applied. A driving method is proposed in which one is at 0 V or less.
However, as a driving method for the problem of decoloring residue due to charge imbalance of an electrochromic device having an oxidizing or reducing electrochromic material on both electrode surfaces, driving is performed at 0 V or less (voltage application with reverse polarity to coloring). Since it is essential to make it possible to eliminate the color degradation, it is required to have a driving method capable of eliminating the uncoloring residue without further deterioration.

  As described above, at present, no driving method is provided to eliminate the decoloring residue without deteriorating the electrochromic device having the oxidizing or reducing electrochromic material on the surfaces of both electrodes as described above.

  The present invention has been made in view of the above-mentioned various problems in the prior art, and it is possible to suppress the decoloring residue without deteriorating the electrochromic device having the oxidizing or reducing electrochromic material on both electrode surfaces. An object of the present invention is to provide a driving method of a chromic element.

  In order to solve the above problems, according to the present invention, there is provided a first electrode, a second electrode facing the first electrode at a distance, and an electrolyte provided between the two electrodes. A first electrochromic layer, comprising at least an oxidizing electrochromic compound or electrochromic composition, formed on the surface of one of the two electrodes, and at least a reducing electrochromic compound or electrochromic composition And driving the electrochromic device comprising the second electrochromic layer formed on the surface of the other of the two electrodes, the method of driving the electrochromic device comprising: applying between the two electrodes Voltage, and at least one of the first electrochromic layer and the second electrochromic layer. A voltage V3 having a threshold voltage V1 or more necessary for causing a color change of the electrochromic compound or the electrochromic composition on one side is V2, has a polarity opposite to V2 and has a smaller absolute value than V2, and A step of alternately applying a voltage V4 having the same polarity as V1 and lower than V1 is performed.

  According to the present invention, it is possible to provide a driving method of an electrochromic device capable of suppressing the decoloring residue without deteriorating the electrochromic device having an oxidizing or reducing electrochromic material on the surfaces of both electrodes.

It is the schematic which shows an example of an electrochromic element. It is the schematic which shows the other example of an electrochromic element. It is the schematic which shows the other example of an electrochromic element. FIG. 5 is a schematic view of a drive waveform in Example 1; FIG. 7 is a schematic view of drive waveforms in Example 2; FIG. 14 is a schematic view of a drive waveform in Example 3; FIG. 7 is a schematic view of a drive waveform in Comparative Example 1; FIG. 10 is a schematic view of a drive waveform in Comparative Example 2;

  Hereinafter, a method of driving an electrochromic device according to the present invention will be described with reference to the drawings. In addition, this invention is not limited to embodiment shown below, It can change in the range which those skilled in the art could concidentize, such as other embodiment, addition, correction, deletion, and any aspect Even within the scope of the present invention, as long as the functions and effects of the present invention can be achieved.

(Each configuration of the electrochromic device)
The electrochromic element driven by the driving method of the present invention is provided between the first electrode 11, the second electrode 13 facing the first electrode 11 with a gap, and the two electrodes. An electrolyte 15, a first electrochromic layer 21, and a second electrochromic layer 22.
The first electrochromic layer 21 contains at least an oxidizing electrochromic compound or an electrochromic composition, and is formed on the surface of one of the two electrodes. In addition, the second electrochromic layer 22 contains at least a reducing electrochromic compound or an electrochromic composition, and is formed on the surface of the other of the two electrodes. Moreover, it has other members as needed.

  FIG. 1 is a cross-sectional view schematically showing the configuration of the electrochromic device in the present embodiment. In FIG. 1, a first support 10, a first electrode 11 formed on the first support 10, and a first electrochromic layer 21 provided in contact with the first electrode 11; A second support 14 which is one support, a second electrode 13 formed on the second support 14, and a second electrochromic layer 22 provided in contact with the second electrode 13 An electrolyte 15 sandwiched between the first electrode 11 and the second electrode 13 is illustrated.

  Among these, at least one of the combinations of the first support 10 and the first electrode 11 and the combination of the second support 14 and the second electrode 13 is transparent. Here, by making both transparent, it is also possible to make a transmission type electrochromic device, and the driving method of the present invention is not limited to a support or an electrode.

  Each structure of the electrochromic element which can apply the drive method of the electrochromic element of this invention is demonstrated below.

<Support>
As the first support 10 and the second support 14, known organic materials and inorganic materials can be used as they are as long as they can support each layer. For example, in the case of a support requiring transparency, a glass support such as non-alkali glass, borosilicate glass, float glass, soda lime glass and the like can be used. Further, as the support, a resin support such as polycarbonate resin, acrylic resin, polyethylene, polyvinyl chloride, polyester, epoxy resin, melamine resin, phenol resin, polyurethane resin, polyimide resin may be used.

Further, the surface of the support may be coated with a transparent insulating layer, a UV cut layer, an antireflective layer, etc. in order to enhance water vapor barrier properties, gas barrier properties, ultraviolet resistance, and visibility. The shape of the support may be rectangular or round and is not particularly limited.
The support which does not require transparency is not particularly limited, and in addition to the material having transparency, general engineering plastics can also be used.

<Electrode layer>
The first electrode 11 and the second electrode 13 are not particularly limited and may be changed as appropriate, but at least one of the two electrodes is preferably a transparent electrode, Both the first electrode 11 and the second electrode 13 may be transparent electrodes. The material of the first electrode 11 and the second electrode 13 is not particularly limited as long as it is a conductive material, and can be appropriately selected according to the purpose. For example, as a material of an electrode which requires transparency, since it is necessary to ensure the transparency of light, a transparent conductive material which is transparent and excellent in conductivity is used. Thereby, the visibility of the color which an electrochromic layer colors can be improved more.

As the transparent conductive material, inorganic materials such as tin-doped indium oxide (hereinafter referred to as ITO), fluorine-doped tin oxide (hereinafter referred to as FTO), and antimony-doped tin oxide (hereinafter referred to as ATO) can be used. In particular, any one of indium oxide (hereinafter referred to as In oxide), tin oxide (hereinafter referred to as Sn oxide) or zinc oxide (hereinafter referred to as Zn oxide) formed by vacuum film formation. It is preferable that it is an inorganic material containing. In oxide, Sn oxide, and Zn oxide are materials which can be easily formed into a film by sputtering, and are materials which can obtain good transparency and electrical conductivity. Particularly preferable materials are InSnO, GaZnO, SnO, In ₂ O ₃ and ZnO.

When vacuum film formation is used, a film thickness of 20 nm to 500 nm is preferable for achieving both conductivity and transparency, and 50 nm to 200 nm is more preferable.
Also useful are transparent silver, gold, copper, carbon nanotubes, network electrodes such as metal oxides, or composite layers thereof. The network electrode is an electrode in which a carbon nanotube, another highly conductive non-permeable material or the like is formed in a fine network shape to have a transmittance. Furthermore, a laminated structure of the network layer and the conductive oxide is also preferable. By forming a laminated structure, the electrochromic layer can be uniformly colored and decolored.

  The material of the electrode not requiring transparency can include a metal material. For example, Pt, Ag, Cu, Au, Cr, rhodium or an alloy of these, or a laminated structure of these may be mentioned. As a manufacturing method, a vacuum evaporation method, a sputtering method, an ion plating method etc. are mentioned, for example.

<Electrochromic layer>
For the electrochromic layer, a material which causes a color change by an oxidation reaction or a reduction reaction is used. As such materials, known electrochromic compounds such as polymers, dyes, metal complexes and metal oxides are used.
Specifically, azobenzene type, anthraquinone type, diarylethene type, dihydroprene type, styryl type, styryl spiropyran type, spirooxazine type, spirothiopyran type, thioindigo type, tetrathiafulvalene type as polymer type and dye type electrochromic compounds Terephthalic acid, triphenylmethane, triphenylamine, naphthopyran, viologen, pyrazoline, phenazine, phenylenediamine, phenoxazine, phenothiazine, phthalocyanine, fluoran, fulgide, benzopyran, Low molecular weight organic electrochromic compounds such as metallocenes and the like, and conductive polymer compounds such as polyaniline and polythiophene are used.

  Among the above, particularly preferably, a dipyridine compound represented by the following general formula (1) is preferably contained. Since these materials have low color development / discoloration potentials, even when an electrochromic device having a plurality of display electrodes is configured, the reduction potential exhibits a good color value of coloring.

  In the formula, R 1 and R 2 each independently represent an alkyl group having 1 to 30 carbon atoms or an aryl group which may have a substituent. X represents a monovalent anion. n, m and l each independently represent 0 or 1. A, B and C each independently represent an aryl group or heterocyclic group having 2 to 20 carbon atoms which may have a substituent.

  In addition, as metal complex type and metal oxide type electrochromic compounds, for example, inorganic electrochromic compounds such as titanium oxide, vanadium oxide, tungsten oxide, indium oxide, iridium oxide, nickel oxide, Prussian blue, etc. may be used. it can.

  The preferred film thickness range of the electrochromic layer is 0.2 to 5.0 μm. When the film thickness is smaller than this range, it is difficult to obtain a color density. If the film thickness is larger than this range, the manufacturing cost increases and the visibility is likely to be reduced due to coloring.

  In the electrochromic device, which is an electrochemical device, when an oxidation reaction (charge giving reaction) occurs on one electrode, a reduction reaction (charge receiving reaction) occurs on the other electrode. Therefore, an oxidized electrochromic compound or an oxidized electrochromic composition, that is, an electrochromic layer containing a material that forms a color when it is changed from a steady state to an oxidized electrochromic compound, is formed on one electrode, and a reduced electrochromic layer is formed on the other electrode. The following advantages can be obtained by forming a compound or reduced type electrochromic composition, that is, an electrochromic layer containing a material that develops a color when it changes from a steady state to a reduced state.

(A) Since the electrochromic compound has a redox potential lower than that of other substances, the coloring voltage can be reduced.
(B) Since the electrochromic compound is more susceptible to transfer of charge than other substances, the amount of charge necessary for color development can be reduced.
(C) Since the irreversible load reaction hardly occurs on the electrode, the degradation of the electrochromic device can be reduced.
(D) The electrochromic compound is more stable in color development than other substances, so memory time can be extended.
(E) Since the electrochromic materials on both electrodes develop color, color with high density can be developed.

  With regard to the color development of the above (e), it is a color mixture of the color developed by the oxidized electrochromic compound and the color developed by the reduced electrochromic compound. For example, when it is desired to display a black color, it is useful to use a color mixture of a plurality of materials because there are not many electrochromic materials that alone generate black color. If the color developed by the oxidized electrochromic compound and the color developed by the reduced electrochromic compound are complementary due to the complementary color relationship, the light control device can be switched between transparency and dark black at high contrast.

Examples of the oxidized electrochromic compounds include styryls, triphenylamines, phenothiazines, iridium oxide, Prussian blue and the like.
Examples of the reduction type electrochromic compound include dipyridyl type, anthraquinone type, terephthalic acid type, tungsten oxide, titanium oxide and the like.

<Electrolyte>
As the electrolyte 15, an electrolytic solution in which a support salt is dissolved in a solvent is generally used. For this reason, it is preferable that the ion conductivity is high.
As the supporting salt, for example, inorganic ion salts such as alkali metal salts and alkaline earth metal salts, quaternary ammonium salts, acids, and supporting salts of alkalis can be used. Specifically, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₃ , LiCF ₃ COO, KCl, NaClO ₃ , NaCl, NaBF ₄ , NaSCN, KBF ₄ , Mg (ClO ₄ ) ₂ , Mg ( BF ₄ ) ₂ , tetrabutylammonium perchlorate, or the like can be used.

  Moreover, as a solvent, for example, propylene carbonate, acetonitrile, γ-butyrolactone, ethylene carbonate, sulfolane, dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, polyethylene Glycols, alcohols and the like are used.

  In addition, as the electrolyte, an ionic liquid which is a non-volatile material can also be used. The ionic liquid is not particularly limited, and any substance which is generally studied and reported may be used. The ionic liquid has a molecular structure that exhibits a liquid over a wide temperature range including room temperature.

  The molecular structure of the ionic liquid is composed of a cationic component and an anionic component, and as the cationic component, for example, N, N-dimethylimidazole salt, N, N-methylethylimidazole salt, N, N-methylpropylimidazole salt, etc. Imidazole derivatives; aromatic salts such as pyridinium derivatives such as N, N-dimethyl pyridinium salt, N, N-methyl propyl pyridinium salt; and tetraalkyl ammonium such as trimethylpropyl ammonium salt, trimethylhexyl ammonium salt, triethylhexyl ammonium salt and the like And aliphatic quaternary ammonium compounds, and the like.

Further, as the anion component, a compound containing fluorine in terms of stability in the air is preferable. For example, BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , PF ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , B (CN) _4- ^{and the} like. An ionic liquid formulated by a combination of these cationic and anionic components can be used.

Moreover, what hardened ionic substances, such as electrolyte solution and an ionic liquid, with resin etc. can be used as electrolyte. This electrolyte is highly safe because it can prevent liquid leakage from the device.
Examples of the cured resin include common materials such as photocurable resins such as acrylic resin, urethane resin, epoxy resin, vinyl chloride resin, ethylene resin, melamine resin, phenol resin, and thermosetting resin. However, materials having high compatibility with the electrolyte are preferred. As such a structure, polyethylene glycol, derivatives of ethylene glycol such as polypropylene glycol and the like are preferable.

Moreover, as said hardening resin, it is preferable to use photocurable resin. This is because the element can be manufactured at a low temperature and in a short time as compared with the method of thinning by evaporating the solvent by thermal polymerization.
A particularly preferred combination is an electrolyte layer composed of a solid solution of a matrix polymer containing an oxyethylene chain or an oxypropylene chain and an ionic liquid. By using this configuration, it is easy to achieve both hardness and high ion conductivity.

<Reflective layer>
The electrochromic device becomes a reflective display device by incorporating a reflective layer. These are also called electronic papers. Unlike conventional display devices such as CRTs, liquid crystal displays, and organic ELs, since there is no light emitting source, it is possible to perform very energy-saving display. The electrochromic device is excellent in transparency, contrast ratio and colorization and is a promising reflective display element.

  The reflective layer 26 is not particularly limited as long as it is a material that reflects light and has a configuration, but when a white reflective layer that scatters and reflects light is used in particular, a white color close to paper can be used as a background, and display with good visibility is possible . As the material of the white reflective layer, in addition to metals and semimetals, inorganic compound films capable of vacuum film formation such as oxides, nitrides and sulfides or titanium oxide, aluminum oxide, zinc oxide, silicon oxide, cesium oxide, The white pigment particle film which consists of metal oxide particles, such as a yttrium oxide, is mentioned. The metal oxide particle film can be easily formed by coating as a paste dispersed in a solution. Particularly preferred materials are titanium oxide particles.

  The thickness of the white reflective layer is preferably 0.1 to 50 μm, and more preferably 0.5 to 20 μm. If the film thickness is smaller than this range, it is difficult to obtain the white reflection effect. If the film thickness is larger than this range, it becomes difficult to maintain the film strength.

<Other components>
There is no restriction | limiting in particular as another member, According to the objective, it can select suitably, For example, an insulating porous layer, a deterioration prevention layer, a protective layer, etc. are mentioned.

-Insulating porous layer-
The insulating porous layer has a function to isolate the two electrodes so as to be electrically insulated from each other, and to retain an electrolyte. The material of the insulating porous layer is not particularly limited as long as it is porous, and it is preferable to use an organic material, an inorganic material, and a composite thereof, which are high in insulating property and durability and excellent in film forming property. .

  As a method of forming the insulating porous layer, for example, a sintering method (polymer fine particles or inorganic particles are partially fused by adding a binder or the like to utilize pores generated between the particles), extraction Method (After forming a component layer with organic substance or inorganic substance soluble in solvent and binder not dissolved in solvent, dissolve organic substance or inorganic substance with solvent to obtain pores), foaming method for foaming, good solvent and poor A phase conversion method in which a mixture of polymers is separated by manipulating a solvent, and a radiation irradiation method in which various kinds of radiation are radiated to form pores are mentioned.

-Deterioration prevention layer-
The role of the anti-deterioration layer is to reverse the chemical reaction with the electrochromic layer, to balance the charge, and to prevent corrosion and deterioration of the two electrodes due to irreversible redox reaction. The reverse reaction also includes acting as a capacitor in addition to the case where the deterioration preventing layer is oxidized and reduced.

  The material of the deterioration preventing layer is not particularly limited as long as it plays a role of preventing corrosion due to irreversible oxidation-reduction reaction of the two electrodes, and can be appropriately selected according to the purpose. For example, antimony tin oxide, nickel oxide, titanium oxide, zinc oxide, tin oxide, or a conductive or semiconductive metal oxide containing a plurality of them can be used.

  The anti-deterioration layer can be composed of a porous thin film that does not inhibit the injection of the electrolyte. For example, conductive or semiconductive metal oxide fine particles such as antimony tin oxide, nickel oxide, titanium oxide, zinc oxide, tin oxide, etc., for example, acrylic type, alkyd type, isocyanate type, urethane type, epoxy type, phenol type etc. By immobilizing the second electrode with the binder, it is possible to obtain a suitable porous thin film which satisfies the electrolyte permeability and the function as the deterioration preventing layer.

-Protective layer-
The role of the protective layer is to protect the element from external stress and chemicals in the cleaning process, to prevent electrolyte leakage, and to prevent the electrochromic element from operating stably such as moisture and oxygen in the air. Such as preventing intrusion.
There is no restriction | limiting in particular as thickness of the said protective layer, Although it can select suitably according to the objective, 1 micrometer or more and 200 micrometers or less are preferable.
As a material of the said protective layer, resin of an ultraviolet curing type and a thermosetting type can be used, for example, An acryl type, a urethane type, an epoxy resin etc. are mentioned specifically ,.

(Other Embodiments in Electrochromic Device)
Next, other embodiments of the electrochromic device driven by the driving method of the present invention will be described.
As described above, an example of the electrochromic device is shown in FIG. In FIG. 1, a first support 10, a first electrode 11 formed on the first support 10, and a first electrochromic layer 21 provided in contact with the first electrode 11; A second support 14 which is one support, a second electrode 13 formed on the second support 14, and a second electrochromic layer 22 provided in contact with the second electrode 13 An electrolyte 15 sandwiched between the first electrode 11 and the second electrode 13 is illustrated.

  Note that at least one of the combinations of the first support 10 and the first electrode 11 and the combination of the second support 14 and the second electrode 13 is transparent. Here, it is also possible to make a transmission type electrochromic device by making both of them transparent, and the driving method of the present invention is not limited to the support or the electrode.

  Next, another embodiment of the electrochromic device to which the driving method of the electrochromic device of the present invention can be applied will be described. In the present embodiment, the electrochromic composition is characterized by including at least an organic electrochromic compound having an adsorption structure and conductive or semiconductive fine particles.

FIG. 2 is a cross-sectional view schematically showing the configuration of the electrochromic device according to the present embodiment. In FIG. 2, a first support 10, a first electrode 11 formed on the first support 10, and an electrochromic layer (reference numeral 24) provided in contact with the first electrode 11; A second support 14 which is one support, a second electrode 13 formed on the second support 14, and a second electrochromic layer 22 provided in contact with the second electrode 13 The electrolyte 15 sandwiched between the first electrode 11 and the second electrode 13 is illustrated.
In the example shown in FIG. 2, the first electrochromic layer is illustrated as the electrochromic layer 24, and can be configured as an electrochromic composition composed of conductive or semiconductive fine particles.

  In the present embodiment, the electrochromic layer includes an electrochromic composition comprising an organic electrochromic compound having an adsorption structure and conductive or semiconductive fine particles. Specifically, a composition structure in which the organic electrochromic compound is adsorbed on the surface of fine particles having a particle diameter of about 5 nm to 50 nm is preferable. The composition develops color by the transfer of charge from the electrode through the fine particles to the organic electrochromic compound (reverse migration decoloring). Therefore, color development and decoloring reaction can be performed efficiently, and power consumption can be reduced.

As an adsorption structure given to an organic electrochromic compound, it is preferred to have a functional group which can be bound to a hydroxyl group directly or indirectly, and the structure is not limited. Preferred examples include phosphonic acid group, phosphoric acid group, carboxyl group, trichlorosilyl group, trialkoxysilyl group, monochlorosilyl group, monoalkoxysilyl group and the like.
The trialkoxysilyl group is preferably a triethoxysilyl group, a trimethoxysilyl group or the like. Among them, a trialkoxysilyl group and a phosphonic acid group, which have high bonding power to the conductive or semiconductive particles, are particularly preferable.

  As the conductive or semiconductive particles, metal oxide particles are preferable in terms of transparency and conductivity. Examples of such metal oxide particles include titanium oxide, zinc oxide, tin oxide, aluminum oxide (approximately alumina), zirconium oxide, cerium oxide, silicon oxide (approximately silica), yttrium oxide, boron oxide, oxide Magnesium, strontium titanate, potassium titanate, barium titanate, calcium titanate, calcium oxide, ferrite, hafnium oxide, tungsten oxide, iron oxide, copper oxide, copper oxide, nickel oxide, cobalt oxide, barium oxide, strontium oxide, vanadium oxide, A metal oxide mainly composed of aluminosilicate, calcium phosphate, aluminosilicate or the like is used.

  Also, these metal oxides may be used alone, or two or more may be mixed and used. It is selected from titanium oxide, zinc oxide, tin oxide, tin oxide, alumina, zirconium oxide, iron oxide, magnesium oxide, indium oxide, tungsten oxide, in view of electrical properties such as electrical conductivity and physical properties such as optical properties. When one or a mixture thereof is used, it is excellent in the response speed of coloration / discoloration.

The particle size of the conductive or semiconductive fine particles is preferably 30 nm or less in average primary particle size. The smaller the particle size, the better the light transmittance to the metal oxide, and the shape with a large surface area per unit volume (hereinafter referred to as "specific surface area") is used. By having a large specific surface area, the electrochromic compound is more efficiently supported, and the color contrast is excellent. The specific surface area of the conductive or semiconductive fine particles is not particularly limited, but can be, for example, 100 m ² / g or more.

  Next, another embodiment of the electrochromic device to which the driving method of the electrochromic device of the present invention can be applied will be described. In the present embodiment, the reflective layer 26 is provided on one of the first electrode side and the second electrode side in a region opposite to the region sandwiched by the first electrode 11 and the second electrode 13. It is characterized by

  FIG. 3 is a cross-sectional view schematically showing the configuration of the electrochromic device according to the present embodiment. In FIG. 3, a first support 10, a first electrode 11 formed on the first support 10, a first electrochromic layer 21 provided in contact with the first electrode 11, and the other A second support 14 which is one support, a second electrode 13 formed on the second support 14, and a second electrochromic layer 22 provided in contact with the second electrode 13 The electrolyte 15 sandwiched between the first electrode 11 and the second electrode 13 is illustrated.

In the configuration of FIG. 3, the reflective layer 26 is provided on the lower surface of the second support 14. The first support 10, the first electrode 11, the second support 14, and the second electrode 13 are all transparent.
As described above, the electrochromic element becomes a reflective display element by incorporating a reflective layer, can provide energy saving display, and is excellent in transparency, contrast ratio, and colorization correspondence, so it is a promising reflective display element. is there.

  The reflective layer 26 is not particularly limited as long as it is a material that reflects light and has a configuration, but it is preferable to use a white reflective layer that scatters and reflects light. The white reflective layer can be as described above.

(Embodiment of driving method)
The driving method according to the present embodiment is a voltage applied between the two electrodes, and the electrochromic compound or the electrochromic composition in at least one of the first electrochromic layer and the second electrochromic layer has a color. A voltage V3 having a threshold voltage V1 or more necessary to cause a change is V2, has a polarity opposite to V2 and has a smaller absolute value than V2, and has the same polarity as V1 and is lower than V1. A step of alternately applying a voltage V4 is performed.

  In the driving method of the present embodiment, other steps may be performed as necessary. Here, an example in the case where the following steps (1) to (5) are performed will be described. The example shown below is an example at the time of performing from (1) process to (5) process in this order.

(1) A step of measuring a voltage V0 between the two electrodes (2) An electrochromic compound or electrochromic in at least one of the first electrochromic layer and the second electrochromic layer between the two electrodes The step of applying a voltage V2 higher than the threshold voltage V1 necessary for the composition to cause a color change (3) the step of applying the V0 between the two electrodes (4) opposite in polarity to the V2 and the polarity A step of alternately applying a voltage V3 having an absolute value smaller than V2 and a voltage V4 having the same polarity as V1 and having a voltage lower than V1 (5) (4) The number of applied V3 and V4 in the step is predetermined Applying the V0 after reaching the number of times

  An example of the drive waveform in the drive method which concerns on FIG. 4 at this embodiment is shown. In the present embodiment, the electrochromic element performs coloring drive and decoloring drive by applying a voltage waveform between both electrodes using a potentiostat.

In the step (1), the voltage before driving for coloring is stored by measuring the voltage V0 between the two electrodes in the electrochromic element.
(2) In the step, a threshold necessary for causing a color change of the electrochromic compound or the electrochromic composition in at least one of the first electrochromic layer 21 and the second electrochromic layer 22 between two electrodes. A voltage V2 higher than the voltage V1 is applied. By applying a voltage V2, the electrochromic device is brought into a colored state.
In the step (3), V0 is applied between the two electrodes. By applying the voltage V0, the electrochromic element can be brought into a transparent state. Here, if charge imbalance occurs, it can not be brought into the same transparent state as before color development, and a decoloring residue occurs.
(4) In the step, a voltage V3 which is reverse to the V2 and has an absolute value smaller than the V2 and a voltage V4 which is the same as the V1 and lower than the V1 are alternately applied.

  In the example shown in FIG. 4, it is illustrated that V3 and V4 are alternately and repeatedly applied N times in the step (4). (4) By applying V3 and V4 alternately a fixed number of times as in the step, it is possible not only to erase the decoloring residue that could not be erased with the voltage V0, but to continue applying the reverse polarity V3 to color development It is also possible to suppress the deterioration of the electrochromic device caused by the above. Furthermore, since the polarity of the applied voltage is changed, precipitates such as ion migration on the electrode surface when using a metal electrode can be prevented.

  When the absolute value of V3 is larger than V2 or V4 is larger than V1, it is not possible to suppress the deterioration or the decoloring residue of the electrochromic device. The threshold voltage V1 necessary for causing the color change of the electrochromic compound or the electrochromic composition varies depending on the structure of the electrochromic compound, the configuration of the electrochromic composition, or the configuration of the electrochromic element, It will be changed as appropriate. The threshold voltage V1 may cause a color change in at least one of the first electrochromic layer 21 and the second electrochromic layer 22, and both may cause a color change.

  The pattern of the applied voltage is not particularly limited and can be changed. For example, it is possible to use a square wave, a triangular wave with a constant voltage drawing speed (Vs), or a sine wave centered on a voltage between V3 and V4. An example of a square wave is shown in FIG. 4 described above, an example of a triangular wave is shown in FIG. 5, and an example of a sine wave is shown in FIG.

  With regard to the number of times of application (repetition period number N), it is preferable that the drive circuit is provided with a table regarding the repetition period number optimized in advance according to the coloring state of the electrochromic element, because the decoloring time can be prevented from extending . Since the number of times of application is changed depending on the electrochromic element, it is difficult to describe a preferable range, but for example, 5 to 100 cycles are preferable, and 5 to 50 cycles are more suitably applied. In the case of such a range, the effect of suppressing the deterioration of the element and the residual color remaining can be obtained.

  (5) In the step (4), V0 is applied after the number of applications of V3 and V4 in the step reaches a predetermined number of times. By applying the voltage V0, it is possible to eliminate the slight charge imbalance generated in the step (4).

  Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to the following examples.

Example 1
In the present example, the electrochromic device having the configuration shown in FIG. 2 was produced as follows, and the evaluation described below was performed.

<Production of First Electrode and Electrochromic Layer>
An ITO film of about 100 nm was formed on a 40 mm × 40 mm glass substrate by a sputtering method in a region of 30 mm × 30 mm and a lead-out portion to fabricate a first electrode 11. The resistance in the plane of the first electrode 11 was about 20 Ω. A titanium oxide nanoparticle dispersion (SP210, manufactured by Showa Titanium Co., Ltd.) was spin-coated thereon, and a titanium oxide particle film was formed by annealing at 120 ° C. for 15 minutes. Furthermore, the electrochromic compound 4,4 '-(1-phenyl-1H-pyrrole-2,5-diyl) bis (1- (4- (phosphonomethyl) benzyl) pyridinium) bromide which is an electrochromic compound that develops a reddish purple color thereon 5 wt% 2.2.3.3. A tetrafluoropropanol solution was spin-coated and annealed at 120 ° C. for 15 minutes to form an electrochromic layer 24 (first electrochromic layer) composed of titanium oxide particles and an electrochromic compound.

<Production of Second Electrode and Second Electrochromic Layer>
An ITO film of about 100 nm was formed on a 40 mm × 40 mm glass substrate by a sputtering method in a region of 30 mm × 30 mm and a lead-out portion to produce a second electrode 13. The resistance in the plane of the second electrode 13 was about 20 Ω. In addition, poly (ethylene glycol) diacrylate, a photopolymerization initiator (IRG184, manufactured by BASF), a compound represented by the following structural formula (A) and 2-butanone in a mass ratio (20: 1: 20: 400) Solution was applied and UV cured under a nitrogen atmosphere to form a second electrochromic layer 22.

<Fabrication of electrochromic device>
As the electrolyte 15, 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide which is an ionic liquid was used. 0.2 wt% of a bead spacer having a particle diameter of 10 μm is put in the electrolyte, and an appropriate amount is dropped on the glass substrate on which the first electrode 11 and the electrochromic layer 24 (first electrochromic layer) are formed. A glass substrate on which the electrode 13 and the second electrochromic layer 22 were formed was bonded to produce an electrochromic device.

<Evaluation>
-Disappearing remaining evaluation-
The electrochromic device having the configuration shown in FIG. 2 was connected to a potentiostat (ModuLab, manufactured by Toyo Technica Co., Ltd.), and voltage waveforms shown in FIG. 4 were applied according to Table 1. The transmittance was measured by USB4000 manufactured by Ocean Optics, Inc., and the average value [%] of the transmittance at a wavelength of 400 nm to 800 nm was calculated. The difference between the transmittance [%] in the initial state and the transmittance [%] after decoloring driving was defined as “remaining in disappearance” [%]. The evaluation criteria that do not disappear are described below.
:: Disappearing residue less than 1% ○: Disappearing residue 1% or more and less than 5% x: Disappearing residue 5% or more

-Durability evaluation-
The process of connecting the electrochromic device having the configuration shown in FIG. 2 to a potentiostat (ModuLab, manufactured by Toyo Technica Co., Ltd.) and applying the voltage waveform shown in FIG. 4 according to Table 1 was repeated 1000 times. The ratio of the first charge to the 1000th charge (the first charge input / the first charge amount) of the charge amount applied to the electrochromic element at the time of coloring was calculated and defined as the charge retention amount. The durability evaluation criteria are described below.
:: Input charge amount retention rate is 95% or more ○: Input charge amount retention rate is 90% or more and less than 95% ×: Input charge amount retention rate is less than 90%

  The obtained evaluation results are shown in Table 1. From the results in Table 1, it can be confirmed that the application of the voltage pattern of FIG. 4 eliminates the uncoloring residue without deteriorating the durability of the electrochromic element.

(Example 2)
The same as Example 1 except that the voltage application pattern shown in FIG. 5 was applied according to Table 2.
The evaluation results obtained are shown in Table 2. From the results in Table 2, it can be confirmed that the application of the voltage pattern shown in FIG. 5 eliminates the uncolored residual without deteriorating the durability of the electrochromic device.

(Example 3)
The same as Example 1 except that the voltage application pattern shown in FIG. 6 was applied according to Table 3.
The obtained evaluation results are shown in Table 3. From the results in Table 3, it can be confirmed that the application of the voltage pattern shown in FIG. 6 eliminates the uncoloring residue without deteriorating the durability of the electrochromic device.

(Example 4)
The electrochromic device having the configuration shown in FIG. 3 was produced as follows, and evaluated in the same manner as in Example 1.
A solution was prepared by mixing polyurethane, white titanium oxide particles (CR50, manufactured by Ishihara Sangyo Co., Ltd.) with an average particle diameter of 250 nm, and a 2.2.3.3 tetrafluoropropanol solution in a ratio of 2:20:78. This solution was spin-coated on the surface of the first electrochromic layer 21 in Example 1 to a film thickness of 20 μm to form a white reflective layer (reflective layer 26). An electrochromic display element was manufactured in the same manner as in Example 1 except for the above.
The voltage application pattern shown in FIG. 4 was applied according to Table 4, and evaluation was conducted in the same manner as in Example 1 except that the disappearance was evaluated below.

-Disappearing remaining evaluation-
The electrochromic device having the configuration shown in FIG. 3 is connected to a potentiostat (manufactured by Toyo Technica Co., Ltd., ModuLab), and the voltage waveform shown in FIG. Were measured, and the average value [%] of reflectance at wavelengths of 400 nm to 800 nm was calculated. The difference between the reflectance [%] in the initial state and the reflectance [%] after decoloring driving is defined as “remaining in disappearance” [%]. The evaluation criteria that do not disappear are described below.
:: Disappearing residue less than 1% ○: Disappearing residue 1% or more and less than 5% x: Disappearing residue 5% or more

  The obtained evaluation results are shown in Table 4. From the results of Table 4, when driven in the same manner as in Example 1, similar effects were obtained.

(Comparative example 1)
The same as Example 1 except that the voltage application pattern shown in FIG. 7 was applied according to Table 5.
The obtained evaluation results are shown in Table 5. From the results in Table 5, it can be confirmed that, with the application of only V0, even if the decoloring time (T3-T2) is extended, the decoloring residue does not disappear.

(Comparative example 2)
Example 8 is the same as Example 1 except that the voltage application pattern shown in FIG. 8 is applied according to Table 6.
The obtained evaluation results are shown in Table 6. From the results in Table 6, it can be confirmed that the durability is lowered when driving is continued by applying V3 in the reverse polarity to the color development.

(Comparative example 3)
Example 4 is the same as Example 1 except that the voltage application pattern shown in FIG. 4 is applied according to Table 7.
The obtained evaluation results are shown in Table 7. From the results in Table 7, it can be seen that the durability decreases when the absolute value of V3 is larger than the absolute value of V2, that the remaining color does not disappear if V4 is higher than V1, and even if there is too little N It can be confirmed that the color remains.

(Comparative example 4)
Example 8 is the same as Example 1 except that the voltage application pattern shown in FIG. 5 is applied according to Table 8.
The obtained evaluation results are shown in Table 8. From the results in Table 8, it can be seen that the durability decreases if the absolute value of V3 is larger than the absolute value of V2, that if V4 is higher than V1 the remaining color disappears even if there is too little N It can be confirmed that the color remains.

(Comparative example 5)
Example 6 is the same as Example 1 except that the voltage application pattern shown in FIG. 6 is applied according to Table 9.
The obtained evaluation results are shown in Table 9. From the results in Table 9, it can be seen that the durability decreases if the absolute value of V3 is larger than the absolute value of V2, that the remaining color does not disappear if V4 is higher than V1, even if there is too little N It can be confirmed that the color remains.

10 first support 11 first electrode 12 electrochromic layer 13 second electrode 14 second support 15 electrolyte 21 first electrochromic layer 22 second electrochromic layer 24 conductive or semiconductive fine particles Organic Electrochromic Compound 26 Reflective Layer

Japanese Patent Application Laid-Open No. 61-261788 Japanese Patent Application Laid-Open No. 61-261789 JP-A-61-261790 Patent No. 462 2941 Patent No. 4622942 Patent No. 462293 gazette Japanese Patent Publication No. 05-023409 JP, 2008-039873, A JP, 2013-140326, A

Claims (4)

A first electrode, a second electrode opposed to the first electrode at a distance, an electrolyte provided between the two electrodes, and at least an oxidative electrochromic compound or electrochromic composition A first electrochromic layer formed on the surface of one of the two electrodes, and at least a reducing electrochromic compound or an electrochromic composition, and the other of the two electrodes And a second electrochromic layer formed on the substrate.
A voltage applied between the two electrodes, and a threshold voltage required for causing a color change in the electrochromic compound or the electrochromic composition in at least one of the first electrochromic layer and the second electrochromic layer A step of alternately applying a voltage V3 having a voltage of V1 or more as V2, a voltage V3 reverse to the voltage V2 and having an absolute value smaller than the voltage V2, and a voltage V4 having the same polarity as the voltage V1 and lower than the voltage V1 And driving the electrochromic device.   The method for driving an electrochromic device according to claim 1, wherein the application pattern of the voltages V3 and V4 is a square wave, a triangular wave or a sine wave.   The method for driving an electrochromic device according to claim 1 or 2, wherein the electrochromic composition includes an organic electrochromic compound having an adsorption structure, and conductive or semiconductive fine particles.   A reflective layer is provided on one of the first electrode side and the second electrode side in a region opposite to a region sandwiched by the first electrode and the second electrode. The driving method of the electrochromic element in any one of claim | item 1 -3.