Oxidation-coloring-type electrochromic material, coating material, color-changeable electrode, and electrochromic element

Abstract

The present invention addresses the problem of providing, in an electrochromic element that exhibits a reversible color change between a black color and a transparent color, an oxidation-coloring-type electrochromic material, a coating material, and a color-changeable electrode which constitute the electrochromic element. The electrochromic element uses, as the oxidation-coloring-type electrochromic material, a material containing one or more nanoparticles selected from NiO, Ni2O3 and NiOOH which undergo reversible color change between a brown color and a transparent color by an electrochemical oxidation-reduction reaction, thereby exhibiting a brown color tone in an oxidized state.

Description

Oxidation-colored electrochromic materials, paints, color-variable electrodes, and electrochromic elements

[0001] The present invention relates to oxidation-colored electrochromic materials, paints, color-variable electrodes, and electrochromic elements.

[0002] An electrochromic element (ECD) is a color-variable element that uses electrochromic materials (EC materials) whose color changes through electrochemical oxidation-reduction. ECDs are used in various applications, such as controlling reflectivity by changing color in automotive mirrors, and improving air conditioning efficiency by controlling the transmittance of sunlight and infrared radiation in car and building windows. Furthermore, applications for ECDs in displays and sunglasses are also being explored.

[0003] In recent years, ECDs have been actively explored for applications such as dimmable glass in building materials and vehicles. Color is extremely important in applications of ECDs, including dimmable glass. In particular, achieving colors such as black, gray, and brown through ECDs is desired. However, most commercially available ECDs currently exhibit a color change between blue and transparent. Materials used in these ECDs include oxides such as tungsten oxide (Patent Document 1), small molecules such as viologen (Patent Document 2), polymers such as PEDOT-PSS (Patent Document 3), and coordination polymers such as metal cyano complexes (Patent Document 4). Using these materials, currently available commercially exhibits a blue-to-transparent color change.

[0004] Furthermore, in recent years, development has progressed primarily on organic polymers as electrochromic materials that can achieve brown and black colors (Patent Document 5, Non-Patent Documents 1-5). However, organic polymer materials generally have issues with light resistance and are not suitable for dimmable glass applications.

[0005] From the standpoint of light resistance and other factors, inorganic materials are considered to have a certain advantage. Among inorganic materials, metal oxides and metal cyano complexes have already been commercialized (Patent Document 6). In the case of dimmable glass applications, it is required that the glass not only retains its color when colored, but also becomes colorless and transparent when decolorized. Furthermore, in order to avoid scattering, it is necessary to form a smooth thin film on a transparent electrode.

[0006] In this context, the present inventors have developed a black-to-transparent electrochromic material using inorganic materials (titanium oxide nanoparticles, titanium nitride nanoparticles, nickel oxide nanoparticles, nickel hydroxide nanoparticles, zirconium oxide nanoparticles, and metallic iridium nanoparticles) (Patent Document 7).

[0007] Japanese Patent Publication No. 08-254717, Japanese Patent Publication No. 2009-215166, Japanese Patent Publication No. 2005-519316, Japanese Patent Publication No. 2011-180469, Japanese Patent Publication No. 2010-33016, Japanese Patent Publication No. 2016-74569, WO2024 / 122611

[0008] Color tuning for black-to-transmissive conjugated copolymer with excellent electrochromic properties via electrochemical copolymerization of two donor-acceptor type monomers, https: / / doi.org / 10.1016 / j.matdes.2020.108903Colorless to black electrochromic devices using subtractive color mixing of two electrochromes: A conjugated polymer with a small organic molecule, https: / / doi.org / 10.1016 / j.orgel.2020.105748Colorless-to-Black Electrochromism from Binary Electrochromes toward Multifunctional Displays, https: / / dx.doi.org / 10.1021 / acsami.0c11840Highly transparent to truly black electrochromic devices based on an ambipolar system of polyamides and viologen, doi:10.1038 / am.2017.57Colorless-to-black electrochromic devices based on ambipolar electrochromic system consisting of cross-linked poly(4-vinyltriphenylamine) and tungsten trioxide with high optical contrast in visible and near-infrared regions, https: / / doi.org / 10.1016 / j.cej.2020.126402

[0009] The EC materials described in Patent Document 7 were all discovered by electrochemically evaluating only single films, and were not evaluated as electrochromic elements. Furthermore, the EC materials shown in Figure 20 of Patent Document 7 all exhibit a reductive coloring reaction. Therefore, when the present inventors fabricated an electrochromic element using a combination of the EC material from Patent Document 7 and Prussian blue (PB), a type of metal cyano complex that is an oxidative coloring material, they found that the response speed was slow and the color change was gradual, resulting in the inability to achieve a suitable black color.

[0010] The present invention has been made in view of the above circumstances, and aims to provide an electrochromic element that exhibits a reversible color change between black and transparent, and an oxidation-colored electrochromic material, paint, and color-variable electrode that constitute the same.

[0011] To solve the above problems, the following oxidation-colored electrochromic materials, paints, color-variable electrodes and electrochromic elements are provided. [1] An oxidation-colored electrochromic material that reversibly changes color between brown and transparent by an electrochemical oxidation-reduction reaction, comprising NiO, Ni ２ O ３[1] An oxidation-coloring electrochromic material comprising one or more nanoparticles selected from NiOOH, exhibiting a brownish hue in an oxidized state. [2] A paint in which the oxidation-coloring electrochromic material of [1] is dispersed in a solvent. [3] The paint of [2], wherein the solvent is an aqueous solvent containing an organic compound. [4] The paint of [2] or [3], wherein the content of the nanoparticles is 0.5% by mass or more and 20% by mass or less. [5] Any paint of [2] to [4], comprising one or more selected from polyvinyl alcohol (PVA), sodium carboxymethylcellulose (CMC), hydroxypropylcellulose (HPC), hydroxyethylcellulose (HEC), polyethylene glycol, polypropylene glycol, trifluoromethanesulfonylimide, methyl methacrylate, polydimethylsiloxane, pectin, xanthan gum, alginic acid, and sodium alginate as a binder. [6] A method for producing the paint of [2], comprising: NiO, Ni in a solvent. ２ O ３[7] A method for manufacturing a paint, comprising a grinding and stirring step of grinding and stirring one or more nanoparticles selected from NiOOH to obtain a dispersion. [8] A color-variable electrode comprising an electrode layer and a first electrochromic layer formed on the electrode layer, wherein the first electrochromic layer is a thin film formed by the paint of claim 2. [9] A black electrochromic element that reversibly changes color between black and transparent by an electrochemical oxidation-reduction reaction, comprising a first electrochromic layer containing a first electrochromic material that exhibits a brownish hue in an oxidized state and a second electrochromic layer containing a second electrochromic material that exhibits a bluish hue in a reduced state.

[10] The black electrochromic element of [9], wherein the first electrochromic material is the oxidation-colored electrochromic material of claim 1.

[11] The black electrochromic element according to [9] or

[10] , wherein the second electrochromic material comprises nanoparticles of tungsten oxide or titanium oxide.

[12] The black electrochromic element according to any one of [9] to

[11] , wherein the first electrochromic layer is a thin film formed by the coating according to [2].

[13] The electrochromic element according to any one of [9] to

[12] , wherein in a transparent state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, and the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more, and in a black state, the visible light transmittance is 10% or less, the solar transmittance is 10% or less, and the colorimetric value L* based on the CIE 1976 Lab* color system is 35 or less.

[14] An electrochromic element that reversibly changes color between a transparent state and a colored state by an electrochemical oxidation-reduction reaction, comprising: a first electrochromic layer containing a first electrochromic material that exhibits a brownish hue in the oxidized state; and a second electrochromic layer containing a second electrochromic material that exhibits a blueish hue in the reduced state, wherein in the colored state, the colorimetric value L* ≤ 35, |a*| ≤ 10, and |b*| ≤ 15 based on the CIE 1976 Lab* color system.

[15] The electrochromic element according to

[14] , wherein in the transparent state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more, and in the colored state, the visible light transmittance is 10% or less, and the solar transmittance is 10% or less.

[16] An electrochromic element that reversibly changes color between a transparent state and a colored state by an electrochemical oxidation-reduction reaction, wherein in the transparent state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, and the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more, and in the colored state, the visible light transmittance is 10% or less, the solar transmittance is 10% or less, and the colorimetric value based on the CIE 1976 Lab* color system is L* ≤ 35, and |a*| ≤ 10, and |b*| ≤ 15.

[17] The electrochromic element according to

[14] or

[16] , wherein in the colored state, the colorimetric value L* ≤ 25.

[18] An electrochromic element that reversibly changes color between a minimum colored state and a maximum colored state by an electrochemical oxidation-reduction reaction, which can be set to at least one intermediate tone located between the minimum colored state and the maximum colored state by applying a predetermined potential, and which maintains the set intermediate tone under conditions where the potential is cut off.

[19] The electrochromic element according to

[18] , wherein in the minimum colored state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, and the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more, and in the maximum colored state, the visible light transmittance is 10% or less, the solar transmittance is 10% or less, and the colorimetric value L* based on the CIE 1976 Lab* color system is 35 or less.

[20] The electrochromic element according to

[18] or

[19] , which can be set to a plurality of intermediate gradations between a minimum colored state and a maximum colored state.

[21] The electrochromic element according to any one of

[18] to

[20] , wherein the amount of change in the measured color value L* based on the CIE 1976 Lab* color system during holding after potential interruption is 10 or less within a predetermined time.

[22] A first electrochromic layer comprising an oxidative colored Ni-based material and tungsten oxide (WO). ３ An electrochromic element according to any one of

[18] to

[21] , comprising a second electrochromic layer comprising the first electrochromic layer and the second electrochromic layer, wherein the electrolyte layer comprises one or more selected from bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, magnesium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hydroxide, lithium phosphate, lithium borate, lithium molybdate, and lithium hexafluorophosphate. An electrochromic element according to any one of [9] to

[13] or

[22] , comprising a second electrochromic layer comprising the first electrochromic layer and the second electrochromic layer, wherein the electrolyte layer comprises one or more selected from bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hydroxide, lithium phosphate, lithium borate, lithium molybdate, and lithium hexafluorophosphate. An electrochromic element according to any one of

[18] to

[23] , wherein in the maximum colored state, the colorimetric value L* based on the CIE 1976 Lab* color system is ≤ 25.

[0012] This is a schematic diagram illustrating the configuration of the color-variable electrode of the present invention. This is a schematic structural diagram (cross-sectional view) showing one embodiment of the electrochromic element (ECD) of the present invention. This is a photograph of the appearance of the oxidation-colored electrochromic coating of the example. This is an electron microscope image of nanoparticles obtained after particle crushing of the oxidation-colored electrochromic material of the example. This is a photograph of the appearance of the coating obtained by various dispersion methods of the oxidation-colored electrochromic material of the example. This is a photograph of the appearance of a thin film made of the coating obtained by various dispersion methods of the oxidation-colored electrochromic material of the example. This is a diagram showing the particle size distribution of the oxidation-colored electrochromic coating of the example. This is a photograph of the appearance of the electrochromic element after fabrication of the example. This is the change in the optical transmission spectrum of the electrochromic element subjected to decolorization treatment by voltage application. This is a photograph of the appearance of the electrochromic element subjected to decolorization treatment by voltage application. This is a diagram showing the cyclic voltammogram of the electrochromic element of the example at ±1.5V. This is a diagram showing the cyclic voltammogram of the electrochromic element of the example at ±2.0V. This figure shows the results of simultaneously monitoring the change in the optical transmission spectrum of the electrochromic element of the example during chronocoulometry measurement at ±1.5V. This figure shows the results of simultaneously monitoring the change in the optical transmission spectrum of the electrochromic element of the example during chronocoulometry measurement at ±2.0V. This is a photograph showing the color change of the electrochromic element of the example when ±1.5V is applied. This is a photograph showing the color change of the electrochromic element of the example when ±2.0V is applied. This figure shows the change in the optical transmission spectrum of an electrochromic element that has undergone decolorization treatment by the voltage application method. This is a photograph of the appearance of an electrochromic element that has undergone decolorization treatment by the voltage application method. This figure shows a cyclic voltammogram of the electrochromic element of the example measured at +2.0V to -1.5V. This figure shows the results of simultaneously monitoring the change in the optical transmission spectrum of the electrochromic element of the example during chronocoulometry measurement at +2.0V to -1.5V. This figure shows a cyclic voltammogram of the electrochromic element of the example measured at +2.0V to -2.0V.This figure shows the results of simultaneously monitoring the change in optical transmission spectrum during chronocoulometry measurement of the electrochromic element of the example from +2.0V to -2.0V. This is a photograph of the appearance of the electrochromic element of the example as it changes color. This is a comparative photograph of the environmental resistance characteristics of the electrochromic element of the example. This figure shows the memory characteristics of the electrochromic element (substrate: ITO / PET) of the example. This figure shows the change in optical transmission spectrum when the thickness of the oxidative-colored electrochromic thin film is changed in the electrochromic element (substrate: ITO / PET) of the example. This figure shows the change in optical reflection spectrum when the thickness of the oxidative-colored electrochromic thin film is changed in the electrochromic element (substrate: ITO / PET) of the example. This figure shows the change in optical transmission spectrum when the thickness of the oxidative-colored electrochromic thin film is changed in the electrochromic element (substrate: FTO / glass) of the example. This figure shows the change in optical reflection spectrum when the thickness of the oxidative-colored electrochromic thin film is changed in the electrochromic element (substrate: FTO / glass) of the example. This figure shows the change in the optical reflection spectrum of electrochromic elements made of oxidation-colored electrochromic materials prepared by various dispersion methods in the examples.

[0013] As a result of various studies, the inventors have found that by using nickel oxide nanoparticles and / or nickel(III) hydroxide nanoparticles as electrochromic materials that exhibit a brownish hue in an oxidized state, and by forming a smooth thin film on an electrode using a dispersion (paint) of this electrochromic material in a solvent by methods such as coating, an oxidation-colored electrochromic material that stably exhibits a color change between brown and transparent can be obtained. In addition, since this material is an oxidation-colored inorganic electrochromic material, the inventors have found that by combining it with a reductive-colored electrochromic material such as tungsten oxide, a black electrochromic element that exhibits a color change between black and transparent can be obtained. Based on these novel findings, the inventors have completed the present invention.

[0014] Hereinafter, an embodiment of the oxidation-colored electrochromic material, paint, color-variable electrode, and black electrochromic element of the present invention will be described.

[0015] <Oxidation-Colored Electrochromic Material and Method for Producing the Same> The oxidation-colored electrochromic material of the present invention reversibly changes color between brown and transparent by an electrochemical oxidation-reduction reaction, and exhibits a brownish hue in the oxidized state. By dispersing the oxidation-colored electrochromic material of the present invention in a solvent, a paint having the above-mentioned properties can be obtained. In this invention, "transparent" does not necessarily mean that the absorption coefficient in the visible light region is 0. What is important is that there is a sufficient difference between the absorbance when colored and the absorbance when colorless and transparent, and it is preferable that the ratio of the absorbance when colored to the absorbance when colorless and transparent is 3 or more, more preferably 4 or more, and particularly preferable 5 or more, between the wavelengths of 450 nm to 550 nm, which are highly sensitive to human vision.

[0016] Furthermore, in this invention, "brown" refers to a color tone in which, for example, the colorimetric value L* based on the CIE 1976 Lab* color system is 30 to 70, a* is 2 to 8, and b* is 9 to 16. Unless otherwise specified, in this specification, L*, a*, and b* are transmission colorimetric values ​​calculated from spectral transmittance (%T) data based on the CIE 1976 Lab* color system.

[0017] One embodiment of the oxidation-colored electrochromic material of the present invention includes nickel oxide nanoparticles and nickel hydroxide nanoparticles in multiple oxidation states. In other words, the oxidation-colored electrochromic material of the present invention is NiO, Ni ２ O ３ It contains one or more nanoparticles selected from NiOOH.

[0018] The particle size (average particle size) of various nanoparticles contained in the oxidation coloring type electrochromic material is preferably small in order to improve the electrochemical response rate (to increase the specific surface area), and is also preferably small in order to form a smooth thin film. Here, the particle size (average particle size) means the particle size at 50% of the integrated value in the particle size distribution determined by the laser diffraction / scattering method or the like. From such a viewpoint, the upper limit of the primary particle size of each nanoparticle is preferably 500 nm or less, more preferably 300 nm or less, and particularly preferably 100 nm or less. The lower limit of the primary particle size of each nanoparticle is not particularly limited, but is actually 4 nm or more. In the present invention, the "primary particle size" refers to the diameter of primary particles, and the equivalent circular diameter thereof may be derived from the half-value width of the peak of the powder X-ray structure analysis. The primary particle size of each nanoparticle can also be measured using, for example, a particle size distribution measuring device by the dynamic light scattering method (DLS).

[0019] <Paint and its manufacturing method> The paint of the present invention contains the above-described oxidation coloring type electrochromic material of the present invention. The paint can be used, for example, for a thin film (electrochromic layer) constituting a black electrochromic element.

[0020] Specifically, the paint of the present invention has one or more kinds of nanoparticles selected from NiO, Ni ２ O ３ , NiOOH dispersed in a solvent and has a pH of 7 or more. Also, depending on conditions such as pH and temperature, the paint of the present invention may contain Ni(OH) ２ O ３ changed from a part of NiO, Ni ２ OOH, etc.

[0021] Any solvent can be used that can disperse the above-mentioned nanoparticles and does not affect the performance of the nanoparticles. In particular, from the viewpoint of nanoparticle dispersibility, the solvent is preferably an aqueous solvent containing an organic compound. Specifically, for example, a solvent in which water is the main solvent and alcohol is added as an additive solvent can be exemplified. Examples of alcohols include one or more from isopropanol, ethanol, methanol, n-propanol, isobutanol, and n-butanol.

[0022] The content (solid content) of nanoparticles in the paint is not particularly limited and can be adjusted as appropriate depending on the application, but for example, a range of 0.5% to 20% by mass can be exemplified.

[0023] The paint of the present invention may contain a binder. The binder is not particularly limited, but examples include one or more binders selected from organic binders or inorganic binders. Examples of organic binders include cellulose derivatives, vinyl resins, fluororesins, silicone resins, acrylic resins, epoxy resins, polyester resins, melamine resins, urethane resins, alkyd resins, etc. Examples of inorganic binders include products obtained by decomposing hydrolyzable silicon compounds such as alkyl silicates, silicon halides, and their partial hydrolysates, organic polysiloxane compounds and their polycondensates, silica, colloidal silica, water glass, silicon compounds, phosphates such as zinc phosphate, metal oxides such as zinc oxide and zirconium oxide, biphosphates, cement, gypsum, lime, enamel frit, etc.

[0024] Furthermore, from the viewpoint of producing a homogeneous thin film with the paint, it is preferable to use one or more selected from, for example, polyvinyl alcohol (PVA), sodium carboxymethylcellulose (CMC), hydroxypropylcellulose (HPC), hydroxyethylcellulose (HEC), polyethylene glycol, polypropylene glycol, trifluoromethanesulfonylimide, methyl methacrylate, and polydimethylsiloxane as the binder.

[0025] The lower limit of the binder content is 0.1% by mass or more, preferably 0.15% by mass or more, based on the paint mass (i.e., when the total paint is 100% by mass). The upper limit of the binder content is 10% by mass or less, preferably 5% by mass or less, more preferably 2% by mass or less, based on the paint mass.

[0026] Further, various other additives may be blended in the paint in addition to the binder. Examples of other additives include an antifoaming agent, a crosslinking agent, a curing catalyst, a pigment dispersant, an emulsifier, a film-forming aid, a thickener, a neutralizing agent, a preservative, and the like.

[0027] One form of the method for producing the paint of the present invention includes the following steps: a first step of blending nickel oxide nanoparticles in a plurality of oxidation states and nickel hydroxide nanoparticles (one or more selected from NiO, Ni ２ O ３ , NiOOH) to obtain predetermined nanoparticles; and a second step of dispersing the nanoparticles in a solvent (preferably an aqueous solvent containing an organic compound).

[0028] In the second step, it can be prepared so that the nanoparticles are suitably dispersed in the solvent in consideration of the performance of the required black electrochromic device.

[0029] In another form of the method for producing the paint of the present invention, in a solvent, a pulverization and stirring step of pulverizing and stirring one or more nanoparticles selected from NiO, Ni ２ O ３ , NiOOH to obtain a dispersion is included.

[0030] The method of pulverization and stirring in the pulverization and stirring step is not particularly limited, but from the viewpoint of enhancing the dispersion stability of the nanoparticles and ensuring the smoothness of the coating film, it is preferably pulverization and stirring using beads (so-called bead mill, rocking mill, vibro mill, etc.). The solvent is preferably an aqueous solvent mainly composed of purified water, and an appropriate amount of the organic compound (for example, alcohols) may be used in combination.

[0031] The beads used for pulverization and stirring may be made of known materials, and examples thereof include zirconia, alumina, glass, polymers, and the like. Among these, the material of the beads is preferably zirconia. Also, the outer diameter of the beads is not particularly limited, and for example, it can be appropriately selected from the range of 0.05 mm to 1.0 mm. Among these, from the viewpoint of obtaining a coating film with excellent transparency in which haze is reduced and cloudiness due to aggregates in the coating film is suppressed, the outer diameter of the beads is preferably about 0.05 mm to 0.5 mm.

[0032] The blending amount of the beads is not particularly limited, and for example, it may be 5 to 20 times the weight of the nanoparticle powder. However, from the viewpoint of enhancing the dispersion stability of the nanoparticles and ensuring the smoothness of the coating film, it is preferably about 8 to 12 times the weight of the nanoparticle powder. Also, the vibration frequency of pulverization and stirring can be appropriately set, for example, in the range of 30 to 120 Hz. Further, the stirring time can be appropriately set, for example, in the range of 0.5 to 24 hours. However, from the viewpoint of obtaining a coating film with excellent transparency in which haze is reduced and cloudiness due to aggregates in the coating film is suppressed, it is preferably 4 hours or more, and more preferably 6 hours or more.

[0033] Furthermore, in the method for producing the coating material of this embodiment, it is preferable to include an ultrasonic stirring step of subjecting the dispersion liquid to ultrasonic stirring treatment after the pulverization and stirring step.

[0034] For the ultrasonic treatment, for example, a commercially available ultrasonic cleaner can be used. Also, the ultrasonic treatment time is not particularly limited, and for example, it can be set from the range of about 10 to 180 minutes.

[0035] According to the ultrasonic treatment, the average particle diameter (d50) of the dispersion liquid can be further reduced, the haze of the coating film can be further decreased, and the surface smoothness can be improved.

[0036] <Variable - color electrode> An embodiment of the variable - color electrode of the present invention will be described.

[0037] The color-variable electrode of the present invention comprises an electrode layer and a first electrochromic layer formed on the electrode layer. The first electrochromic layer is a thin film formed by the paint of the present invention as described above. That is, the first electrochromic layer contains the oxidation-colored electrochromic material of the present invention as described above.

[0038] Figure 1 is a schematic diagram illustrating the configuration of the color-variable electrode of the present invention. The color-variable electrode 100a in the configuration illustrated in Figure 1 is composed of a first electrochromic layer 10, a first transparent electrode layer 40, and a first insulating layer 60, all laminated together. The first electrochromic layer 10 and one side of the transparent electrode layer 40 are connected, and the other side of the transparent electrode layer 40 (the side opposite to the first electrochromic layer 10) is connected to the first insulating layer 60.

[0039] (1) First electrochromic layer 10 The first electrochromic layer 10 is a thin film formed from a paint containing the oxidation-coloring electrochromic material of the present invention as described above. The nanoparticles contained in the paint are brown in the oxidized state and colorless and transparent in the reduced state. That is, in one embodiment of the method for manufacturing a color-variable electrode of the present invention, the method includes a step of forming a thin film (first electrochromic layer 10) containing an electrochromic material that is brown in the oxidized state on an electrode layer using the paint of the present invention as described above.

[0040] The thickness of the first electrochromic layer 10 is set appropriately according to the purpose, for example, 20 to 1500 nm. The thickness of the first electrochromic layer 10 may be constant or not (i.e., it may vary depending on the position in the planar direction).

[0041] (2) First transparent electrode layer 40 The first transparent electrode layer (electrode layer) 40 is a layer made of a transparent conductive material. The conductive material is not particularly limited as long as it does not deteriorate to a degree that poses practical problems when used as an electrochemical element, such as corrosion. Specifically, the conductive material can be, for example, conductive oxides such as indium tin oxide (ITO), zinc oxide and those doped with metals such as aluminum, silver, and titanium, precious metals such as gold and platinum, alloys and metals with corrosion resistance due to a passive film such as stainless steel and aluminum, and carbon materials such as graphene and carbon nanotubes.

[0042] The thickness of the first transparent electrode layer 40 is set appropriately according to the purpose, for example, 100 to 300 nm. The thickness of the first transparent electrode layer 40 may be constant or not (i.e., it may vary depending on the position in the planar direction).

[0043] However, from the viewpoint of increasing the contact area between the first electrochromic layer 10 and the first transparent electrode layer 40 and improving the electrochemical response rate, the first transparent electrode layer 40 may be designed to have an irregular thickness. Specifically, the surface of the first transparent electrode layer 40 can be made uneven (i.e., the surface smoothness can be reduced). The protruding portions on the surface of the first transparent electrode layer 40 can be formed, for example, from a conductive material.

[0044] The first transparent electrode layer 40 may contain known additives for the purpose of improving adhesion with the first electrochromic layer 10 and for the purpose of suppressing corrosion. Examples of known additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, tackifiers, color inhibitors, flame retardants, and antistatic agents.

[0045] Furthermore, when considering applications for the color-variable electrode 100a such as dimmable glass or dimmable film, it is necessary for it to be transparent. Therefore, in the embodiment shown in Figure 1, a first transparent electrode layer 40 is exemplified. However, the color-variable electrode 100a of the present invention also includes forms in which a non-transparent electrode layer is used.

[0046] Furthermore, another thin film made of an electrochromic material that gives a different color change from the first electrochromic layer 10 can be laminated on the first electrochromic layer 10.

[0047] (3) First insulating layer 60 The first insulating layer 60 is a layer made of a transparent insulating material. For example, the first insulating layer 60 can be formed from resin or glass. Examples of resins include polyethylene terephthalate (PET), polycarbonate, and polyethylene naphthalate (PEN). The first insulating layer 60 may contain known additives such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, tackifiers, color inhibitors, flame retardants, and antistatic agents.

[0048] The thickness of the first insulating layer 60 and the second insulating layer 70 is, for example, 50 μm to 1.1 mm. The thickness of the first insulating layer 60 and the second insulating layer 70 may be constant or not (i.e., they may differ depending on their position in the planar direction).

[0049] In addition, the first insulating layer 60 in the color-variable electrode 100a of the present invention is not necessarily required and can be omitted.

[0050] <First Embodiment of Electrochromic Element (ECD)> (Black Electrochromic Element (ECD)) The black electrochromic element (ECD) of the present invention reversibly changes color between black and transparent by an electrochemical oxidation-reduction reaction. The ECD of the present invention comprises a first electrochromic layer containing a first electrochromic material that exhibits a brownish hue in the oxidized state, and a second electrochromic layer containing a second electrochromic material that exhibits a bluish hue in the reduced state.

[0051] An embodiment of the black electrochromic element (ECD) of the present invention will be described. Figure 2 is a schematic structural diagram (cross-sectional view) showing an embodiment of the ECD of the present invention.

[0052] In the ECD200, an electrolyte layer 30 is sandwiched between the first color variable electrode 100a and the second color variable electrode 100b.

[0053] The ECD200 is driven by applying voltage to the first color variable electrode 100a and the second color variable electrode 100b. That is, the following states 1 and 2: (State 1) The first electrochromic layer 10 is in an oxidized state and the second electrochromic layer 20 is in a reduced state. (State 2) The first electrochromic layer 10 is in a reduced state and the second electrochromic layer 20 is in an oxidized state. Color changes between these states can be achieved by applying voltage.

[0054] For example, when ECD200 is used as a dimmable glass, a first transparent electrode layer 40 and a second transparent electrode layer 50 are used as electrode layers, and a transparent material is used as the electrolyte. This is called a transmissive ECD. In the form of a transmissive ECD, the color of ECD200 is a mixture of the first electrochromic layer 10 and the second electrochromic layer 20.

[0055] In the case of a transmissive ECD, the second electrochromic layer 20 must have stable electrochemical properties and be a material that exhibits the required color change. On the other hand, in the case of a reflective ECD, the second electrochromic layer 20 only needs to have stable electrochemical properties.

[0056] Furthermore, in the ECD200, the second color variable electrode 100b includes a second electrochromic material (second electrochromic layer 20) that is colorless (transparent) in the oxidized state and turns blue in the reduced state.

[0057] Below, we will explain in more detail the ECD shown in Figure 2, using the form of a transmissive ECD as an example.

[0058] Specifically, the ECD 200 includes a first electrochromic layer 10 (an example of a "thin film made of a coating containing nickel oxide nanoparticles in multiple oxidation states and nickel hydroxide nanoparticles"), a second electrochromic layer 20 (for example, an example of a "tungsten oxide thin film"), an electrolyte layer 30, a first transparent electrode layer 40, a second transparent electrode layer 50, a first insulating layer 60, and a second insulating layer 70. The ECD 200 is constructed by laminating these layers (10, 20, 30, 40, 50, 60, 70).

[0059] The electrolyte layer 30 is located between the first electrochromic layer 10 and the second electrochromic layer 20. The first transparent electrode layer 40 is located on the surface of the first electrochromic layer 10 opposite to the electrolyte layer 30. The second transparent electrode layer 50 is located on the surface of the second electrochromic layer 20 opposite to the electrolyte layer 30. The first insulating layer 60 is located on the surface of the first transparent electrode layer 40 opposite to the first electrochromic layer 10. The second insulating layer 70 is located on the surface of the second transparent electrode layer 50 opposite to the second electrochromic layer 20.

[0060] The first electrochromic layer 10 and the second electrochromic layer 20 are layers having electrochromic properties, and their color changes reversibly through oxidation-reduction reactions (the colored state and the decolorized state change reversibly). The first electrochromic layer 10 is colored brown in the oxidized state and decolorizes (becomes colorless and transparent) in the reduced state. The second electrochromic layer 20 is decolorized (becomes colorless and transparent) in the oxidized state and is colored in a bluish tone in the reduced state.

[0061] (1) First color variable electrode 100a The first color variable electrode 100a is constructed by laminating the first electrochromic layer 10 described above, the first transparent electrode layer 40, and the first insulating layer 60. The first color variable electrode 100a is the same as the color variable electrode of the present invention described above, so its description will be omitted below.

[0062] (2) Second color variable electrode 100b The second color variable electrode 100b, like the first color variable electrode 100a, consists of an electrochromic material and an electrode layer (conductive material), and may have the same degree of structural freedom as the first color variable electrode 100a. For example, the second color variable electrode 100b may also be a mixture of multiple electrochromic materials.

[0063] In the configuration shown in Figure 2, the second color variable electrode 100b is constructed by laminating a second electrochromic layer 20, a second transparent electrode layer 50, and a second insulating layer 70.

[0064] (2-1) Second electrochromic layer 20 The second electrochromic layer 20 contains a material that differs from the first electrochromic layer 10 in terms of the coloring and decolorization changes due to the oxidation-reduction reaction, and preferably contains tungsten oxide nanoparticles, titanium oxide nanoparticles, or other oxide nanoparticles, and it is desirable that it exhibits a blue hue in the reduced state. That is, the second electrochromic layer 20 may be in the form of a tungsten oxide thin film, a titanium oxide thin film, or other oxide thin film.

[0065] The upper limit of the primary particle size in tungsten oxide nanoparticles is, for example, 300 nm or less, preferably 100 nm or less, and more preferably 50 nm or less, from the viewpoint of increasing the specific surface area to improve the electrochemical response rate and forming a smooth thin film. The lower limit of the primary particle size in tungsten oxide nanoparticles is not particularly limited, but is, for example, 4 nm or more, preferably 5 nm or more, and more preferably 6 nm or more.

[0066] The thickness of the second electrochromic layer 20 is set appropriately according to the purpose, for example, 300 to 3000 nm. The thickness of the second electrochromic layer 20 may be constant or not (i.e., it may vary depending on its position in the planar direction).

[0067] (3) Electrolyte layer 30 The electrolyte layer 30 is a layer containing an electrolyte. The first electrochromic layer 10 and the second electrochromic layer 20 undergo an electrochromic reaction in the electrolyte.

[0068] The electrolyte used in the electrolyte layer 30 preferably contains, for example, a (trifluoromethanesulfonyl)imide salt. Examples of (trifluoromethanesulfonyl)imide salts include one or more selected from bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, and magnesium bis(trifluoromethanesulfonyl)imide. Other electrolytes that can be used include lithium perchlorate, lithium hydroxide, lithium phosphate, lithium borate, lithium molybdate, and lithium hexafluorophosphate.

[0069] The electrolyte content in the electrolyte layer 30 is not particularly limited, but from the viewpoint of improving the electrochemical response rate in the ECD 200, it is, for example, 0.1 to 1.5 mol / kg, and preferably 0.5 to 1.5 mol / kg.

[0070] Furthermore, the electrolyte layer 30 may contain a solvent or resin in addition to the electrolyte. As the solvent contained in the electrolyte layer 30, a known solvent capable of dissolving the electrolyte contained in the electrolyte layer 30 can be used, for example, linear carbonate esters such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate; cyclic carbonate esters such as ethylene carbonate, propylene carbonate, and butylene carbonate; aliphatic carboxylic acid esters such as methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and methyl trimethylacetate; aromatic carboxylic acid esters such as methyl benzoate and ethyl benzoate; lactones such as γ-butyrolactone and γ-valerolactone; lactams such as ε-caprolactam and N-methylpyrrolidone; tetrahydrofuran, 2 - One or more can be selected from cyclic ethers such as methyltetrahydrofuran, tetrahydropyran, and 1,3-dioxolane; linear ethers such as 1,2-diethoxyethane and ethoxymethoxyethane; sulfones such as ethylmethylsulfone, sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane; nitriles such as acetonitrile, propionitrile, and methoxypropionitrile; phosphate esters such as trimethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, and triethyl phosphate; alcohols such as ethanol and 2-propanol; glycols such as ethylene glycol, propylene glycol, and polyethylene glycol; and water.

[0071] The resin contained in the electrolyte layer 30 is not particularly limited, and one or more resins can be selected from known resins such as acrylic resin, urethane resin, silicone resin, epoxy resin, vinyl chloride resin, ethylene resin, melamine resin, phenolic resin, methyl methacrylate resin, polyvinyl alcohol resin, polyvinyl acetal resin, and polyethylene oxide resin. By containing a resin in the electrolyte layer 30, the mechanical strength of the electrolyte layer 30 can be improved.

[0072] The electrolyte layer 30 may optionally contain various other additives, as long as they do not impair the function of the electrolyte layer 30. Examples of known additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, tackifiers, color inhibitors, flame retardants, and antistatic agents.

[0073] The thickness of the electrolyte layer 30 is set appropriately according to the purpose, for example, 50 μm to 0.3 mm. The thickness of the electrolyte layer 30 may be constant or not (i.e., it may vary depending on the position in the planar direction).

[0074] As described above, the ECD 200 changes between state 1 and state 2 when a voltage is applied. In this case, if the second electrochromic layer 20 is made of an electrochromic material consisting of, for example, tungsten oxide nanoparticles and the electrolyte layer 30 is made of a transparent material, the ECD 200 will show a color change between black and transparent.

[0075] The present invention relates to a method for manufacturing a black electrochromic element (ECD), which includes a step of laminating a color-variable electrode and an electrolyte layer. An example of the manufacturing method of an ECD is described below. For example, a commercially available substrate with transparent electrodes (e.g., ITO-coated glass) is used as the first transparent electrode layer 40 and the second transparent electrode layer 50. Similarly, the glass corresponds to the first insulating layer 60 and the second insulating layer 70. The two substrates are referred to as the first substrate (second transparent electrode layer 50 + second insulating layer 70) and the second substrate (first transparent electrode layer 40 + first insulating layer 60).

[0076] First, a first film-forming substrate (second color variable electrode 100b) is manufactured by forming a second electrochromic layer 20 on a first substrate. In this manufacturing method, coating methods such as wet coating processes such as slit coating, spin coating, bar coating, and spray coating are selected, but not only coating methods, but also vacuum deposition and sputtering methods can be selected. Similarly, a second film-forming substrate (first color variable electrode 100a) is manufactured by forming a first electrochromic layer 10 on a second substrate. An electrolyte layer 30 is formed on the first film-forming substrate (second color variable electrode 100b) using a dispenser. Furthermore, a sealing structure is formed on the outer periphery using an adhesive or UV-curing resin. Alternatively, this sealing structure can be formed using commercially available electronic device sealing tape.

[0077] Subsequently, the second film-forming substrate (first color variable electrode 100a) is placed over the first film-forming substrate (second color variable electrode 100b) from above, and the two substrates are pressed and bonded in a vacuum chamber. If sealing tape is used, bonding can be performed at room temperature and atmospheric pressure without any problems. In this way, an ECD 200 is obtained having the structure of first insulating layer 60 / first transparent electrode layer 40 / first electrochromic layer 10 / electrolyte layer 30 / second electrochromic layer 20 / second transparent electrode layer 50 / second insulating layer 70.

[0078] Preferably, the black electrochromic element of the present invention has a visible light transmittance of 70% or more, a solar transmittance of 50% or more, and a colorimetric value L* based on the CIE 1976 Lab* color system of 85% or more in the transparent state, and a visible light transmittance of 10% or less, a solar transmittance of 10% or less, and a colorimetric value L* based on the CIE 1976 Lab* color system of 35% or less in the black state.

[0079] <Second Embodiment of Electrochromic Element (ECD)> Some explanations of aspects common to the first embodiment described above will be omitted. The electrochromic element of this embodiment reversibly changes color between a transparent state and a colored state through an electrochemical oxidation-reduction reaction.

[0080] In this embodiment, the electrochromic element, in its colored state, satisfies the following color values ​​based on the CIE 1976 Lab* color system: L* ≤ 35, |a*| ≤ 10, and |b*| ≤ 15. That is, the colored state of the electrochromic element in this embodiment can be visually evaluated as a dark color range (black to dark gray) that is close to achromatic. Furthermore, it is preferable that the color value of the electrochromic element in this embodiment, in its colored state, is L* ≤ 25.

[0081] The electrochromic element of this embodiment may, similar to the first embodiment, comprise a first electrochromic layer containing a first electrochromic material that exhibits a brownish hue in an oxidized state, and a second electrochromic layer containing a second electrochromic material that exhibits a bluish hue in a reduced state. In this case, the first electrochromic layer is a thin film formed by the paint of the present invention as described above.

[0082] In this embodiment, the electrochromic element preferably has a visible light transmittance of 70% or more, a solar radiation transmittance of 50% or more, and a colorimetric value L* of 85% or more in the transparent state, and a visible light transmittance of 10% or less and a solar radiation transmittance of 10% or less in the colored state.

[0083] <Third Embodiment of Electrochromic Element (ECD)> Some explanations of aspects common to the first embodiment described above will be omitted. The electrochromic element of this embodiment reversibly changes color between a transparent state and a colored state through an electrochemical oxidation-reduction reaction.

[0084] In this embodiment, the electrochromic element has a visible light transmittance of 70% or more, a solar transmittance of 50% or more, and a colorimetric value L* of 85 or more based on the CIE 1976 Lab* color system in the transparent state, and in the colored state, a visible light transmittance of 10% or less, a solar transmittance of 10% or less, and a colorimetric value L* ≤ 35, |a*| ≤ 10, and |b*| ≤ 15 based on the CIE 1976 Lab* color system.

[0085] The colored state of the electrochromic element in this embodiment can be visually evaluated as a dark color range (black to dark gray) that is close to achromatic. Furthermore, it is preferable that the colorimetric value of the electrochromic element in this embodiment in the colored state is L* ≤ 25.

[0086] <Fourth Embodiment of Electrochromic Element (ECD)> Some explanations of aspects common to the first embodiment described above will be omitted. The electrochromic element of this embodiment reversibly changes color between a minimum colored state and a maximum colored state through an electrochemical oxidation-reduction reaction.

[0087] The "minimum colored state" refers to the state in which, under predetermined measurement conditions, a decolorizing potential or charge is applied to the element, and the transmittance at a specific wavelength becomes substantially minimum, after which the measured value stabilizes. The "maximum colored state" refers to the state in which, under predetermined measurement conditions, a coloring potential or charge is applied to the element, and the transmittance at a specific wavelength becomes substantially maximum, after which the measured value stabilizes. The determination of reaching the "minimum colored state" and the "maximum colored state" can be performed, for example, by measuring absorbance (Abs.) after applying a constant potential or constant current under predetermined measurement conditions. In this case, the point at which the absorbance hardly changes with respect to the application time can be considered the maximum and minimum values.

[0088] In this embodiment, the electrochromic element preferably has a visible light transmittance of 70% or more, a solar transmittance of 50% or more, and a colorimetric value L* of 85 or more in the minimum colored state, and a visible light transmittance of 10% or less, a solar transmittance of 10% or less, and a colorimetric value L* of 35 or less in the maximum colored state.

[0089] In the electrochromic element of this embodiment, in the minimum colored state, it may appear almost colorless and transparent (clear) to the naked eye, with clouding suppressed. In contrast, in the maximum colored state, it may appear to the naked eye as a dark color range (black to dark gray) that is close to achromatic. Such visual evaluations are consistent with high visible light transmittance (e.g., 70% or more), high solar transmittance (e.g., 50% or more), and high colorimetric value L* (e.g., 85 or more) in the minimum colored state, and with low visible light transmittance (e.g., 10% or less), low solar transmittance (e.g., 10% or less), and low colorimetric value L* (e.g., 35 or less) in the maximum colored state.

[0090] The electrochromic element of this embodiment can be set to at least one intermediate level between the minimum and maximum coloring states by applying a predetermined potential, and the set intermediate level is maintained under conditions where the potential is cut off. Here, "intermediate level" refers to any coloring level between the minimum and maximum coloring states that can be reproduced by setting a predetermined potential, current, or charge amount.

[0091] In this embodiment, it is preferable that the electrochromic element can be set to a plurality of intermediate levels between the minimum coloring state and the maximum coloring state. The number of intermediate levels is not particularly limited and may be, for example, four or more levels, eight or more levels, or sixteen or more levels.

[0092] Intermediate tones are preferably stably maintained under the retention conditions after potential interruption. Specifically, the change in the measured color value L* after a predetermined time (e.g., 5 to 90 minutes) is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less.

[0093] The electrochromic element of this embodiment comprises a first electrochromic layer containing an oxidatively colored Ni-based material and tungsten oxide (WO ３ It is preferable to include a second electrochromic layer containing the first electrochromic material. Furthermore, similar to the first embodiment, it may include a first electrochromic layer containing a first electrochromic material that exhibits a brownish hue in an oxidized state, and a second electrochromic layer containing a second electrochromic material that exhibits a blueish hue in a reduced state. In this case, it is preferable that the first electrochromic layer is a thin film formed by the paint of the present invention as described above. In this case, it is also preferable to include an electrolyte layer similar to that of the first embodiment between the first electrochromic layer and the second electrochromic layer, and specifically, it is preferable that the electrolyte layer contains one or more selected from bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, magnesium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hydroxide, lithium phosphate, lithium borate, lithium molybdate, and lithium hexafluorophosphate.

[0094] In this embodiment, it is preferable that the electrochromic element has a colorimetric value L* ≤ 25 in the maximum color state.

[0095] The elements described in the first, second, third, and fourth embodiments above can be combined, substituted, or selectively adopted from each other insofar as they satisfy the spirit and intended effects of the present invention.

[0096] The electrochromic element of the present invention (typically an electrochromic element that reversibly changes color between black and transparent) can realize a device (color-variable electrode, electrochromic element) that can stably achieve a color change between black and transparent without using organic electrochromic materials. This electrochromic element is useful, for example, in dimmable glass, dimmable film, displays, indicators, dimmable mirrors, and the like.

[0097] The oxidation-colored electrochromic material, paint, color-variable electrode, and electrochromic element of the present invention are not limited to the embodiments described above.

[0098] The present invention will be described in more detail below based on examples, but the present invention is not limited in any way to the following examples.

[0099] <Preparation Example 1> Preparation of a coating containing an oxidation-colored electrochromic material A coating containing an oxidation-colored electrochromic nanomaterial was prepared as follows.

[0100] Using 70 mL of water and 30 mL of isopropanol as solvents, 1 g of nickel oxide nanoparticles in multiple oxidation states and nickel hydroxide nanoparticles were suspended and stirred at 1000 rpm for 2 days. The pH was adjusted to be 7 or higher. Multiple nickel oxide nanoparticles in multiple oxidation states and nickel hydroxide nanoparticles (NiO, Ni ２ O ３ A paint (oxidative coloring type nickel oxide paint) was obtained in which one or more nanoparticles selected from NiOOH were dispersed in a solvent.

[0101] A photograph of the appearance of the obtained paint is shown in Figure 3. As shown in Figure 3, it was confirmed that nanoparticles can be suitably dispersed in the solvent at a pH of 7 or higher, and that a dispersed paint can be obtained.

[0102] Furthermore, the particle size distribution of this paint is shown in Figure 4. As shown in Figure 4, the nanoparticles contained in the paint obtained in Preparation Example 1 have a solid content of 1% or less, and the secondary particle diameter has an average particle size of about 500 nm.

[0103] <Preparation Example 2> Preparation of a coating containing an oxidation-colored electrochromic material A coating containing an oxidation-colored electrochromic nanomaterial was prepared as follows.

[0104] Using zirconia balls with a diameter of 0.1 mm, 50 ml of iBoy was placed in a solution containing water and nickel oxide nanoparticles at solid content concentrations of 5%, 10%, and 15%. The iBoy was placed in a rocking mill grinding and stirring machine, and stirring was performed at a vibration frequency of 60 Hz for 8 hours. The weight of the zirconia balls added was set to 10 times the weight of the nickel oxide nanoparticle powder.

[0105] Figure 5 shows the results of observing the obtained powder with a transmission electron microscope. By using this method to break down particles, it is possible to obtain particle sizes of less than one-tenth (10-20 nm).

[0106] Figure 6 shows photographs of paints subjected to control tests: one stirred only with a stirrer, and another subjected to ultrasonic stirring after crushing with a rocking mill. With stirrer stirring alone, even after stirring for three days, the particles settled as soon as stirring stopped. However, in the paint that was crushed with a rocking mill and then ultrasonically stirred, the liquid color changed to dark gray, and its dispersibility was maintained for several months or more even after stirring stopped.

[0107] Figure 7 shows photographs of each paint deposited on FTO / glass using the spin coating method. With stirrer agitation alone, coarse particles were present, resulting in a frosted glass-like film visible to the naked eye. However, with paints that were crushed in a rocking mill and then further agitated with ultrasound, a uniform and beautiful film could be obtained.

[0108] <Example 1> An electrode with an oxidatively colored electrochromic thin film was fabricated using the paint (oxidatively colored nickel oxide paint) obtained in the electrode fabrication example, as described below. PVA (polyvinyl alcohol) was added to the paint to improve adhesion with the ITO coated glass. An oxidatively colored nickel oxide thin film was formed on the ITO coated glass using this paint, and an electrode (color-variable electrode) was fabricated. The thickness of the fabricated thin film was approximately 700 nm.

[0109] <Example 2> Fabrication of a Black Electrochromic Element A black electrochromic element in the form illustrated in Figure 2 was fabricated by the following method. The first electrochromic layer is composed of the oxidation-colored electrochromic thin film fabricated as described above. The second electrochromic layer is composed of a reduction-colored electrochromic thin film (tungsten oxide coated thin film) fabricated by the following method.

[0110] <Tungsten Oxide Coated Thin Film> 15 g of tungsten oxide nanoparticles (powder sample) was suspended in 85 mL of water, and then PVA was added to lower the surface tension and the mixture was stirred to obtain a coating containing tungsten oxide nanoparticles. PVA was added so that its concentration was 5 wt% relative to the solid content of the tungsten oxide nanoparticles.

[0111] Using a coating containing tungsten oxide nanoparticles, a thin film of tungsten oxide nanoparticles (hereinafter referred to as "tungsten oxide thin film 1") was formed as a second electrochromic layer on the surface of a laminate of a substrate and a transparent electrode.

[0112] Specifically, a tungsten oxide thin film 1 was prepared on an FTO-coated glass substrate by spin coating using a paint containing tungsten oxide nanoparticles. First, the viscosity of the slurry was adjusted to approximately 15 mPa·s by filtering before use. 250 μL was measured out with a micropipette and dropped onto a 50 mm square FTO-coated glass substrate placed in a spin coater. The spin coater was rotated at 200 rpm for 180 seconds, then at 600 rpm for 10 seconds, and finally at 1600 rpm for 10 seconds to form a thin film. The prepared thin film was air-dried to obtain the tungsten oxide thin film 1. The thickness of the tungsten oxide thin film 1 was approximately 1000 nm.

[0113] <Tungsten Oxide Deposited Film> In addition to coating using a dispersion, a tungsten oxide thin film (hereinafter referred to as "tungsten oxide thin film 2") was formed on an FTO-coated glass substrate by vacuum deposition. The film thickness is approximately 500 nm.

[0114] <Black Electrochromic Element> A black electrochromic element that changes color from black to colorless transparent was fabricated using the following procedure. Specifically, an electrochromic element was fabricated by sandwiching an electrolyte layer between an FTO-coated glass substrate on which an oxidatively colored nickel oxide thin film was formed and an FTO-coated glass substrate on which a tungsten oxide thin film was formed, with the first substrate and the second substrate on the outside. Figure 11 shows photographs of the appearance of each obtained element. Tables 1 and 2 show the assembly conditions for each element and the results of measuring the haze of the elements as they were fabricated. Here, the differences in the tungsten oxide thin film and the differences in the electrolyte (cation species) were compared.

[0115]

[0116]

[0117] First, since the fabricated element was brownish in color, a decolorization treatment was performed using the voltage application method. After observing the reaction with various voltages, it was determined that a voltage application of approximately +2V was necessary to make the oxidation-colored nickel oxide film transparent. Furthermore, the voltage application decolorization treatment was faster with a lithium-based electrolyte and with the tungsten oxide thin film 2 (Figure 12). The appearance of the element after decolorization treatment using the voltage application method is shown in Figure 13.

[0118] Electrochemical measurements were performed on the pre-treated elements under the conditions shown in Table 3. Here, a tungsten oxide thin film was used as the working electrode and an oxidized nickel oxide thin film as the counter electrode, connected to the electrochemical measuring device.

[0119]

[0120] Figure 11 shows the results of measuring the cyclic voltammogram of each electrochromic element at ±1.5V with a scan rate of 5 millivolts / second. Each electrochromic element was confirmed to exhibit good electrochemical reactions. In particular, the color change reaction current was higher for the element using the tungsten oxide thin film 1, and also higher for the element using the lithium-based electrolyte.

[0121] Figure 12 shows the results of measuring the cyclic voltammogram of each electrochromic element at ±2.0V with a scan rate of 5 millivolts / second. Each electrochromic element was confirmed to exhibit a good electrochemical reaction. In particular, the element using tungsten oxide thin film 2 showed that the reaction almost converged when the voltage on the decolorization side was applied up to +2.0V. In contrast, the element using tungsten oxide thin film 1 converged the decolorization reaction with an applied voltage of approximately +1.5V.

[0122] Figure 13 shows the results of simultaneously monitoring changes in the optical transmission spectrum during ±1.5V chronocoulometry measurement. The difference in contrast is thought to be due to the difference in film thickness between tungsten oxide thin film 1 and tungsten oxide thin film 2. Furthermore, the optical transmission spectrum of the device using tungsten oxide thin film 1 showed lower transmittance in the near-infrared band when colored. Similarly, Figure 14 shows the results of simultaneously monitoring changes in the optical transmission spectrum during ±2.0V chronocoulometry measurement.

[0123] Figure 15 is a photograph showing the color change of each electrochromic element when ±1.5V is applied. Comparing the colors of each device visually and in images (white background), the element using a potassium-based electrolyte with a tungsten oxide thin film 2 showed the closest to black coloration when -1.5V was applied.

[0124] Figure 16 is a photograph showing the color change of each electrochromic element when ±2.0V is applied. At an applied voltage of -2.0V, all elements changed color to almost black. In the element using the tungsten oxide thin film 1, it can be seen that the area near the outer edge has changed to blue. This is because the oxidative-colored nickel oxide thin film at the outer edge is thin, so the coloring state of only the tungsten oxide thin film 1 is exposed.

[0125] For performance comparison, electrolyte solutions containing potassium, lithium, and magnesium as cation species, as shown in Table 4, were prepared. The first and second electrochromic layers were prepared under the conditions shown in Table 5, and by combining these thin films, electrochromic elements were fabricated under the conditions shown in Table 6.

[0126]

[0127]

[0128]

[0129] First, similar to the decolorization treatment described above, a decolorization treatment of the oxidative-colored nickel oxide thin film was performed by applying voltage. The rate of the decolorization reaction of the oxidative-colored nickel oxide thin film by voltage-applied aging treatment clearly differed depending on the electrolyte, with magnesium-based and lithium-based electrolytes showing a faster reaction and potassium-based electrolytes showing a slower reaction (Figure 17). Furthermore, the appearance of the device after the decolorization treatment is shown in Figure 18.

[0130] Figure 19 shows the results of cyclic voltammogram measurements of each electrochromic element at a scan rate of 5 millivolts / second from +2.0V to -1.5V. Each electrochromic element was confirmed to exhibit a good electrochemical reaction. Regarding the peak current values ​​generated during the color change reaction in CV measurements, no significant differences were observed due to differences in electrolytes.

[0131] Figure 20 shows the results of simultaneously monitoring the change in optical transmission spectrum during chronocoulometry measurements from +2.0V to -1.5V. No differences were observed in charge amount due to differences in electrolytes. Summarizing the behavior from +2.0V to -1.5V, the coloring reaction proceeded fastest with devices using potassium-based electrolytes and slowest with devices using lithium-based electrolytes. The decolorization reaction proceeded fastest with devices using lithium-based electrolytes and slowest with devices using potassium-based electrolytes.

[0132] Figure 21 shows the results of measuring the cyclic voltammogram of each electrochromic element at a scan rate of 5 millivolts / second from +2.0V to -2.0V. When the voltage used to induce the coloring reaction was changed to -2.0V, it was observed that lithium-based electrolyte devices and magnesium-based electrolyte devices exhibited a two-step color change reaction during the decolorization process.

[0133] Figure 22 shows the results of simultaneously monitoring the change in optical transmission spectrum during chronocoulometry measurements from +2.0V to -2.0V. For all three types of electrolytes used in the devices, the color transmittance at -2.0V applied was less than 5% across a wide range from the visible light band to the near-infrared band, resulting in a nearly black color. Summarizing the behavior from +2.0V to -2.0V, the color reaction rate differed by about half between the potassium-based electrolyte device and the lithium-based electrolyte device, with the potassium-based electrolyte device showing the fastest reaction rate. The decolorization reaction was fastest for the magnesium-based electrolyte device and slowest for the potassium-based electrolyte device.

[0134] Figure 23 shows photographs of the appearance of each electrochromic element as it changes color. As shown in Figure 23, the color of all three devices immediately after assembly was the color of the first electrochromic layer. When the device undergoes a coloring reaction, the second electrochromic layer takes on a bluish tint. It is thought that the synergistic effect of the brownish color of the first electrochromic layer absorbing blue and green light and the blue color of the second electrochromic layer absorbing red light blocks most of the light, resulting in an appearance of dark gray or almost black.

[0135] Figure 24 shows a device (PB / WO) combining a Prussian blue (PB) coated film and a tungsten oxide thin film, which are oxidation-colored electrochromic materials. ３ ) and an element combining an oxidatively colored nickel oxide film and a tungsten oxide thin film (the black electrochromic element of the present invention: NiO / WO ３ The image shows the appearance of the product over time. PB / WO ３ In elements combining these materials, degradation progresses due to the sealing condition of the outer periphery, causing the surrounding area to turn blue. Analysis has confirmed that this is because PB is oxidized by air and humidity penetrating from the outer periphery, impairing the color change reaction. On the other hand, NiO / WO ３ The advantage of a device combining these elements is that it does not use PB, thus avoiding environmental degradation and offering long-term stability.

[0136] Table 7 shows the optical properties associated with the color change of each electrochromic element. As a comparative example, a Prussian blue (PB) coated film and a tungsten oxide thin film (PB / WO) are shown, which are oxidation-colored electrochromic materials. ３ This shows the performance when combined with the following:

[0137]

[0138] Previous PB / WO ３ In elements combining these, the visible light transmittance in the colored state is also about 15%, but NiO / WO ３ In elements combining these, the figure is less than 4%, and solar transmittance is similarly improved from about 11% to about 1%. In addition, the colorimetric value L*, which represents brightness and darkness within chromaticity, is also improved by PB / WO３ In elements combining these, the figure is around 50%, but NiO / WO ３ In the element combining these, the color is dark, at about 18%. Thus, the advantage of using nickel oxide-based materials that exhibit brown coloring during oxidation as oxidation-colored electrochromic materials lies in the improved color tone and light-shielding performance. That is, NiO / WO ３ In the combined element, it was confirmed that in the transparent state (minimum coloring state), the visible light transmittance was 70% or more, the solar transmittance was 50% or more, and the colorimetric value L* was 85 or more. In the colored state (maximum coloring state), it was confirmed that the visible light transmittance was 10% or less, the solar transmittance was 10% or less, and the colorimetric value was L* ≤ 35, |a*| ≤ 10, and |b*| ≤ 15.

[0139] Figure 25 shows the memory characteristics of the electrochromic element. It shows the change in transmittance when the applied voltages of 0.0V, -0.5V, -1.0V, -1.5V, 0.5V, 1.0V, and 1.5V are turned off. In this way, a characteristic optical transmission spectrum is shown at each voltage, and this transmittance can be maintained. That is, intermediate gradations between the minimum and maximum color states are reproduced well according to each set potential, and these intermediate gradations are maintained for a predetermined time even after the potential is cut off. For example, as shown in Table 8, it was confirmed that the amount of variation in the measured color value L* was within 10 within a predetermined time (5 to 60 minutes).

[0140]

[0141] <Example 3> Fabrication of a Black Electrochromic Element A black electrochromic element in the form illustrated in Figure 2 was fabricated by the following method. ITO / PET was used as the substrate, and the first electrochromic layer was composed of the oxidation-colored electrochromic thin film fabricated in Example 2. The second electrochromic layer was composed of a reduction-colored electrochromic thin film (tungsten oxide coated thin film) fabricated by the method of Example 2. The method for fabricating the black electrochromic element follows that of Example 2, but here we show the effect of changing the film thickness of the oxidation-colored electrochromic thin film on the transmittance in the colored state.

[0142] Figures 26 and 27 show the changes in optical transmission spectra and optical reflection spectra when the thickness of oxidation-colored electrochromic thin films was set to 300 nm, 800 nm, 1100 nm, and 1400 nm, and the thickness of reductive-colored electrochromic thin films was fixed at 700 nm. As the thickness of the oxidation-colored electrochromic thin film increased, the transmittance in the colored state decreased further. On the other hand, it was confirmed that the reflection spectrum was hardly affected in either the colored or decolorized state.

[0143] Table 9 shows the optical properties associated with the color change of each electrochromic element. It was suggested that as the thickness of the oxidation-colored electrochromic thin film increases, the L* value in the decolorized state decreases, indicating that the element becomes darker.

[0144]

[0145] <Example 4> Fabrication of a Black Electrochromic Element A black electrochromic element in the form illustrated in Figure 2 was fabricated by the following method. FTO / glass was used as the substrate, and the first electrochromic layer was composed of the oxidation-colored electrochromic thin film fabricated in Example 2. The second electrochromic layer was composed of a reduction-colored electrochromic thin film (tungsten oxide coated thin film) fabricated by the method of Example 2. The method for fabricating the black electrochromic element follows that of Example 2, but here the effect of changing the film thickness of the oxidation-colored electrochromic thin film on the transmittance in the colored state is shown.

[0146] Figures 28 and 29 show the changes in optical transmission spectra and optical reflection spectra when the thickness of oxidation-colored electrochromic thin films was set to 300 nm, 800 nm, 1100 nm, and 1400 nm, and the thickness of reductive-colored electrochromic thin films was fixed at 700 nm. As the thickness of the oxidation-colored electrochromic thin film increased, the transmittance in the colored state decreased further. On the other hand, it was confirmed that the reflection spectrum was hardly affected in either the colored or decolorized state.

[0147] Table 10 shows the optical properties associated with the color change of each electrochromic element. It was suggested that as the thickness of the oxidation-colored electrochromic thin film increases, the L* value in the decolorized state decreases, indicating that the film becomes darker.

[0148]

[0149] <Example 5> Fabrication of a Black Electrochromic Element A black electrochromic element in the form illustrated in Figure 2 was fabricated by the following method. FTO / glass was used as the substrate, and the first electrochromic layer was composed of the oxidation-colored electrochromic thin film fabricated in Example 2. The second electrochromic layer was composed of the reduction-colored electrochromic thin film (tungsten oxide coated thin film) fabricated by the method of Example 2. The method for fabricating the black electrochromic element followed that of Example 2, but here the properties were evaluated when the mixing conditions of the same material were changed by particle crushing.

[0150] Figure 30 shows the changes in optical transmission spectra when an oxidation-colored electrochromic nanomaterial is stirred with a stirrer, crushed with a rocking mill, and then crushed with ultrasonic waves after rocking mill crushing. As shown in Figure 30, even with the same material, stirring with a stirrer alone results in poor dispersibility and low reactivity due to the coarse particle size. On the other hand, crushing with a rocking mill reduces the grain size, as shown in Figure 5, increasing the specific surface area when a film is deposited and improving reactivity. Furthermore, when ultrasonic waves are crushed after rocking mill crushing, the grain size is further reduced, increasing the specific surface area when a film is deposited and improving reactivity.

[0151] Although embodiments and modifications based thereon have been described above, the present invention is not necessarily limited thereto, and those skilled in the art will be able to find various alternative embodiments and modifications without departing from the spirit of the invention or the scope of the claims.

[0152] 10: First electrochromic layer 20: Second electrochromic layer 30: Electrolyte layer 40: First transparent electrode layer 50: Second transparent electrode layer 60: First insulating layer 70: Second insulating layer 100a: First color variable electrode 100b: Second color variable electrode 200: ECD

Claims

1. An oxidative color-changing electrochromic material that reversibly changes color between brown and transparent by an electrochemical oxidation-reduction reaction, comprising NiO, Ni ２ O ３ An oxidation-colored electrochromic material comprising one or more nanoparticles selected from NiOOH, exhibiting a brownish hue in an oxidized state.

2. A paint in which the oxidation-coloring electrochromic material of claim 1 is dispersed in a solvent.

3. The paint according to claim 2, wherein the solvent is an aqueous solvent containing an organic compound.

4. The paint according to claim 2, wherein the content of the nanoparticles is 0.5% by mass or more and 20% by mass or less.

5. The paint according to claim 2, comprising as a binder one or more selected from polyvinyl alcohol (PVA), sodium carboxymethylcellulose (CMC), hydroxypropylcellulose (HPC), hydroxyethylcellulose (HEC), polyethylene glycol, polypropylene glycol, trifluoromethanesulfonylimide, methyl methacrylate, polydimethylsiloxane, pectin, xanthan gum, alginic acid, and sodium alginate.

6. A method for manufacturing the paint according to claim 2, wherein NiO, Ni in a solvent ２ O ３ A method for producing paint, comprising a grinding and stirring step of grinding and stirring one or more nanoparticles selected from NiOOH to obtain a dispersion liquid.

7. A method for manufacturing paint according to claim 6, comprising an ultrasonic stirring step of ultrasonically stirring the dispersion after the grinding and stirring step.

8. A color-variable electrode comprising an electrode layer and a first electrochromic layer formed on the electrode layer, wherein the first electrochromic layer is a thin film formed by the paint of claim 2.

9. A black electrochromic element that reversibly changes color between black and transparent by an electrochemical oxidation-reduction reaction, comprising: a first electrochromic layer containing a first electrochromic material that exhibits a brownish hue in the oxidized state; and a second electrochromic layer containing a second electrochromic material that exhibits a bluish hue in the reduced state.

10. The black electrochromic element according to claim 9, wherein the first electrochromic material is the oxidation-colored electrochromic material of claim 1.

11. The black electrochromic element according to claim 9, wherein the second electrochromic material comprises nanoparticles of tungsten oxide or titanium oxide.

12. The black electrochromic element according to claim 9, wherein the first electrochromic layer is a thin film formed by the paint of claim 2.

13. An electrochromic element according to claim 9, wherein in a transparent state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, and the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more; and in a black state, the visible light transmittance is 10% or less, the solar transmittance is 10% or less, and the colorimetric value L* based on the CIE 1976 Lab* color system is 35 or less.

14. An electrochromic element that reversibly changes color between a transparent state and a colored state by an electrochemical oxidation-reduction reaction, comprising: a first electrochromic layer containing a first electrochromic material that exhibits a brownish hue in the oxidized state; and a second electrochromic layer containing a second electrochromic material that exhibits a blueish hue in the reduced state, wherein in the colored state, the electrochromic element satisfies the CIE 1976 Lab* colorimetric value L* ≤ 35, |a*| ≤ 10, and |b*| ≤ 15.

15. An electrochromic element according to claim 14, wherein in a transparent state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, and the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more, and in a colored state, the visible light transmittance is 10% or less and the solar transmittance is 10% or less.

16. An electrochromic element that reversibly changes color between a transparent state and a colored state by an electrochemical oxidation-reduction reaction, wherein in the transparent state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, and the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more; and in the colored state, the visible light transmittance is 10% or less, the solar transmittance is 10% or less, and the colorimetric value based on the CIE 1976 Lab* color system is L* ≤ 35, |a*| ≤ 10, and |b*| ≤ 15.

17. An electrochromic element according to claim 14 or claim 16, wherein the colorimetric value L* ≤ 25 in the colored state.

18. An electrochromic element that reversibly changes color between a minimum colored state and a maximum colored state by an electrochemical oxidation-reduction reaction, and which can be set to at least one intermediate tone located between the minimum colored state and the maximum colored state by applying a predetermined potential, and which maintains the set intermediate tone under conditions where the potential is cut off.

19. An electrochromic element according to claim 18, wherein in the minimum colored state, the visible light transmittance is 70% or more, the solar transmittance is 50% or more, and the colorimetric value L* based on the CIE 1976 Lab* color system is 85 or more, and in the maximum colored state, the visible light transmittance is 10% or less, the solar transmittance is 10% or less, and the colorimetric value L* based on the CIE 1976 Lab* color system is 35 or less.

20. An electrochromic element according to claim 18, which can be set to a plurality of intermediate gradations between the minimum coloring state and the maximum coloring state.

21. The electrochromic element according to claim 18, wherein the amount of change in the measured color value L* based on the CIE 1976 Lab* color system during holding after potential interruption is within 10 within a predetermined time.

22. A first electrochromic layer containing an oxidatively colored Ni-based material and tungsten oxide (WO ３ The electrochromic element according to claim 18, further comprising a second electrochromic layer containing ).

23. An electrochromic element according to claim 9 or 22, comprising an electrolyte layer between the first electrochromic layer and the second electrochromic layer, wherein the electrolyte layer contains one or more selected from bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, magnesium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hydroxide, lithium phosphate, lithium borate, lithium molybdate, and lithium hexafluorophosphate.

24. The electrochromic element according to claim 18, wherein, in the maximum colored state, the colorimetric value L* based on the CIE 1976 Lab* color system is ≤ 25.

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