WO2018230557A1

WO2018230557A1 - Electrochromic element and smart window

Info

Publication number: WO2018230557A1
Application number: PCT/JP2018/022395
Authority: WO
Inventors: 佐藤　英次; ひなつ大鐘; 伸之伊藤; 智彦中川; 知輝鴻池
Original assignee: シャープ株式会社
Priority date: 2017-06-16
Filing date: 2018-06-12
Publication date: 2018-12-20

Abstract

This electrochromic element is provided with: first and second transparent electrodes facing each other; and a nano-crystalline layer provided on a second transparent electrode-side surface of the first transparent electrode. The transmission spectrum of the electrochromic element changes according to the applied voltage. Changes in the transmission spectrum involve changes in the transmittance of near-infrared light and visible light. When the state of the electrochromic element is switched from a first state having a relatively low transmittance of the near-infrared light to a second state having a relatively high transmittance of the near-infrared light, the changes in the transmission spectrum include: a first change in which the color of the transmitted light becomes a warm color; or a second change in which the color of the transmitted light does not become a cold color.

Description

Electrochromic devices and smart windows

This disclosure relates to an electrochromic device and a smart window.

An electrochromic element whose optical properties reversibly change when a voltage is applied is known. As one of products using an electrochromic element, there is a smart window capable of electrically controlling light transmittance.

As a kind of smart window, a type capable of controlling the transmittance of infrared light (hereinafter sometimes referred to as “infrared type”) has been proposed.

Patent Documents

1 and 2 disclose electrochromic elements used in infrared type smart windows. Non-Patent Document 1 discloses various nanocrystals used as an electrochromic material.

US Patent No. 9341913 Special table 2014-518405 gazette

Even if an infrared type smart window is provided in the window to control the amount of infrared light entering the room, the effect is limited as described below.

If the amount of incident infrared light is controlled, the room temperature can be controlled to some extent, and air conditioning efficiency is improved. In addition, since the surface temperature of the person who is at the window, that is, the person who receives direct sunlight, can be controlled, the comfort at the window is improved. However, it is not possible to obtain an effect beyond that of roughly controlling the surface temperature and room temperature of a human subject to direct sunlight. In particular, it is difficult for a person away from the window to feel the effect when sufficient air conditioning is performed.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide an electrochromic device and a smart window that can further experience the effect of controlling the transmittance of infrared light.

An electrochromic device according to an embodiment of the present disclosure is provided on a surface of a first transparent electrode and a second transparent electrode facing each other, and a surface of the first transparent electrode on the second transparent electrode side, and includes a plurality of metal oxide nanoparticles. A nanocrystal layer including particles, and an electrolyte layer provided between the nanocrystal layer and the second transparent electrode, wherein a transmission spectrum of the electrochromic element is the first transparent electrode and the second transparent electrode. It changes according to the voltage applied between the electrodes, the change in the transmission spectrum is accompanied by a change in transmittance of light in the near infrared region and light in the visible region, the state of the electrochromic element, The change in the transmission spectrum when switching from the first state where the light transmittance in the near infrared region is relatively low to the second state where the light transmittance in the near infrared region is relatively high is as follows. ,in front A first change in which the color of the transmitted light transmitted through the electrochromic element is a warm color, or a second change in which the color of the transmitted light transmitted through the electrochromic element is not a cold color including.

In one embodiment, the change in the transmission spectrum when the state of the electrochromic element is switched from the first state to the second state is such that the color of transmitted light transmitted through the electrochromic element is a cold color system. A third change is made such that the color becomes a warm color.

In one embodiment, each of the first and second changes is a change in which at least one of a ^* and b ^* in the L ^* a ^* b ^* color system is increased.

In one embodiment, each of the first and second changes is a change in which both a ^* and b ^* are increased.

In certain embodiments, the first and the amount of change in the a ^* in each of the second variation .DELTA.a ^* is -0.01 or more, the b ^* of the variation [Delta] b ^* is 1.60 or more.

In certain embodiments, wherein each of the first and second change is the change of L ^* is increased in the L ^* a ^* b ^* color system.

In one embodiment, the change amount ΔL ^* of L ^* in each of the first and second changes is 1.90 or more.

In one embodiment, each of the first and second changes is defined by a change amount ΔL ^* , Δa ^*, and Δb ^* of L ^* , a ^*, and b ^{* in} the L ^* a ^* b ^* color system. This is a change in which the color difference ΔE is 2.15 or more.

In one embodiment, the color difference ΔE is 2.70 or more.

In one embodiment, the plurality of metal oxide nanoparticles are a plurality of antimony-doped tin oxide nanoparticles.

In one embodiment, an average particle diameter of the plurality of antimony-doped tin oxide nanoparticles is 20 nm or less.

In one embodiment, the average particle diameter of the plurality of antimony-doped tin oxide nanoparticles is 8 nm or less.

In one embodiment, the nanocrystal layer has a thickness of 3000 mm or more.

In one embodiment, the first transparent electrode, the second transparent electrode, and the nanocrystal layer are interposed between the first transparent electrode and the second transparent electrode to change a transmission spectrum of the electrochromic device. When a voltage is applied, no oxidation-reduction reaction occurs, and the electrochromic element does not include an electrode that causes a change in the transmission spectrum due to the oxidation-reduction reaction when a voltage is applied.

In one embodiment, the electrochromic device further includes a spacer provided between the nanocrystal layer and the second transparent electrode.

In one embodiment, the electrochromic device detects the first transparent electrode and the first transparent electrode when detecting that a current exceeding a predetermined threshold flows between the first transparent electrode and the second transparent electrode. Disconnect the connection between the first transparent electrode and the second transparent electrode so that no current flows between the two transparent electrodes, or connect the power source to the first transparent electrode and the second transparent electrode. An overcurrent protection circuit for switching to a circuit different from the circuit connecting the electrodes is further provided.

In one embodiment, the predetermined threshold value changes according to the energization time for the electrochromic element.

In one embodiment, the electrochromic element has a voltage between the first transparent electrode and the second transparent electrode when a charge amount charged in the electrochromic element exceeds a predetermined charge amount threshold. An overcurrent protection circuit is further provided that stops the application or lowers the absolute value of the applied voltage.

In one embodiment, the first transparent electrode is divided into a plurality of sub-electrodes.

In one embodiment, the second transparent electrode is divided into a plurality of sub-electrodes.

A smart window according to an embodiment of the present disclosure includes an electrochromic element having any one of the configurations described above.

According to the embodiment of the present disclosure, an electrochromic element and a smart window that can further experience the effect of controlling the transmittance of infrared light are provided.

1 is a cross-sectional view schematically showing an electrochromic device 100 according to an embodiment of the present disclosure. It is a chromaticity diagram of the L ^* a ^* b ^* color system. It is a graph which shows the comfort curve of Kruitoff. It is a graph which shows the example of the transmission spectrum in a 1st state and a 2nd state at the time of using ATO particle | grains whose average particle diameter is 20 nm or less as a metal oxide nanoparticle. It is a graph which shows the example of the transmission spectrum in a 1st state and a 2nd state at the time of using ITO particle | grains whose average particle diameter is 20 nm or less as a metal oxide nanoparticle. It is a graph which shows the transmission spectrum in case the average particle diameter of ATO nanoparticle is 20 nm, and the transmission spectrum in case the average particle diameter of ATO nanoparticle is 8 nm. 3 is a graph showing a transmission spectrum of Example 1. 6 is a graph showing a transmission spectrum of Example 2. 6 is a graph showing a transmission spectrum of Example 3. 10 is a graph showing a transmission spectrum of Example 4. 10 is a graph showing a transmission spectrum of Example 5. 6 is a graph showing a transmission spectrum of Comparative Example 1. 10 is a graph showing a transmission spectrum of Comparative Example 2. 3 is a graph showing a transmission spectrum of Example 1. 6 is a graph showing a transmission spectrum of Example 2. (A) And (b) is a figure which shows the example of the structure by which the 1st transparent electrode 1 was divided | segmented into the some sub electrode 1a. 2 is a cross-sectional view schematically showing an electrochromic device 100 including a spacer 7. FIG. It is a figure which shows the example of the other structure of the seal part. 1 is a cross-sectional view schematically showing an electrochromic element 100 including an overcurrent protection circuit 20.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the following embodiment.

[Overall structure of electrochromic element]
With reference to FIG. 1, an electrochromic device 100 according to this embodiment will be described. FIG. 1 is a cross-sectional view schematically showing an electrochromic device 100.

The electrochromic element 100 includes a first transparent electrode 1 and a second transparent electrode 2, a nanocrystal layer 3, and an electrolyte layer 4, as shown in FIG.

The first transparent electrode 1 and the second transparent electrode 2 are arranged so as to face each other. The first transparent electrode 1 and the second transparent electrode 2 are each transparent and substantially colorless. The first transparent electrode 1 and the second transparent electrode 2 are electrically connected to a power source 5. The first transparent electrode 1 is supported on the first substrate 11. The second transparent electrode 2 is supported on the second substrate 12. The first substrate 11 and the second substrate 12 are each transparent and substantially colorless.

The nanocrystal layer 3 is provided on the surface of the first transparent electrode 1 on the second transparent electrode 2 side. The nanocrystal layer 3 includes a plurality of metal oxide nanoparticles. The metal oxide nanoparticles are particulate crystals (nanocrystals) having a particle size of several nm to several tens of nm.

The electrolyte layer 4 is provided between the nanocrystal layer 3 and the second transparent electrode 2. The electrolyte layer 4 is surrounded by the seal portion 6.

The metal oxide nanoparticles contained in the nanocrystal layer 3 are electrochromic materials. Therefore, the transmission spectrum of the electrochromic device 100 including the nanocrystal layer 3 changes according to the voltage applied between the first transparent electrode 1 and the second transparent electrode 2. This change in the transmission spectrum is accompanied by a change in light transmittance in the near infrared region. Therefore, the electrochromic element 100 of this embodiment can control the transmittance of near infrared light. In the specification of the present application, the near-infrared region refers to a wavelength range of about 800 nm or more and about 2500 nm or less. Since most of the infrared light radiated from the sun is near-infrared light, the acquisition rate of solar heat from sunlight can be controlled by controlling the transmittance of the near-infrared light. For example, near-infrared light can be prevented from entering the room in summer, and near-infrared light can be taken into the room in winter. The principle that the nanocrystal layer 3 exhibits electrochromism will be described later.

Here, the transmission of the electrochromic element 100 is switched from a state in which the light transmittance in the near infrared region is relatively low to a state in which the light transmittance in the near infrared region is relatively high. Focus on spectral changes. Hereinafter, the former state is referred to as a “first state”, and the latter state (that is, a state where light transmittance in the near infrared region is higher than the first state) is referred to as a “second state”. In this embodiment, the change in the transmission spectrum at this time is accompanied by not only the change in the transmittance of light in the near infrared region but also the change in the transmittance of light in the visible region. The change in the transmission spectrum at this time is the “first change” in which the color of the transmitted light (transmitted light transmitted through the electrochromic element 100) becomes a warm color, or the color of the transmitted light is cold. It includes a “second change” that is no longer a system color. Further, the change in the transmission spectrum at this time may include a “third change” in which the color of the transmitted light changes from a cold color to a warm color. Hereinafter, these “first change”, “second change”, and “third change” may be collectively referred to as “warm color change”. The visible region is generally a range where the wavelength is about 400 nm or more and less than about 800 nm.

Hereinafter, an effect obtained when the transmission spectrum change at the time of switching from the first state to the second state includes the above-described warm color system change will be described.

寒 A warm feeling is known as a universal effect of color. Cold colors make you feel cool, and warm colors make you feel warm. Therefore, by changing the color of visible light in conjunction with the control of the transmittance of near-infrared light, it is possible to feel warmth and coolness with a visual effect. For example, switching from the first state to the second state described above increases the transmittance of near-infrared light, that is, causes more near-infrared light to enter, and is a person who receives room temperature or direct sunlight. This is an operation to increase the surface temperature of the body. Therefore, if the change in the transmission spectrum at the time of switching includes the warm color change described above, that is, if the transmittance change in the visible region is the warm color change described above, the warmth due to the visual effect is felt. Can do. In addition, this effect can be experienced not only by a person at the window but also by a person away from the window. Therefore, indoor comfort can be further improved.

In addition, when a change from the first state to the second state occurs, a warm color change occurs. In other words, when switching from the second state to the first state, This means that a change opposite to the warm color change occurs. That is, the transmission spectrum change in the visible region when switching from the second state to the first state is a “fourth change” in which the color of the transmitted light becomes a cold color, and the color of the transmitted light is A “fifth change” that does not result in a warm color, or a “sixth change” that changes the color of transmitted light from a warm color to a cold color. Hereinafter, these “fourth change”, “fifth change”, and “sixth change” may be collectively referred to as “cold color system change”.

Switching from the second state to the first state lowers the near-infrared light transmittance, that is, blocks more of the near-infrared light, and reduces the surface temperature of a person receiving room temperature or direct sunlight. This is an operation for lowering. Therefore, when the change in transmittance in the visible region at the time of switching is the above-described cold color change, it is possible to feel coolness due to the visual effect.

As described above, the electrochromic device 100 according to the present embodiment allows the user to feel warmth and coolness by using the visual effect of color in addition to the room temperature / surface body temperature control by controlling the transmittance of near infrared light. It is possible to improve indoor comfort. Therefore, the effect by controlling the transmittance of infrared light can be further experienced.

[Preferred chromaticity / lightness change]
The warm color is a color that gives a warm impression from the sight. Cold color is a color that gives a cold impression from the sight. In general, warm colors correspond to R (red), YR (yellow red) and Y (yellow) in the Munsell hue ring, and cold colors correspond to BG (blue green) and B (blue) in the Munsell hue ring. ) And PB (purple blue).

FIG. 2 shows a chromaticity diagram of the L ^* a ^* b ^* color system. In the L ^* a ^* b ^* color system, L ^* indicates lightness, and a ^* and b ^* indicate chromaticity. As can be seen from FIG. 2, the warm color system changes (first change, second change and third change) approximately correspond to an increase in a ^* and / or b ^* . Therefore, it can be said that the warm color system change is a change in which at least one of a ^* and b ^* in the L ^* a ^* b ^* color system increases. Warm change may be a change in only one of a ^* and b ^* is increased, it may be a change in both a ^* and b ^* increases. As will be described later in detail, in the warm color change, the change amount Δa ^* of a ^* is preferably −0.01 or more, and the change amount Δb ^* of b ^* is preferably 1.60 or more. Incidentally, a ^* variation .DELTA.a ^* is preferably 120 or less, b ^* is the amount of change [Delta] b ^*, it is preferably 120 or less. Further, as can be seen from FIG. 2, the cold color system changes (fourth change, fifth change and sixth change) approximately correspond to a decrease in a ^* and / or b ^* .

A change in brightness may occur when switching from the first state to the second state or when switching from the second state to the first state. FIG. 3 is a graph showing the range of comfortable illuminance for each color temperature with the color temperature on the horizontal axis and the illuminance on the vertical axis, and is called a “Kruitoff comfort curve”. In the upper left area in FIG. 3, the light feels hot and in the lower right area, the light feels gloomy. On the other hand, light is comfortable in the area between these. For example, if the illuminance is high at a certain color temperature and feels uncomfortable, it can be made comfortable by reducing the illuminance. Therefore, for example, when switching from the second state to the first state in summer, comfort can be improved by reducing the illuminance (brightness). In addition, lowering the transmittance in the visible region in summer means that the solar heat is shielded accordingly, and the air conditioning efficiency is improved.

Change of brightness in the L ^* a ^* b ^* color system, corresponding to a change in L ^*. Therefore, it can be said that the warm color system change is preferably a change in which L ^* in the L ^* a ^* b ^* color system increases. Moreover, it can be said that the cold color system change is preferably a change in which L ^* in the L ^* a ^* b ^* color system decreases. The change amount ΔL ^* of L ^* in the warm color system change is preferably 1.90 or more, as will be described in detail later.

Further, the degree of color change at the time of switching from the first state to the second state can also be expressed by a color difference ΔE in the L ^* a ^* b ^* color system. The color difference ΔE is defined by the change amounts ΔL ^* , Δa ^*, and Δb ^* of L ^* , a ^*, and b ^* as in the following equation.
ΔE = (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ) ^1/2

As described in detail later, the warm color system change is preferably a change in which the color difference ΔE is 2.15 or more and 130 or less, and more preferably a change in which the color difference ΔE is 2.70 or more and 78 or less.

[Preferred examples of metal oxide nanoparticles]
As the metal oxide nanoparticles, for example, antimony-doped tin oxide (ATO) nanoparticles can be suitably used. In FIG. 4, the example of the transmission spectrum in a 1st state and a 2nd state at the time of using ATO particle | grains whose average particle diameter is 20 nm or less as a metal oxide nanoparticle is shown. In the example shown in FIG. 4, in the first state, a negative voltage is applied to the first transparent electrode 1 with reference to the potential of the second transparent electrode 2, and in the second state, the second transparent electrode A positive voltage is applied to the first transparent electrode 1 with reference to the potential of the electrode 2. As shown in FIG. 4, the transmission spectrum in the first state and the transmission spectrum in the second state are different in the near-infrared region. The transmittance in the near infrared region in the second state is higher than the transmittance in the near infrared region in the first state. Also, as shown in FIG. 4, the transmission spectrum in the first state and the transmission spectrum in the second state are different in the visible region. In the first state, the transmittance in the visible region is relatively low, and the transmittance is almost the same in the entire visible region. On the other hand, in the second state, the transmittance in the visible region is relatively high, and in particular, the transmittance on the long wavelength side is high.

For comparison, FIG. 5 shows an example of transmission spectra in the first state and the second state when tin-doped indium oxide (ITO) nanoparticles having an average particle diameter of 20 nm or less are used as metal oxide nanoparticles. Show. As shown in FIG. 5, the transmission spectrum in the first state and the transmission spectrum in the second state are different in the near-infrared region. However, the transmission spectrum in the first state and the transmission spectrum in the second state are almost the same in the visible region. Therefore, in the example shown in FIG. 5, even if the first state and the second state are switched, the color change hardly occurs.

The average particle size of ATO nanoparticles is preferably 1 nm or more and 20 nm or less, and more preferably 8 nm or less. FIG. 6 shows a transmission spectrum when the nanocrystal layer 3 including ATO nanoparticles having an average particle diameter of 20 nm is formed with a thickness of about 1 μm, and the thickness of the nanocrystal layer 3 including ATO nanoparticles having an average particle diameter of 8 nm. The transmission spectrum when formed at a thickness of about 1 μm is shown.

FIG. 6 shows that when the average particle diameter is 8 μm, the change in the transmission spectrum when switching from the first state to the second state is larger than when the average particle diameter is 20 μm. In particular, the change in the transmission spectrum in the near infrared region is remarkable. Further, when the average particle size is 8 μm, the transmittance in the visible region is higher than when the average particle size is 20 μm.

[Principle of operation of nanocrystal layer]
Here, the principle that the nanocrystal layer 3 exhibits electrochromism will be described.

As described in Non-Patent Document 1, by injecting electrons into a transparent conductive oxide (TCO) nanostructure such as an ITO (Tin-doped Indium-Oxide) nanocrystal layer, near-infrared It is known that the transmission spectrum of a region can be changed. In short, the principle is to shift the absorption wavelength by localized surface plasmon resonance (LSPR) of the TCO nanostructure by applying a voltage. This will be described in more detail below.

The resonance frequency of LSPR is proportional to the plasma frequency ωp. The plasma frequency ωp is expressed by the following formula.
ω _p ² = N · e ² / (m · ε ₀ )

Here, N is the electron density, e is the charge of the electron, m is the effective mass of the electron, and ε0 is the dielectric constant of the vacuum. Accordingly, when a negative voltage is applied to the TCO nanostructure to increase the electron density, the plasma frequency ωp increases, and the resonance frequency of the LSPR also increases. Therefore, the resonance wavelength of LSPR becomes short (that is, shifts to the short wavelength side). By adjusting the carrier density of the TCO nanostructure, the resonance wavelength of the LSPR can be set in the near infrared region, so that the transmission spectrum in the near infrared region can be changed.

Note that the function of changing the transmission spectrum in this way is not unique to the ITO nanocrystal layer containing ITO nanoparticles. In principle, the above-described functions can be achieved if the nanoparticles are sized so as to cause LSPR (for example, 100 nm or less), and the nanocrystal layer can inject electrons from the transparent electrode. . As nanoparticles, nanoparticles of various metal oxides such as ATO, PTO (phosphorus-doped tin oxide), AZO (aluminum-doped zinc oxide), GZO (gallium-doped zinc oxide) can be used.

[Example 1]
A prototype example (Example 1) of the electrochromic element 100 was manufactured as follows, and the optical characteristics thereof were verified.

First, glass substrates were prepared as the first substrate 11 and the second substrate 12, respectively. Next, titanium-doped indium oxide (Titanium-doped Indium Oxide: InTiO), which becomes transparent in the near infrared region, was deposited on the first substrate 11 by sputtering to form the first transparent electrode 1. Similarly, the second transparent electrode 2 was formed on the second substrate 12.

Subsequently, a dispersion of ATO nanoparticles is applied on the first transparent electrode 1 by spin coating, dried on a hot plate at 140 ° C. for 1 minute, and then fired at 200 ° C. for 60 minutes, A nanocrystal layer 3 was formed. The ATO nanoparticle dispersion used is commercially available for the formation of an antistatic film (manufactured by Dainippon Paint Co., Ltd.). The particle size of the ATO nanoparticles is 8-30 nm, and the dispersion medium is methyl isobutyl ketone and isoform. It is a mixed solution with butanol.

Thereafter, a UV curable resin material containing 2 wt% of a resin spacer having a particle size of 10 μm is applied on the outer periphery of the nanocrystal layer 3 or the second transparent electrode 2 so that the injection port partially exists. Subsequently, both the substrates were overlapped and irradiated with ultraviolet rays to form the seal portion 6. Next, an EC (Ethylene carbonate) / DEC (Diethyl Carbonate) mixed solution (EC: DEC = 1: 2) containing 1 mol / L LiBF ₄ is injected from the injection port as an electrolytic solution, and then UV curable resin is used. The electrolyte layer 4 was formed by sealing with a material.

Thus, the electrochromic element 100 of Example 1 was obtained. FIG. 7 shows a transmission spectrum when the potential of the second transparent electrode 2 is 0 V and DC voltages of −3 V and +3 V are applied to the first transparent electrode 1. From FIG. 7, it can be seen that the transmission spectrum in the near-infrared region changes greatly according to the switching of the polarity of the applied voltage. Further, it can be seen that when the transmittance in the near infrared region is low, the transmittance in the visible region is relatively low, and the transmittance is almost the same in the entire visible region. Furthermore, it can be seen that in the state where the transmittance in the near infrared region is high, the transmittance in the visible region is relatively high, and in particular, the transmittance on the long wavelength side is high.

Therefore, when the electrochromic element 100 of Example 1 is installed in a window and the near infrared light transmittance is high in winter, the color of the transmitted light is slightly warm. Thereby, in addition to the effect which takes in the solar heat of sunlight, the effect which a warm color color gives can be acquired. On the other hand, when the transmittance of near-infrared light is low, the visible region has a low transmittance as a whole, and the warm color is lost from the transmitted light. Thereby, in addition to the effect which shields the solar heat of sunlight, the feeling of being hot can be improved.

When L ^* , a ^*, and b ^* were measured in the −3 V application state, L ^* = 83.28, a ^* = 0.01, and b ^* = 0.16. In contrast, in the + 3V applied ^{^{state, L * = 88.48, a *}} = 0.62, was b ^* = 2.12. Therefore, when the change amount of L ^* at the time of switching from the -3V application state to the + 3V application state is ΔL ^* , the change amount of a ^* is Δa ^* , and the change amount of b ^* is Δb ^* , ΔL ^* = 5. 20, Δa ^* = 0.61, and Δb ^* = 1.96.

As already explained, the warm color system change approximately corresponds to an increase in a ^* and / or b ^* . In this embodiment, L ^* also increases when switching from the -3V applied state to the + 3V applied state (when switching so that the transmittance of near-infrared light is increased), so that comfort is further improved. I can say that.

[Examples 2 to 5, Comparative Examples 1 and 2]
As a method for producing the metal oxide nanoparticles themselves, there are a method by pulverization, a method by fine particle growth in a liquid phase or a gas phase, and the like. In addition, when the metal oxide nanoparticles are dispersed in the dispersion medium, there are various options such as the type of surfactant, the type of the dispersion medium, and the method of applying energy when dispersed. Therefore, it can be said that the dispersion of metal oxide nanoparticles can be obtained by various methods.

The electrochromic device 100 of Examples 2 to 5 and the electrochromic device of Comparative Example 1 were prepared using an ATO nanoparticle dispersion obtained by a method different from that of Example 1. Moreover, the electrochromic element of the comparative example 2 was produced using the ITO nanoparticle dispersion liquid. In Example 3, ATO nanoparticles for forming a heat-absorbing film manufactured by Dainippon Paint Co., Ltd., in Example 4, ELCOM and ATO manufactured by JGC Catalysts & Chemicals Co., Ltd., and in Comparative Example 1 manufactured by Mitsubishi Materials Corporation. ATO dispersion was used. Further, Comparative Example 2 using the ITO nanoparticle dispersion was the same as Example 1 except that the dispersion medium was toluene and baking after drying on a hot plate was performed at 200 ° C. for 120 minutes. Made.

FIGS. 8 to 13 show the transmission of Examples 2 to 5 and Comparative Examples 1 and 2 when the potential of the second transparent electrode 2 is 0 V and the DC voltage of −3 V and +3 V is applied to the first transparent electrode 1. The spectrum is shown.

From FIG. 8, in the second embodiment, as in the first embodiment, as the applied voltage is switched from −3V to + 3V, the colorless dark state changes to the warm color bright state (that is, “first” Change "occurs). Further, from FIGS. 9 and 10, in Examples 3 and 4, the change from the dark-colored dark state to the colorless and bright state (that is, the “second change” occurs) in accordance with the switching of the applied voltage. Recognize. Further, it can be seen from FIG. 11 that in Example 5, the cold color system changes from the dark color system to the warm color system (that is, a “third change” occurs) as the applied voltage is switched.

In addition, it can be seen from FIG. 12 that in Comparative Example 1, even when the applied voltage is switched, the change in transmittance is small over the entire near-infrared region and visible region. Furthermore, it can be seen from FIG. 13 that in Comparative Example 2, the transmittance in the near-infrared region changes with switching of the applied voltage, but the transmittance in the visible region hardly changes.

Table 1 shows ΔL ^* , Δa ^* , Δb ^*, and ΔE ^* when the applied voltage is switched from −3 V to +3 V for Examples 1 to 5 and Comparative Examples 1 and 2.

From Table 1, it can be seen that in Examples 1 to 5, b ^* increases by 1.60 or more as the applied voltage is switched. In Examples 1 to 5, it can be seen that a ^* hardly changes or increases by 0.50 or more as the applied voltage is switched. On the other hand, in Comparative Examples 1 and 2, there is little change in a ^* and b ^* . Table 1 also shows that in Examples 1 to 5, L ^* increases by 1.90 or more as the applied voltage is switched. On the other hand, in Comparative Examples 1 and 2, there is little change in L ^* .

From the results shown in Table 1, it can be said that Δa ^* is preferably −0.01 or more and Δb ^* is preferably 1.60 or more in the warm color change. Note that Δa ^* in the warm color change is more preferably 0.50 or more. Further, ΔL ^* in the warm color system change is preferably 1.90 or more. Further, the warm color system change is preferably a change in which the color difference ΔE is 2.15 or more, and more preferably a change in which the color difference ΔE is 2.70 or more.

Table 1 also shows the thickness of the nanocrystal layer. The thickness of the nanocrystal layer was obtained by scraping a part of the layer after forming the nanocrystal layer and measuring the level difference of the part with a step meter. In Examples 1 to 5, in which a large change is observed in L ^* , a ^*, and b ^* when the applied voltage is switched, the thickness of the nanocrystal layer is 9000 mm or more. In contrast, in Comparative Example 1 in which the change in L ^* , a ^*, and b ^* is small when the applied voltage is switched, although the same ATO nanoparticles as in Examples 1 to 5 are used, the thickness of the nanocrystal layer The height was 2410cm. Therefore, from the viewpoint of greatly changing L ^* , a ^* , and b ^* , the thickness of the nanocrystal layer is preferably 3000 mm or more, and more preferably 9000 mm or more. Further, the thickness of the nanocrystal layer is preferably 40000 mm or less, and more preferably 20000 mm or less.

In the description so far, the state where the voltage of −3 V is applied to the first transparent electrode 1 is the first state, and the state where the voltage of +3 V is applied is the second state. However, switching between the first state and the second state does not necessarily involve switching the polarity of the applied voltage. The first state and the second state may be switched by changing the magnitude of the applied voltage while maintaining the same polarity.

FIG. 14 shows a transmission spectrum of Example 1 in a state where voltages of −3V, −2V, −1V, 0V, + 1V, + 2V, and + 3V are applied to the first transparent electrode 1. FIG. 15 shows the transmission spectrum of Example 2 when the first transparent electrode 1 is applied with voltages of −3V, −2V, 0V, + 2V, and + 3V. As can be seen from FIGS. 14 and 15, there are cases where the transmittance in the near-infrared region and the visible region can be greatly changed even when the magnitude of the applied voltage is changed with the same polarity. For example, in the first embodiment, the + 1V application state may be the first state, and the + 3V application state may be the second state.

Subsequently, specific examples and preferred configurations of each component of the electrochromic element 100 will be described.

[Nanocrystalline layer]
When the metal oxide nanoparticles contained in the nanocrystal layer 3 are ATO nanoparticles, as described above, the average particle diameter of the ATO nanoparticles is preferably 20 nm or less, and more preferably 8 nm or less. .

The metal oxide used as the material for the metal oxide nanoparticles is not limited to ATO. For example, a material that absorbs light in the visible region, such as a composite tungsten oxide represented by CsxWyO ₃ (where x and y indicate composition ratios) and lanthanum hexaboride, can be used. AZO (Aluminum-doped Zinc Oxide) and GZO (Gallium-doped Zinc Oxide) are almost transparent materials in the visible region, but the composition ratio and thickness are set. Depending on the case, absorption in the visible region is observed when a voltage is applied, and these can also be used.

The method for forming the nanocrystal layer 3 is not particularly limited. The nanocrystal layer 3 can be formed by applying a liquid or semi-solid in which metal oxide nanoparticles are dispersed on the first substrate 11 and performing baking. The dispersion of metal oxide nanoparticles may be applied by a spin coating method, or may be applied by a printing method using a paste to which a vehicle is appropriately added. Further, the coating may be performed by a bar coating method, a slit coating method, a gravure coating method or a die coating method. If the firing temperature is such that organic components on the nanocrystal surface are removed and sintering is suitably performed, sufficient solvent resistance can be obtained. However, if the firing temperature is too high and the sintering proceeds excessively, there is a possibility that an LSPR having a desired wavelength cannot be obtained. When coating is performed by a spin coating method using a dispersion of ATO nanoparticles, for example, baking may be performed at a temperature of 200 ° C. to 300 ° C. for 30 minutes.

[substrate]
As the first substrate 11 and the second substrate 12, for example, glass substrates can be used. Moreover, the plastic substrate formed from resin materials, such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), and a polyimide, may be sufficient. These illustrated substrates may be provided with a gas barrier layer formed from an inorganic material or an organic material. In the case where a glass substrate is used, it may be thinned by etching after the two substrates are bonded together.

[Transparent electrode]
As the material of the first transparent electrode 1 and the second transparent electrode 2, in addition to InTiO, a material that transmits near-infrared light such as tantalum-substituted tin oxide using anatase-type titanium dioxide as a seed layer or ITO with adjusted carrier density Can be used. The first transparent electrode 1 and the second transparent electrode 2 can be formed by depositing these materials on the first substrate 1 and the second substrate 2 by sputtering, vapor deposition, coating, or the like.

Moreover, it is preferable that the material of the first transparent electrode 1 and the second transparent electrode 2 has a characteristic of reflecting far-infrared light. In order to keep the room temperature high in winter, it is necessary to prevent infrared light from being emitted from the room to the outdoors. Infrared light radiated from the room is classified as far-infrared light having a wavelength of about 10 μm. Therefore, if the first transparent electrode 1 and the second transparent electrode 2 have the characteristic of reflecting far-infrared light, the state of the nanocrystal layer 3 is controlled so that the transmittance of near-infrared light is increased. However, the indoor heat does not escape to the outdoors as radiant heat, and an ideal state can be realized. Further, even when control is performed so that the transmittance of near-infrared light is lowered in summer, it is possible to prevent the far-infrared light from the outside from entering the room, so that an ideal state can be realized.

When the electrochromic element 100 is not intended for display, the electrode extraction (connection to the external wiring) of the first transparent electrode 1 may be performed at one place or at a plurality of places. . In the case of one place, the assembly process of the electrochromic element 100 can be simplified and the routing of the wiring can be simplified. In the case of a plurality of locations, a partial response speed delay can be prevented even when there is a resistance component between the first transparent electrode 1 and the second transparent electrode 2, that is, when a current flows.

The first transparent electrode 1 may be divided into a plurality of electrically independent sub-electrodes. When the first transparent electrode 1 is divided into a plurality of sub-electrodes, the transmission spectrum can be changed for each region corresponding to the sub-electrodes. FIGS. 16A and 16B show examples of a configuration in which the first transparent electrode 1 is divided into a plurality of sub-electrodes 1a.

In the example shown in FIG. 16 (a), the electrode lead-out portions EP are gathered in one place by routing the plurality of sub-electrodes 1a. An unnecessary voltage drop can be prevented by disposing the lead-out portion of the sub-electrode 1a away from the operation portion of the electrochromic element 100 such as the outside of the seal portion 6 or under the seal portion 6.

In the example shown in FIG. 16B, the plurality of sub-electrodes 1a are directly connected to the wiring without being routed. That is, the electrode extraction part EP is dispersed in a plurality of places.

As with the first transparent electrode 1, the second transparent electrode 2 may be divided into a plurality of electrically independent sub-electrodes or may not be divided.

[Electrolyte layer]
The electrolyte layer 4 is made of, for example, an electrolytic solution. As the electrolyte of the electrolytic solution, a material that is easily ionized such as lithium hexafluorophosphate (LiPF ₆ ), sodium hexafluorophosphate (NaPF ₆ ), lithium borofluoride (LiBF ₄ ), or the like can be used. As the solvent for the electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), a mixture of EC and DC, propylene carbonate, or the like can be used. Moreover, you may use the gel which melt | dissolved polyvinyl butyral etc. in these. Further, for example, an ionic liquid composed of a cyclic quaternary ammonium cation and an imide anion may be used.

The electrolyte layer 4 may be composed of a solid electrolyte. For example, a solid electrolyte such as polyethylene oxide containing a lithium salt may be used, or a plastic crystal may be used.

[Spacer]
When the electrolyte layer 4 is made of a low-viscosity material such as an electrolytic solution, the electrochromic element 100 defines the distance (cell thickness) between the first substrate 11 and the second substrate 12 as shown in FIG. It is preferable to provide a spacer 7 for the purpose. In the configuration illustrated in FIG. 17, the spacer 7 is provided between the nanocrystal layer 3 and the second transparent electrode 2. The spacer 7 can be formed by a photolithography process using a photosensitive resin material. The spacer 7 is, for example, 10 μm square and 10 μm high. The formation method of the spacer 7 is not limited to the photolithography process, but may be a screen printing method, for example.

The spacer 7 is preferably formed on the second substrate 12 side (on the second transparent electrode 2). When the spacer 7 is provided on the first substrate 11 side, if the spacer 7 is formed before the nanocrystal layer 3 is formed, the thickness of the nanocrystal layer 3 may be uneven due to the influence of the spacer 7, or the spacer 7 may be There is a possibility that leakage with the second transparent electrode 2 occurs due to the covering of 3. Moreover, when the spacer 7 is formed on the nanocrystal layer 3, the residue of the photolithographic process remains on the nanocrystal layer 3, and there is a possibility that the change in the transmission spectrum is hindered.

When the electrolyte layer 4 is composed of a solid electrolyte, it is not necessary to provide the spacer 7 if the solid electrolyte has an appropriate elasticity.

[Seal part]
As a material of the seal portion 6, for example, a UV curable resin material can be used.

FIG. 18 shows an example of another configuration of the seal portion 6. In the example shown in FIG. 18, the seal portion 6 has two

regions

6 a and 6 b formed from different materials (seal materials). Hereinafter, the region 6a positioned relatively inside is referred to as an “inside region”, and the region 6b positioned relatively outside is referred to as an “outside region”.

The inner region 6a is formed of a sealing material having higher solvent resistance than the sealing material forming the outer region 6b. On the other hand, the outer region 6b is formed of a sealing material having a stronger adhesive force than the sealing material forming the inner region 6a.

As described above, the inner region 6a that is in contact with the electrolyte layer 4 (electrolyte) is formed of a sealing material having high solvent resistance, and the outer region 6b is formed of a sealing material having a strong adhesive force. High reliability and strong adhesion can be achieved at the same time.

[Production method]
When manufacturing the electrochromic element 100, various methods and processes used for manufacturing a liquid crystal panel, a dye-sensitized solar cell, and the like can be used. When a plastic substrate (resin substrate) is used as the first substrate 11 and the second substrate 12, the bonding process can be continuously performed by a roll-to-roll method, so that the manufacturing cost can be reduced. It is. Further, the reliability of the electrochromic device 100 can be improved by performing a series of steps in a deoxygenated dry atmosphere.

[Effect of the configuration not including the counter electrode]
As a conventional electrochromic element, a configuration including a counter electrode containing a metal oxide is known (for example, FIG. 2 of Non-Patent Document 1). In this configuration, when the optical properties are changed by voltage application, the redox reaction of the counter electrode is performed electrochemically. This is because sufficient charges are taken in and out based on the oxidation-reduction reaction in order to transition the TCO nanostructure to the colored state. However, in the oxidation reaction and reduction reaction at the counter electrode, if an impurity such as oxygen is present, a side reaction different from the original purpose occurs. It is known that electrochromic by LSPR does not show a clear electrochemical reaction, but due to the presence of the side reaction described above, the configuration including the counter electrode has poor repeatability with respect to changes in optical properties. There's a problem.

In the configuration illustrated in FIG. 1, the electrochromic element 100 does not include a counter electrode on the second transparent electrode 2. The first transparent electrode 1, the second transparent electrode 2, and the nanocrystal layer 3 apply a voltage between the first transparent electrode 1 and the second transparent electrode 2 in order to change the transmission spectrum of the nanocrystal layer 3. Then, the redox reaction does not occur, and the electrochromic device 100 does not include an electrode in which the transmission spectrum changes due to the redox reaction when a voltage is applied.

As already explained, LSPR does not show a clear electrochemical reaction. Therefore, the electrochromic device 100 that does not include a counter electrode made of a substance that causes an oxidation-reduction reaction can avoid deterioration in repetitive characteristics due to a side reaction of the oxidation-reduction reaction. In the electrochromic element 100, the wavelength of plasmon absorption in the near infrared region can be changed by the charge movement on the first transparent electrode 1 and the second transparent electrode 2 that occurs when a voltage is applied.

The electrochromic element 100 may further include an overcurrent protection circuit 20 as shown in FIG. When the overcurrent protection circuit 20 detects that a current exceeding a predetermined threshold value flows between the first transparent electrode 1 and the second transparent electrode 2, the overcurrent protection circuit 20 prevents the current from flowing between the electrodes. The connection is cut off or the connection destination of the power source 5 is switched to a circuit different from the circuit connecting the electrodes. The overcurrent protection circuit 20 can suppress reactions other than electrochromic due to LSPR (for example, side reactions including oxidation-reduction reactions).

Even if each member constituting the electrochromic element 100 does not perform the oxidation-reduction reaction within the voltage range applied by the power supply 5, impurities generated by the manufacturing and / or transmission spectrum switching, etc. As a result, side reactions including redox reactions may occur. Even in such a case, the side reaction can be prevented by preventing the current from flowing through the electrochromic device 100 when the current flowing through the circuit exceeds a predetermined threshold due to the current generated by the side reaction in the overcurrent protection circuit 20. It is possible to suppress the deterioration of the element. If a short circuit occurs due to physical damage or the like, the overcurrent protection circuit 20 can prevent abnormalities such as heat generation.

The predetermined threshold for the current detected by the overcurrent protection circuit 20 does not always need to be a constant value. For example, the predetermined threshold value may change according to the energization time for the electrochromic element 100. Here, let us consider the elapsed time t from when the application of voltage to the electrochromic element is started or when the polarity of the applied voltage is reversed. At this time, when the electrochromic element 100 in which the first transparent electrode 1 and the second transparent electrode 2 face each other is regarded as a capacitor, a large current flows when the electrochromic element is charged. For the charging period tc, for example, the current at tc = 5 s is Ia. At this time, for example, when the area of the electrodes (the first transparent electrode 1 and the second transparent electrode 2) is 1 m2, the overcurrent protection circuit 20 performs current control so that Ia = 1A is not exceeded, thereby causing a short circuit. Sometimes abnormalities such as heat generation can be prevented. Furthermore, in the period exceeding tc, charging of the electrochromic element 100 is completed, so that a large current Ia during charging does not flow. Therefore, the overcurrent protection circuit 20 controls the current so that the current Ib smaller than Ia (for example, Ib = 100 mA) is not exceeded, so that the oxidation-reduction reaction of the substance between the electrodes can be suppressed. Current control includes, for example, a constant current circuit whose set value is Ia and a constant current circuit whose set value is Ib, and selects either of these two constant current circuits by a switch having a timer function. It may be realized by. However, since tc, Ia, and Ib depend on the interelectrode distance and the electrode area, respectively, a predetermined threshold (Ia and Ib) may be set according to the interelectrode distance and the electrode area. As described above, the overcurrent protection circuit 20 may set the current threshold as the first threshold during a predetermined period from the start of charging, and set the current threshold as the second threshold smaller than the first threshold after the predetermined period has elapsed. The current control by the overcurrent protection circuit 20 may be performed by limiting the current, or by controlling the absolute value of the applied voltage to be small.

The overcurrent protection circuit 20 flows between the first transparent electrode 1 and the second transparent electrode 2 in consideration of other elements of the current as long as the side reaction can be suppressed and deterioration of the element can be prevented. The structure which controls an electric current may be sufficient. For example, the integrated value of the current from when the voltage is applied or when the polarity of the applied voltage is reversed, that is, the charge amount may be reflected in the control. The product CV of the predetermined voltage V applied between the electrodes and the capacitance C formed between the two electrodes is the amount of charge charged in each electrode. The charge amount CV or a value obtained by multiplying the charge amount CV by a coefficient (preferably 1 or more) may be used as the charge amount threshold value. The overcurrent protection circuit 20 specifies the amount of charge charged in the electrode from the applied current and the elapsed time t. When the charged charge amount exceeds the charge amount threshold value, the overcurrent protection circuit 20 stops applying the voltage between the electrodes (disconnects the connection between the electrode and the power supply 5) or applies The absolute value of the voltage may be reduced. Thereby, it can suppress that the oxidation-reduction reaction of the substance between the electrodes of the electrochromic element 100 occurs. For example, when the above-described coefficient is 1.5, the overcurrent protection circuit 20 can limit the applied voltage after a sufficient charge is charged between the electrodes after polarity inversion.

[Smart Window]
The electrochromic device 100 in the embodiment of the present disclosure is suitably used for a smart window.

The electrochromic element 100 itself may be a smart window, or a laminated structure in which the electrochromic element 100 is bonded to a plate glass may function as a smart window.

Moreover, one of the plurality of plate glasses constituting the multilayer glass may be replaced with the electrochromic element 100. For example, an electrochromic element 100 may be substituted for a central plate glass among three plate glasses constituting a double glass having a triple glass structure. However, in that case, six interfaces between a solid such as glass and a gas such as air are formed. At these interfaces, since interface reflection occurs, the transmittance of light including visible light is lowered. Therefore, an antireflection film such as an AR (Anti-Reflective) film, an LR (Low-Reflective) film, or a moth-eye film is preferably provided on these interfaces (including both surfaces of the electrochromic element 100).

DESCRIPTION OF SYMBOLS 1 1st transparent electrode 1a Sub electrode 2 2nd transparent electrode 3 Nanocrystal layer 4 Electrolyte layer 5 Power supply 6 Seal part 6a Inner area | region 6b Outer area | region 7 Spacer 11 1st board | substrate 12 2nd board | substrate 20 Overcurrent protection circuit 100 Electrochromic element

Claims

A first transparent electrode and a second transparent electrode facing each other;
A nanocrystal layer provided on a surface of the first transparent electrode on the second transparent electrode side and including a plurality of metal oxide nanoparticles;
An electrolyte layer provided between the nanocrystal layer and the second transparent electrode;
With
A transmission spectrum of the electrochromic device changes according to a voltage applied between the first transparent electrode and the second transparent electrode;
The change in the transmission spectrum is accompanied by a change in transmittance of light in the near infrared region and light in the visible region,
The state of the electrochromic element is switched from the first state in which the light transmittance in the near infrared region is relatively low to the second state in which the light transmittance in the near infrared region is relatively high. When the transmission spectrum changes, the first change is such that the color of the transmitted light transmitted through the electrochromic element is a warm color, or the color of the transmitted light transmitted through the electrochromic element is a cold system An electrochromic device including a second change that is no longer in color.
The change in the transmission spectrum when the state of the electrochromic element is switched from the first state to the second state is that the color of transmitted light transmitted through the electrochromic element changes from a cold color to a warm color. The electrochromic device according to claim 1, wherein the electrochromic device includes a third change that results in the following color.
3. The electrochromic device according to claim 1, wherein each of the first change and the second change is a change in which at least one of a * and b * in the L * a * b * color system is increased.
4. The electrochromic device according to claim 3, wherein each of the first and second changes is a change in which both a * and b * increase.
Wherein the first and the amount of change in the a * in each of the second variation .DELTA.a * is -0.01 or more, the b * is the change amount [Delta] b * is 1.60 or more, in claim 3 or 4 The electrochromic device described.
Wherein each of the first and second variation, L * a * b * is a change in L * is increased in the color system, the electrochromic device according to any one of claims 1 to 5.
The electrochromic device according to claim 6, wherein a change amount ΔL * of L * in each of the first and second changes is 1.90 or more.
Each of the first and second changes has a color difference ΔE defined by change amounts ΔL * , Δa *, and Δb * of L * , a *, and b * in the L * a * b * color system. The electrochromic device according to claim 1, wherein the electrochromic device is a change of 15 or more.
The electrochromic device according to claim 8, wherein the color difference ΔE is 2.70 or more.
The electrochromic device according to any one of claims 1 to 9, wherein the plurality of metal oxide nanoparticles are a plurality of antimony-doped tin oxide nanoparticles.
The electrochromic device according to claim 10, wherein an average particle diameter of the plurality of antimony-doped tin oxide nanoparticles is 20 nm or less.
The electrochromic device according to claim 10, wherein an average particle diameter of the plurality of antimony-doped tin oxide nanoparticles is 8 nm or less.
The electrochromic device according to any one of claims 10 to 12, wherein the nanocrystal layer has a thickness of 3000 mm or more.
A smart window comprising the electrochromic device according to any one of claims 1 to 13.