Patent Application
20220214590
The present disclosure relates to an electrochemical device, including an electrolytic solution between opposing electrodes and being capable of depositing/solving a mirror layer of Ag by an electrochemical reaction.
There is provided a display device or a dimmer filter capable of controlling the intensity of transmitted light by using an electrodeposition (ED) material and varying optical properties of the ED material.
A display device is provided, including a transparent electrode on an opposing surface of a pair of glass substrates, and an electrolytic solution containing a solvent, a supporting electrolyte, an ED material containing Ag, and a mediator containing Cu, between the electrodes, and being capable of precipitating an Ag mirror surface on a negative electrode by applying a predetermined voltage across the electrodes, thereby extinguishing the mirror surface by voltage release.
The transparent electrode having light transmission properties can be formed by indium tin oxide (ITO), indium zinc oxide (IZO) or the like. An ED material containing Ag may use AgNO3, AgClO4, AgBr or the like.
The mediator containing Cu may use CuCl2, CuSO4, CuBr2 or the like. A mediator refers to any material that oxidizes/reduces with electrochemically lower energy than silver and is preferably a salt of a divalent copper ion, and may use CuCl2, CuSO4, CuBr2 or the like.
The supporting electrolyte may be any electrolyte capable of promoting oxidation/reduction reaction or the like of an ED material, and may use, for example, a lithium salt such as LiCl, a potassium salt such as KCl, a sodium salt such as NaCl or the like.
The solvent may be one capable of stably holding an ED material or the like, and may use, for example, a polar solvent such as water, a nonpolar organic solvent, an ionic liquid, an ionic conductive polymer, a polymer electrolyte or the like.
In the absence of an applied voltage, an ED element is transparent to light. When Ag precipitates on a flat transparent electrode by application of a predetermined voltage, a mirror surface appears. When the ED element is left in the absence of an applied voltage or in a state under application of a voltage of reverse polarity, the precipitated Ag layer solves to recover a transparent state. There is a need for increasing as much as possible a mirror finishing response speed (an ON response speed) upon power ON and a transparentizing response speed (an OFF response speed) upon power OFF.
Concerning an Ag-precipitating ED element using a Cu mediator, there is a proposal to improve the OFF response speed by using, as a solvent, a mixed solvent in which one or more types of non-water solvent, for example, N,N-dimethylformamide (DMF), to dimethyl sulfoxide (DMSO), as disclosed, for example, in the International Publication No. WO2016/021190.
An ED element using a Cu mediator appears a little bit colored yellow. This is considered to be due to the influence of a mediator containing Cu such as CuCl2 or the like. To form an ED element having a high transmittance, there is desirably no coloring by a mediator.
There is a proposal to avoid coloring of an electrolytic solution and improve a transmittance by using a mediator containing Ge (such as GeCl4) or Ta (such as TaCl5) instead of a mediator containing Cu, as disclosed, for example, in the Unexamined Japanese Patent Application Publication No. 2018-017781.
By using, for example, the above-mentioned mixed solvent, it is possible to improve the OFF response speed although coloring and a low transmittance of an electrolytic solution have not been improved. On the other hand, while it is possible to improve the OFF response speed by using a mixed organic solvent containing mainly DMSO, the coagulating point of DMSO is 18° C. and the mixed solvent cannot be used, as is, at low temperatures. While it is possible to decrease the coagulating point by arranging the composition of a mixed solvent, there are high limitations of the composition for used at low temperatures of −30° C. or less, which hinders improvement of the OFF response speed.
While it is possible to avoid coloring of an electrolytic solution thus offering a high transmittance in a transmitting state by using the above-mentioned mediators containing Ge or Ta, the OFF response speed is low, which will cause the observer to feel that the switching speed is low. For example, the OFF response speed of an N,N-dimethylacetamide (DMA) electrolytic solution using a mediator containing Ta is 47.1 seconds, and the OFF response speed is still lower in the case of a mediator containing Ge.
An example embodiment of the present disclosure aims to provide a high OFF response speed and improve a transmittance in a transparent state at the same time.
According to an example embodiment,
there is provided an electrochemical device including a first substrate and a second substrate disposed face-to-face and each including an opposing electrode disposed on an opposing surface, and an electrolytic solution provided between the first substrate and the second substrate containing a solvent, a supporting electrolyte, a mediator, and an electrodeposition material containing Ag wherein the mediator contains one or more of Mo, Sn, Nb, Sb, and Ti.
For example, while DMA is used as a solvent, a high OFF response speed is available and a high transmittance is obtained in a transparent state when any one of Mo, Sn, Nb, Sb and Ti is used as a mediator.
As illustrated in
As illustrated in
As illustrated in
As a solvent capable of keeping a liquid phase in a temperature range of a melting point of −20° C. or less and a boiling point of 100° C. or more, dimethylacetamide DMA is selected. AgBr of 200 mM as an ED material containing Ag, LiBr of 800 mM as a supporting electrolyte, and selected mediator species of 30 mM are dissolved in a solvent to prepare an electrolytic solution.
As mediators according to the example embodiment, MoCl5 (Mo has an ionic valence of 5), SnCl4 (Sn has an ionic valence of 4), SbCl5 (Sb has an ionic valence of 5), NbCl5 (Nb has an ionic valence of 5), and TiI4(Ti has an ionic valence of 4) are used. Cu[II] according to the related art and Ta[V] employed in previous research are also used as mediators according to the reference example, together with Mo[V], Sn[IV], Sb[V], Nb[V] and Ti[IV].
An electrolytic solution 30 is injected into an empty cell by using the vacuum-pressure impregnation method. An injection port after the injection is encapsulated with UV-curable resin TB3035B from ThreeBond Co., Ltd. to configure an electrochemical device. The electrochemical device is in a transparent state in the absence of an applied voltage and transmissive to light. The capillary injection method, the one drop filling (ODF) method or the like may be used instead of the vacuum-pressure impregnation method.
As illustrated in
As illustrated in
First, a transmittance of each sample in a state where a drive circuit is not operating is evaluated by using a compact fiber spectroscopic measuring device USB 4000. A light intensity without a sample is assumed as 100% and a transmittance is obtained from a relative light intensity of transmitted light that has passed through a sample in a resting state. As the transmittance, a visual sensitivity transmittance is calculated.
Transmittance data in a transparent state obtained through measurement are summarized in the chart of
The ON response speed is defined as a time (in seconds) required until the transmittance drops to 10% of an initial transmittance following application of an ON voltage in a transparent state. The OFF response speed is defined as a time (in seconds) required until the transmittance increases from 15% to 90% of the initial transmittance following application of an OFF voltage in a state where a mirror surface is formed.
When an electrochemical element is used as a smart window as a window including, for example, a dimming function, a high ON response speed and a high OFF response speed are desirable for earlier practices of desired shading or daylighting. While it is possible to decrease an original response speed, it is often practically difficult to increase the original response speed.
The two rightmost columns of
From these experiment results, it is possible to assume that the use of a salt containing Mo[V], Sn[IV], Sb[V], Nb[V], or Ti[IV] as a mediator is effective. Materials containing Mo[V] are MoCl5, MoBr5, MoI5, Mo(NO3)5 and the like. Materials containing Sn[IV] are SnCl4, SnBr4, Snl4, Sn(NO3)4 and the like. Materials containing Sb[V] are SbCl5, SbBr5, SbI5, Sb(NO3)5 and the like. Materials containing Nb[V] are NbCl5, NbBr5, NbI5, Nb(NO3)5 and the like. Materials containing Ti[IV] are TiCl4, TiBr4, TiI4, Ti(NO3)4 and the like.
Note that a solvent is not limited to DMA. When used for an electrochemical element to be used in contact with open air, a solvent only needs to keep a liquid phase in a temperature range of around −20° C. to 100° C. and stably hold an ED material or the like. For example, triethylene glycol dimethyl ether TGM, propylene carbonate PC, or N-methylpyrrolidone NMP may be used.
An Ag salt is not limited to AgBr. AgNO3, AgClO4, AgCl or the like may be used instead of AgBr. A supporting salt is not limited to LiCl. An Li salt such as LiNO3, LiClO4, LiBr, LiI or the like instead of LiCl, an Na salt such as NaNO3, NaClO4, NaCl, NaBr, NaI or the like, and a K salt such as KNO3, KClO4, KCl, KBr, KI or the like may be used.
A thickness of an electrolytic solution is not limited to 100 μm. By selecting a spacer diameter, it is possible to change an inter-electrode distance (thickness of electrolytic solution). Practically, the thickness of an electrolytic solution may be selected within the range of 1 μm to 1000 μm, both inclusive.
While an example case has been described where an Ag layer is deposited on an Ag layer on a flat transparent electrode to form a mirror surface, a dimming function can be provided except by a mirror surface. An Ag layer may be deposited on a transparent electrode having asperities. It is also possible to deposit Ag on a base electrode having submicron asperities to form an Ag layer having black color featuring strong light absorption/reflection, or increase a diameter of asperities to form micron-order asperities thus providing an Ag layer having white color.
While an electrochemical device capable of providing a transparent state has been described, one of a pair of substrates may be opaque. When at least one substrate can be formed into a transparent and reflection or diffuse reflection state, it is possible to provide an electrochemical device capable of offering a variable state.
It is also possible to provide an electrochemical device such as a display or an ND filter showing stable properties as disclosed in Patent Literature 2, by using an electrochemical cell having stable properties.
While this disclosure has been described in accordance with the example embodiment, the foregoing description is by no means restrictive. Materials, numeric values and the like are not to be taken in a limiting sense. Persons skilled in the art will recognize that various changes, improvements or combinations may be made.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-078120 | Apr 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/015662 | 4/7/2020 | WO | 00 |
