JP2001174852A - Electrochromic light-controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochromic light-controlling device capable of improving memory property and being driven at a low cost. SOLUTION: In the electrochromic light-controlling device, an electrochromic color developing electrode and a counter electrode are arranged facing each other through a gap, and in the gap is filled with an electrolyte containing lithium iodide or sodium iodide and a material which reacts with iodine to form an inclusion compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control device utilizing an electrochromic phenomenon, and more particularly, to an electrochromic light control device having improved memory properties.

[0002]

2. Description of the Related Art Various types of dimming devices have been put to practical use by utilizing an electrochromic phenomenon in which coloring and decoloring are performed reversibly electrochemically by energization.
For example, a dimming window that controls the amount of sunlight transmitted to adjust the brightness of a room utilizes the fact that the degree of coloring (density of color) due to this electrochromic phenomenon changes continuously with applied voltage. It is. Further, anti-glare mirrors and the like that enable adjustment of partitions and reflectance have been put to practical use.

There are various types of electrochromic dimming devices. For example, as shown in FIG. 5, an electrochromic coloring film 5 is formed on a first conductive substrate provided with a conductive film 3 on a substrate 1. An electrochromic coloring electrode formed of a film and a second conductive substrate (a counter electrode) formed by forming a conductive film 4 on the substrate 2 are arranged with a gap therebetween with the conductive films facing each other. An electrolyte 6 is roughly enclosed in the gap by using a sealing material 7. Lead wires 8 and 9 are connected to the conductive films 3 and 4, respectively. As the electrochromic coloring film 5, a thin film made of a reduced coloring oxide such as WO ₃ is generally used. As the electrolyte 6, an organic electrolyte containing a redox agent such as lithium iodide or sodium iodide in an organic solvent is used. Used.

As shown in FIG. 6, a predetermined DC voltage is applied to the electrochromic dimming element through the lead wires 8 and 9 so that the electrochromic coloring electrode has a negative potential and the counter electrode has a positive potential. When applied,
The following iodine ion oxidation reaction occurs on the surface of the conductive film 4 of the counter electrode: 3I ⁻ → I ₃ ⁻ + 2e ⁻ , and the following reaction occurs in the electrochromic coloring film 5: xM ⁺ + WO ₃ + xe ⁻ → M _x WO ₃ (M ⁺ = Li ⁺ , Na ⁺ , H ⁺ ) occurs, and the reduction product (M _x WO ₃ ) turns blue. In addition, when the polarity of the applied voltage is reversed, the above-mentioned reactions are reversed to return to the original transparent state (decoloration).

[0005]

Since the conventional electrochromic dimming device has the above-described structure, when the circuit is opened after coloring, when the circuit is opened, Iodine which is an oxidant generated on the counter electrode side during coloring is obtained. ₃ ^- is diffused into the colored electrochromic film 5 to gradually decolor the electrochromic film 5. For this reason, in the conventional electrochromic dimming element, in order to maintain a certain colored state,
It is necessary to supply a surplus of electric charges in a pulsed or continuous manner, resulting in high power consumption and high driving cost.

In particular, at a high temperature of 60 ° C. or more, the maintenance of this colored state, that is, a significant decrease in memory properties, is a serious problem in practical use as, for example, a light control window. Furthermore, thickened by the addition of polymer to the electrolyte 6 in order to improve the memory effect, I ₃ ^- has been devised a method of inhibiting the diffusion of the electrochromic color film 5, the electrode spacing is narrow, the Filling the voids with the high-viscosity electrolyte 6 was very difficult in practice.

The present invention has been made in view of the above circumstances, and has as its object to provide an electrochromic dimming element which has improved memory properties and can be driven at low cost.

[0008]

In order to achieve the above object, the present invention provides an electrochromic coloring method comprising forming an electrochromic coloring film made of a reduced coloring type oxide on a first conductive substrate. In an electrochromic dimming device, an electrode and a counter electrode made of a second conductive substrate are arranged to face each other via a gap, and an electrolyte containing lithium iodide or sodium iodide is filled in the gap. The electrolyte may further include a substance that reacts with iodine to form an inclusion compound. In particular, as a substance that reacts with the iodine to form a inclusion compound,
Preference is given to using cyclodextrins.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an electrochromic dimming device of the present invention. The configuration itself may be the same as that of a conventional electrochromic dimming device.
That is, similarly to the electrochromic dimming device shown in FIG. 5, an electrochromic electrode formed by forming an electrochromic coloring film 5 on a first conductive substrate provided with a conductive film 3 on a substrate 1; And a second conductive substrate (counter electrode) formed by forming a conductive film 4 on the conductive film 2 with a conductive material facing each other with a gap therebetween, and an electrolyte 6 filled in the gap with a sealing material such as an epoxy resin. 7 and is roughly constructed. In addition, lead wires 8 and 9 are provided on each conductive film 3 and 4.
Is connected.

[0010] The first substrate 1 and the second substrate 2 are
Each can be a light-transmitting substrate or a non-light-transmitting substrate depending on the application. For example, in the case of a dimming window, a translucent substrate is used for both substrates, and in the case of an anti-glare mirror, a non-translucent substrate is used for one. As a translucent substrate,
For example, polyester, polysulfone, cellulose triacetate, polycarbonate, polyimide, polystyrene,
What processed plastic or glass, such as polymethylpentene, into a film or board is mentioned. Also,
The translucent substrate may be colored in addition to being colorless and transparent.
On the other hand, examples of the non-translucent substrate include a metal plate of aluminum, stainless steel, copper, or the like, or a substrate in which the metal is formed on a suitable base material. The thickness, size, shape, and the like of these substrates are appropriately selected depending on the purpose, and it is preferable that the substrates have smoothness depending on applications.

The conductive films 3 and 4 are non-light-transmitting depending on the application.
Any translucent can be used, but translucent
Is desirable. Specifically, for example, In_TwoO_Three: Sn, S
nO _Two: F, ZnO: Al, etc. are vacuum deposited on the above substrate
Method, electron beam vacuum evaporation, sputtering, etc.
A film is formed by a known method. The film thickness is particularly limited
, But usually between 50 nm and 1000 nm
150n so that the rate is high and the sheet resistance is 10Ω / □ or less
m to 300 nm is desirable.

The electrochromic coloring film 5 includes
For example, WO ₃ , MoO ₃ , V ₂ O ₅ , Nb ₂ O ₃ , TiO ₂
Such oxides are preferably formed by forming a film on the conductive film 3 by a known method such as a vacuum evaporation method, an electron beam vacuum evaporation method, and a sputtering method. In addition,
Although the film thickness is not particularly limited, it is usually 10 nm to 2000 n.
m, and desirably 100 nm to 500 nm.

The redox agent contained in the electrolyte 6 is desirably one containing iodine and capable of being stably oxidized and reduced in the electrolyte, such as lithium iodide and sodium iodide. The content of the redox agent is not particularly limited as long as it exhibits an electrochromic phenomenon.
M, preferably 0.1 to 1.0M.

In the present invention, the electrolyte 6 contains, in addition to the above redox agent, a substance that reacts with iodine to form a inclusion compound (hereinafter, referred to as an inclusion compound forming substance).
Examples of this inclusion compound-forming substance include cyclodextrins such as methyl β cyclodextrin, triacetyl β cyclodextrin, and methyl β cyclodextrin. The amount of the clathrate-forming material is iodine, according to the oxidation reaction of iodine and the I ₃ ^- to spread in the form of, in theory if 1/3 equivalent amount of iodine concentration, i.e. a redox agent Good, but may be more. However, excessive addition results in a relatively small amount of redox agent, which adversely affects responsiveness.

The base material of the electrolyte 6 is a solvent capable of dissolving both the above-mentioned redox agent and the inclusion compound-forming substance. Organic solvents such as tetrahydrofuran, dimethoxyethane, N, N, N ', N'-tetraethylsulfamide can be suitably used.

The electrolyte 6 may be a polymer solid electrolyte containing a redox agent and a inclusion compound-forming substance, in addition to an electrolytic solution in which a redox agent and a inclusion compound-forming substance are dissolved in an organic solvent. Examples of the polymer material that can be used include various materials described in JP-A-10-232413.

The electrolyte 6 preferably has an ionic conductivity of 10 ^-4 S / cm or more at room temperature from the viewpoint of responsiveness.
It is desirable to appropriately adjust the amounts of the redox agent and the cyclodextrin, the solvent, and the type of the polymer material.

The method of manufacturing the electrochromic light modulating device of the present invention is not particularly limited, but as an example, an electrochromic color forming electrode on which the electrochromic color forming film 5 is formed and a counter electrode are formed by opposing conductive films. It is manufactured by a method in which the above-mentioned electrolyte 6 is filled in a gap formed by disposing the spacer and a spacer is provided around the periphery thereof and sealed with a sealing material 7.

The coloring / decoloring mechanism of the electrochromic light control device of the present invention configured as described above is the same as that of the conventional electrochromic light control device. That is, when a predetermined DC voltage is applied through the respective lead wires 8 and 9 so that the electrochromic coloring electrode has a negative potential and the counter electrode has a positive potential, reduction products are generated and color is formed in the electrochromic film 5. .

[0020] At the same time, a conductive film 4 on the surface of the counter electrode an oxidation reaction occurs iodine ions as described above, the resulting oxidant I ₃ ^- is gradually diffused into the electrochromic film 5. In the conventional electrochromic dimming device, as described above, this I ₃ ⁻ reaches the electrochromic film 5 and oxidizes the reduction product to decolorize it. On the other hand, in the electrochromic dimming device of the present invention, FIG.
Since the inclusion compound-forming substance indicated by reference numeral 10 is present in the electrolyte 6, I ₃ ⁻ is sequentially captured as an inclusion compound before reaching the electrochromic film 5. As a result, I ₃ ^- electrochromic diffusion into electrochromic film 5 can be significantly suppressed in,
The memory property is greatly improved.

[0021]

The present invention will be described below in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<Preparation of Electrochromic Coloring Electrode>
5 cm × 5 cm ITO glass (In ₂ O ₃ on glass:
500 nm thick W on a transparent conductive glass (SnO ₂ deposited thereon) at a film formation rate of 2-3 nm / sec at room temperature.
O ₃ was deposited to produce an electrochromic coloring electrode.

<Preparation of Electrochromic Light Control Device>
The electrochromic coloring electrode and 10 cm × 10 c
m of ITO glass (counter electrode) was opposed to each other, and the periphery was sealed with an epoxy resin to a width of 5 mm to prepare an empty cell. In addition, various solvents were prepared by using γ-butyrolactone (GBL) as a solvent and dissolving 0.5M of LiI in which methyl β-cyclodextrin (MβCD) was dissolved in a range of 0 to 0.15M. A liquid was prepared. Then, a predetermined amount of each electrolytic solution is vacuum-injected into the empty cell, and the injection port is sealed with an epoxy resin. Then, a lead wire is connected to each of the electrochromic coloring electrode and the counter electrode to perform electrochromic dimming for testing. An element was manufactured. The performance of each electrochromic light control device was evaluated based on the following tests.

<Coloring / Decoloring Test> 1.5 times so that the electrochromic color developing electrode side becomes a negative electrode and the counter electrode side becomes a positive electrode.
When a voltage of V was applied, it was uniformly colored blue,
When a voltage of 1.0 V was applied, the film returned to the original transparent state.
The time required for coloring from 70% to 20% by applying 1.5 V as a coloring / erasing test is defined as a coloring time,
The time required for application of -1.0 V to return to the original transparency was defined as the decoloring time, and the response time of each electrochromic light control device was measured. The results are shown in FIG. 2, where the coloring time does not depend much on the MβCD concentration,
It can be seen that the higher the βCD concentration, the longer the tendency.

<Memory test> After coloring each electrochromic dimming device at room temperature to a transmittance Tv of 20%, the circuit was opened and the transmittance Tv was measured one hour after the circuit was opened. Further, the electrochromic light control device stored at 90 ° C. for 48 hours in a thermostat was taken out, and the transmittance Tv2 was also measured.
After coloring to 0%, open the circuit and 1 hour after the transmittance
Tv was measured. The results are shown in FIG. In the figure, the solid line indicates the transmittance Tv (= 20%) at the initial stage of coloring, the closed circle indicates the measurement result of the electrochromic light control element before being put in the thermostat, and the open triangle indicates the electrochromic light stored at 90 ° C. It is a measurement result about an optical element. The electrochromic light control device before the thermostatic bath has a very small decrease in transmittance regardless of the amount of MβCD added, and has good memory properties. It can be seen that it is damaged. However, also in the electrochromic light control device stored at a high temperature, it can be seen that the memory property improves as the amount of MβCD added increases.

<Weather Resistance Test> The transmittance of each electrochromic dimming device was measured after irradiating it with high-intensity ultraviolet rays for 50 times using a SunTester (manufactured by Heraeus).
FIG. 4 shows the results. In the figure, ● represents the transmittance before irradiation,
◆ indicates the transmittance after irradiation, but the transmittance of each electrochromic dimming device is lower than that before irradiation, especially in the case of the electrochromic dimming device in which an electrolyte solution containing no MβCD is sealed. Those having a transmittance of about 65% were colored by being reduced to about 40% by irradiation, and hardly disappeared even when a normal coloring voltage of -1.0 V was applied. On the other hand, it was found that the addition of MβCD reduced the decrease in transmittance due to ultraviolet irradiation, enabled decoloration, and suppressed irreversible coloring.

[0027]

As described above, in the electrochromic light control device according to the present invention, the electrochromic light control device produced at the time of coloring by adding the inclusion compound forming substance (cyclodextrin) to the electrolyte containing LiI or NaI as a redox agent. I ₃ ^- is prevented from being included in the inclusion compound-forming substance and diffusing into the electrochromic film, and the memory property is greatly improved. Therefore, in various light control applications such as a light control window, a reduction in power consumption and a reduction in driving cost can be realized.

Further, in the conventional electrochromic light control device, irreversible coloring was exhibited by irradiation with ultraviolet light.
This can also be significantly suppressed, and the reliability in applications where sunlight is directly applied, such as glass for vehicles and windows of buildings, is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an electrochromic light control device of the present invention.

FIG. 2 is a graph showing the results of measurement of the coloring / decoloring time in the coloring / decoloring test of the examples, while changing the amount of cyclodextrin added.

FIG. 3 is a graph showing the results of measuring the transmittance in the memory test of the examples while changing the amount of cyclodextrin added.

FIG. 4 is a graph showing the results of measuring the transmittance in the weather resistance test of the examples while changing the amount of cyclodextrin added.

FIG. 5 is a cross-sectional view showing a conventional electrochromic light control device.

FIG. 6 is a diagram for explaining the operation principle of a conventional electrochromic dimming device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Substrate 3 Conductive film 4 Conductive film 5 Electrochromic coloring film 6 Electrolyte 7 Seal 8 Lead wire 9 Seed wire 10 Inclusion compound forming substance (cyclodextrin)

Claims (2)

[Claims] An electrochromic color-forming electrode formed by forming an electrochromic color-forming film made of a reduced color-forming oxide on a first conductive substrate, and a counter electrode made of a second conductive substrate. In an electrochromic dimming device in which the opposing electrodes are arranged via a gap and an electrolyte containing lithium iodide or sodium iodide is sealed in the gap, the electrolyte further reacts with iodine to include the inclusion compound. An electrochromic dimming device comprising a substance that forms 2. The electrochromic light control device according to claim 1, wherein the substance that reacts with iodine to form a inclusion compound is cyclodextrin.