JPH0320159B2 - - Google Patents

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to an electrochromic device, and in particular has an electrochromic layer that exhibits high light-shielding properties when colored and becomes almost completely colorless and transparent when decolored. Related to electrochromic devices.

"Prior art and its problems" Various electrochromic devices (hereinafter abbreviated as ECD) have been proposed in the past.
Typical examples include the following:

(1) An electrochromic layer (hereinafter referred to as EC) is a thin film of an inorganic material such as tungsten trioxide (WO ₃ ) deposited on an electrode substrate by a physical vapor deposition method such as a vacuum evaporation method or a sputtering method.
It's called a layer. ) used as

(2) A dye material such as viologen or pyrazoline is thinly applied onto the electrode substrate, and this coating is used as the EC layer.

(3) A thin film made of a conductive organic polymer such as polythiophene or polypyrrole is formed on an electrode substrate using an electrolytic polymerization method, and this is used as an EC layer.

By the way, in general, the EC material that forms the EC layer as described above can alternately develop and decolor in a short period of time through electrochemical oxidation or reduction, so it can be used for other purposes besides display elements. It is expected to be applied to light control glass, optical shutters, etc.

However, even if an attempt is made to apply ECD using an inorganic material such as WO ₃ for the EC layer to light control glass, it is difficult to form the EC layer over a large area because the EC layer is formed using a physical vapor deposition method. In this case, it is necessary to increase the size of the electrode substrate (target) of the EC layer and the vacuum chamber of the manufacturing equipment, which inconveniently leads to a rise in manufacturing costs.

In addition, in ECDs that use dye-based materials such as viologen in the EC layer, the dye in the EC material develops color when it becomes insolubilized in the supporting electrolyte, and discolors when it becomes solubilized. , there may be problems with the reversibility of soluble and insoluble,
I am concerned about the display lifespan.

In contrast, it is made of conductive organic polymers such as polythiophene formed by electrolytic polymerization.
ECDs using an EC layer are attracting attention because the EC layer has excellent display stability and because the EC layer can be easily formed on a large-area electrode substrate, it is cost-effective. There is. However, the conventional EC materials used in this type of ECD are limited to colors such as red, blue, yellow, and reddish-brown.For example, bronze is a color suitable for light-shielding glass, which has a high-class feel in addition to its light-shielding properties. There was some dissatisfaction with not being able to get Brown. In addition, in the EC layer during decolorization,
There were also problems such as the color at the time of coloring remained and was not completely erased.

"Means for solving the problem" In this invention, the solution is to use a conductive organic polymer obtained by electrolytic polymerization of O-aminophenol and its derivatives as the EC material forming the EC layer. And so.

``Example'' The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of the ECD of the present invention. This ECD is roughly composed of a conductive substrate 1 for an active electrode, a conductive substrate 2 for a counter electrode, and an EC layer 3.

The conductive substrate 1 for the working electrode is made of, for example, indium tin oxide (ITO), on one side of the transparent glass plate 4.
Transparent conductive metal oxides such as tin oxide (SnO ₂ ) and indium oxide (In ₂ O ₃ ), metals such as gold, platinum, aluminum, and chromium, and semiconductors such as silicon and gallium arsenide are deposited using vacuum evaporation or sputtering methods. The working electrode 5 is provided in the form of a thin film by a method such as that described above. Also,
The counter electrode conductive substrate 2 is substantially similar to the substrate 1 described above, in which a counter electrode 7 made of the transparent conductive metal oxide or metal is formed in the form of a thin film on one surface of a transparent glass plate 6 by vapor deposition. It is what it is.
These both conductive substrates 1 and 2 are connected to the working electrode 5.
and counter electrode 7 are arranged in a positional relationship such that they face each other.

A thin film-like EC layer 3 made of a conductive organic polymer obtained by electrolytically polymerizing O-aminophenol and its derivatives is formed on the working electrode 5 of the working electrode conductive substrate 1.

The above O-aminophenols and their derivatives (hereinafter referred to as O-aminophenols) have the general formula [In the formula, R ₁ , R ₂ and R ₃ are all CnH ₂ n+ ₁
(However, n=0, 1, 2, 3). ], specifically, for example, O-aminophenol, 2-amino-3-methylphenol, 2-amino-6-
Methylphenol, 2-methylaminophenol and the like are used, but are not limited thereto.

Further, spacers 8, 8 are arranged between both conductive substrates 1, 2, respectively, and these spacers 8,
In the sealed space surrounded by 8, the counter electrode 7, and the EC layer 3,
A solvent 9 containing a supporting electrolyte is enclosed. Various types of plastics can be used as the spacers 8, 8, and epoxy resin, low-melting glass, etc. can be used to seal between the spacers 8, 8 and the conductive substrates 1, 2. is used.

Next, an example of a method for manufacturing an ECD having such a configuration will be described. First, a transparent conductive material such as ITO, In ₂ O ₃ or SnO ₂ is deposited on one surface of each of the transparent glass plates 4 and 6 by a method such as vacuum evaporation to form the working electrodes 5 and 6 with a predetermined film thickness. A counter electrode 7 is formed to obtain transparent conductive substrates 1 and 2.

Next, an EC layer 3 made of a conductive organic polymer obtained by electrolytically polymerizing O-aminophenols is formed on the working electrode 5 of the conductive substrate 1 to a predetermined thickness.

Here, the electrolytic polymerization is carried out in a two-electrode system using a working electrode (working electrode 5) and a counter electrode, or in a three-electrode system using a working electrode (working electrode 5), a counter electrode, and a reference electrode. Since the electrolytic setting potential is determined based on the rising potential of the maximum oxidation peak of , a three-electrode type having a reference electrode is preferable, but is not limited thereto. The counter electrode used in this electrolytic polymerization is insoluble platinum, graphite, etc., and the reference electrode is a sodium saturated calomel electrode (SSCE),
A saturated calomel electrode (SCE) or the like is used.

The electrolytic bath also contains O-aminophenols, water that dissolves them and does not react with the supporting electrolyte, solvents such as acetonitrile and propylene carbonate, and chlorides such as LiCl and NaCl.
perchlorates _{such as LiClO4} ( _C4H9 ) _4NClO4 ,
(C ₄ H ₉ ) ₄ NBF ₄ and other tetrafluoroborates,
Supporting electrolytes such as sulfates such as Na ₂ SO ₄ and tetrafluoroacetates such as CF ₃ COONa are used, but perchlorates, perchlorates, etc. are used as supporting electrolytes.
It is desirable to use an acidic substance such as HCl, H ₂ SO ₄ or CF ₃ COOH to make the electrolytic bath an acidic bath with a pH of 6 or less, preferably 3 or less. Further, the supporting electrolyte concentration is preferably about 0.1 to 1 mol/approximately, and the O-aminophenol monomer concentration is desirably about 0.01 to 0.5 mol/approximately.

The electrolytic mode for polymerizing the O-aminophenol monomer is preferably a potential scanning method or a constant potential method. In the potential scanning method, triangular wave potentials in the forward and reverse directions are alternately applied between the potential E ₁ and a higher potential E ₂ . Further, in the constant potential method, a constant potential E ₃ is applied.

In the ECD according to the present invention, it is desirable to appropriately determine the electrolytic setting voltage in the electrolytic polymerization method for forming the EC layer 3. Specifically, first, a cyclic voltammogram of an electrolytic bath system in which electrolytic polymerization is to be performed is measured by cyclic voltammetry. Cyclic voltammetry sweeps the potential proportional to time from an initial voltage E ₀ at which no Faraday current flows, and then reverses the potential sweep direction at the reversal potential E 〓 to maintain the same potential sweep speed (usually 10 ^-3 to 10 ^-1 The current-potential curve obtained by this _triangular wave potential sweep is called a cyclic voltammogram.

FIG. 2 shows an example of this cyclic voltammogram. This cyclic voltammogram is
O-aminophenol is 50 mmol/
For an electrolytic bath with Na ₂ SO ₄ and H ₂ SO ₄ containing 0.5 mol of SO ₄ ^2- ions and pH=1.0, the initial potential E ₀ −
It was obtained at 0.4 V (vs. SCE), reversal potential E + 1.0 V (vs. SCE), and potential sweep rate of 50 mV/sec.

Such a cyclic voltammogram shows the status of the redox reaction of monomers (O-aminophenols) on the working electrode during electrolysis.
In the graph shown in the figure, it can be seen that an oxidation reaction occurs above the horizontal axis, and a reduction reaction occurs below the horizontal axis, and one or more oxidation peaks and one or more reduction peaks appear in each of the oxidation region and the reduction region.

Then, the rising potential (indicated by B in FIG. 2) of the maximum oxidation peak (indicated by A in FIG. 2) in this cyclic voltammogram is determined from the graph.

In the electrolytic polymerization for forming the EC layer 3, a potential higher than this rising potential is set as the electrolytic set potential. If the electrolysis mode is a constant potential method, electrolysis may be performed while keeping the electrolysis setting voltage constant. Also, if the electrolysis mode is the potential scanning method,
The high potential _E2 is the electrolytic set potential, and the low potential _E1 is the rising potential of the reduction peak on the lowest potential side of the cyclic voltammogram (indicated by C in Figure 2).
The following potentials may be used. Furthermore, the combination of the potential scanning method and the constant potential method only needs to satisfy the above conditions, and the combination pattern and number of combinations are free.

In addition, the rising potential of the maximum oxidation peak in the cyclic voltammogram is determined by the monomer in the electrolytic bath,
Since it varies depending on the solvent, the type and concentration of the supporting electrolyte, etc., it is necessary to measure the cyclic voltammogram of the system each time the composition of the electrolytic bath changes to determine the above-mentioned rising potential. In addition, in the case of the potential scanning method, the potential sweep speed is arbitrary, but it is usually 10
It is preferably about mV/sec to 1000 mV/sec, and the number of scans is also arbitrary, but since the number of scans is proportional to the film thickness of the obtained polymer, it is usually determined by the film thickness.

By performing electrolytic polymerization under such conditions, the EC layer 3 can be obtained by depositing a thin film-like conductive organic polymer in which O-aminophenols are polymerized on the surface of the working electrode.

Next, the conductive substrates 1 and 2 are made to face each other, the EC layer 3 and the counter electrode 7 are faced to each other, and spacers 8 and 8 are placed between the conductive substrates 1 and 2.
are arranged to form a closed space, and a solvent 9 containing a supporting electrolyte is sealed in this space to assemble a closed cell. The solvent 9 may be an aqueous solvent or a non-aqueous solvent such as acetonitrile or propylene carbonate, as long as the ECD can be driven, and a method in which protons are present is particularly preferred in terms of operating characteristics, display stability, and the like. In addition, the aqueous solvent 9 includes HCl,
The operational characteristics of the EC layer 3 can be improved by adding acid substances such as H ₂ SO ₄ , HNO ₃ , CF ₃ COOH, CH ₃ COOH.

Protons can be added to the nonaqueous solvent 9 by adding CH ₃ SO ₃ H (methanesulfonic acid), CF ₃ COOH (trifluoroacetic acid), acetic anhydride, or the like. In addition, as the supporting electrolyte, almost the same as the supporting electrolyte during electrolytic polymerization described above,
Chlorides such as LiCl, NaCl, LiClO ₄ ,
( _C4H9 ) _{4NClO4 ,} perchlorates _such as _TBAClO4 ,
Tetrafluoroborates such as (C ₄ H ₉ ) ₄ NBF ₄ and TBABF ₄ , sulfates such as Na ₂ SO ₄ , and tetrafluoroacetates such as CF ₃ COONa can all be used. Then, the solvent 9 containing this supporting electrolyte is
The pH is 6 or less, preferably 3 or less, and the supporting electrolyte concentration is desirably about 0.1 to 1 mol/degree.

In this ECD, the EC layer 3 was formed by electrolytic polymerization in a separate process before being assembled into a cell, but a solvent containing O-aminophenol monomers and a supporting electrolyte was placed in the closed space inside the cell. After injection and electrolytic polymerization, the solvent may be replaced with a solvent that does not contain the O-aminophenol monomer and then assembled.

For the ECD obtained in this way, the EC
Since the layer 3 is made of a conductive organic polymer obtained by electrolytically polymerizing O-aminophenols, the EC layer 3 develops a bronze brown color in the oxidized state and exhibits high light-shielding properties, and in the reduced state The color becomes almost completely colorless and transparent. Also, in this example
In the ECD, both conductive substrates 1 and 2 are transparent, so if the spacers 8 and 8 are made of transparent plastic or removed, it can be used as a completely transmissive element. Furthermore, since the EC layer 3 is formed by electrolytic polymerization, the EC layer 3 is uniform and has a large area.
It is easy to form and can be used as, for example, large-sized light-shielding glass.

In addition, when the counter electrode 7 is made of a metal material such as gold, platinum, aluminum, or chromium, the counter electrode 7
It can also be used as a reflective element with a reflector as a reflective plate, and in the case where the working electrode 5 is made of the above-mentioned metal material, by using a transparent metal oxide for the counter electrode 7, it can also be used as a reflective element. Available for use.

“Example” Experimental example 1 In an aqueous solution of 0.5MNa ₂ SO ₄ −H ₂ SO ₄ (PH=1.0)
After dissolving 50 mM O-aminophenol and eliminating _O2 in the solution with _N2 , a platinum wire was used as a counter electrode, a saturated calomel electrode (SCE) was used as a reference electrode, and an ITO glass (10
Ω/□) was used as the working electrode to perform scanning electrolysis to form a thin film on the working electrode. In this solution system, the rising potential of the maximum oxidation peak observed in the cyclic voltammogram during polymerization was 450 mV (vs. SCE).
The scanning speed was 50 mV/sec, and the potential was scanned from -400 mV to +700 mV. The amount of electric charge applied during polymerization was measured with a coulomb meter, and the film thickness was measured with a surface roughness meter.

The thickness of the obtained thin film reached approximately 0.6 μm after 200 scans, and the area was 10 cm×10 cm. Next, we investigated the transmission spectrum of this thin film and found that
As shown in the graph of Figure 3, in the oxidation state,
It can be seen that a large absorption peak characteristic of bronze brown appears around 440 nm, and the above absorption peak almost disappears in the reduced state. and,
This thin film was extremely uniform, with variations in film thickness within ±5%.

As a comparative example, three-particulate tungsten (WO ₃ )
When the transmission spectrum of a thin film (film thickness approximately 0.6 μm) consisting of the following was investigated, the results shown in the graph of FIG. 5 were obtained. As is evident from this graph, 440nm
There are no absorption peaks nearby.

Next, this thin film was used as an EC layer to fabricate an ECD as shown in Figure 1. As the supporting electrolyte solution, an aqueous solution of 0.2M LiCl ₄ -CHClO ₄ (PH=1.0) was used. When the ECD was driven by reversing the voltage applied to the EC layer (vs. SCE) between +0.6V and -0.6V every 3 minutes, the transmittance changed significantly, and the change lasted for several minutes. Finished within. The graph in Figure 4 shows the relationship between the applied voltage and the response current, and the relationship between the applied voltage and the transmittance of the EC layer.
As is clear from this graph, the ECD having an EC layer made of a conductive organic polymer obtained by electrolytically polymerizing O-aminophenol has excellent color change responsiveness to potential reversal of applied voltage. .

Experimental Example 2 Under the same electrolytic conditions as in Experimental Example 1, a thin film (about 0.6 μm thick) of poly(2-amino-3-methylphenol) was formed on the working electrode. This thin film is
Almost the same transmission spectrum as O-aminophenol in Experimental Example 1 was obtained, and in the oxidized state, the transmission spectrum was 440 nm.
It has a large absorption peak in the vicinity, and in the reduced state,
This peak had almost completely disappeared. Further, the uniformity of the film was also comparable to that of O-aminophenol.

Next, this thin film was used as an EC layer to fabricate an ECD as shown in Figure 1. And, as supporting electrolyte solution, 1M CH ₃ SO ₃ H−0.2M LiClO ₄
A propylene carbonate solution of As a result, although the operating speed of the ECD was slightly slower than that of the ECD of Experimental Example 1, a significant change in transmittance was observed due to potential reversal.

"Effects of the Invention" As explained above, in the ECD of the present invention, a conductive organic polymer obtained by electrolytically polymerizing O-aminophenols is used as the EC material of the EC layer. Therefore, when the EC layer is colored, it can develop a luxurious bronze brown color and exhibit high light-shielding properties, and when the color is erased, it becomes almost completely colorless and transparent, and the color when colored remains without fading. This results in excellent effects such as no blemishes.

Furthermore, if the EC layer is made uniform over a large area by electrolytic polymerization, it can be used as light-shielding glass or the like. Furthermore, since no color remains after decoloring, it can be suitably used as a light shutter.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of the ECD of the present invention, and FIG. 2 is a graph showing a cyclic voltammogram used when forming the EC layer of the ECD of the present invention by electrolytic polymerization. Figure 3 is
FIG. 4, a graph showing the absorption spectrum of the EC layer of the ECD of this invention, shows the relationship between the applied voltage and response current to the EC layer of the ECD of this invention, and the relationship between the applied voltage and
It is a graph showing the relationship with the transmittance of the EC layer. FIG. 5 is a graph showing the absorption spectrum of a thin film made of WO ₃ used for the EC layer of a conventional ECD. 3...EC layer (electrochromic layer).

Claims (1)

[Claims] 1. The electrochromic layer has a general formula [In the formula, R ₁ , R ₂ and R ₃ are all CnH ₂ n+ ₁
(However, n=0, 1, 2, 3). ] An electrochromic device comprising a conductive organic polymer obtained by electrolytically polymerizing O-aminophenols represented by: