JPH0217092B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrochromic (EC) device using an electrochromic (EC) material.

[Prior art] In recent years, EC elements using EC materials have been used as display elements,
It is beginning to be used as anti-glare mirrors, dimming windows, etc.

EC elements using such EC materials are usually constructed by interposing a reduction coloring type EC material such as tungsten oxide or molybdenum oxide and an electrolyte containing ions that can color the EC material between electrode substrates. There is.

Coloring is achieved by applying a negative voltage to the first electrode substrate having a layer of a reduction coloring type EC material such as tungsten oxide. In the case of a normal EC display element, an oxidation reaction occurs at the counter electrode of the second electrode substrate, so the counter electrode is formed by mixing tungsten oxide, vanadium oxide, etc. with carbon, resin, etc. as necessary. It is used as such. Further, as an electrolyte, one in which a lithium ion source material such as lithium perchlorate is added to an organic solvent such as propylene carbonate or γ-butyrolactone is known.

However, since the counter electrode of this EC display element is made of the above-mentioned material, it is always colored, or becomes colored when the EC material on the first electrode substrate is decolored, so it is difficult to use a reflective type. It could only be used as a display element.

In response to this, in recent years it has been proposed to utilize the memory properties of EC elements to use them as light control bodies. However, when used as a light control body, it must be of a transmissive type, and a configuration similar to that of conventional EC display elements cannot be adopted, and there are problems with the counter electrode. In other words, the counter electrode is simply ITO.
In the case of a transparent electrode made of (indium oxide-tin oxide), even if a voltage is applied between both substrates, the speed at which the EC material on the first electrode substrate is colored and faded is extremely slow with the electrolyte described above. It was something to put away. This is because lithium ions perform redox on the EC material side of the first electrode substrate, but the lithium ions perform redox on the EC material side of the first electrode substrate.
This is because redox caused by perchlorate ions is not reversible on the ITO side of the electrode substrate. If an unreasonably high voltage is applied to increase the speed of coloring and decoloring, problems such as reduction of ITO and decomposition of the electrolyte will occur, making it impractical.

In order to solve this problem, the present inventors have proposed that the counter electrode be a simple ITO transparent electrode and that the electrolyte contain an iodine compound.

By adding this iodine compound to the electrolyte, iodine ions undergo a redox reaction between I ^- /I ₃ ^- , so the EC substance on the first electrode substrate can be colored and decolored without causing deterioration of ITO or the electrolyte. can be done.

[Problems to be solved by the invention] The electrolyte to which such an iodine compound is added is
This did not cause many problems when the EC element was not used under direct sunlight such as indoors, but problems sometimes occurred under strong light such as under direct sunlight. In other words, during decolorization during light irradiation, the reduction reaction of I ₃ ^- → I ^- on the ITO electrode may not proceed smoothly, and the ITO electrode may be reduced, reducing the lifespan of the EC element. This caused the problem of having to do so.

For this reason, there has been a demand for a transmission type EC element in which the reaction on the opposing electrode of the second electrode substrate proceeds smoothly even under strong light such as direct sunlight.

[Means for Solving the Problems] The present invention has been made to eliminate the above-mentioned drawbacks of conventional EC elements, and provides a first electrode substrate having a layer of a reduced EC material such as tungsten oxide. In the EC device, an EC element is formed by facing a second electrode substrate and sandwiching an electrolyte containing an iodine compound therebetween. The present invention provides an EC element characterized by the following.

That is, in the EC element of the present invention, an iodine compound serving as an iodine ion source material with excellent reaction speed and durability is added to the electrolyte as a redox agent, and Prussian blue is the main component in the counter electrode of the second electrode substrate. By providing the oxidative color-forming EC material layer, the second electrode substrate is also transparent when the EC material on the first electrode substrate is decolored, and the redox reaction on the counter electrode of the second electrode substrate is rapid. It is possible to allow the process to progress to a state where it is difficult to cause deterioration of the electrode or decomposition of the electrolyte.

Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is an end view showing the basic configuration of the present invention.

Both the first electrode substrate and the second electrode substrate 1A, 1B have a transparent conductive film 2A, such as tin oxide, indium oxide, or tin oxide-indium oxide (ITO), on the surface of a substrate such as glass or plastic.
An electrode formed by forming 2B by a known method such as coating, vapor deposition, or sputtering is used. In addition, if necessary, thin wire leads made of metals such as aluminum, chromium, titanium, or conductive paste can be attached to this transparent conductive film in the form of a wire.
They may be laminated in a grid pattern or the like.

Note that in cases where light does not need to pass through the EC element, such as from a dimming mirror, one side of the substrate does not need to be transparent, and ceramic or metal such as aluminum or titanium may be used, or it may be used as an electrode. Alternatively, a reflective electrode made of titanium nitride, zirconium nitride, hafnium nitride, or the like may be used. Furthermore, when used as a light control mirror, both of the electrode substrates may be transparent, and a mirror surface may be formed on the back surface of one of the electrode substrates.

A reduction coloring type EC material layer 3 is formed on one of the electrode substrates (first electrode substrate). As this reduction coloring type EC material, a known reduction coloring type EC material can be used, and it may be formed by a known manufacturing method such as vapor deposition, solution coating and firing, etc. Specifically, tungsten oxide, molybdenum oxide, molybdenum oxide, Although titanium, iridium oxide, etc. are available, tungsten oxide or a tungsten oxide-based material containing titanium oxide as a main component is preferable.

On the other hand, on the other electrode substrate (second electrode substrate), an oxidized color-forming EC material layer 4 containing Prussian blue (Fe ₄ ³⁺ [Fe(CN) ₆ ] ₃ ) as a main component is formed.
It may be formed by a known method for producing Prussian blue. For example, electrolytic film formation may be performed from a mixed solution of an aqueous solution of ferric chloride and an aqueous solution of potassium ferricyanide. An apparatus for forming a Prussian blue thin film by this process is shown in FIG. 2 and will be described in more detail. FIG. 2 is a schematic diagram of a Prussian blue film forming apparatus, in which a container 11 contains a mixed solution 12 of the above-mentioned ferric chloride aqueous solution and potassium ferricyanide aqueous solution, an electrode substrate 13 on which a Prussian blue thin film is to be formed, An electrode 14 made of Pt, Ni, ITO, etc., which serves as a counter electrode, and a saturated calomel electrode 15, which serves as a reference electrode, are arranged. A Prussian blue thin film is formed on the electrode substrate 13 by energizing the electrode substrate 13 as a negative electrode and the electrode 14 as a positive electrode. The thickness of this Prussian blue thin film can be controlled by the amount of current applied.

However, in the present invention, redox on the second electrode substrate side is not performed only with the oxidized color-forming EC material layer containing Prussian blue as the main component;
The main method is redox I ^- /I ₃ ^- of iodine ions using iodine compounds. For this reason, the oxidative color-forming EC material layer of the second electrode substrate, which has Prussian blue as its main component, has an iodine ion redox I ^- /
Since it is sufficient to fulfill the role of supporting I ₃ ^- , a high effect can be obtained even if it is thin.

First electrode substrate 1A formed in this way
and the second electrode substrate 1B, the electrode surfaces thereof face each other and the electrolyte 5 is sandwiched between them. In this case, a seal 6 made of a sealing material is usually formed around both electrode substrates. This seal is essential when the electrolyte is liquid, and after forming the seal, the electrolyte is injected through the injection port and the injection port is sealed. Furthermore, if the electrolyte is a gel electrolyte, it is preferable to inject it at the same time as sealing. Further, if the electrolyte is a polymer electrolyte, the seal may not be provided.

The electrolyte used in the present invention is a mixture of an organic solvent and an iodine compound serving as a source of iodine ions as a redox agent.

This organic solvent may be any solvent as long as it can dissolve the iodine compound and cause the EC substance to change color.
In addition to propylene carbonate and γ-butyrolactone, which are used in conventional EC display elements, butyl alcohol, sulfolane, hindered cyclic carbonate, dimethyl sulfoxide, and the like can be used.

As the iodine compound serving as the iodine ion source for this redox agent, metal iodides such as lithium iodide and sodium iodide, and ammonium-based iodides such as ammonium iodide and tetraethylammonium iodide are used. The amount of the iodine compound to be added to the solvent may range from 0.001M/ to a saturation amount, and usually about 0.1 to 1M/.

In addition, when using ammonium-based iodides, etc., or when using metal iodides that form cations that do not color or fade the EC material, use a cation source material containing cations such as protons and lithium ions that color the EC material layer. Added for ion implantation into the material layer. This cation source substance is
Examples include lithium perchlorate, sodium perchlorate, lithium boron tetrafluoride, and sodium boron tetrafluoride. The amount of the cation source substance to be added to the solvent may range from 0.001 M/ to a saturation amount, and usually about 0.1 to 1 M/.

In the present invention, when used as a light control body, it is preferable to further add a gelling agent to the electrolyte from 1 wt % to a saturation amount to increase the viscosity of the electrolyte solution and cause it to gel. From the viewpoint of the manufacturing process and prevention of electrode short circuits, it is preferable that the polymer used as the gelling agent is adjusted to have a viscosity of about 10 ³ to ^{10 5} cps when dissolved in an organic solvent.

As this gelling agent, known gelling agents such as polyvinyl butyral type, polyvinyl acetate type, polyethylene oxide type, polyacrylonitrile type, polymethyl methacrylate type, polyvinyl pyrrolidone type, etc. A variety of polymers can be used.

However, among these polymers, it is desirable to use a polymer that has good weather resistance, particularly against direct sunlight, is stably soluble in the above-mentioned solvent, is electrochemically stable, and has adhesive properties to the electrode substrate. Specifically, polyethylene oxide-based, polyacrylonitrile-based, polymethyl methacrylate-based, or polyvinylpyrrolidone-based polymers are preferred.

The dimmer has a relatively large area and is often used vertically, and the electrolyte solution tends to fall downward due to hydrostatic pressure, causing the lower part of the EC element to bulge out. If pressed, there is a risk that the two electrode substrates will come into contact and cause a short circuit. However, such accidents can be prevented by adding a polymer to the electrolyte to form a gel electrolyte. Furthermore, even if the electrode substrate is damaged for some reason, the electrolyte and the electrode substrate are unlikely to scatter and are safe. Furthermore, since the electrolyte is less likely to leak, the strength of the seal does not need to be low, and the area of the seal portion can be reduced, which has the advantage of reducing stress on the substrate and optical distortion.

The EC element of the present invention is suitable for use as a light control body as described above, but when used as a small transmission type display, it has a cycle life of 10 ^{to 6} times or more, and can be used as a display. However, by devising a drive system, it can be put to practical use.

[Example] Examples of the present invention will be described below.

Example 1 An electrode substrate was manufactured by coating a 10 cm square glass substrate with an ITO film to a thickness of 1500 Å by vapor deposition to form a transparent electrode. A WO ₃ film having a thickness of 5000 Å was deposited on the transparent electrode of this electrode substrate to form a reduction coloring type EC material layer, thereby manufacturing a first electrode substrate.

In addition, a Prussian blue thin film with a thickness of 700 Å was formed on the transparent electrode of the other electrode substrate using a device as shown in Fig. 2 at a current flow rate of 2 mC/cm ² . was manufactured.

The Prussian blue thin film on this second electrode substrate was colored blue, and its transmittance was 68%.

The first electrode substrate and the second electrode substrate are arranged so that the electrode surfaces face each other, the periphery is sealed with a sealing material, and an electrolyte containing 0.75M of lithium iodide dissolved in γ-butyrolactone is placed inside. The injection port was sealed and an EC device was manufactured.

This EC element has a transmittance of 74% when formed into a cell, 75% when decolored and 10% when colored, even without reducing the Prussian blue thin film using the third electrode.
It was possible to color and erase the colors.

In addition, a repeated coloring/decoloring test (decoloring at 1.0 V for 30 seconds ← → coloring at −1.5 V for 17 seconds) was conducted in a weather meter. As a result, it was possible to operate the device for more than 300 hours without causing any defects such as foaming.

For comparison, an EC element (Comparative Example 1) was manufactured by injecting an electrolyte prepared by dissolving 0.75M lithium perchlorate in γ-butyrolactone and sealing the injection port. In the device of Comparative Example 1, the Prussian blue thin film was initially colored blue.
It was necessary to form a third electrode within the device and apply a voltage between the third electrode and the Prussian blue thin film to reduce the Prussian blue thin film. As a result of repeated coloring/decoloring tests in a weather meter, defects such as foaming occurred after 50 to 100 hours.

In addition, as the second electrode substrate, a substrate with only transparent electrodes and no Prussian blue thin film was used, and this and the first electrode substrate of Example 1 formed a cell, and Lithium iodide was added to the same γ-butyrolactone as in Example 1 at 0.75M/
Inject the dissolved electrolyte and seal the injection port.
An EC element (Comparative Example 2) was manufactured.

The EC element of Comparative Example 2 was capable of decoloring by 75% when decoloring and by 10% when coloring. In addition, Example 1
As a result of repeated coloring and fading tests conducted in a weather meter similar to the above, foaming occurred after 50 to 100 hours.

Furthermore, the coloring efficiency of the EC element of Comparative Example 2 when the amount of charge is the same is approximately higher than that of Example 1.
It was 10% lower.

Example 2 In the same manner as in Example 1, an electrolyte containing 0.75M lithium iodide/30wt% polyvinyl butyral dissolved in γ-butyrolactone was injected into the interior.
An EC device was manufactured by sealing the injection port.

The coloring/decoloring performance of this EC element was similar to that of Example 1. Furthermore, since this EC element was gelled with the polymer polyvinyl butyral, it was safe because even if the electrode substrate was damaged, the electrolyte and electrode substrate were unlikely to scatter.

In addition, an EC device was manufactured with the same configuration using a glass substrate of 30 cm square. Even when this large EC element was placed in a vertical position, the electrolyte solution did not fall downward due to hydrostatic pressure and the lower part of the EC element did not bulge out.

Examples 3 to 5 The thickness of the Prussian blue thin film was 1000 Å and 2000 Å.
A second electrode substrate with a Prussian blue thin film was manufactured in the same manner as in Example 1, with a thickness of 4000 Å.

These Prussian blue thin films are initially colored blue, and their transmittance is 65% at a film thickness of 1000 Å.
It was 56% at 2000 Å and 41% at 4000 Å. This EC
An EC device was manufactured in the same manner as in Example 2 using the second electrode substrate.

These EC elements are 70%, 68%, and 68%, respectively, when they are made into cells.
It had a transmittance of 60%, and even without reducing the Prussian blue thin film using a third electrode, it was possible to change the color by 75% when decoloring and by 10% when coloring.

Furthermore, the coloring/decoloring performance of these EC elements was similar to that of Example 2. Furthermore, these EC elements
Since the electrolyte is gelled, there is no problem of safety when the electrode substrate is damaged or swelling when placed vertically.

Example 6 An EC device was manufactured in the same manner as in Example 2, except that the same amount of polyethylene oxide was used instead of 30 wt% polyvinyl butyral as an electrolyte gelling agent. This EC device was also manufactured in the same manner as in Example 2. showed the performance of

Example 7 An EC device was manufactured in the same manner as in Example 2 except that the same amount of polyvinylpyrrolidone was used instead of 30 wt% polyvinyl butyral as an electrolyte gelling agent. This EC device was also manufactured in the same manner as in Example 2. showed the performance of

Example 8 An EC device was manufactured in the same manner as in Example 2 except that dimethyl sulfoxide was used instead of γ-butyrolactone as the organic solvent of the electrolyte. This EC device also showed the same performance as Example 2.

Example 9 Sulfolane was used instead of γ-butyrolactone as the organic solvent of the electrolyte, and as a gelling agent.
An EC device was manufactured in the same manner as in Example 2 except that the same amount of polyethylene oxide was used in place of 30 wt% polyvinyl butyral, and this EC device also showed the same performance as Example 2.

In particular, this EC element had higher durability in repeated coloring and fading tests in a weather meter.

Example 10 0.75M/ammonium iodide was used instead of 0.75M/lithium iodide, which is the iodine compound of Example 9, and further, as a lithium ion source.
An EC device was manufactured in the same manner as in Example 2 except that 0.75M/Lithium perchlorate was used.

This EC element also showed the same performance as Example 9.

[Effects of the Invention] In the EC element of the present invention, by using a substrate on which only electrodes such as ITO are formed as the second electrode substrate, the reduction of ITO, etc., which has been a problem, can be avoided.
By improving the reversibility of I ^- / ^I ₃ -redox, the effect of reducing it can be obtained. This makes it possible to obtain a long service life even when the coloring and fading are repeated under harsh conditions such as under direct sunlight.

In addition, in the reduced EC material layer such as tungsten oxide, an oxidized color-forming type containing Prussian blue as the main component is added.
By using an EC material layer in combination, the coloring effect can be improved. In other words, without reducing the light transmittance during decoloring, and due to high coloring,
It is possible to increase the degree of coloring and lower the light transmittance without reducing the life of the EC material. However, in the present invention, redox on the second electrode substrate side is not performed only with the oxidized color-forming EC material layer containing Prussian blue as the main component;
Since the main component is I ^- /I ₃ ^- , the oxidation color forming type mainly composed of Prussian blue of this second electrode substrate
The EC material layer can be effective even if it is thin, and may not contribute significantly to the degree of coloration.

In addition, unlike EC elements that simply use tungsten oxide and Prussian blue, there is no need to provide a third electrode to initially erase the Prussian blue, and the structure can be simplified as it can be colored and erased as is. At the same time, it is also easy to drive.

Furthermore, by adding a polymer to this electrolyte and causing it to gel, even when used as an EC element with a large area, a spacer is not required and problems such as deformation of the electrode substrate and short circuits are less likely to occur. Furthermore, even if the substrate is damaged, the electrolyte and the substrate are unlikely to scatter. Furthermore, since the electrolyte itself is difficult to flow, it does not require a strong seal, so EC
The device can be easily manufactured, and optical distortion is less likely to occur because the stress of the seal against the substrate is reduced.

[Brief explanation of drawings]

FIG. 1 is an end view showing the basic configuration of the present invention. Figure 2 is a schematic diagram of a Prussian blue film forming apparatus. Electrode substrate: 1A, 1B, transparent conductive film: 2A, 2
B. Reduction coloring type EC material layer: 3. Oxidation coloring type EC material layer
EC material layer: 4, electrolyte: 5, seal: 6.

Claims (1)

[Claims] 1. A first electrode substrate having a layer of a reduced electrochromic material such as tungsten oxide and a second electrode substrate are opposed to each other, and an electrolyte containing an iodine compound is sandwiched therebetween. 1. An electrochromic device characterized in that an oxidative color-forming electrochromic material layer containing Prussian blue as a main component is formed on a second electrode substrate. 2. The electrochromic device according to claim 1, wherein the electrolyte contains a polymer that increases the viscosity of the electrolyte solution and gels the electrolyte solution. 3. The electrochromic device according to claim 1, wherein the iodine ion source material is lithium iodide and functions as a cation source. 4. The electrochromic device according to claim 1, wherein the reduction coloring type electrochromic material is an electrochromic material containing tungsten oxide as a main component.