JP4110762B2 - Method for producing tungsten oxide fine particles having electrochromic characteristics - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing tungsten oxide fine particles exhibiting electrochromic characteristics, a coating liquid in which the tungsten oxide fine particles are dispersed, and an electrochromic device manufactured using the coating liquid.
[0002]
[Prior art]
Electrochromic devices that use electrochromism, in which the color of a substance changes reversibly due to an oxidation-reduction reaction by applying voltage, have long-term memory characteristics, have no viewing angle dependency, consume less power, and interfere with external light. Since it has the advantage that it cannot be used, its application to light control elements, display elements, etc. has been studied.
[0003]
Such an electrochromic element generally has a laminated structure in which a transparent electrode, an electrolyte, and an electrochromic layer are combined. For example, substrate / transparent conductive film / reduction colored electrochromic layer mainly composed of tungsten oxide / electrolyte layer / oxidized colored electrochromic layer mainly composed of nickel oxyhydroxide / transparent conductive film / substrate The laminated structure is as follows. The reduction coloring electrochromic layer is a layer that develops color by reduction, and the oxidation coloring electrochromic layer is a layer that develops color by oxidation.
[0004]
In addition to metal compounds such as tungsten oxide and nickel oxyhydroxide, materials such as metal complexes and organic dyes are known as substances having electrochromic properties constituting these electrochromic layers. Moreover, in order to form an electrochromic layer made of these materials, sputtering, vacuum deposition, electric field film formation, chemical film formation, or the like is used.
[0005]
One promising application of the electrochromic device is a light control glass capable of changing the light shielding property or transparency of a window of a house or the like. In particular, in the 1980s, research and development were actively conducted from the viewpoint of energy saving. However, since the film was formed by using the sputtering method, the production cost was high and it was not widely used in general.
[0006]
[Problems to be solved by the invention]
As a method for producing an electrochromic element at a low cost, for example, a method in which an organic tungsten compound dissolved in an organic solvent is applied to the surface of a substrate and thermally decomposed to form an electrochromic layer of tungsten oxide (Japanese Patent Laid-Open No. 56). No. -38379) is known.
[0007]
However, in this pyrolysis method, it is necessary to heat the substrate uniformly, and problems such as non-uniform electrochromic properties occur if there is uneven temperature, so a uniform electrochromic layer is produced in a large area It was difficult to do. In addition, when the base material that can be used is limited in terms of heat resistance required for heating, or when ITO (tin-added indium oxide) is used for the transparent conductive film, oxygen defects in ITO are reduced during heating, and the desired conductivity There was a problem that the rate could not be obtained.
[0008]
There has also been proposed a method of obtaining fine particles of an electrochromic material such as tungsten oxide by sublimating and evaporating the material in a container introduced with an inert gas such as argon (Japanese Patent Laid-Open No. 7-207260). According to this method, fine particles with less defects and contamination can be obtained, the particle diameter can be easily controlled, and the particle size distribution is sharp. However, it is necessary to use a large vacuum device. The cost was unavoidable.
[0009]
In view of such conventional circumstances, an object of the present invention is to provide a method for producing tungsten oxide fine particles exhibiting electrochromic characteristics at a low cost by a simple method. Moreover, in order to produce an inexpensive electrochromic device having uniform characteristics even in a large area by a simple coating method, a coating liquid in which the electrochromic fine particles are dispersed, and an electrochromic device fabricated using this coating solution, particularly An object is to provide an electrochromic element suitable for use in light control glass.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the method for producing fine tungsten oxide particles exhibiting electrochromic characteristics provided by the present invention is to dissolve tungsten hexachloride in alcohol and evaporate the solvent as it is, or evaporate the solvent after heating to reflux. Then, by heating at 100 ° C. to 500 ° C., a powder made of tungsten trioxide or a hydrate thereof or a mixture of both is obtained.
[0011]
In addition, according to the present invention, a method for producing tungsten oxide microparticles having electrochromic characteristics is obtained by dissolving tungsten hexachloride in alcohol and further adding water to cause precipitation, and then removing the obtained precipitate from a solvent. It separates and heats at 100 to 500 degreeC, The powder which consists of tungsten trioxide or its hydrate, or a mixture of both is obtained, It is characterized by the above-mentioned.
[0012]
The present invention relates to a coating liquid in which tungsten oxide fine particles exhibiting electrochromic properties obtained by the above method are dispersed in a liquid, the aggregate of the tungsten oxide fine particles in the coating liquid or the average dispersed particles of monodisperse particles Provided is a coating liquid for producing an electrochromic device, which has a diameter of 200 nm or less.
[0013]
In the coating liquid for producing an electrochromic device of the present invention, the coating liquid contains at least one of a proton conductive material or an ion conductive material, and / or an ultraviolet curable resin, a thermosetting resin, or a metal alkoxide hydrolysis polymerization. Or at least one of sol-gel silicate.
[0014]
Moreover, this invention provides the electrochromic element characterized by including the electrochromic layer formed by apply | coating and hardening the said coating liquid for electrochromic element preparation on the base material with a transparent conductive film. In particular, the substrate comprises a transparent resin film and provides a flexible film-like electrochromic element.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the raw material tungsten hexachloride (WCl₆) In a state of having a stable characteristic after being reacted in alcohol and heat-treated (WO₃) As fine particles. Further, the fine particles are dispersed in a liquid to form a coating solution, which is coated and cured on a substrate with a transparent conductive film to constitute an electrochromic device. Therefore, it is possible to produce an electrochromic element that is inexpensive and capable of stable light control as compared with a film obtained by a thermal decomposition method. Various materials such as metal compounds, metal complexes, and organic dyes are known as materials exhibiting electrochromic properties, but tungsten oxide is most preferable in consideration of weather resistance, cost, coloring efficiency, and the like.
[0016]
First, a method for producing tungsten oxide fine particles according to the present invention will be described. Raw material tungsten hexachloride is dissolved in alcohol. At this time, since it reacts violently and generates heat, it is preferably added little by little. Further, since tungsten hexachloride reacts with air, this operation is desirably performed in a non-oxidizing atmosphere such as nitrogen gas or a rare gas such as argon, or in a vacuum. Tungsten hexachloride dissolved in alcohol is considered to exist in the state of alkoxide as chlorine dissociates and alcohol and tungsten ions react. The alcohol to be used is not particularly limited as long as tungsten hexachloride can be dissolved.
[0017]
In the first method of the present invention, tungsten oxide fine particles are obtained by evaporating and removing the solvent from this solution. In the second method, the solution is heated to reflux, and then the solvent is removed by evaporation. This heating and refluxing is performed to promote bonding between tungsten and oxygen and form a precursor of tungsten oxide. The solvent removal method may be any method that can evaporate the solvent, such as natural drying or heat drying, and at this time, it is considered that a network of oxygen and tungsten is formed. However, in the case of heat drying, care must be taken because the state of the oxide obtained varies depending on the heating temperature. Furthermore, in the third method, water is added to the above solution to precipitate a white gel substance, and then the precipitate is separated from the liquid to obtain tungsten oxide fine particles.
[0018]
The tungsten oxide fine particles separated from the solvent are then heat-treated at a temperature of 100 to 500 ° C. Since the state of the obtained oxide varies depending on the drying temperature at the time of removing the solvent and the temperature at the time of the heat treatment, heating is performed at a necessary temperature according to the target electrochromic characteristics. Specifically, as a result of examining by changing the temperature, it was found that tungsten oxide was obtained in a hydrated state at a temperature of 200 ° C. or lower. It was also found that anhydrous tungsten oxide can be obtained in a crystalline state when heated at 300 ° C. or higher. At temperatures above 200 ° C. and below 300 ° C., a mixture of tungsten oxide hydrate and anhydride is obtained.
[0019]
The tungsten oxide fine particles obtained by the method of the present invention exhibit good electrochromic characteristics regardless of the drying temperature or the heat treatment temperature. The drying temperature and the heat treatment temperature are determined depending on the application and the manufacturing process. However, in the case of a light control glass used for a window of an automobile or a house, it is desirable to perform the treatment at a temperature of 100 ° C. or higher. There is also a theory that water of crystallization is an important factor for electrochromic properties, but the tungsten oxide microparticles according to the present invention evaporate into water in an anhydrous crystal state by heat treatment at 300 ° C. or higher. It was confirmed that the electrochromic characteristics satisfying the above were exhibited.
[0020]
By dispersing the tungsten oxide fine particles obtained by the method of the present invention in a liquid, a coating liquid for producing an electrochromic device can be obtained. The dispersion medium liquid may be a known solvent, such as alcohol, ketone, ether, ester or the like. Moreover, as a dispersion method, what is necessary is just to obtain the target dispersed particle diameter, and specifically, ultrasonic irradiation, a ball mill, a bead mill, a sand mill, etc. are mentioned.
[0021]
In general, the relationship between the particle size and transparency of the light-transmitting film is derived from the film structure unique to the fine particle dispersed ink coating film. When ink is applied to a transparent substrate, agglomerates of solution and fine particles form a thin film on the substrate surface. Further, by evaporating the solvent, a structure in which fine particle aggregates are deposited on the surface of the base material is obtained. It is also possible to create a state in which the resin component penetrates and fills the gaps where the fine particle aggregates are deposited by further applying or penetrating resin or the like from above the deposited layer. If various resins are included as a binder in the ink, when the ink is applied to the substrate and the solvent is dried, the aggregate of fine particles is dispersed in the binder. In such a state, a difference in refractive index occurs at the interface between each fine particle aggregate and the gap medium (air, resin binder, etc.), thereby scattering light. When the scattering is large, the transparency is lost like frosted glass, which is not preferable when considering application to light control glass or the like.
[0022]
In order to improve the transparency, it is necessary to reduce the aggregates of the fine particles present in the film. The human eye is sensitive to light having a wavelength of about 380 nm to 780 nm, particularly sensitive to light near 550 nm, and the sensitivity decreases toward the long wavelength side and the short wavelength side centering on that region. . When the scatterer (fine particle aggregate) has the same size as the light wavelength (visible light region wavelength centered at 550 nm), the light scattering becomes the largest (this is called the Mie region). Further, when the dispersed particle size of the fine particle aggregate is reduced, a Rayleigh region is obtained, and the scattered light intensity decreases in inverse proportion to the sixth power of the radius of the fine particle aggregate, so that the transparency is remarkably improved. That is, in order to maintain this transparency, the particle diameter of the fine particle aggregate in the film is preferably 200 nm or less, more preferably 100 nm or less, and particularly preferably 50 nm or less. On the other hand, when the particle diameter of the fine particle aggregate exceeds 300 nm, the scattered light increases to become a frosted glass.
[0023]
In the coating liquid for producing an electrochromic device according to the present invention, the dispersion particle diameter of the tungsten oxide fine particles in the liquid can be changed according to the intended use by adjusting the dispersion method and conditions. In the case of a light control glass application, the average dispersed particle size of the aggregates or monodisperse particles of tungsten oxide fine particles in the coating solution is 200 nm or less, preferably 100 nm or less, more preferably 50 mn or less. As described above, the smaller the average dispersed particle size, the better the transparency. The dispersed particle diameter of the tungsten oxide fine particles in the coating solution is maintained even in the electrochromic layer after film formation.
[0024]
It is possible to reduce the dispersed particle size by pulverizing and dispersing treatment when adjusting the coating liquid, but the smaller the particle size, the more re-aggregated or the larger the agglomerated as the solvent evaporates when applied to the substrate. There is a tendency to end up. Therefore, it is preferable to add an effective dispersant in order to stably maintain a fine dispersed particle size.
[0025]
Examples of the dispersant include alkoxides, polymers, and surfactants, all of which act on the particle surface, and the ionization state of the particle surface, the surface potential, and the type of dispersion solvent. Selected by etc. By adding the dispersant, the dispersed particles are not re-agglomerated, and can be stably dispersed in the liquid and further dispersed stably in the film. In addition, although the kind and addition amount of a dispersing agent are suitably selected in consideration of the influence on the electrochromic device and the electrochromic characteristics, the addition amount is 50% or less of the weight of the tungsten oxide fine particles so as not to deteriorate the electrochromic characteristics. It is preferable to do.
[0026]
In order to bind the tungsten oxide fine particles to the substrate, a binder can be included in the coating solution. Considering the starting principle of the electrochromic element, the binder that fills the gaps between the fine particles is preferably one having ionic conductivity or proton conductivity. The conductive ions can be selected according to the electrochromic material, and typical examples include lithium ions or hydrogen ions. Examples of the ion conductive material include an organic / inorganic hybrid ion conductive resin, tantalum oxide, and the like, and examples of the proton conductive material include Nafion (trade name) manufactured by DuPont.
[0027]
Further, as a binder to be added to the coating solution, an existing resin, sol-gel silicate, or the like can be used alone or in combination with the above-described ion conductive material or proton conductive material. Examples of the existing resin binder include an ultraviolet curable resin, a thermosetting resin, a thermoplastic resin, a room temperature curable resin, and a hydrolysis polymer of a metal alkoxide such as tetraethoxysilane (TEOS). These binders may also be appropriately selected in consideration of electrochromic characteristics or depending on adhesion to the substrate. If the substrate is a transparent resin film such as PET, an ultraviolet curable resin is desirable in consideration of the production speed. Moreover, if it is base materials, such as glass, an electrochromic element can also be produced by heating using a thermosetting resin or a sol-gel silicate binder.
[0028]
In general, an electrochromic element is a reduction-colored electrochromic layer mainly composed of a base material / transparent conductive film / tungsten oxide / electrolyte layer / oxidized-colored electrochromic layer mainly composed of nickel oxyhydroxide. It is a laminated structure of / transparent conductive film / base material. Some have a laminated structure of base material / transparent conductive film / electrolyte layer / electrochromic layer / transparent conductive film / base material.
[0029]
The electrochromic device of the present invention uses a material formed by applying and curing the electrochromic device-forming coating liquid on a substrate with a transparent conductive film as a reduction-colored electrochromic layer in the above laminated structure. . The reduction coloring type electrochromic layer is mainly composed of the tungsten oxide fine particles of the present invention, but other reduction coloring type electrochromic materials such as niobium oxide, lithium niobate, molybdenum oxide, titanium oxide, tin oxide, ATO, cobalt lithium acid, Prussian blue, etc. can be used in combination.
[0030]
On the other hand, the oxidation coloring type electrochromic layer was selected from oxidation coloring type electrochromic materials such as nickel oxide, nickel hydroxide, nickel oxyhydroxide, iridium oxide, rhodium oxide, cobalt oxide, cobalt hydroxide and the like. One or more types are the main components. The oxidative coloring type electrochromic material is not limited to these, and any material capable of oxidative coloring may be used. The electrochromic material used for the electrochromic layer of the reduction coloring type or oxidation coloring type layer may be colored in an oxidation state or a reduction state, and such materials include vanadium oxide, indium nitride, tin nitride and the like. is there.
[0031]
As the substrate, transparent resin, glass or the like can be used, and it may be a hard board or a flexible film. In particular, for use as a light control glass by pasting on existing window glass etc., polyethylene terephthalate, polyester, polyethylene, polypropylene, nylon, polyvinyl chloride, polycarbonate, polyvinyl alcohol, polymethyl methacrylate, fluororesin, ethylene, vinyl A transparent resin film such as alcohol is preferred.
[0032]
As the transparent conductive film provided on the transparent substrate, ITO (tin-added indium oxide), ATO (antimony-added tin oxide), FTO (fluorine-added tin oxide), AZO (aluminum-added zinc oxide), GZO (gallium-added zinc oxide) , Au, Ag, Pt and other precious metal thin films can be used. Since the conductivity is a factor that determines the speed of coloring and decoloring, the surface resistance of the transparent conductive film is preferably low.
[0033]
As the electrolyte layer, a known organic or inorganic electrolyte can be used, and any transparent ionic conductor may be used. The conductive ions can be selected in accordance with the electrochromic material, and typical examples include lithium ions or hydrogen ions. These ionic conductors desirably have high ionic conductivity, are transparent and stable, and have high adhesion to the substrate. Specifically, a proton conductive resin such as Nafion (trade name) manufactured by DuPont Co., Ltd., an ion conductive resin of an organic-inorganic hybrid, tantalum oxide, and the like can be given. In addition, these ionic conductors and existing resins and sol-gel silicates such as ultraviolet curable resins, thermosetting resins, thermoplastic resins, room temperature curable resins, hydrolyzed polymers of metal alkoxides such as TEOS, etc. should be used. You can also.
[0034]
It is also possible to laminate the laminate of the base material / transparent conductive film / reduction coloring type electrochromic layer and the lamination of the oxidation coloring type electrochromic layer / transparent conductive film / base material with an electrolyte layer. In this case, a resin for lamination such as a vinyl chloride copolymer is mixed in the electrolyte layer.
[0035]
The method for applying the electrochromic device preparation coating liquid of the present invention on a substrate with a transparent conductive film is not particularly limited as long as a uniform coating film is obtained. For example, a bar coating method, a gravure coating method, A method such as a dip coating method, a spin coating method, or a roll coating method can be appropriately selected and used.
[0036]
According to such a coating method, it is possible to easily apply to a curved surface as well as a flat substrate. Furthermore, since it can apply | coat also to flexible film-like base materials, such as PET film, for example, an electrochromic layer is formed on two PET film base materials with a transparent conductive film, and it adheres and it is flexible. A film-like electrochromic device can be produced. Moreover, even if the area is large, an electrochromic element having uniform characteristics can be obtained stably.
[0037]
This flexible film-like electrochromic element can be affixed on a flat surface or a curved surface with an adhesive or the like, and can be affixed to, for example, an existing window of a house, a building, an automobile, or the like. Moreover, since the electrochromic device itself can operate at a voltage of about 1 to 5 volts, it can be easily operated using a small battery as a power source, and a power source can be incorporated into the film-like electrochromic device itself. Is possible.
[0038]
【Example】
In the following examples, tungsten oxide fine particles exhibiting electrochromic characteristics were produced, and an electrochromic device was produced by a simple coating method using a coating liquid in which the tungsten oxide fine particles were dispersed.
[0039]
The optical characteristics were measured based on JIS A 5459 (1998) (light source: A light), and the visible light transmittance and solar transmittance were calculated. However, the measurement sample was not attached to glass, and the film itself was used. Further, the haze value was measured based on JIS K 7105. The average dispersed particle size in the coating solution was measured by a measuring device using a dynamic light scattering method (manufactured by Otsuka Electronics Co., Ltd .: ELS-800), and the average value was used.
[0040]
[Example 1]
In nitrogen gas, 350 g of ethanol was added to WCl.₆Was slowly added in small portions to dissolve. The solution was kept at 70 ° C. to evaporate the solvent, and further heat-treated at 100 ° C. to obtain a light yellow powder. When this powder was identified by XRD, WO₃It was found that this was a crystalline state of (1) powder.
[0041]
The obtained powder (1) was heat-treated at 200 ° C. and identified by XRD.₃It was found that it was in the crystalline state of (2) powder. In addition, when the same powder (1) was heat-treated at 300 ° C. and identified by XRD, WO₃Was found to be in the crystalline state (3). Furthermore, when the same powder (1) was heat-treated at 400 ° C. and identified by XRD, WO₃Was found to be in the crystalline state (4).
[0042]
As described above, the powder (1) is a tungsten trioxide hydrate crystal when heat-treated at 200 ° C. or lower, and dehydrated into a crystal of tungsten trioxide by heat treatment at 300 ° C. or higher. It was.
[0043]
[Example 2]
In nitrogen gas, 350 g of ethanol was added to WCl.₆Was slowly added in small portions to dissolve. The solution was refluxed at 50 ° C. until it became colorless and transparent, and then the solvent was evaporated at 70 ° C., followed by heat treatment at 100 ° C. to obtain a light yellow powder. When the obtained powder was identified by XRD, WO₃A broad halo pattern appears at the diffraction position of₃It was expected to be in the amorphous state of hydrate (5 powder).
[0044]
The obtained powder (5) was heat-treated at 200 ° C. and identified by XRD.₃A broad halo pattern appears at the diffraction position of₃It was found that the hydrate was in an amorphous state (6). In addition, when the same powder (5) was heat-treated at 300 ° C. and identified by XRD, WO₃Was found to be in the crystalline state (7). Furthermore, when the same powder (5) was heat-treated at 400 ° C. and identified by XRD, WO₃Was found to be in the crystalline state (8 powder).
[0045]
(5) The powder that was heated and refluxed until it became colorless and transparent as described above was in an amorphous state of tungsten trioxide hydrate by heat treatment at 200 ° C. or lower, and dehydrated by heat treatment at 300 ° C. or higher. It has been found that it becomes a crystal of tungsten trioxide.
[0046]
[Example 3]
(7) 100 g of the powder produced in Example 2 above, 10 g of a silane coupling agent, and 900 g of ethanol are mixed, and this solution is dispersed by a ball mill to produce a dispersion A having an average dispersed particle size of 80 nm or less. did.
[0047]
Next, 50 g of this dispersion A was mixed with 10 g of an ultraviolet curable resin diluted with ethanol to 5% (manufactured by Toa Gosei Co., Ltd., UV3701) and a proton conductive resin diluted with ethanol to 5% (DuPont Corporation). ), Nafion) 10 g was added and mixed with stirring to prepare coating solution A.
[0048]
The coating liquid A was applied with a bar coater onto an 80 μm thick PET film (surface resistance 60Ω / □) coated with FTO (fluorine-added tin oxide) as a transparent electrode. This was dried at 70 ° C. for 1 minute to evaporate the solvent, and further irradiated with ultraviolet rays from a high pressure mercury lamp to cure the film. The obtained film had high transparency and a haze value of 1.2%.
[0049]
Next, in order to investigate the electrochromic properties of this membrane, this membrane was placed in a dilute sulfuric acid aqueous solution of pH 1 and a substrate coated with FTO was used as the counter electrode, and a voltage of 3 V was applied. Showed the color tone. At this time, the visible light transmittance of the film was 21%, and the solar radiation transmittance was 15%. Next, when the applied voltage was applied in the reverse direction, the color of the film immediately disappeared and became transparent. At this time, the visible light transmittance of the film was 76%, and the solar radiation transmittance was 67%.
[0050]
The transmission profile during coloring and decoloring of the film of Example 3 is shown in FIG. From this result, the film of the above-mentioned (7) powdered tungsten oxide has a transmittance that changes depending on the voltage, the transmittance difference between colored and decolored is 55% in visible light transmittance, and the solar radiation transmittance. It can be seen that good electrochromic characteristics are obtained.
[0051]
[Example 4]
(6) 100 g of the powder produced in Example 2 above, 10 g of a silane coupling agent, and 900 g of ethanol are mixed, and this solution is dispersed by a ball mill to prepare a dispersion B having an average dispersed particle size of 100 nm or less. did.
[0052]
Next, 10 g of an ultraviolet curable resin (UV3701, manufactured by Toa Gosei Co., Ltd.) diluted to 5% with ethanol and a proton conductive resin (DuPont Co., Ltd.) diluted to 5% with ethanol were added to 50 g of this dispersion B. ), Nafion) 10 g was added and mixed by stirring to prepare coating solution B.
[0053]
The coating liquid B was applied with a bar coater onto an 80 μm-thick PET film (surface resistance 60Ω / □) coated with FTO. This was dried at 70 ° C. for 1 minute to evaporate the solvent, and further irradiated with ultraviolet rays from a high pressure mercury lamp to cure the film. The obtained film was highly transparent and had a haze value of 2.3%.
[0054]
Next, in order to investigate the electrochromic properties of this membrane, this membrane was placed in a dilute sulfuric acid aqueous solution of pH 1 and a substrate coated with FTO was used as the counter electrode, and a voltage of 3 V was applied. Showed the color tone. At this time, the visible light transmittance of the film was 32%, and the solar radiation transmittance was 20%. Next, when the applied voltage was applied in the reverse direction, the color of the film immediately disappeared and became transparent. At this time, the visible light transmittance of the film was 74%, and the solar radiation transmittance was 64%.
[0055]
From this result, it can be seen that the transmittance of the film composed mainly of tungsten oxide powder as described in (6) above varies depending on the voltage and has good electrochromic characteristics.
[0056]
[Example 5]
(3) 100 g of the powder produced in Example 1 above, 10 g of a silane coupling agent, and 900 g of ethanol were mixed and dispersed with a ball mill to prepare a dispersion C having an average dispersed particle size of 100 nm or less.
[0057]
Next, 50 g of this dispersion C was mixed with 10 g of an ultraviolet curable resin (UV3701 manufactured by Toa Gosei Co., Ltd.) diluted to 5% with ethanol and a proton conductive resin (DuPont Co., Ltd.) diluted to 5% with ethanol. ), Nafion) 10 g was added and mixed by stirring to prepare coating solution C.
[0058]
The coating liquid C was applied by spray onto an 80 μm-thick PET film (surface resistance 60Ω / □) coated with FTO. This was dried at 70 ° C. for 1 minute to evaporate the solvent, and further irradiated with ultraviolet rays from a high pressure mercury lamp to cure the film. The obtained film was highly transparent and had a haze value of 2.7%.
[0059]
Next, in order to investigate the electrochromic properties of this membrane, this membrane was placed in a dilute sulfuric acid aqueous solution of pH 1 and a substrate coated with FTO was used as the counter electrode, and a voltage of 3 V was applied. Showed the color tone. At this time, the visible light transmittance of the film was 19%, and the solar radiation transmittance was 14%. Next, when the applied voltage was applied in the reverse direction, the color of the film immediately disappeared and became transparent. At this time, the visible light transmittance of the film was 69%, and the solar radiation transmittance was 57%.
[0060]
From this result, it can be seen that the transmittance of the film composed mainly of tungsten oxide of the above (3) powder changes with voltage and has good electrochromic characteristics.
[0061]
[Example 6]
(2) 100 g of the powder produced in Example 1 above, 10 g of a silane coupling agent, and 900 g of ethanol were mixed and dispersed with a ball mill to prepare a dispersion D having an average dispersed particle size of 120 nm or less.
[0062]
Next, 50 g of the dispersion D was mixed with 10 g of an ultraviolet curable resin diluted with ethanol to 5% (manufactured by Toa Gosei Co., Ltd., UV3701) and a proton conductive resin diluted with ethanol to 5% (DuPont Co., Ltd.). ), Nafion) 10 g was added and stirred and mixed to prepare coating solution D.
[0063]
The coating liquid C was applied on an 80 μm-thick PET film (surface resistance 60Ω / □) coated with FTO with a bar coater. This was dried at 70 ° C. for 1 minute to evaporate the solvent, and further irradiated with ultraviolet rays from a high pressure mercury lamp to cure the film. The obtained film was highly transparent and had a haze value of 2.9%.
[0064]
Next, in order to investigate the electrochromic properties of this membrane, this membrane was placed in a dilute sulfuric acid aqueous solution of pH 1 and a substrate coated with FTO was used as the counter electrode, and a voltage of 3 V was applied. Showed the color tone. At this time, the visible light transmittance of the film was 10%, and the solar radiation transmittance was 11%. Next, when the applied voltage was applied in the reverse direction, the color of the film immediately disappeared and became transparent. At this time, the visible light transmittance of the film was 55%, and the solar radiation transmittance was 40%.
[0065]
From this result, it can be seen that the transmittance of the film composed mainly of tungsten oxide powder as described in (2) above changes depending on the voltage and has good electrochromic characteristics.
[0066]
[Comparative Example 1]
(8) 100 g of the powder produced in Example 2 above, 3 g of the silane coupling agent, and 900 g of ethanol were mixed and dispersed by a ball mill to prepare a dispersion E having an average dispersed particle diameter of 400 nm.
[0067]
Next, 50 g of this dispersion E was mixed with 10 g of an ultraviolet curable resin (UV3701 manufactured by Toa Gosei Co., Ltd.) diluted to 5% with ethanol and a proton conductive resin (DuPont Co., Ltd.) diluted to 5% with ethanol. ), Nafion) 10 g was added and mixed with stirring to prepare coating solution E.
[0068]
The coating liquid E was applied with a bar coater onto an 80 μm-thick PET film (surface resistance 60Ω / □) coated with FTO. This was dried at 70 ° C. for 1 minute to evaporate the solvent, and further irradiated with ultraviolet rays from a high pressure mercury lamp to cure the film. The obtained film had low transparency and a haze value of 72.5%.
[0069]
As described above, even in the case of the film having the above-mentioned (8) powdered tungsten oxide as a main component, since the average dispersed particle diameter is as large as 400 nm, the light scattering is large, resulting in loss of transparency and dimming. It was inappropriate for applications such as windows.
[0070]
  "Comparative Example 2"
  the aboveExample 1Manufactured with(2) powder100 g, 10 g of a silane coupling agent, and 900 g of ethanol were mixed and dispersed with a ball mill to prepare dispersion F having an average dispersed particle size of 100 nm or less.
[0071]
Next, 10 g of an ultraviolet curable resin (UV3701, manufactured by Toa Gosei Co., Ltd.) diluted to 5% with ethanol was added to 50 g of this dispersion F, but the proton conductive resin was not added and mixed with stirring. Thus, a coating solution F was obtained.
[0072]
The coating liquid F was applied with a bar coater onto an 80 μm-thick PET film (surface resistance 60Ω / □) coated with FTO. This was dried at 70 ° C. for 1 minute to evaporate the solvent, and further irradiated with ultraviolet rays from a high pressure mercury lamp to cure the film. The obtained film had high transparency and a haze value of 3.2%.
[0073]
Next, in order to investigate the electrochromic properties of this membrane, this membrane was placed in a dilute sulfuric acid aqueous solution of pH 1 and a substrate coated with FTO was used as the counter electrode, and a voltage of 3 V was applied. Showed the color tone. At this time, the visible light transmittance of the film was 38%, and the solar radiation transmittance was 24%. Next, an applied voltage was applied in the reverse direction. At this time, the visible light transmittance of the film was 45%, and the solar radiation transmittance was 29%.
[0074]
From this result, even if the film is composed mainly of powdered tungsten oxide (2) above, when it does not contain proton conductive resin, the difference between coloring and decoloring of the film due to voltage application is small. It was found that the color efficiency was not good.
[0075]
【The invention's effect】
According to the present invention, tungsten oxide fine particles exhibiting electrochromic characteristics can be produced at a low cost by a simple method that does not require a special apparatus or the like. Further, an inexpensive electrochromic element having uniform characteristics even in a large area can be produced by a simple coating method using a coating liquid in which the electrochromic fine particles are dispersed.
[0076]
The electrochromic device according to the present invention can provide industrial products with high versatility such as a light control device and a display device, and is particularly suitable for light control glass, and by using a flexible film-like substrate, A light control window can be obtained by pasting on an existing window glass.
[Brief description of the drawings]
FIG. 1 is a graph showing transmission profiles during coloring and decoloring of an electrochromic film produced in Example 3.

Claims (1)

  Tungsten trioxide or its hydrate or a mixture of both by dissolving tungsten hexachloride in alcohol and evaporating the solvent as it is, or heating and refluxing, evaporating the solvent and then heating at 100 to 500 ° C. A method for producing tungsten oxide fine particles exhibiting electrochromic characteristics, characterized in that a powder comprising:

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