JP5965258B2 - Electrochromic device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrochromic device having an electrochromic thin film exhibiting electrochromic characteristics and a method for manufacturing the same.

  The electrochromic property is a property that causes a reversible optical property change by applying electric energy. Generally, the electrochromic property causes the color tone or the like of a substance by an electrochemical redox reaction caused by a change in flowing current. It shows the characteristic that the color changes reversibly. Since the electrochromic smart window using this can electrically change the transmittance of the window glass, a high energy saving effect can be obtained.

  Transition metal oxides are used as electrochromic materials. For example, reduction-colored tungsten oxide and molybdenum oxide are colorless and transparent in an oxidized state, but are colored blue when reduced. Further, oxidation-colored nickel hydroxide and cobalt hydroxide are yellowish and transparent in a reduced state, but when oxidized, they are colored dark brown.

  In recent years, application of oxidative coloring electrochromic elements using cobalt hydroxide to light control glass and displays is expected. The inventors of the present application have proposed a method for producing a thin film with improved electrochromic properties by lowering the substrate temperature when forming an electrochromic thin film using cobalt hydroxide (Non-patent Document 1). .

Kyoung Moo Lee, Yoshio Abe, Midori Kawamura, and Kyung Ho Kim, “Effects of Substrate Temperature on Electrochromic Properties of Cobalt Oxide and Oxyhydroxide Thin Films Prepared by Reactive Sputtering Using O2 and H2O Gases” Jpn. J. Appl. Phys., Vol .51 (2012), 045501

  However, although the cobalt hydroxide thin film produced by the method described in Non-Patent Document 1 has improved electrochromic properties, when the oxidation-reduction reaction is repeated, the color change hardly appears, and the cycle durability is improved. There was a problem that it was low. In addition, there is a problem that the transmittance during decolorization is low.

  Accordingly, an object of the present invention is to provide an electrochromic device having a high transmittance at the time of decolorization and an improved cycle durability when the detachable color is repeated, and a method for producing the same.

  According to the present invention, a pair of transparent electrodes having a pair of transparent electrode layers provided opposite to each other on a pair of opposed substrates, an electrolyte layer and an electrochromic layer sandwiched between the pair of transparent electrode layers, In the electrochromic device in which the light transmittance changes depending on the voltage applied between the layers, an electrochromic device in which the electrochromic layer is a composite thin film of hydroxide and hydrated oxide is provided.

  The electrochromic layer uses a composite thin film of hydroxide and hydrated oxide to show excellent electrochromic properties, high transmittance during decolorization (reduced state), and repeated detachable color An electrochromic element with improved cycle durability can be obtained.

The hydroxide is preferably cobalt hydroxide or nickel hydroxide. Thereby, excellent electrochromic characteristics can be obtained. Here, cobalt hydroxide is cobalt hydroxide having a valence of trivalent (CoOOH), a mixture of cobalt oxide (Co ₃ O ₄ ) and CoOOH, and divalent cobalt hydroxide (Co (OH) ₂ ) and CoOOH. Nickel hydroxide is nickel hydroxide with a valence of nickel (NiOOH), a mixture of nickel oxide (NiO) and NiOOH, and divalent nickel hydroxide (Ni (OH) ₂ ). And a mixture of NiOOH.

The hydrated oxide is preferably hydrated niobium oxide, hydrated zirconium oxide, or hydrated tantalum oxide. Since these hydrated oxides are transparent, the transmittance at the time of decolorization (reduced state) can be improved by compounding with cobalt hydroxide. In addition, since the hydrated oxide exhibits proton conductivity, it does not inhibit the excellent electrochromic properties of cobalt hydroxide. Furthermore, since the hydrated oxide has better chemical stability in the aqueous electrolyte solution than the cobalt hydroxide, the cycle durability when the detachable color is repeated can be improved. Here, hydrated niobium oxide is Nb ₂ O ₅ .nH ₂ O, hydrated zirconium oxide is ZrO ₂ .nH ₂ O, hydrated tantalum oxide is Ta ₂ O ₅ .nH ₂ O, and hydrated water. The number n of molecules is about 0.2 to 6.

  The electrochromic layer is a composite thin film of cobalt hydroxide and hydrated niobium oxide, and the niobium concentration is preferably 43 at.% Or less. Thereby, even when the detachable color is repeated, it is possible to maintain high transmittance and to obtain high cycle durability.

  The electrochromic layer is a composite thin film of cobalt hydroxide and hydrated zirconium oxide, and the zirconium concentration is preferably 37 at.% Or less. Thereby, even when the detachable color is repeated, it is possible to maintain high transmittance and to obtain high cycle durability.

  The electrochromic layer is a composite thin film of nickel hydroxide and hydrated zirconium oxide, and the zirconium concentration is preferably 22 at.% Or less. Thereby, even when the detachable color is repeated, it is possible to maintain high transmittance and to obtain high cycle durability.

  The composite thin film is preferably formed by reactive sputtering using water vapor. As a result, the electrochromic characteristics can be improved, and a large-area electrochromic thin film can be produced, thereby obtaining a large size electrochromic element.

  According to the present invention, an electrochromic device manufacturing method includes a first transparent electrode forming step of forming a first transparent electrode on a surface of a first transparent substrate, and a surface of the formed first transparent electrode. An electrochromic layer forming step of forming an electrochromic layer by a thin film, a second transparent electrode forming step of forming a second transparent electrode on the surface of the second transparent substrate, and a surface of the formed second transparent electrode A counter electrode film forming step for forming a counter electrode film, a first transparent substrate having a first transparent electrode and an electrochromic thin film formed on the surface, and a second transparent electrode and a counter electrode film formed on the surface. And an assembly process for laminating the transparent substrate with an electrolyte layer interposed therebetween. In the electrochromic layer forming process, a composite of hydroxide and hydrated oxide is formed by reactive sputtering using water vapor. To form a thin film.

  Thereby, while improving the transmittance | permeability at the time of decoloring (reduced state), the electrochromic element which improved cycle durability can be obtained.

  In the electrochromic layer forming step, it is preferable to use a composite target in which a plurality of second target metal chips having a predetermined area are provided on the surface of the first target metal. Thereby, a large-area electrochromic thin film can be produced, and a uniform composite film can be formed.

  According to the present invention, by forming a composite thin film of hydroxide and hydrated oxide by reactive sputtering using water vapor, excellent electrochromic properties are exhibited, and the transmittance during decolorization (reduced state) is It is possible to obtain an electrochromic element that is high and has improved cycle durability when the detachable color is repeated.

  In addition, cobalt hydroxide or nickel hydroxide is used as the hydroxide, and hydrated niobium oxide, hydrated zirconium oxide, or hydrated tantalum oxide is used as the hydrated oxide. State) is higher, and the cycle durability when the detachable color is repeated can be remarkably improved.

  According to the present invention, in the electrochromic layer forming step, the composite thin film of hydroxide and hydrated oxide is formed by reactive sputtering using water vapor, thereby improving the transmittance during decolorization (reduced state). In addition, an electrochromic device with improved cycle durability can be obtained. Further, since a uniform electrochromic thin film having a large area can be easily produced by using the method of the present invention, it is possible to produce a large area electrochromic element required for a smart window.

It is sectional drawing which shows roughly the structure of the electrochromic element which concerns on this invention. It is a flowchart which shows schematically the manufacturing method of the electrochromic element shown in FIG. It is a flowchart which shows the formation method of an electrochromic thin film roughly. It is a top view which shows the structure of a composite target roughly. It is a figure which shows the relationship between Nb chip number and Nb density | concentration in an electrochromic thin film. It is a figure which shows the X-ray-diffraction pattern of the Co-Nb composite electrochromic thin film produced by changing Nb density | concentration. It is a figure which shows the infrared absorption spectrum of the Co-Nb composite electrochromic thin film produced by changing Nb density | concentration. It is a figure which shows the transmission spectrum in alkaline aqueous solution electrolyte of the Co-Nb composite electrochromic thin film produced by changing Nb density | concentration. It is a figure which shows the cycle dependence of the transmittance | permeability change in the alkaline aqueous solution electrolyte of the Co-Nb composite electrochromic thin film produced by changing Nb density | concentration. It is a figure which shows the relationship between the number of Zr chips and the Zr density | concentration in an electrochromic thin film. It is a figure which shows the transmission spectrum in alkaline aqueous solution electrolyte of the Co-Zr composite electrochromic thin film produced by changing Zr density | concentration. It is a figure which shows the cycle dependence of the transmittance | permeability change in the alkaline aqueous solution electrolyte of the Co-Zr composite electrochromic thin film produced by changing Zr density | concentration. It is a figure which shows the transmission spectrum in alkaline aqueous solution electrolyte of the Ni-Zr composite electrochromic thin film produced by changing Zr density | concentration. It is a figure which shows the cycle dependence of the transmittance | permeability change in the alkaline aqueous solution electrolyte of the Ni-Zr composite electrochromic thin film produced by changing Zr density | concentration. It is a figure which shows the cycle dependence of the transmittance | permeability change in the weak acidic aqueous solution electrolyte of the Ni-Zr composite electrochromic thin film produced by changing Zr density | concentration.

  FIG. 1 schematically shows the configuration of an electrochromic device according to a first embodiment of the present invention, FIG. 2 shows the main steps of the method for manufacturing the electrochromic device shown in FIG. 1, and FIG. 4 shows the main steps of the electrochromic thin film forming method, FIG. 4 shows the structure of the composite target used when forming the electrochromic thin film, and FIG. 5 shows the relationship between the number of Nb chips and the Nb concentration in the electrochromic thin film. FIG. 6 shows an X-ray diffraction pattern of a Co—Nb composite electrochromic thin film prepared by changing the Nb concentration, and FIG. 7 shows a Co—Nb composite electrochromic thin film prepared by changing the Nb concentration. FIG. 8 shows an infrared absorption spectrum. FIG. 8 shows alkaline water-soluble Co—Nb composite electrochromic thin films prepared by changing the Nb concentration. Shows the transmission spectrum in the electrolyte, Fig. 9 shows the cycle dependence of the transmittance change in an alkaline aqueous electrolyte of Co-Nb composite electrochromic thin film prepared by changing the Nb concentration.

  As shown in FIG. 1, the electrochromic device 100 includes a first transparent substrate 10, a first transparent electrode 20, an electrochromic thin film 30, an electrolyte layer 40, a counter electrode film 50, and a second transparent electrode. 60 and the 2nd transparent substrate 70 are provided with the laminated structure laminated | stacked in this order.

  The first transparent substrate 10 is a transparent glass substrate or a resin transparent sheet processed into a predetermined dimension.

  The first transparent electrode 20 is formed on the surface of the first transparent substrate 10, and indium oxide (ITO) to which 5 to 10% of tin is added is the same as in the case of a liquid crystal display or a solar cell. Alternatively, a tin oxide thin film to which fluorine or antimony is added is used. The film thickness is about 100 to 200 nm.

The electrochromic thin film 30 is a composite thin film of cobalt hydroxide (CoOOH) and hydrated niobium oxide (Nb ₂ O ₅ .nH ₂ O) formed on the surface of the first transparent electrode 20. The film thickness is, for example, about 100 nm to 1 μm. In this electrochromic thin film 30, the niobium concentration (Nb / (Co + Nb)) is 43 at.% Or less.

  The electrolyte layer 40 is an aqueous electrolyte, and in this embodiment, an aqueous solution of potassium hydroxide having a concentration of about 0.1 to 1 mol / L is used. In addition, you may use the lithium type electrolyte which added about 0.1-1 mol / L lithium perchlorate to the propylene carbonate of an organic material. Further, a solid electrolyte such as a polymer electrolyte or a proton conductive hydrated oxide may be used. In terms of ion conductivity, the aqueous electrolyte has the highest conductivity and is suitable for high-speed response. The thickness of the electrolyte layer is about 1 μm for a thin-film solid electrolyte, and can be used from several tens of μm to about several mm for a liquid electrolyte.

The counter electrode film 50 is made of cerium oxide (CeO ₂ ). The film thickness is about 100 nm to 1 μm. In this embodiment, the counter electrode film 50 is a cerium oxide film having a film thickness of 100 nm formed by using a sputtering method.

  The second transparent electrode 60 is formed on the surface of the second transparent substrate 70 and has the same configuration as the first transparent electrode 20 described above. The second transparent substrate 70 is the same transparent glass substrate or resin transparent sheet as the first transparent substrate.

  A manufacturing process of the electrochromic element 100 in the present embodiment will be described. As shown in FIG. 2, when the electrochromic element 100 is manufactured, first, a first transparent substrate film having a thickness of 200 nm is formed on the surface of the prepared first transparent substrate 10 using a sputtering method. The electrode 20 is stacked (step S11). Here, a transparent glass substrate was used as the first transparent substrate 10.

Next, a composite film of cobalt hydroxide and hydrated niobium oxide having a film thickness of 100 nm is laminated on the surface of the formed first transparent electrode 20 as the electrochromic thin film 30 by using a sputtering method (step S12). Here, the method of forming the composite film of cobalt hydroxide and hydrated niobium oxide is performed according to the procedure shown in FIG. As shown in FIG. 3, a reactive sputtering method using water vapor (H ₂ O) as a reactive gas was used for forming the electrochromic thin film. First, a glass substrate on which a transparent electrode is laminated is placed on a substrate holder in a film forming chamber of an RF magnetron sputtering apparatus (step S1). Next, a composite metal target of cobalt (first target metal) and niobium (second target metal) prepared in advance is placed on the cathode in the film formation processing chamber (step S2). As shown in FIG. 4, the composite metal target of cobalt and niobium is obtained by providing a square cobalt target having a diameter of 50 mm and a plurality of square (10 mm × 10 mm) Nb chips. FIG. 4 shows the case of four Nb chips. Next, water vapor (H ₂ O) is circulated in the film forming chamber as a reaction gas (step S3). In this state, high frequency power is applied, and a composite film of cobalt hydroxide and hydrated niobium oxide is formed on the substrate by reactive sputtering (step S4). Here, for example, the substrate temperature is maintained at 10 ° C., the supply amount of water vapor gas is 0.3 cc / min, the water vapor gas pressure is 50 mTorr, the RF power is 50 W, and cobalt hydroxide and hydrated niobium oxide are formed on the substrate. A composite film is formed.

  On the other hand, the second transparent electrode 60, which is an ITO transparent electrode film having a thickness of 200 nm, is laminated on the surface of the second transparent substrate 70 by using a sputtering method (step S13). Here, a transparent glass substrate was used as the second transparent substrate 70.

Next, a counter electrode film 50 of cerium oxide (CeO ₂ ) having a thickness of 100 nm is stacked on the surface of the formed second transparent electrode 60 by using a sputtering method (step S14).

  Next, for example, the spacer 40a is formed on the outer periphery of the surface of the first transparent substrate 10 on which the electrochromic thin film 30 is formed (step S15).

  Next, the first transparent substrate 10 on which the first transparent electrode 20 and the electrochromic thin film 30 are formed, and the second transparent substrate 70 on which the second transparent electrode 60 and the counter electrode film 50 are formed, The spacers 40a are pasted together (step S16).

  Next, a KOH alkaline aqueous electrolyte (pH = 13) having a concentration of 0.1 mol / L is injected into the gap formed by the spacer 40a (step S17). Thereby, a laminated structure of glass substrate / ITO film / composite film / electrolyte layer / counter electrode film / ITO film / glass substrate is formed. Finally, the electrolyte inlet is sealed so that the electrolyte does not leak (step S18). Thereby, the electrochromic element 100 is completed.

  The influence of niobium on the performance of the electrochromic thin film was examined for the electrochromic thin film 30 produced by the above method.

  An electro produced using only a disk-shaped cobalt target having a diameter of 50 mm and a composite target in which a plurality of square (10 mm × 10 mm) Nb chips are arranged on a disk-shaped cobalt target having a diameter of 50 mm. As a result of examining the niobium concentration in the chromic thin film by fluorescent X-ray analysis, as shown in FIG. 5, the niobium concentration in the electrochromic thin film increases as the number of Nb chips increases. Based on this result, the niobium concentration in the electrochromic thin film can be controlled by selecting the number of Nb chips.

  Further, the structure of a sample of a composite film of cobalt hydroxide and hydrated niobium oxide with niobium concentrations of 0 at.%, 6 at.%, 17 at.%, And 43 at.% Was measured by an X-ray diffraction method. As shown in FIG. 6, no clear diffraction peak was observed in all the samples, and it was found that the structures were close to amorphous. Note that the sample used in the measurement of FIG. 6 was prepared on a silicon substrate, and the sharp diffraction peak observed at a diffraction angle of about 33 ° is the diffraction peak of silicon used for the substrate.

Further, the absorption spectrum was measured by infrared spectroscopy for a sample of a composite film of cobalt hydroxide and hydrated niobium oxide with niobium concentrations of 0 at.%, 6 at.%, 17 at.%, And 43 at.%. As shown in FIG. 7, in the sample having a low niobium concentration, peaks corresponding to Co—O bonds were observed in the vicinity of 660 cm ⁻¹ and 570 cm ⁻¹ , but the peak intensity decreased with increasing niobium concentration. On the other hand, a broad absorption peak due to a hydrogen-bonded OH group that appears in the vicinity of 3300 cm ⁻¹ is recognized in all samples regardless of the niobium concentration, and the formation of hydroxides and hydrated oxides can be confirmed. In addition, the sample produced on the silicon substrate with little infrared absorption was used for the measurement of infrared spectroscopy.

  Also, a sample of a composite film of cobalt hydroxide and hydrated niobium oxide with niobium concentrations of 0 at. 6%, 17 at. 43% and 43 at.% Was decolorized in 0.1 M KOH alkaline aqueous electrolyte for 5 minutes. The transmission spectrum after coloring (applying −0.44 V vs. Ag / AgCl) and coloring (applying +0.56 V vs. Ag / AgCl) was measured. As shown in FIG. 8, the sample having a niobium concentration of 17 at.% Has the largest transmittance change width of 35% at a wavelength of 600 nm, and no added cobalt hydroxide even when the niobium concentration is increased to 43 at. It turned out that the transmittance | permeability change comparable as a thin film is shown. Moreover, compared with the sample with niobium concentration of 0 at.%, The sample added with niobium has a high transmittance at the time of decolorization, indicating that it is almost transparent.

  Further, a sample of a composite film of cobalt hydroxide and hydrated niobium oxide having a niobium concentration of 0 at.%, 6 at.%, 17 at.%, And 43 at.% Was scanned in a 0.1 M KOH alkaline aqueous electrolyte. The potential width is −0.44 to +0.56 V vs. The change in transmittance was measured when cyclic voltammetry was repeated 100 cycles under the conditions of Ag / AgCl and a potential scanning speed of 20 mV / s (one cycle was 100 seconds). As shown in FIG. 9, it was found that in the sample having a niobium concentration of 0 at.%, The transmittance change width after 100 cycles was greatly reduced to 65% of the initial transmittance change width. However, in the sample having a niobium concentration of 17 at.%, 95% of the initial transmittance change width is maintained even after 100 cycles, and it can be confirmed that the cycle durability is high. In the sample having a niobium concentration of 43 at.%, The transmittance change width is small. This is because, as the niobium concentration increases, the response speed of the detachable color becomes slow. Therefore, the change width of the transmittance can be widened by slowing the potential scanning speed.

  As described above, the electrochromic device 100 includes the electrochromic thin film 30 made of a composite thin film of cobalt hydroxide and hydrated niobium oxide. In the electrochromic thin film forming step, a composite thin film of cobalt hydroxide and hydrated niobium oxide is formed by reactive sputtering using water vapor using a composite metal target of cobalt and niobium.

  As a result, an electrochromic element that exhibits excellent electrochromic characteristics, has high transmittance during decolorization (reduced state), and has improved cycle durability when repeated detachable colors can be obtained.

  Also, cobalt hydroxide is used for the hydroxide and hydrated niobium oxide is used for the hydrated oxide, so that the transmittance at the time of decolorization is higher and the cycle durability when the detachable color is repeated. Can be significantly improved.

  The electrochromic layer is a composite thin film of cobalt hydroxide and hydrated niobium oxide, and the niobium concentration is 43 at.% Or less, preferably 6 at.% To 17 at.%. Thereby, even when the detachable color is repeated, high transmittance can be maintained and high cycle durability can be obtained.

  Hereinafter, the electrochromic device 200 according to the second embodiment of the present invention will be described.

  The electrochromic element 200 includes a first transparent substrate 10, a first transparent electrode 20, an electrochromic thin film 30A, an electrolyte layer 40, a counter electrode film 50, a second transparent electrode 60, and a second transparent electrode. A stacked structure in which the substrate 70 is sequentially stacked is provided.

  In the electrochromic element 200, the material configuration of the first transparent substrate 10, the first transparent electrode 20, the electrolyte layer 40, the counter electrode film 50, the second transparent electrode 60, and the second transparent substrate 70 is shown in FIG. Therefore, the detailed description is omitted.

  The electrochromic thin film 30 </ b> A is a composite thin film of cobalt hydroxide and hydrated zirconium oxide formed on the surface of the first transparent electrode 20. The film thickness is, for example, about 100 nm to 1 μm. In the electrochromic thin film 30A, the zirconium concentration (Zr / (Co + Zr)) is 37 at.% Or less.

  In the method of manufacturing the electrochromic element 200, the first transparent electrode 20 described above is formed except that a composite thin film of cobalt hydroxide and hydrated zirconium oxide as the electrochromic thin film 30A is formed on the surface of the first transparent electrode 20. This is the same as the embodiment.

As a method for forming a composite thin film of cobalt hydroxide and hydrated zirconium oxide, a reactive sputtering method using water vapor (H ₂ O) as a reaction gas was used (see FIG. 3). First, a glass substrate on which a transparent electrode is laminated is placed on a substrate holder in a film forming chamber of an RF magnetron sputtering apparatus (step S1). Next, a composite metal target of cobalt (first target metal) and zirconium (second target metal) prepared in advance is placed on the cathode in the film forming chamber (step S2). As shown in FIG. 4, the cobalt-zirconium composite metal target is obtained by providing a plurality of square (10 mm × 10 mm) Zr chips on a disc-shaped cobalt target having a diameter of 50 mm. Next, water vapor (H ₂ O) is circulated in the film forming chamber as a reaction gas (step S3). In this state, high frequency power is applied, and a composite film of cobalt hydroxide and hydrated zirconium oxide is formed on the substrate by reactive sputtering (step S4). Here, for example, the substrate temperature is kept at 10 ° C., the supply amount of water vapor gas is 0.3 cc / min, the water vapor gas pressure is 50 mTorr, the RF power is 50 W, and cobalt hydroxide and hydrated zirconium oxide are formed on the substrate. The composite film is formed.

  For the electrochromic thin film prepared by the above method, the influence of zirconium on the performance of the electrochromic thin film was examined. FIG. 10 shows the relationship between the number of Zr chips and the Zr concentration in the electrochromic thin film, FIG. 11 shows the transmission spectrum of a Co—Zr composite electrochromic thin film prepared by changing the Zr concentration, and FIG. 12 shows the Zr concentration. The cycle dependence of the transmittance | permeability change of the Co-Zr composite electrochromic thin film produced by changing is shown.

  Electrochromic produced using only a disk-shaped cobalt target having a diameter of 50 mm and a composite target in which a plurality of square (10 mm × 10 mm) Zr chips are arranged on a disk-shaped cobalt having a diameter of 50 mm. As a result of examining the zirconium concentration in the thin film by fluorescent X-ray analysis, as shown in FIG. 10, the Zr concentration in the electrochromic thin film increases as the number of Zr chips increases. Based on this result, the zirconium concentration in the electrochromic thin film can be controlled by selecting the number of Zr chips.

  In addition, a sample of a composite film of cobalt hydroxide and hydrated zirconium oxide having a zirconium concentration of 13 at. 37%, 74 at.% Was decolorized (-0. 0%) in a 0.1 M KOH alkaline aqueous electrolyte for 5 minutes. The transmission spectrum after 44 V vs. Ag / AgCl was applied and colored (+0.56 V vs. Ag / AgCl was applied) was measured. As shown in FIG. 11A, it was found that the sample with a zirconium concentration of 13 at.% Had the largest change width of the transmittance at a wavelength of 600 nm of 20%. Further, as shown in FIG. 11 (c), when the zirconium concentration is increased to 74 at.%, The transmittance change width is greatly reduced, which is inappropriate as an electrode material for an electrochromic device.

  In addition, a scanning potential width of −0.44 to +0.56 V vs. a sample of a composite film of cobalt hydroxide and hydrated zirconium oxide having a zirconium concentration of 13 at.%, 37 at.%, And 74 at.% Was used. The change in transmittance was measured when cyclic voltammetry was repeated 100 cycles under the conditions of Ag / AgCl and a potential scanning speed of 20 mV / s (one cycle was 100 seconds). As shown in FIG. 12 (a), in the sample having a zirconium concentration of 13 at.%, It can be confirmed that there is no significant decrease in the transmittance change width even after 100 cycles and the cycle durability is high.

  As described above, the electrochromic element 200 includes the electrochromic thin film 30A made of a composite thin film of cobalt hydroxide and hydrated zirconium oxide. In the electrochromic thin film forming step, a composite thin film of cobalt hydroxide and hydrated zirconium oxide is formed by reactive sputtering using water vapor using a composite metal target of cobalt and zirconium. Thereby, this embodiment can obtain the same effects as those of the first embodiment described above.

  Hereinafter, an electrochromic device 300 according to a third embodiment of the present invention will be described.

  The electrochromic element 300 includes a first transparent substrate 10, a first transparent electrode 20, an electrochromic thin film 30B, an electrolyte layer 40, a counter electrode film 50, a second transparent electrode 60, and a second transparent electrode. A stacked structure in which the substrate 70 is sequentially stacked is provided.

  In the electrochromic element 300, the material configurations of the first transparent substrate 10, the first transparent electrode 20, the electrolyte layer 40, the counter electrode film 50, the second transparent electrode 60, and the second transparent substrate 70 are shown in FIG. This is the same as in the case of the first embodiment, and thus detailed description thereof is omitted.

  The electrochromic thin film 30 </ b> B is a composite thin film of nickel hydroxide and zirconium hydrate oxide formed on the surface of the first transparent electrode 20. The film thickness is, for example, about 100 nm to 1 μm. In the electrochromic thin film 30A, the zirconium concentration (Zr / (Ni + Zr)) is 22 at.% Or less.

  In the method of manufacturing the electrochromic device 300, the first transparent electrode 20 described above is formed except that a composite thin film of nickel hydroxide and hydrated zirconium oxide as the electrochromic thin film 30B is formed on the surface of the first transparent electrode 20. This is the same as the embodiment, and thus detailed description thereof is omitted.

  For the electrochromic thin film prepared by the above method, the influence of zirconium on the performance of the electrochromic thin film was examined. FIG. 13 shows the transmission spectrum of the Ni—Zr composite electrochromic thin film prepared by changing the Zr concentration, and FIG. 14 shows the cycle dependence of the transmittance change of the Ni—Zr composite electrochromic thin film prepared by changing the Zr concentration. Is shown.

  A sample of a composite film of nickel hydroxide and hydrated zirconium oxide having a zirconium concentration of 0 at. 11 at. 22 at. 63 at.% Was decolorized (−) in a 0.5 M KOH alkaline aqueous electrolyte for 5 minutes. The transmission spectrum after 0.44 V vs. Ag / AgCl was applied and colored (+0.56 V vs. Ag / AgCl was applied) was measured. As shown in FIG. 13, the zirconium concentration is 11 at. % Of samples showed the largest change in transmittance at a wavelength of 600 nm of 70%. Further, even if the zirconium concentration is increased to 22 at.%, If the attaching / detaching color time is sufficiently long, the transmittance change width similar to that of the 0 at.% Sample can be obtained. On the other hand, when the zirconium concentration is increased to 63 at.%, The transmittance change width is greatly reduced, which is inappropriate as an electrode material for an electrochromic device.

  Further, the scanning potential width is −0.44 to +0.0 with respect to the sample of the composite film of nickel hydroxide and hydrated zirconium oxide with zirconium concentration of 0 at.%, 11 at.%, 22 at.%, And 63 at.%. 56V vs. The change in transmittance was measured when cyclic voltammetry was repeated 100 cycles under the conditions of Ag / AgCl and a potential scanning speed of 20 mV / s (one cycle was 100 seconds). As shown in FIG. 14, in the samples having a zirconium concentration of 0 at.% And 11 at.%, A decrease in the transmittance change width is not recognized even after 100 cycles, and it can be confirmed that the cycle durability is high.

  As described above, the electrochromic element 300 includes the electrochromic thin film 30B made of a composite thin film of nickel hydroxide and hydrated zirconium oxide. In the electrochromic thin film forming step, a composite thin film of nickel hydroxide and hydrated zirconium oxide is formed by reactive sputtering using water vapor using a composite metal target of nickel and zirconium. Thereby, this embodiment can obtain the same effects as those of the first embodiment described above.

  Usually, the structure of the electrochromic element is a laminated structure of glass substrate / transparent electrode (ITO film) / electrochromic thin film / electrolyte layer / counter electrode film / transparent electrode (ITO film) / glass substrate. The material of the electrochromic thin film is a material that changes color by oxidation-reduction reaction, and a material that is colored in a reduced state such as tungsten oxide or a material that is colored in an oxidized state such as cobalt hydroxide or nickel hydroxide is used. It is done. The material of the counter electrode film performs a redox reaction opposite to that of the electrochromic electrode, and functions to store and release ions. As the material of the counter electrode film, when using a transparent material that hardly changes color due to the redox reaction, such as cerium oxide, or when using an electrochromic material that is colored in a redox state opposite to the material of the electrochromic thin film There is. For example, if reduction-colored tungsten oxide is used for the electrochromic thin film material and oxidation-colored nickel hydroxide is used for the counter electrode material, the electrochromic thin film material and the counter electrode material can be attached and detached at the same time in a complementary manner. High coloring efficiency can be obtained. An element having this structure is referred to as a complementary electrochromic element. However, tungsten oxide exhibits stable electrochromic properties in an acidic aqueous solution, but dissolves easily in an alkaline aqueous solution. On the other hand, nickel hydroxide and cobalt hydroxide show stable electrochromic characteristics in an alkaline aqueous solution, but dissolve easily in a strongly acidic aqueous solution. Therefore, in order to realize a complementary electrochromic device using tungsten oxide as the material of the electrochromic thin film and nickel hydroxide as the material of the counter electrode film, it is necessary to use a neutral or weakly acidic aqueous solution.

Therefore, in order to investigate the possibility of application to complementary electrochromic devices, a detachable color cycle test of a composite film of nickel hydroxide and hydrated zirconium oxide in 1 mM H ₂ SO ₄ + 1M KCl weakly acidic aqueous electrolyte. Went. As a result, as shown in FIG. 15, the additive-free nickel hydroxide thin film dissolves in about 100 cycles and shows no change in transmittance, whereas the composite film added with 11 at. As can be seen from FIG. From this result, it can be confirmed that the composite oxide of hydroxide and hydrated oxide has a great effect not only in alkaline aqueous electrolyte but also in cycle durability improvement in weak acidic aqueous electrolyte.

  In the electrochromic device 100 of the above-described embodiment, the hydrated oxide is hydrated niobium oxide. In the electrochromic devices 200 and 300, the hydrated oxide is hydrated zirconium oxide. Is not limited to this. For example, hydrated tantalum oxide may be used as the hydrated oxide.

  Further, in the electrochromic devices 100 and 200 of the above-described embodiments, the composite target is formed by forming a plurality of 10 mm × 10 mm square Nb chips on a disc-shaped cobalt target having a diameter of 50 mm. It is not limited to. In addition, an electrochromic thin film can be similarly produced using an alloy target obtained by alloying two or more kinds of metals.

  All the embodiments described above are illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in other various modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

  The electrochromic device of the present invention can be used for light control glass, an antiglare mirror for automobiles, and electronic paper.

DESCRIPTION OF SYMBOLS 10 1st transparent substrate 20 1st transparent electrode 30, 30A, 30B Electrochromic thin film 40 Electrolyte layer 40a Spacer 50 Counter electrode film 60 2nd transparent electrode 70 2nd transparent substrate 100, 200, 300 Electrochromic element

Claims (8)

A pair of transparent electrode layers provided opposite to each other on a pair of opposing substrates, an electrolyte layer and an electrochromic layer sandwiched between the pair of transparent electrode layers, and applied between the pair of transparent electrode layers In an electrochromic device in which the light transmittance changes depending on the applied voltage,
The electrochromic layer is a composite thin film of hydroxide and hydrated oxide.   The electrochromic device according to claim 1, wherein the hydroxide is cobalt hydroxide or nickel hydroxide.   The electrochromic device according to claim 1, wherein the hydrated oxide is hydrated niobium oxide, hydrated zirconium oxide, or hydrated tantalum oxide.   2. The electrochromic device according to claim 1, wherein the electrochromic layer is a composite thin film of cobalt hydroxide and hydrated niobium oxide, and the niobium concentration is 43 at.% Or less.   2. The electrochromic device according to claim 1, wherein the electrochromic layer is a composite thin film of cobalt hydroxide and hydrated zirconium oxide, and a zirconium concentration is not more than 37 at.%.   2. The electrochromic device according to claim 1, wherein the electrochromic layer is a composite thin film of nickel hydroxide and hydrated zirconium oxide, and a zirconium concentration is 22 at.% Or less. A first transparent electrode forming step of forming a first transparent electrode on the surface of the first transparent substrate;
An electrochromic layer forming step of forming an electrochromic layer of a thin film on the surface of the formed first transparent electrode;
A second transparent electrode forming step of forming a second transparent electrode on the surface of the second transparent substrate;
A counter electrode film forming step of forming a counter electrode film on the surface of the formed second transparent electrode;
A first transparent substrate having a first transparent electrode and an electrochromic layer formed on the surface, and a second transparent substrate having a second transparent electrode and a counter electrode film formed on the surface, with an electrolyte layer interposed therebetween. An assembly process for stacking,
In the electrochromic layer forming step, a composite thin film of hydroxide and hydrated oxide is formed by reactive sputtering using water vapor. 8. The electro according to claim 7 , wherein the electrochromic layer forming step uses a composite target in which a plurality of second target metal chips having a predetermined area are provided on the surface of the first target metal. A method for manufacturing a chromic element.

Images