Electrochromic elements and eyeglass lenses

Abstract

To provide: an electrochromic element which comprises an electrode layer that is free from the occurrence of a crack: and an eyeglass lens which uses the electrochromic element.SOLUTION: An electrochromic element according to the present invention comprises electrode layers and an electrochromic layer. Preferably, the electrode layers are transparent electrode layers that are formed of an amorphous material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrochromic device capable of reversibly controlling electrochromism for decolorization and coloring by electricity, and a spectacle lens using the same.

Background Art

[0002] An electrochromic device that utilizes an electrochromism phenomenon in which a redox reaction occurs reversibly by applying a voltage and the color changes reversibly is used, for example, as a spectacle lens. The electrochromic device is formed in a laminated structure having an electrode layer and an electrochromic layer on the surface of a substrate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described in Patent Document 1, a transparent electrode layer made of ITO or the like is generally used for the electrode layer. When an electrochromic (EC) device is incorporated into a spectacle lens, in order to produce a prescription lens with a predetermined diopter, it is necessary to adjust the shape of the device so that the convex surface and the concave surface form a substantially spherical surface. Since it is difficult to produce a device with a spherical shape from the beginning, usually, a planar EC device is produced and then processed into a spherical shape.

[0005] However, when performing spherical processing, a problem occurs in that cracks occur in the transparent electrode made of ITO. The cracks become a factor that inhibits the function of the device or reduces the long-term reliability.

[0006] The present invention aims to solve the above problems and to provide an electrochromic element having an electrode layer capable of suppressing crack formation, and an eyeglass lens using the same. [Means for solving the problem]

[0010] The electrochromic element in the present invention is an electrochromic element having an electrode layer and an electrochromic layer, wherein the electrode layer includes conductive fibers in a transparent electrode layer, and the conductive fibers but Mixed within the transparent electrode layer The transparent electrode layer is ITO, the conductive fibers are a composite of carbon nanotubes and silver nanowires, and the conductive fibers are arranged in a mesh-like pattern. It is characterized by the following:

[0011] In the present invention, the conductive fibers are preferably carbon nanotubes or metal nanowires.

[0012] In the present invention, the electrode layer can be configured to include the conductive fibers in a transparent electrode layer.

[0013] In this invention, the electrochromic element can be formed in a curved shape.

[0014] The eyeglass lens of the present invention is characterized by having an electrochromic element as described in any of the above. [Effects of the Invention]

[0015] According to the electrochromic element of the present invention and the eyeglass lens using the same, the occurrence of cracks can be suppressed by improving the material of the electrode layer. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic cross-sectional view of an electrochromic element in an embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view showing an electrochromic element in an embodiment of the present invention that has been processed into a spherical shape. [Figure 3] Figure 3 is a perspective view showing cracks occurring in eyeglasses using a conventional electrochromic element. [Figure 4] Figure 4A is a schematic cross-sectional view showing an example of an electrode layer in an embodiment of the present invention, and Figure 4B is a schematic plan view of Figure 4A. [Figure 5] Figure 5 is a perspective view of eyeglasses using an electrochromic element according to an embodiment of the present invention. [Modes for carrying out the invention]

[0017] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). First, the overall structure of the electrochromic element 10 will be described.

[0018] <Overall structure of an electrochromic element> Electrochromic (EC) elements are devices that utilize the electrochromic phenomenon, which causes a reversible oxidation-reduction reaction by applying voltage to both electrodes, resulting in a reversible change in color. For example, electrochromic elements can be used as eyeglass lenses, functioning as sunglasses in bright light and as clear lenses in dark light. They can be operated by a switch or automatically adjusted to the optimal brightness.

[0019] Figure 1 is a schematic cross-sectional view of the electrochromic element 10. The electrochromic element 10 comprises a pair of first substrates 1 and second substrates 2, a first electrode layer 4 and a second electrode layer 5 arranged inside each of the substrates 1 and 2, and an electrochromic layer 6 provided between the electrode layers 4 and 5. Furthermore, the electrochromic layer 6 is composed of a reduction layer 7 arranged on the first electrode layer 4 side, an oxide layer 8 arranged on the second electrode layer 5 side, and an electrolyte layer 9 provided between the reduction layer 7 and the oxide layer 8.

[0020] As shown in FIG. 1, both ends of the first substrate 1 and the second substrate 2 extend outside the electrochromic layer 6, and a seal layer 14 is provided between the substrates 1 and 2 and around the electrochromic layer 6. The seal layer 14 is an existing insulating resin material, and the substrates 1 and 2 are adhered by the seal layer 14.

[0021] The electrochromic element 10 is in the form of a film. For example, it can constitute a spectacle lens in which the electrochromic film of FIG. 1 is adhered to the surface of a lens substrate (not shown). Alternatively, using the first substrate 1 and the second substrate 2 as the lens substrate, a spectacle lens can also be constituted by the electrochromic element 10 shown in FIG. 1.

[0022] The substrates 1 and 2 constituting the electrochromic element 10 are, for example, in the form of a film or a sheet, and are required to be transparent and have a high transmittance. The substrates 1 and 2 are, for example, moldable resin substrates such as polycarbonate resin, acrylic resin, epoxy resin, and phenol resin, or glass substrates. The substrates 1 and 2 being formed of polycarbonate resin is advantageous in terms of obtaining transparency and high transmittance and in terms of manufacturing cost.

[0023] The reduction layer 7 constituting the electrochromic layer 6 is a layer that develops color with a reduction reaction. Existing reduction-type electrochromic compounds can be used for the reduction layer 7. Without being limited to whether they are organic or inorganic, for example, azobenzene-based, anthraquinone-based, diarylethene-based, dihydropyran-based, dipyridine-based, styryl-based, styrylspiropyran-based, spirooxazine-based, spiropthiopyran-based, thioindigo-based, tetrathiafulvalene-based, terephthalic acid-based, triphenylmethane-based, triphenylamine-based, naphthopyran-based, viologen-based, pyrazoline-based, phenazine-based, phenylenediamine-based, phenoxazine-based, phenothiazine-based, phthalocyanine-based, fluoran-based, fulgide-based, benzopyran-based, metallocene-based, tungsten oxide, molybdenum oxide, iridium oxide, titanium oxide, etc. can be mentioned.

[0024] The oxide layer 8 constituting the electrochromic layer 6 is a layer that develops color in response to oxidation reactions. Existing oxidative electrochromic compounds can be used for the oxide layer 8. While not limited to organic or inorganic compounds, examples include compositions containing radical polymerizable compounds with triarylamines, Prussian blue-type complexes, nickel oxide, iridium oxide, and the like.

[0025] The electrolyte layer 9 constituting the electrochromic layer 6 preferably possesses electronic insulation and ionic conductivity, and is also transparent. The electrolyte layer 9 may be a solid electrolyte, a gel, or a liquid. A gel is preferable in order to maintain high ionic conductivity. Although not limited, existing electrolyte materials such as alkali metal salts, alkaline earth metal salts, and other inorganic ionic salts, quaternary ammonium salts, and acids can be used.

[0026] Figure 2 is a schematic cross-sectional view of an electrochromic element molded into a spherical shape. The electrochromic element 10 of this embodiment can be applied, for example, to eyeglass lenses. In this case, the electrochromic element must be processed into a spherical shape, but it is difficult to manufacture a spherical element from the beginning. Therefore, generally, a planar electrochromic element 10 as shown in Figure 1 is manufactured, and then a process such as pressing it into a predetermined mold while heating is performed to mold the electrochromic element 10 into a spherical shape.

[0027] <Conventional challenges in electrochromic devices> Incidentally, ITO (indium tin oxide) is commonly used for the electrode layers 4 and 5 of the electrochromic element 10 from the viewpoint of transparency and conductivity.

[0028] Conventionally, commonly used ITO films are crystalline, which makes them prone to cracking when the electrochromic element 10 is processed into a three-dimensional curved surface.

[0029] As described above, the electrochromic element 10 can be applied to, for example, eyeglass lenses, and the electrochromic element 10 can be bent into a three-dimensional curved surface. However, when this is done, cracks sometimes occur in the ITO film formed on almost the entire surface of the electrochromic element 10. That is, as shown in Figure 3, when an electrochromic element in which electrode layers 4 and 5 are made of ITO is applied to the lens 101 of eyeglasses 100, damage due to cracks 102 sometimes occurs on the inner surface of the lens 101. The cracks 102 can range from large ones visible to the naked eye to tiny microcracks that are only visible under a microscope, but all of them hinder the function of the element or reduce its long-term reliability.

[0030] <Regarding the electrode layer of the first embodiment> The electrode layers of this embodiment will now be described. First, as shown in Figure 1, each electrode layer 4 and 5 is in contact with each substrate 1 and 2, respectively, or is arranged on the substrate surface via a functional layer such as a reflection suppression layer.

[0031] The required characteristics for electrode layers 4 and 5 include transparency, high transmittance, and excellent conductivity. As mentioned above, cracks can occur in ITO films, so it is desirable to use an electrode material that does not crack even when formed from a planar shape to a spherical shape, instead of ITO.

[0032] Therefore, as a result of diligent research, the inventors have found that a conductive amorphous (non-crystalline) material is used as the material for electrode layers 4 and 5, and that electrode layers 4 and 5 are formed as transparent electrode layers made of amorphous material.

[0033] The conductive amorphous material may be either an inorganic material or an organic material, or a hybrid material. As an inorganic material, IZO (indium zinc oxide) is preferably used. As an organic material, while the material is not limited, it is preferable to use conductive polymer materials such as poly(3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS), polyacetylene, polypyrrole, polyaniline, polythiophene, poly(p-phenylene), polyfluorene, poly(p-phenylene vinylene), polythienene vinylene, polyacene, or graphene. The above electrode materials have a certain degree of flexibility and can be arranged in a random layering distribution, allowing for redundancy against localized disconnections. Therefore, by using these materials in the electrode layers 4 and 5 of the electrochromic element 10, cracks can be suppressed in the electrode layers 4 and 5 when the electrochromic element 10 is formed into a three-dimensional curved surface.

[0034] In the first embodiment, it is particularly preferable to use IZO for the first electrode layer 4 and the second electrode layer 5. As a material for transparent electrode films, IZO has low resistance when formed at room temperature, high transmittance, amorphous stability, excellent surface smoothness, bending resistance, and excellent etching properties. In addition, IZO generates few nodules and is extremely resistant to arcing, thus suppressing particles. Below, we will explain that electrodes using IZO have superior basic characteristics as transparent electrodes compared to conventional electrodes using ITO.

[0035] [Comparison of ITO and IZO characteristics] IZO has superior conductivity compared to ITO. For example, let's compare the resistivity (mΩ·cm) of ITO and IZO with respect to their annealing temperature (°C). In this case, IZO can maintain a lower resistivity compared to ITO in the annealing temperature range of approximately 0 to 200°C. Specifically, the resistivity of IZO is 0.5 (mΩ·cm) or less, preferably 0.4 (mΩ·cm) or less. Thus, IZO has lower resistivity and superior conductivity compared to ITO when deposited at room temperature or during low-temperature annealing.

[0036] IZO has superior optical properties compared to ITO. For example, it has been found that the transmittance of IZO is higher than that of ITO in the visible light range of 400 nm to 780 nm wavelength. Specifically, the transmittance of IZO is about 80% or more, preferably 83% or more, more preferably 85% or more, even more preferably 87% or more, and most preferably 90% or more, at annealing temperatures in the range of 0°C to 180°C. Thus, IZO has higher transmittance compared to ITO when film deposition is performed at room temperature or during low-temperature annealing.

[0037] IZO has superior bending resistance compared to ITO. For example, when an IZO film and an ITO film (with a transparent polyimide base material) are placed on a table with a variable tilt angle, and each film is bent while changing the tilt angle of the table (10 to 90 degrees) in the direction that brings both ends of each film closer together, it is found that IZO has a lower resistance change rate (ΔR / R0) with respect to the number of bends than ITO, and has superior bending resistance. In other words, it is found that ITO is more prone to cracking when bent than IZO. The resistance change rate (ΔR / R0) can be expressed as the rate of the change in resistance ΔR relative to the resistance value R0 when the number of bends is zero. The resistance change rate (ΔR / R0) of IZO (without annealing) is 0.03% or less, preferably 0.02% or less, and more preferably 0.01% or less, when the number of bends is 30,000 or less. Thus, IZO has higher bending resistance compared to ITO.

[0038] From the above, IZO has lower resistance, superior conductivity, and high transmittance compared to ITO. Furthermore, it has excellent bending resistance and good amorphous stability, and is less prone to cracking compared to ITO. Therefore, when IZO is used as the electrode layers 4 and 5 of the electrochromic element 10, cracks are suppressed when forming the electrochromic element 10 from the planar structure in Figure 1 to the spherical structure in Figure 2, and defects are less likely to occur.

[0039] <Regarding the electrode layer of the second embodiment> In the second embodiment, the pair of first electrode layers 4 and second electrode layers 5 consist of a large number of conductive fibers. That is, the transparent electrode layer in the second embodiment is formed as a single layer structure of conductive fibers. The conductive fibers are not limited, but are submicron-sized fibers (tubes or wires), and it is preferable to use carbon nanotubes (CNTs) or metal nanowire materials. The metal nanowire material is not limited, but it is preferable to use silver (Ag) nanowires. It is also preferable to use a combination of these materials, and it is particularly preferable to use a combination of carbon nanotubes (CNTs) and silver (Ag) nanowires. By using these materials in the electrode layer, redundancy can be provided against localized disconnections, and uniform power supply can be maintained across the entire surface of the device.

[0040] In this embodiment, by forming the conductive fibers in a mesh-like matrix, the transparency of the electrode layers 4 and 5 can be ensured, as well as the stability of the conductive path.

[0041] <Regarding the electrode layer of the third embodiment> The electrode layer of the third embodiment differs from that of the second embodiment in that it includes conductive fibers in the transparent electrode layer. For example, as shown in Figures 4A and 4B, the electrode layers 4 and 5 are constructed by laminating a large number of conductive fibers 13 on the surface of a transparent electrode layer 15 formed on the surface (inner surface) of substrates 1 and 2. As shown in Figure 4B, the conductive fibers 13 form a uniform mesh-like matrix across the entire surface of the transparent electrode layer 15. The conductive fibers 13 may also be mixed within the transparent electrode layer 15.

[0042] Here, the transparent electrode layer 15 shown in Figures 4A and 4B may be ITO, or it may be a transparent electrode layer made of a conductive amorphous material as in the first embodiment. For example, in the third embodiment, the transparent electrode layer 15 is ITO, and the conductive fiber 13 is preferably a composite of carbon nanotubes (CNTs) and silver (Ag) nanowires.

[0043] By using the electrode structure shown in Figures 4A and 4B, even if a break occurs in electrode layers 4 and 5, for example, if the transparent electrode layer 15 is ITO and a crack occurs in the ITO film, redundancy due to conductive fibers will emerge, and by making that part conductive, uniform power supply will be maintained across the entire surface of the element.

[0044] Furthermore, in the third embodiment, the conductive fibers 13 can be interposed at the first interface 11 between the first electrode layer 4 and the reduction layer 7 shown in Figures 1 and 2, and at the second interface 12 between the second electrode layer 5 and the oxide layer 8. As a result, each electrode layer 4, 5 and the electrochromic layer 6 are in contact, allowing for a stable electrochromic phenomenon to be obtained and excellent responsiveness to be maintained.

[0045] <Application> While this embodiment does not limit the applications of the electrochromic element, it can be preferably applied to photochromic eyeglass lenses. In eyeglass lenses, an electrochromic element 10 processed into a three-dimensional curved surface as shown in Figure 2 is used. The electrochromic element 10 is, for example, an electrochromic film, and eyeglass lenses can be used in which a lens substrate is molded to the second substrate 2 side.

[0046] Figure 5 is a perspective view of eyeglasses 200 using an electrochromic element according to an embodiment of the present invention. In the embodiment of the present invention, by forming the electrochromic element three-dimensionally into a spherical or curved shape and using it as an eyeglass lens 201, eyeglasses 200 that do not develop cracks can be manufactured.

[0047] The electrochromic element of this embodiment may be applied to applications other than eyeglass lenses. For example, electrochromic light-adjusting devices and anti-glare mirrors. [Industrial applicability]

[0048] The electrochromic element and eyeglass lens using the same of the present invention make it possible to provide redundancy against localized wire breaks, suppress the occurrence of cracks, and maintain uniform power supply across the entire surface of the EC element. [Explanation of Symbols]

[0049] 1. First substrate 2. Second substrate 3 Electrochromic film 4. First electrode layer 5. Second electrode layer 6. Electrochromic layer 7. Reduction layer 8. Oxidation layer 9 Electrolyte layer 10 Electrochromic elements 11 First interface 12 The second interface 13 Conductive Fibers 14 sealing layer 15 Transparent electrode layer 100, 200 glasses 101, 201 lenses 102 Crack

Claims

1. An electrochromic element having an electrode layer and an electrochromic layer, The electrode layer includes conductive fibers in the transparent electrode layer, and the conductive fibers are mixed within the transparent electrode layer. An electrochromic element characterized in that the transparent electrode layer is made of ITO, the conductive fibers are a composite of carbon nanotubes and silver nanowires, and the conductive fibers are arranged in a mesh-like pattern.

2. The electrochromic element according to claim 1, characterized in that the electrochromic element is formed in a curved shape.

3. An eyeglass lens characterized by having the electrochromic element described in claim 2.

Images