JPH04328723A - Electrochromic element - Google Patents

Abstract

PURPOSE:To obtain the electrochromic element which prevents the penetration of a radiation curing adhesive onto an electrochromic(EC) electrode and has excellent durability by using the above-mentioned adhesive for sealing. CONSTITUTION:A microporous film of polyethylene which is impregnated with an electrolyte soln. prepd. by dissolving lithium trifluoromethane sulfonate as an electrolyte into polyethylene glycol monoethr is used as a solid electrolyte thin film 11. The film of WO3 is formed on the transparent electrode 13 formed on a transparent glass substrate as the EC electrode 14 and a counter electrode 16 is formed by forming the film of the transparent electrode on the glass substrate 15. The solid electrolyte thin film 11 is crimped between the glass substrates 12 and 15 and the circumference is sealed with the urethane acrylate adhesive having good affinity to the respective constituting electrode layers and the electrolyte film. The curing time is shortened in this way.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an electrochromic device, and more specifically, to a sealing technique for an electrochromic device using a thin electrolyte film obtained by filling the pores of a solid polymer porous thin film with an electrolyte. .

0002

2. Description of the Related Art There is growing interest in devices that utilize the electrochromic (EC) phenomenon in which the color of a substance changes reversibly depending on voltage. Electrochromic element (EC
D) has characteristics such as being bright and easy to see, capable of large-area display, and having memory properties (low power consumption).
Applications that take advantage of these characteristics include large display boards such as stock price displays, message boards, and information boards, as well as light control elements for automobile anti-glare mirrors, light control glass (windows), and sunglasses.

[0003] The structure of ECD consists of an electrolyte placed between an electrochromic electrode (WO3) and a counter electrode, and when a voltage is applied between the two electrodes, WO3 is cathodically reduced by ions from the electrolyte and electrons from the power source, and becomes colored. It is something to do. The counter electrode can also be constituted by an electrochromic electrode and used for colored display. Furthermore, a panel that seals an electrolyte between an electrochromic electrode (WO3) and a counter electrode is generally made using an epoxy adhesive.

0004

[Problems to be Solved by the Invention] However, when we actually created an electrochromic device using an epoxy adhesive, we found that the curing time for the epoxy adhesive was approximately 30 minutes.
Because of the long time, it soaked into the electrochromic electrode during that time, and the electrode surface covered with adhesive no longer functioned as an electrochromic device. This is because the electrochromic device is a current device that utilizes electrode reactions, and is not a problem with electrode devices like liquid crystal panels.

[0005] Furthermore, electrochromic elements are often used outdoors, such as electrochromic windows, but epoxy adhesives do not necessarily have excellent light resistance and have the problem of insufficient durability. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve such problems and provide an electrochromic element that prevents the adhesive from seeping onto the electrochromic electrode and has excellent durability.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention uses, as an electrolyte, an electrolyte thin film formed by filling the pores of a solid polymer porous thin film with an ionic conductor,
An electrochromic device comprising the electrolyte thin film sandwiched between transparent substrates having electrochromic electrodes formed on their surfaces and sealed, characterized in that a radiation-curable adhesive is used for said sealing. Provide an element.

The electrolyte used in the present invention consists of an electrolyte thin film formed by charging an ionic conductor into the pores of a solid polymer porous thin film. This electrolyte thin film can be handled as a solid as a whole, there is no fear of liquid leakage, and it has excellent ionic conductivity. Further, it is possible to make the film thinner. Such a solid polymer porous thin film has a thickness of 0.1 μm to 50 μm, a porosity of 40% to 90%,
Those having a breaking strength of 200 kg/cm2 or more and an average through-hole diameter of 0.001 μm to 1.0 μm are preferably used.

[0008] The thickness of the thin film is generally 0.1 μm to 50 μm.
and preferably 0.1 μm to 25 μm. If the thickness is less than 0.1 μm, it is difficult to put it to practical use because of the reduced mechanical strength as a support film and the ease of handling. On the other hand, if it exceeds 50 μm, it is not preferable from the viewpoint of keeping the effective resistance low. The porosity of the porous thin film is 4
0% to 90%, preferably 60% to 90%
% range. If the porosity is less than 40%, the ionic conductivity as an electrolyte will be insufficient, while if it exceeds 90%, the functional strength as a support membrane will be low, making it difficult to put it into practical use.

The average diameter of the through-holes is generally 0.001 μm to 1.0 μm, although it is sufficient that the ionic conductor can be immobilized in the holes.
It is 0 μm. The preferred average through-hole diameter depends on the material of the polymer membrane and the shape of the pores. The breaking strength of polymer membranes is generally 2
00kg/cm2 or more, preferably 500kg
/cm2 or more, it is suitable for practical use as a support film. The porous thin film used in the present invention functions as a support for the ion conductor as described above, and is made of a polymeric material with excellent mechanical strength.

From the viewpoint of chemical stability, for example, polyolefin, polytetrafluoroethylene, polypinylidene fluoride can be used, but from the viewpoint of the design of the porous structure of the present invention and the ease of achieving both thinning and mechanical strength. One example of a suitable polymeric material is one having a weight average molecular weight of 5×10
5 or more polyolefin. That is, a crystalline linear polyolefin, which is an olefin homopolymer or copolymer, and whose weight average molecular weight is 5 x 105 or more,
Preferably it is 1 x 105 to 1 x 107. Examples include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, and the like. Among these, polyethylene or polypropylene having a weight average molecular weight of 5×10 5 or more is preferred. The weight average molecular weight of the polyolefin influences the mechanical strength of the resulting permeable membrane. Ultra-high molecular weight polyolefins enable the formation of ultra-thin and high-strength films by ultra-stretching, and are used as supports for highly ionic conductive thin films with low effective resistance. Although a polyolefin having a weight average molecular weight of less than 5×10 5 can be used at the same time, an ultra-thin and high-strength film cannot be obtained by ultra-stretching in a system that does not contain a polyolefin having a weight average molecular weight of 5×10 5 or more. The porous thin film as described above can be manufactured by the following method. Ultra-high molecular weight polyolefin is heated and dissolved in a solvent such as liquid paraffin in an amount of 1% to 15% by weight to form a uniform solution. A sheet is formed from this solution and rapidly cooled to form a gel-like sheet. The amount of solvent contained in this gel sheet is
Extraction with a volatile solvent such as methylene chloride yields 10% to 90% by weight. This gel-like sheet is heated at a temperature below the melting point of the polyolefin and stretched to an areal magnification of 10 times or more. The solvent contained in this stretched film is extracted and removed with a volatile solvent such as methylene chloride, and then dried.

Another example of a suitable polymeric material is polycarbonate, in which case the solid polymer porous thin film is prepared by irradiating the polycarbonate thin film with charged particles in a nuclear reactor and alkali etching the tracks traversed by the charged particles. It can also be produced by a method of forming holes using a method. Such thin films are commercially available as polycarbonate and polyester products, for example Nuclepore membranes.

In addition, polyester, polymethacrylate, polyacetal, polyvinylidene chloride, tetrafluoropolyethylene, etc. can be used. The ionic conductor used in the present invention is a composite of an alkali metal salt or protonic acid and a polar polymer such as polyether, polyester, or polyimine, or a network or crosslinked polymer containing these polymers as segments. Complexes with molecules can be used. Polyethers such as polyethylene glycol, polypropylene glycol, or copolymers thereof are commercially available in liquid and powder forms with different molecular weights and degrees of polymerization, and can be easily used. That is, polyethers such as polyethylene glycol, polyethylene glycol monoether, polyethylene glycol diether, polypropylene glycol, polypropylene glycol monoether, polypropylene glycol diether,
Or poly(
oxyethylene/oxypropylene) glycol, poly(oxyethylene/oxypropylene) glycol monoether, or poly(oxyethylene/oxypropylene) glycol diether, condensates of these polyoxyalkylenes and ethylenediamine, phosphoric acid Esters, saturated fatty acids, aromatic esters, etc. can be used. Furthermore, copolymers of polyethylene glycol and dialkylsiloxane (for example, Naruse et al., Poly
mer preprints, Japan Vol.
34, No. 7, 2021-2024 (1985
), and JP-A-60-217263), copolymers of polyethylene glycol and maleic anhydride (e.g. C.C. Lee et al., Polymer, 1982.
Vol. 23 May 681-689), and copolymers of monomethyl ether of polyethylene glycol and methacrylic acid (for example, N. Kobayashi
et al., J. Physical Chemistry. V
ol. 89, No. 6, 987-991 (198
5)) form a complex with alkali metal ions, and the ionic conductivity at room temperature is 10-5 to 10-4S・c.
m-1, and is suitable as a material constituting a thin film electrolyte useful in the present invention.

The above polyethers may have a molecular weight of 150 or more, and the polymers include propylene carbonate, γ-butyrolactone, ethylene carbonate, methylfuran, dimethoxyethane, dioxolane, tetrahydrofuran, acetonitrile, One or more solvents selected from dimethylformamide, dimethylsulfoxide, methyltetrahydrofuran, sulfolane, methylthiophene, methylthiazole, and ethoxymethoxyethane may be added.

[0014] An alkali metal or alkaline earth metal salt or protonic acid can be used to form a complex with these polymer compounds. Examples of anions include halogen ions, perchlorate ions, thiocyanate ions, trifluoromethanesulfonate ions, and borofluoride ions. Lithium fluoride (LiF), sodium iodide (NaI), lithium iodide (LiI), lithium perchlorate (LiClO4), sodium thiocyanate (NaSCN), lithium trifluoromethanesulfonate (LiCF3SO3), lithium borofluoride ( LiB
F4), lithium hexafluorophosphate (LiPF6),
Specific examples include phosphoric acid (H3PO3), sulfuric acid (H2SO4), trifluorinated methanesulfonic acid, tetrafluorinated ethylenesulfonic acid C2F4(SO3H)2, and hexafluorinated butanesulfonic acid C4F6(SO3H)4.

The method of filling an ionic conductor into a thin polymer film is as follows: (1) An ionic conductor dissolved in a solvent or an ionic conductor finely dispersed in a sol or gel form in a solid polymer porous - Remove the solvent after impregnating, coating or spraying on a porous thin film; - Forming a film after mixing a solution of an ionic conductor or its sol or gel-like dispersion solution in the manufacturing process of a porous thin film; Methods such as impregnating, coating, or spraying a conductive monomer or soluble precursor into a solid polymer porous thin film, and then reacting within the pores can be used.

The sealing structure of the electrochromic device of the present invention is not particularly limited, and may be, for example, a structure as shown in FIGS. 1 to 3. Although FIG. 1 will be explained in detail in a later example, FIG.
Figure 3 shows a structure in which a spacer 4 made of a PET film or the like is arranged and bonded 5, and in consideration of the thin solid electrolyte film 1 of the present invention, a sealing member 6 is used for one of the glass electrodes 2 and 3. It has a structure that is sealed on the sides.

As a sealing adhesive for an element having such a structure, an ultraviolet curable adhesive is preferably used as a radiation curable adhesive in the present invention. The ultraviolet curable adhesive is made by adding a reactive diluent, a copolymerization initiator, an additive, an organic solvent, etc. to a polymerizable oligomer. As polymerizable oligomers, polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate,
There are silicon acrylates, etc., and as reactive diluents,
N-vinyl-2-pyrrolidone, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxyethyl acryloyl phosphate or 1-6-hexanediol diacrylate, 1-3-butanediol diacrylate, neopentyl Examples include glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, and the like. These are used to control the viscosity, improve adhesion and flexibility of the composition.

As the photopolymerization initiator, benzoin ethers such as isopropyl benzoin ether and isobutyl benzoin ether, ketals such as 1-hydroxycyclohexylphenyl ketone and benzyl dimethyl ketal, 2-hydroxy-2-methyl-propiophenone,
Acetophenone series such as 4-isopropyl-2-hydroxy-2-methyl-propiophenone, benzophenone series such as benzophenone and methyl o-benzoylbenzoate, and thioxanthone series such as 2-methylthioxanthone and 2-chlorothioxanthone can be used.

The viscosity of the adhesive is 7,000 to 50,000 centistokes, more preferably 10,000 to 450 centistokes, to prevent it from penetrating into the electrochromic electrode surface.
00 centistokes is preferred. The adhesive is applied and cured using visible light, ultraviolet light, etc. The lamp is a high pressure mercury lamp (254, 313, 365, 405 nm
), ultra-high pressure mercury lamp (250-600nm), metal highland lamp (250-600nm), xenon lamp (300-110nm), ultraviolet fluorescent lamp (300-40nm)
0nm), but there are also excimer lasers (Xe
Cl, XeF, KrF) can also be used. When curing with only visible light, a neon helium laser or the like is also used.

[0020] There are two types of electrodes for electrochromic devices: cathodic materials that are colored by reduction and anodic materials that are colored by oxidation. In WO3, which is a typical reduction coloring material, WO3 absorbs H+ (Li) from the electrolyte.
+ ) and when electrons from the power source are injected, a reaction of WO3 (colorless) +x H + +xe=H x WO3 (blue) takes place. Although this reaction is reversible, H x WO
When the power circuit is opened in the state of 3, the color turns blue (reduction state).
is retained for a long time. In addition to WO3, reduction colorants include IrOx, MoO3, MoS2, V2O5, M
gWO4, Nb2O5, TiO2, W4O8 (C2
O4)x etc. can also be used. EC electrode is 5
The thickness is about 00 to 1500 Å, and it is formed on a transparent conductive film.

The transparent conductive film is a current collecting electrode and is made of indium tin oxide (ITO), tin oxide, or the like. Thickness is 10
00 to 2000 Å is common. The transparent conductive film is formed on a transparent substrate such as a glass plate. In addition, at the opposite pole, H2・
A material that generates little O3, has good reversibility with respect to electrochemical redox reactions, and has a large capacitance is used. Specific examples include garbon, a composite material of a reduction metal compound and carbon, or a composite material of a metal oxide and carbon. The thickness of the counter electrode is approximately 1000 Å to 10 μm.

A voltage is applied from a power source between the EC electrode and the counter electrode, and when WO3 is reduced, a negative voltage is applied, and the voltage is about 1.3 to 2.8V. Also, there is an EC on the opposite side.
The electrode (electrode II) can be arranged, and the electrode I (WO3
) In addition to the reduction coloring described above, if an oxidation coloring type electrode material such as IrO x is used for the electrode II, an ECD with high coloring efficiency can be produced. Furthermore, WO3 having a different crystal state may be used for the electrode II. Alternatively, NiO x , CoO x , Priscian blue, polyaniline, etc. may be used.

[0023]

[Function] By using an ultraviolet curing adhesive as the sealing adhesive, the curing time is shortened, and intrusion into the surface of the electrochromic electrode is prevented, and the curing adhesive has excellent durability. In addition, the solid thin film electrolyte of the present invention has sufficient ionic conductivity at an environmental temperature, for example, -10°C to 30°C, so it has a wide operating temperature range, and since the electrolyte is a flexible solid thin film, , easy to assemble and handle. Therefore, it is possible to easily provide an element with no liquid leakage, a uniform thickness, and a large area, and various shapes can be selected.

[0024]

EXAMPLE An electrochromic device having the structure shown in FIG. 1 was manufactured. The solid electrolyte thin film 11 is a microporous polyethylene film impregnated with an electrolyte solution in which lithium trifluoromethanesulfonate as an electrolyte is dissolved in polyethylene glycol monoether, and has a thickness of 4 μm.
, an ionic conductivity of 2×10 −4 S/cm was used.

As the EC electrode 14, WO3 is deposited to a thickness of 3 on a transparent electrode (ITO, 2000 Å thick) formed on a transparent glass substrate (non-alkali glass, 3 mm thick).
The film was formed to a thickness of 000 Å. The counter electrode 16 has a transparent electrode (ITO, 2000 Å thick) formed on a glass substrate 15 (non-alkali glass, 3 mm thick). A solid electrolyte thin film 11 was sandwiched between glass substrates 12 and 15 as shown in FIG. 1, and the periphery was sealed with a urethane acrylate adhesive having good affinity with the glass substrate, each constituent electrode layer, and the electrolyte membrane. In a seal structure such as that shown in FIG. 1, the adhesive viscosity is preferably higher than 3000 centistokes.

For comparison, an epoxy adhesive was used instead of a UV-curable adhesive and cured by heating. Curing is at 25°C.
It was 30 minutes. A comparison of the EC element characteristics of the thus obtained Examples and Comparative Examples is shown in the table below. Here, a test was conducted to determine whether sealing performance could be achieved with a highly volatile solvent, here benzyl cyanide. In the case of epoxy adhesives, the curing time was measured at 40°C. The curing time was defined as the time required for the shear strength to reach 50 kgf/cm2. Epoxy adhesives that cure at high temperatures are not preferred because they degrade the performance of the electrochromic device. Therefore, since an adhesive that cures at room temperature is used, the curing time becomes longer and more penetration into the electrode layer occurs.

[0027]U
V-curing adhesive Epoxy adhesive sealing performance 60℃, 800h
r 60℃, 300hr Curing time 20
seconds 40 minutes (40
°C) Penetration into the electrode No peeling characteristics Good
Slightly poor

0028
]

Effects of the Invention In the EC element according to the present invention, since the seal hardens in a short time, the adhesive is prevented from seeping into the EC electrode, no inoperable area is generated, and the EC element has excellent hardening properties.
Durability such as long-term heat-resistant sealability and light resistance is improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an electrochromic (EC) device according to an example.

FIG. 2 is a cross-sectional view of an EC element.

FIG. 3 is a cross-sectional view of an EC element.

[Explanation of symbols]

11...Solid electrolyte thin film 12...Glass substrate 13...Transparent electrode 14...EC electrode (WO3) 15...Glass substrate 16...Opposite 17...Seal

Claims (1)

[Claims] [Claim 1] An electrolyte thin film formed by filling the pores of a solid polymer porous thin film with an ionic conductor is used as an electrolyte, and the electrolyte thin film is sandwiched between transparent substrates having electrochromic electrodes formed on the surface. An electrochromic device comprising a sealed electrochromic device, characterized in that a radiation-curable adhesive is used for the sealing.