JPH04204521A - Flexible electrochromic element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] FIELD OF THE INVENTION The present invention relates to flexible electrochromic devices.

More specifically, the present invention relates to a flexible electrochromic device using a porous polymer thin film whose pores are filled with an ionic conductor as an electrolyte.

[Conventional technology]

There is growing interest in devices that apply the electrochromic (EC) phenomenon, in which the color of a material changes reversibly depending on voltage. Electrochromic devices (ECDs) have characteristics such as being bright and easy to read, capable of large-area display, and having memory properties (low power consumption). Applications that take advantage of these characteristics include stock price displays and message boards. , large display boards such as information boards, and light control elements for automobile anti-glare mirrors, light control glass (windows), sunglasses, etc. In particular, substrates made of flexible organic films have the advantage of being able to be applied to curtainless windows for homes, architecture, and automobiles by being used by attaching them to glass or by forming them into curved shapes. , is attracting attention.

The structure of ECD consists of an electrolyte placed between an electrochromic electrode (Wo+) and a counter electrode, and when a voltage is applied between both electrodes, hot is cathodically reduced by ions from the electrolyte and electrons from the power source, resulting in coloring. be. The counter electrode can also be constituted by an electrochromic electrode and used for colored display.

[Problem to be solved by the invention]

Electrolytes are divided into liquid electrolytes and solid electrolytes. A liquid electrolyte has high ionic conductivity and therefore has excellent responsiveness, but it is undesirable for liquid to enter the element from a structural standpoint. Due to the structure and assembly of the element, measures against liquid leakage are required, and even if measures against liquid leakage are taken, there is no guarantee that liquid leakage will not occur due to damage or during use, and if liquid leakage occurs, it may cause staining of surrounding parts etc. There are also problems. Solid electrolytes do not pose any problems when handling such liquids, but there is a problem of poor responsiveness because there is no solid electrolyte with high ionic conductivity.

Therefore, an object of the present invention is to provide a flexible ECD having a solid electrolyte with high ionic conductivity.

[Failure to solve the problem]

In order to achieve the above object, the present invention uses an electrolyte thin film formed by filling the pores of a solid polymer porous thin film with an ionic conductor as an electrolyte, and uses a flexible organic film as an electrode base material. A flexible electrochromic element is provided.

The electrolyte used in the present invention consists of an electrolyte thin film formed by charging ionic conductors 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 film thickness of 0.
1-50 feet, porosity 40%-90%, breaking strength 2
00kg/af1 or more, average through hole diameter is 0. OObm+
-0.7 porcelain is preferably used.

The thickness of the thin film is generally 0.1 tnn to 50 μm,
Preferably it is 0.1 tm to 25 knots. Thickness is 0.1
If it is less than tnn, it is difficult to put it into practical use because of the reduction in mechanical strength as a support film and the ease of handling. On the other hand, if it exceeds 50 feet, it is not preferred from the viewpoint of keeping the effective resistance low. The porosity of the porous thin film is 40%~
It is good to set it to 90%, preferably in the range of 60% to 90%. 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 0.0011M1 to 0.7Nl, although it is sufficient that the ionic conductor can be immobilized in the holes. 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 200 kg/c+
Having f1 or more, more preferably 500 kg/ci or more, is suitable for practical use as a support membrane.

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, polyvinylidene 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, suitable materials are used. One example of a polymeric material is a polyolefin, especially one with a weight average molecular weight of 5 x 105 or more. 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 1 x 1
06 to 1×107. Examples include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, and the like. Among these, the weight average molecular weight is 5X10'
The above polyethylene or polypropylene is preferred.

The weight average molecular weight of the polyolefin influences the mechanical strength of the resulting permeable membrane. Ultra-high molecular weight polyolefins are
Ultra-stretching enables the formation of ultra-thin and high-strength films, which can be 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 x 10' can be used at the same time, in a system that does not contain a polyolefin having a weight average molecular weight of 5 x 105 or more, an ultra-thin and high strength film cannot be obtained by ultra-stretching.

The porous thin film as described above can be manufactured by the following method. An 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-like sheet is extracted with a volatile solvent such as methylene chloride.
0% 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 the solid polymer porous thin film is made by irradiating the polycarbonate thin film with charged particles in a nuclear reactor and etching the tracks of the charged particles with alkali to form pores. It can also be produced by a method of forming. Such membranes are coated with polycarbonate and polyester products, for example as nucleopore membranes.

In addition, polyester, polymethacrylate, polyacetal, polyvinylidene chloride, tetrafluoropolyethylene, etc. can be used.

Ionic conductors used in the present invention include complexes of alkali metal salts or protonic acids and polar polymers such as polyether, polyester, and polyimine, and aromatic compounds such as benzyl cyanamide. Complexes of compounds and alkali metal salts or protic acids, or complexes with network or crosslinked polymers containing these polymers as segments can be used. Liquid and powdered reagents with different molecular weights and degrees of polymerization are commercially available and can be easily used. Namely, polyethylene glycol, polyethylene glycol, monoether, polyethylene glycol φ diether, polypropylene glycol, Polyethers such as polypropylene glycol monoether and polypropylene glycol diether, or poly(
oxyethylene/oxypropylene) glycol, poly(oxyethylene/oxypropylene) glyco - engraving of specifications (no changes to the contents) monoether, or poly(oxyethylene/oxypropylene) glycol dietenove 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.
Polymer Preprints, Japan V
ow, 34. No. 7.2021-2024 (19
85) and JP-A No. 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 (e.g., N, Kobayas
hi et al., J. Physical Chemistry.

Vol, 89. No. 6.987-991 (1985
) are suitable as materials constituting the thin film electrolyte useful in the present invention.

The above-mentioned polyethers may have a molecular weight of 150 or more (no change in content), and the above-mentioned polymers include propylene carbonate, γ-butyrolactone, ethylene carbonate, methylfuran, Dimethoxyethane, dioxolane, tetrahydrofuran, acetonitrinohebenzonitrinopedimethylformamide, dimethylsulfoxide,
One or more solvents selected from methyltetrahydrofuran, sulfolane, methylthiophene, methylthiazole, ethoxymethoxyethane, benzyl cyanide, etinope benzoate and α-trinitrile may be added.

An alkali metal or alkaline earth metal salt or a 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 (
Nal), lithium iodide (Lil), lithium perchlorate (1 mouth of LiC), sodium thiocyanate (N
aSCN) ,) Copying of the litz chemical specification (no changes to the contents) Lithium tansulfonate (LiCF3SO3), Lithium borofluoride (LiBF, ), Lithium hexafluorophosphate (L+PFe), Phosphoric acid (l13PO3)
, sulfuric acid (H2S04), trifluoromethanesulfonic acid,
Tetrafluoroethylene sulfonic acid [C2F4(SO3H
)2), hexafluorobutanesulfonic acid [C2F6
(S03H)4], etc. can be cited as a specific example.

As a method of filling ionic conductors into a polymer thin film,
■Remove the solvent after impregnating, coating or spraying an ionic conductor dissolved in a solvent, or an ionic conductor finely dispersed in a solvent in the form of a sol or gel, into a solid polymer porous thin film;■ In the porous thin film manufacturing process, a film is formed after mixing a solution of an ionic conductor or its sol or gel-like dispersion solution. ■ Impregnation of a monomer or soluble precursor of an ionic conductor into a solid polymer porous thin film. Do you want me to do it?
After coating or spraying, a method such as ``reacting within the pores'' can be used.

Another feature of the electrochromic device of the present invention is that the electrode base material is a flexible organic film.As the flexible organic film, polyester, polycarbonate, polyacrylate, polyether siphon, etc. are used. High (over 80%) and sheet resistance of 10
A sheet resistance of 0 Ω or less is suitable, but in particular, a sheet resistance of 50 Ω or less is suitable.
Ω or less is more desirable.

The thickness of the organic film is desirably thin from the point of view of flexibility and transparency, and is suitably 200 JMl or less, but especially 10
0p or less is more desirable.

Electrochromic electrode (electrode ■) is titanium oxide Ti
O2, vanadium oxide V2O5, neodymium oxide Nd2
O5, tungsten oxide WO3, molybdenum oxide MOO
Alternatively, a heteropolyacid containing one or more of tungsten, cobalt, molybdenum, and vanadium can be used by forming a film.

The counter electrode (electrode ■) is an iridium oxide Ir[b
+, nickel oxide N1Ox, chromium oxide Crh, cobal oxide) COOX, manganese oxide Mn0X, oxide o
Iron and cobalt-based organometallic compounds such as siaum RhOx, Prussian blue, phthalocyanine, viologen, and derivatives thereof are used. Moreover, polypyrrole and polyaniline can also be used.

Furthermore, it is also possible to use an electrode that undergoes a reduction reaction and an oxidizing electrode that does not develop color, such as zirconia oxide ZrOx.

The solid electrolyte thin film and the organic film with electrodes as described above can be simply laminated in close contact to form an electrochromic device.

[For production]

In the ECD of the present invention, the electrolyte is at an ambient temperature, for example, =10
Because it has sufficient ionic conductivity at ℃~30℃,
It has a wide operating temperature range and is easy to assemble and handle because the electrolyte and the substrate with electrodes are flexible solid thin films. Therefore, it is possible to easily provide a device with no liquid leakage, a uniform thickness, and a large area.It is also easy to apply to curved surfaces, and various shapes can be selected, making it possible to use display devices. It is also suitable for various uses such as curtainless windows and engraving specifications (no change in content).

〔Example〕

This will be explained with reference to the drawings. FIG. 1 is a perspective view of a flexible electrochromic device 10 according to an example, and a schematic developed view of its cross section.

As a base material, size: 30 cm x 40 cm, thickness: 1
00 Liao, 1T on polyester film 1 with transmittance of 84%
Using a sheet (sheet resistance 88Ω) on which O was formed,
To lower the T○ resistance, low-temperature firing silver paste is printed in a grid pattern and fired, and then tungsten oxide (1'+0
3> as electrode I, and polyaniline as electrode I[,
A film was formed as No. 4. The thickness of ITO electrode 2 is 800~25
00 people, the thickness of electrode I, 3 is 800-7000 people,
The thickness of electrode I[, 4 is 800-7000 Å.

The immobilized liquid film electrolyte 5 was manufactured by immobilizing an electrolyte solution of polyethylene glycol dimethyl ether and LiCF3SO3 on a polyethylene microporous membrane having a thickness of 9 walls and a pore diameter of 0.02J.

The special voltage applied to the obtained flexible electrochromic element was L5V for reduction of tungsten oxide (times) and -0.1V for oxidation, and rectangular wave constant voltage control was performed. The application cycle was 10 seconds for both redox and oxidation.

The response of the electrochromic device was 20% transmittance within 7 seconds from the l1109 oxidation state. The cycle life was 104 times or more when 1.5V to -0.1V was applied.

〔Effect of the invention〕

According to the present invention, flexible EC using solid thin film electrolyte
D is provided, and this flexible ECD does not require leakage measures and is flexible, so it is easy to handle, safe, and
The responsiveness of CD is also improved, and it can be applied to curved surfaces, making it highly applicable.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a flexible electrochromic device according to an example, and a schematic developed view of its cross section. 2... IT○ electrode, 3... Electrode work, 4... Electrode ■, 5... Immobilized liquid film electrolyte, 10... Flexible electrochromic element.

Claims (1)

[Claims] 1. A thin electrolyte film formed by filling the pores of a solid polymer porous thin film with an ionic conductor is used as the electrolyte, and a flexible organic film is used as the electrode base material. Flexible electrochromic device. 2. The flexible electrochromic device according to claim 1, which is a display device. 3. The flexible electrochromic device according to claim 1, which is a light control device.