JP7073771B2 - Electrochromic materials and their manufacturing methods - Google Patents

Description

The present invention relates to an electrochromic material and a method for producing the same.

As an electro-optical element using an electrochromic material, for example, the one described in Patent Document 1 is known. This type of electro-optic element is also referred to as an electrochromic element. The electrochromic material is a material whose optical properties such as a light absorption spectrum are reversibly changed by an electrochemical oxidation reaction and a reduction reaction. This type of electro-optical element can be applied to, for example, a dimming window or a dimming mirror for a vehicle.

Japanese Unexamined Patent Publication No. 2015-184632

In this kind of electrochromic material, it is possible to impart good properties by controlling the orientation structure. The present invention has been made in view of the circumstances exemplified above.

The method for producing an electrochemical material according to claim 1 is to put a monomer having an arylene unit structure having a monocycle or more including at least a thiophene ring, a pyridine ring, a pyrrole ring or a furan ring or a heteromonocyclic compound in a liquid crystal electrolyte. It includes a step of electrochemically polymerizing in a liquid crystal state after forming an oligomer.

As a result of diligent studies, the inventor of the present invention has devised a method for obtaining an electrochromic material by oligomerizing the above-mentioned monomer in a liquid crystal electrolyte and then electrochemically polymerizing it in a liquid crystal state. Specifically, the oligomerization can be carried out by adding Lewis acid to the monomer in the liquid crystal electrolyte. As the liquid crystal electrolyte, a cholesteric liquid crystal electrolyte in which a nematic liquid crystal substance and an optically active molecule are mixed can be used. Cholesterol derivatives can be used as the optically active molecule.

According to such a method, the oriented electrochromic material can be stably formed with good film forming property. The formed electrochromic material has good orientation, which gives it good properties.

The reference numerals in parentheses attached to each means in the above and the columns of claims indicate an example of the correspondence between the means and the specific means described in the embodiments described later. Therefore, the technical scope of the present invention is not limited by the above description of the reference numeral.

It is sectional drawing which shows the schematic apparatus structure of the electro-optic element provided with the electrochromic layer formed by the electrochromic material which concerns on one Embodiment of this invention. It is sectional drawing which shows the schematic apparatus structure of the electro-optic element for evaluation of the electrochromic layer which concerns on Example. It is a polarizing optical microscope image of the electrochromic layer shown in FIG. 1. It is a graph which shows the electro-optic property of the electrochromic layer shown in FIG. It is a graph which shows the electro-optic property of the electrochromic layer shown in FIG. It is a graph which shows the electro-optic property of the electrochromic layer shown in FIG.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that, if various modifications applicable to one embodiment are inserted in the middle of a series of explanations regarding the embodiment, the understanding of the embodiment may be hindered. It will be described together after the explanation.

(Constitution)
First, the configuration of the electro-optical element 1 according to the present embodiment will be described with reference to FIG. 1. As shown in FIG. 1, the electro-optical element 1 has a working electrode 2, an electrochromic layer 3, a counter electrode 4, and an electrolyte 5.

The working electrode 2 is so-called ITO glass, and is configured by forming an ITO film 22 on a substantially colorless and transparent glass layer 21. ITO is an abbreviation for Indium Tin Oxide.

The electrochromic layer 3 is formed of an electrochromic material, that is, a conductive polymer material having optical activity. The electrochromic layer 3 is formed on the working electrode 2 by electrochemical polymerization using the working electrode 2. Specifically, the electrochromic layer 3 is formed on the ITO film 22.

More specifically, in the electrochromic layer 3, a monomer having an arylene unit structure having a monocycle or more including at least a thiophene ring, a pyridine ring, a pyrrole ring, or a furan ring or a heteromonocyclic compound was oligomerized in a liquid crystal electrolyte. Later, it is formed by electrochemical polymerization in a liquid crystal state. Specifically, the electrochromic layer 3 is formed by oligomerizing the above-mentioned monomer in a liquid crystal electrolyte by adding Lewis acid and then electrochemically polymerizing it in a liquid crystal state. Therefore, the electrochromic layer 3 contains Lewis acid and has a predetermined orientation. Specifically, the electrochromic layer 3 has a spiral orientation.

The arylene unit structure may include, for example, the same kind of thiophene ring, pyridine ring, pyrrole ring or furan ring, specifically, bithiophene, terthiophene, bipyridine and the like. Alternatively, for example, a thiophene ring and a pyridine ring may coexist. Further, for example, it may further contain a phenyl ring. The arylene unit structure means a structure in which these rings are bonded. Therefore, in this structure, various substituents such as an alkyl group, an alkoxy group, an amino group, and an amide group other than the chiral substituent may be bonded to the ring.

Examples of the arylene unit include bithiophene, terthiophene, 1,4-di (2-thienyl) phenylene, 2,5-di (2-thienyl) pyridine, 3,4-ethylenedioxythiophene derivative (EDOT), and 4, , 4'-di (2-furyl) biphenyl and the like are exemplified. As the three-ringed monomer, those in which their molecular structures are connected at the para position are particularly considered. Of course, it is not limited to this.

Examples of the heteromonocyclic compound include those containing heteroatoms such as nitrogen atom, oxygen atom and sulfur atom, for example, thiophene, pyridine, pyrrole, furan and the like.

Examples of Lewis acid include iron (III) chloride, copper (II) chloride, zinc chloride, aluminum chloride, boron trifluoride, and itterbium trifluoromethanesulfonate (III). Lewis acid can be contained in the electrochromic layer 3 in an amount corresponding to or exceeding at least unavoidable impurities.

The electrolyte 5 is provided between the electrochromic layer 3 and the counter electrode 4. The electrolyte 5 may be a liquid electrolyte or a solid electrolyte.

(Outline of manufacturing method)
The electro-optical element 1 having the above configuration is manufactured by the following manufacturing method.
(1) A monomer having a monocyclic or higher arylene unit structure or a heteromonocyclic compound containing at least a thiophene ring, a pyridine ring, a pyrrole ring or a furan ring is oligomerized in a liquid crystal electrolyte.
(2) An electrochromic layer 3 is formed on the working electrode 2 by electrochemically polymerizing in a liquid crystal state in a liquid crystal electrolyte using at least the working electrode 2.
(3) The electro-optical element 1 is assembled by using the working electrode 2 on which the electrochromic layer 3 is formed, the counter electrode 4, and the electrolyte 5.

The electrochemical polymerization is carried out in the cholesteric liquid crystal electrolyte. Further, a supporting salt or the like can be appropriately added to the cholesteric liquid crystal electrolyte. The cholesteric liquid crystal electrolyte is prepared by mixing a nematic liquid crystal substance and an optically active molecule.

Examples of the nematic liquid crystal substance include 3CB, 4CB, 6CB, 7CB, 9CB, alkylazobenzene, phenylazomethine-based compounds and the like. Optically active molecules are also referred to as chiral inducers. The optically active molecule may be a chiral compound, and examples thereof include cholesterol derivatives, amino acids, sugars, myltenal, α or β-pinene, and the like. Among them, the cholesrol derivative is preferable as it is excellent in convenience.

In the present invention, it is considered that the above-mentioned monomer, nematic liquid crystal, optically active molecule, and supporting salt are each blended in the following ranges, for example.
Monomer: 1-8 mol%
Nematic liquid crystal: 90-96 mol%
Optically active molecule: 1-5 mol%
Supporting salt: 0.1-1.0 mol%

As an apparatus for electrochemical polymerization, for example, the cell structure described in JP-A-2008-22316 can be adopted. However, the present invention is not limited to this. That is, various configurations can be used as the cell having an electrode. It is considered that the distance between the electrodes is in the range of 0.1 to 5 mm.

The operating conditions such as voltage, time, and temperature can be appropriately determined according to the target monomer and the properties of the required polymer. For example, the voltage is 1 to 5 V, the energization time is 1 to 5 hours, and the temperature is in the liquid crystal temperature range.

(Example)
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to such examples.

0.24 mg of pyrrol, which is a monomer, 15.3 mg of Cholesteryl oleyl carbonate (COC), which is an optically active molecule, 1.3 mg of tetrabutylammonium perchlorate (TBAP), which is a supporting salt, and Lewis. An electrolytic solution composed of a liquid crystal electrolyte was prepared by dissolving 0.60 mg of iron (III) chloride as an acid in 200 mg of liquid crystal 5CB (4-pentyl-4'-Cyanobiphenyl).

A cell having a structure in which a spacer having a thickness of about 200 mm Teflon (registered trademark) was sandwiched between two pieces of ITO glass having a size of 1 cm × 5 cm was produced. The prepared electrolytic solution is injected into this cell, and a DC voltage of 3.0 V is applied between the ITO electrodes of the two ITO glasses for 30 minutes under temperature conditions where the liquid crystal state is maintained, specifically at room temperature. did. As a result, a polypyrrole film was obtained on the surface of the ITO electrode of ITO glass. The obtained polypyrrole film was washed with hexane and tetrahydrofuran (THF) and dried in air.

FIG. 2 shows a schematic configuration of an electro-optic element 1 for evaluating various characteristics in the polypyrrole film formed by the above embodiment. The electro-optic element 1 for evaluation has a structure similar to the cell structure described in Japanese Patent Application Laid-Open No. 2008-22301.

Specifically, referring to FIG. 2, the evaluation electro-optical element 1 is a reference electrode in a quartz cuvette 60 in addition to a working electrode 2, an electrochromic layer 3, a counter electrode 4, and an electrolyte 5. It is formed by arranging 61.

The working electrode 2 is an ITO glass to which polypyrrole is electrodeposited among the above pair of ITO glasses. A platinum wire was used as the counter electrode 4, and Ag / Ag ⁺ was used as the reference electrode 61. As the electrolyte 5, two types, a liquid electrolyte and a solid electrolyte, were used. As the liquid electrolyte, an acetonitrile solution containing 0.1 M TBAP was used. As the solid electrolyte, a solid electrolyte composed of an acetonitrile solution containing 0.1 M TBAP and polymethacrylate was used.

FIG. 3 is a polarizing optical microscope image of the polypyrrole film formed by the above embodiment. As shown in FIG. 3, a good orientation (specifically, a spiral orientation) was formed on the polypyrrole film. In addition, a large number of bump-shaped fine protrusions were formed on the surface of the polypyrrole film along the spiral orientation.

FIG. 4 shows a change in the ultraviolet-visible light absorption spectrum when the applied voltage between the working electrode 2 and the counter electrode 4 is changed. FIG. 5 shows the change in the circular dichroism spectrum when the applied voltage between the working electrode 2 and the counter electrode 4 is changed. In the figure, the solid line indicates the case of 0.3 V, that is, the oxidized state. On the other hand, the dotted line indicates the case of −0.7 V, that is, the reduced state. As shown in FIGS. 4 and 5, good electrochromic properties were obtained according to this example.

FIG. 6 shows the cycle characteristics of the circular dichroism spectrum. That is, FIG. 6 shows the durability of the electrochromic characteristics when the change from the reduced state (that is, the applied voltage −0.7 V) to the oxidized state (that is, the applied voltage 0.3 V) is performed for a plurality of cycles. As shown in FIG. 6, according to this embodiment, good electrochromic characteristics were maintained even when the change from the reduced state to the oxidized state was performed a plurality of times.

As described above, in this example, by oligomerizing pyrrole with Lewis acid, an electrochromic material made of polypyrrole with good orientation (specifically, spiral orientation) could be obtained. On the other hand, as a comparative example, when the oligomerization was not performed, the orientation in polypyrrole could not be stably generated.

In addition, as another comparative example, except that after oligomerization, the liquid crystal electrolyte is electrochemically polymerized in a state where the liquid crystal electrolyte is isotropic by raising the temperature to a temperature at which the liquid crystal state is destroyed (specifically, 50 ° C. or higher). , Polypyrrole was formed under the same conditions as in the above Examples. In this case as well, the orientation in polypyrrole could not be stably generated.

As previously reported in JP-A-2008-223016, etc., when the monomer has a relatively complicated structure of two or more rings, the orientation (specifically, the orientation (specifically) is performed without performing oligomerization by adding Lewis acid. An electrochromic material having good electrochromic properties was obtained.

On the other hand, according to the present invention, even when the monomer is a monocyclic compound having a simple structure such as pyrrole, it is made into an oligomer by the addition of Lewis acid, so that it has a good orientation (specifically, it has a good orientation (specifically,). An electrochromic material having (spiral orientation) was obtained with high film forming property and stable yield.

Further, when comparing the polarized optical microscope images between the case of the present invention and the previously reported case in JP-A-2008-22316, in the previously reported case, the semi-cylindrical relatively large protrusions are in the shape of fingerprints. It was formed. On the other hand, in the case of the present invention, as described above, a large number of bump-shaped fine protrusions were formed along the spiral orientation. That is, in the case of the present invention, the surface area of the electrochromic material constituting the electrochromic layer 3 is larger than that in the past. It is considered that the above-mentioned improvement in durability is due to such an increase in surface area.

(Modification example)
The present invention is not limited to the above embodiment. Therefore, the above embodiment can be changed as appropriate. Hereinafter, a typical modification will be described. In the following description of the modification, the differences from the above embodiment will be mainly described. Further, in the above-described embodiment and the modified example, the same or equal parts are designated by the same reference numerals. Therefore, in the following description of the modification, the description in the above embodiment may be appropriately incorporated with respect to the components having the same reference numerals as those in the above embodiment, unless there is a technical contradiction or a special additional explanation.

The present invention is not limited to the above examples. That is, the present invention is not limited to the case where the monomer is a monocyclic compound having a simple structure such as pyrrole. That is, if the monomer has an arylene unit structure of a monocycle or more including at least a thiophene ring, a pyridine ring, a pyrrole ring, or a furan ring, or a monomer having a heteromonocyclic compound, good orientation (specifically, by oligomerization in the liquid crystal electrolyte) is achieved. An electrochromic material having a spiral orientation) can be formed with high film forming property and stable yield.

The method of oligomerizing the monomer in the liquid crystal electrolyte is not limited to the addition of Lewis acid. That is, other types of oligomer-forming agents may be used as long as the electrochromic properties after film formation are not affected.

It goes without saying that the elements constituting the above embodiment are not necessarily essential except when it is clearly stated that they are essential and when they are clearly considered to be essential in principle. In addition, when numerical values such as the number, numerical value, quantity, and range of components are mentioned, the specification is made except when it is clearly stated that it is indispensable or when it is clearly limited to a specific number in principle. The present invention is not limited to the number of. Similarly, except when the shape, direction, positional relationship, etc. of the constituent elements are mentioned, when it is clearly stated that it is particularly essential, or when it is limited to a specific shape, direction, positional relationship, etc. in principle. The present invention is not limited to the shape, direction, positional relationship, and the like.

Modifications are also not limited to the above examples. Also, a plurality of variants can be combined with each other. Further, all or part of the embodiment and all or part of the modifications may be combined with each other.

1 Electro-optical element 2 Working electrode 21 Glass layer 22 Conductive film 3 Electrochromic layer 4 Opposite electrode 5 Electrolyte 60 Cuvet 61 Reference electrode

Claims (4)

A monomer having an arylene unit structure of a monocycle or more including at least a thiophene ring, a pyridine ring, a pyrrole ring or a furan ring or a heteromonocyclic compound is oligomerized in a liquid crystal electrolyte and then electrochemically polymerized in a liquid crystal state. Manufacturing method of chromic material. The oligomerization is carried out by adding Lewis acid to the monomer in the liquid crystal electrolyte.
The method for producing an electrochromic material according to claim 1. The liquid crystal electrolyte is a cholesteric liquid crystal electrolyte in which a nematic liquid crystal substance and an optically active molecule are mixed.
The method for producing an electrochromic material according to claim 1 or 2. The optically active molecule is a cholesterol derivative.
The method for producing an electrochromic material according to claim 3.

Images