JP2934933B2 - Electrochromic display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochromic display device capable of displaying red and colorless color using an oxidation-reduction reaction of an iron-phenanthroline complex which can be formed into a film by an electrolytic deposition method.

[0002]

2. Description of the Related Art Conventionally, a red electrochromic material, a bathophenanthroline iron complex having a phenol group, is a tris (basophenanthroline diphenol) iron (II) complex (hereinafter Fe (BPDP)) having a bonding structure shown in FIG.
₃ ), which is disclosed in Japanese Patent Laid-Open No.
No.-29220, a film was formed by an electrolytic deposition method, and sodium perchlorate (NaCl) was used as a supporting electrolyte.
In an acetonitrile electrolyte containing O ₄ ) at a concentration of 0.1 mol / l, a color change (red and pale yellow) of 10,000 times or more and a response speed of 0.5 seconds or less are achieved using Prussian blue as a counter electrode. I was able to.

However, this Fe (BPDP) ₃ film is composed of a display electrode electrochromic material 4 and a counter electrode inside each of transparent substrates 1 and 8 having transparent conductive films 1 and 7 formed on one side as shown in FIG. In an electrochromic display element in which an electrochromic material 6 is provided and opposed to each other with the background material 5 interposed therebetween, and a space surrounded by the sealing material 3 on the upper and lower sides is filled with an electrolyte 9, acetonitrile (adhesive However, there is no sealing material 3 that can withstand such a problem, and there is a problem that the configuration of the element is difficult.

[0004] The problem of the driving electrolyte is a very important point in forming an electrochromic display element. On the other hand, if an aqueous solution can be used for the electrolytic solution 9, various adhesives (for example, UV curing type) can be used as the sealing material 3, which is a great merit. However, in the previous experiment, Fe (BPDP) _{3 as the} display electrode material 4 was driven in an aqueous solution containing sodium chloride (NaCl) at a concentration of 0.1 mol / l using Prussian blue for the counter electrode material 6. Since it was confirmed that remarkable deterioration of characteristics was caused, water could not be used as the driving electrolyte.

[0005] The Fe (BPDP) ₃ film changes from red to light yellow when the iron complex is oxidized from divalent to trivalent, and returns to the original red color by being reduced again.
This series of reactions is shown in Chemical formula 1.

[0006]

Embedded image

As can be seen from the above formula 1, F
Since the e (BPDP) ₃ film is positively charged, a − charge, ie, an anion, for compensating the charge must be incorporated into the film. In addition, during coloring, the color cannot be returned to the original red color unless anions are released into the electrolytic solution. Therefore, it is considered that the stability of repetitive driving is considerably affected by the type of anion.

[0008]

The problem to be solved is to find an optimum supporting electrolyte in order to improve the stability of repetitive driving of an electrochromic display element composed of Fe (BPDP) ₃ as a display electrode material. That is.

[0009]

SUMMARY OF THE INVENTION The present invention relates to Fe (BPD).
By changing the supporting electrolyte combined with P) ₃ from conventional NaCl to tetrafluoroboronate (NaBF ₄ ), the problem of the repeated driving life is improved.

[0010]

EXAMPLES Examples of experiments performed below will be described as examples. The supporting electrolyte for driving examined was a cation (cation) of sodium (Na ⁺ ) and a concentration of 0.1 mol / l.
And supporting electrolytes having different anions were prepared. This electrolyte comprises sodium chloride (NaCl), sodium perchlorate (NaClO ₄ ), sodium nitrate (NaNO).
₃ ) 4 of sodium tetrafluoroborate (NaBF ₄ )
Kind. In the evaluation method, cyclic voltammetry was continuously measured on the electrode on which the Fe (BPDP) ₃ film was formed, and the change in peak current value of the obtained voltammogram was traced to evaluate the stability of repeated driving. Cyclic voltammetry was performed by a three-electrode method, using platinum as a counter electrode and a saturated calomel electrode as a reference electrode. The scanning speed at this time is 20 mV / s.
ec, the scanning potential width was set at 0 V ← → + 1.5 V vs.

As a result, as shown in FIG. 3, in most cases, while the current value of the cyclic voltammogram decreases, only NaBF ₄ has a small decrease rate, and the result that the number of times of repeated life is improved several times is obtained. Was. At this time, the ion necessary for the repetitive driving of Fe (BPDP) ₃ is an anion, so that the counter cation is not limited to sodium in the case of BF ₄ salt, and H ⁺ , Li ⁺ ,
There is no problem even if it is K ⁺ , Rb ⁺ or the like. NaBF ₄
Can be driven without any problem as long as the addition concentration is in the range of 0.01 mol / l to 1 mol / l.
It is desirably in the range of ol / l to 0.5 mol / l.

In this case, the effect of the present invention was confirmed by the evaluation using the three-electrode method. For example, an electrochromic material such as Prussian blue, tungsten oxide (WO ₃ ), or metal phthalocyanine, whose reduction reaction is stable, was used as the counter electrode material. If it does, it cannot be overemphasized that the electrochromic display member which can display red easily can be made into an element.

[0013]

As described above, in an electrochromic display device using an iron-phenanthroline complex obtained by an electrolytic deposition method, as a result of using an aqueous solution of tetrafluoroboronate as a driving electrolyte, The effect that the repetition drive life was improved several times compared with the conventional aqueous solution system was obtained. As a result, an organic polymer-based adhesive can be used as a sealant for forming an electrochromic display element, and it is possible to provide an electrochromic display element capable of displaying red, which has been conventionally difficult.

[Brief description of the drawings]

FIG. 1 is a structural formula of Fe (BPDP) ₃ .

FIG. 2 is a sectional view of an electrochromic display element.

FIG. 3 is an evaluation result of a repetitive driving life.

[Explanation of symbols]

 1, 8 transparent substrate 2, 7 transparent conductive film 3 sealing material 4 display electrode electrochromic material 5 background material 6 counter electrode electrochromic material 9 electrolyte

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Ei 3-15-1 Tsuneda, Ueda City, Nagano Prefecture Shinshu University, Department of Functional Polymer Science (72) Inventor Hiroyoshi Shirai 3-15-, Tsuneda, Ueda City, Nagano Prefecture 1 Shinshu University Faculty of Textile Science and Technology Department of Functional Polymers (58) Fields surveyed (Int. Cl. ⁶ , DB name) G02F 1/15-1/163

Claims (1)

(57) [Claims] An electrochromic display device capable of displaying red and colorless by utilizing an iron-phenanthroline complex capable of forming a film by an electrolytic deposition method as a display electrode electrochromic material and utilizing its oxidation-reduction reaction. An electrochromic display element, wherein an aqueous solution of tetrafluoroboronate is used as an electrolytic solution.