JPH07104528B2 - Electrochromic display element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrochromic display element, and more particularly to an electrochromic display element having excellent display stability and a short discoloration time. .

(Prior art and its problems) Conventionally, an electrochromic display element (Elcetro Chromi
c device; hereinafter, abbreviated as ECD. ), An ECD using an indium tin oxide (ITO) layer for the anode of the display electrode is known.

The drawing shows an example of such an ECD. The ECD of this example has an ITO layer 2 for an anode as an anode on each of the facing surfaces of the glass plates 1 and 1 facing each other by a vacuum deposition method or a sputtering method. , Providing the cathode ITO layer 3 as a cathode,
Further, an electrochromic layer (hereinafter referred to as an EC layer) 4 made of a polymer obtained by electrolytically oxidatively polymerizing a monomer is formed in the center of the surface of the anode ITO layer 2.

Spacers 5 and 5 are arranged between the glass plates 1 and 1, and a closed space surrounded by the spacers 5 and 5, the cathode ITO layer 3 and the EC layer 4 is filled with Cl ⁻ , Br ⁻ , ClO ₄ ^-, BF ₄ ^- electrolyte solution 6 containing anion such as are filled.

However, in this ECD, since the EC layer is weakly bonded to the surface of the anode ITO layer 2, when the potential is repeatedly inverted between the anode ITO layer 2 and the cathode ITO layer 3, There were problems such as wrinkles on the EC layer 4 and peeling off, resulting in poor display stability.

(Means for Solving Problems) Therefore, in the ECD of the present invention, a high-molecular polymer having a property of swelling in an electrolyte solution used for forming an EC layer on an anode has a conductive fineness. Using a conductive polymer film obtained by mixing powders and molding into a film, as an anode,
I tried to solve the above problems.

That is, the surface of the anode is swollen with the electrolyte solution, when the monomer is electrolytically oxidatively polymerized thereon to form the EC layer, the electrolyte solution containing the monomer permeates to the surface and the inside of the anode, Electrolytic oxidative polymerization occurs not only on the surface of the anode but also inside the anode, and the anode and the EC layer are strongly joined to each other in such a manner that they are entangled with each other at the interface. Therefore, this ECD
Shows excellent display stability without wrinkling of the EC layer or peeling of the EC layer from the anode even when the potential is repeatedly inverted. Since the area where the exchange reaction is performed becomes large, the time required for discoloration becomes short.

(Example) Hereinafter, the ECD of the present invention will be described in detail with reference to the above drawings.

Reference numeral 7 in the figure is an ECD. As shown in the drawing, the ECD 7 of this example is a laminated structure, and glass plates facing each other.
A conductive polymer film (hereinafter abbreviated as a conductive film) 8 is bonded as an anode to one of the facing surfaces of 1 and 1, and the other is used as a cathode by using a vacuum deposition method or a sputtering method on the other facing surface. The ITO layer 3 is provided, and the EC layer 4 is formed by electrolytically oxidatively polymerizing a monomer on the central portion of the surface of the conductive film 8.

Spacers 5 and 5 are arranged between the glass plates 1 and 1, and a closed space surrounded by the spacers 5 and 5, the anode ITO layer 2 and the EC layer 4 is filled with Cl ⁻ , Br ⁻ , ClO ₄ ^-, BF ₄ ^- electrolyte solution 6 containing anion such as are filled.

The conductive film 8 is formed by kneading a conductive fine powder with a high molecular weight polymer and then molding it into a film by a press molding method.

As the above-mentioned high molecular weight polymer, one whose surface is swollen even in the electrolyte solution used when the EC layer 4 is electrolytically oxidatively polymerized is selected. Desirably, the surface layer of the obtained conductive film swells by several μm. Further, the selection of the high molecular polymer to be used is determined in consideration of the combination with the electrolyte solution.

The conductive fine powder is selected such that it does not react with the electrolytic solution of the electrolytic oxidative polymerization, specifically, fine powder obtained by coating SnO ₂ on TiO ₂ is preferably used, but is not limited thereto. is not. The amount of the conductive fine powder to be added to 100 parts by weight of the high molecular weight polymer is in the range of 20 to 150 parts by weight, and if the amount is less than 20 parts by weight, the conductivity of the obtained conductive film 8 is sufficiently obtained. If the amount exceeds 150 parts by weight, the electroconductivity of the electroconductive film 8 becomes excessive, which is uneconomical.

Further, as the monomer which is the precursor compound of the EC layer 4, a compound whose polymer exhibits EC characteristics is selected, and specifically, aniline, thiophene, pyrrole and the like are preferably used. Therefore, examples of the polymer forming the EC layer 4 include polyaniline, polythiophene, and polypyrrole.

Further, as the material dispersed in the conductive film 8,
It is also possible to use a colorant with the conductive fine powder. As the colorant, one that does not react with the conductive fine powder or the electrolytic solution of electrolytic oxidation polymerization is selected, and specifically, a cyanine-based or azo-based pigment is used.

In the ECD having such a structure, the surface of the conductive film 8 is swollen with an electrolyte solution used for electrolytic oxidation polymerization, and when the EC layer 4 is formed by electrolytic oxidation polymerization on this,
Since the electrolyte solution containing the monomer penetrates into the surface of the conductive film 8 and the inside thereof, electrolytic oxidation polymerization occurs not only on the surface of the conductive film 8 but also inside thereof, and the conductive film 8 and the EC layer 4 are separated from each other. Entangling each other at their interfaces results in strong bonding. Therefore, this ECD
Wrinkles on the EC layer 4 even if the potential is repeatedly inverted,
Since the EC layer 4 is not peeled off from the conductive film 8 and the display stability is excellent, and the surface of the conductive film 8 swells to increase the area for performing an electron exchange reaction with the EC layer 4. , The time required for discoloration becomes short.

Further, in the above-mentioned examples, the surface of the conductive film is swollen in the electrolyte solution, but the surface of the conductive film may be swollen in advance with the solvent used for the electrolyte solution. ECD having a conductive film treated in this way
In that case, it is possible to obtain the same effects as those of the above-described embodiment.

Next, the method for producing the ECD of the present invention will be described in detail.
For example, first add 100 parts by weight of low-density polyethylene to TiO ₂ and
Add 50 parts by weight of conductive fine powder coated with nO ₂ at 160 ℃
After kneading with a roll of No. 1 and press-molding, a conductive film 8 having a thickness of 1 mm is produced. One surface of the conductive film 8 is brought into contact with nitrobenzene heated to 60 ° C. for 1 hour so that the surface is swollen. Next, the glass plate 1 is joined to the other surface of the conductive film 8 to form the conductive film 8
At the current density of 3 mA / cm ^{2 in} a solution obtained by adding Bu ₄ NBF ₄ and monomer (thiophene) to nitrobenzene to 0.1 mol / l using a platinum plate as the counter electrode. It was electrolytically oxidatively polymerized for 20 minutes to form a composite with this film 8 on the conductive film 8. An EC layer (polythiophene thin film) 4 is formed. Next, the ITO layer 3 for the cathode is formed on one surface of another glass plate 1 by a vacuum deposition method or the like. next,
These glass plates 1 and 1 are made to face each other and the cathode ITO layer 3 and
Face the EC layer 4 and place the spacers 5, 5 between the glass plates 1, 1.
To form a closed space, and the space is filled with an electrolyte solution (0.1 mol / l Bu ₄ NBF ₄ -acetonitrile solution) 6.

(Example) Hereinafter, an experimental example is shown and the effect of this invention is clarified.

To 100 parts by weight of low-density polyethylene, 50 parts by weight of conductive fine powder obtained by coating TiO ₂ with SnO ₂ was added, and the mixture was kneaded with a roll at 160 ° C. and press-molded to produce a conductive film having a thickness of 1 mm. The surface conductivity of this film is 100Ω /
I met you in Russia. One side of this conductive film was contacted with nitrobenzene heated to 60 ° C. for 1 hour. When the weight change before and after this treatment was measured, it was increased by about 0.5% after the treatment, and it was confirmed that the surface was slightly swollen.
Next, a glass plate is bonded to the other surface of the conductive film to use this film as an electrode, a platinum plate is used as a counter electrode, and Bu ₄ NBF ₄ and thiophene are added to nitrobenzene to give 0.1 mol / l, respectively. In the solution thus obtained, a polythiophene thin film was formed on the conductive film by electrolytic oxidation polymerization at a current density of 3 mA / cm ² for 20 minutes. Next, an ITO layer for a cathode was formed on one surface of another glass plate by a vacuum vapor deposition method. next,
These glass plates were mutually opposed to, 0.1 mol / l of Bu ₄ NBF ₄ ^- was prepared ECD acetonitrile solution as an electrolyte solution.

In addition, instead of the conductive film of ECD above, ITO for cathode is used.
The ECD of the comparative example was prepared under the same conditions as the above ECD, except that the layers were used.

The color change characteristics and color change time of these two ECDs were examined.

(B) Color change characteristic test: The state of the polythiophene thin film was examined by repeatedly reversing the electric potential, and in the ECD satisfying the conditions of the present invention, the polythiophene thin film did not change even after 100 electric potential reversals and no peeling was observed . However, in the ECD of the comparative example, wrinkles were observed in the polythiophene thin film at the 65th potential inversion, and partial peeling was observed at the 80th time.

(B) Discoloration time test: When the voltage required was 2 V and the time required for discoloration of blue-red was measured, ECD satisfying the conditions of the present invention
Then, it was about 150 milliseconds, and with ECD of the comparative example, it was 500 milliseconds.

As is clear from these experimental results, the ECD satisfying the conditions of the present invention is stable in the polythiophene thin film (EC layer) even when the potential is reversed and the time required for discoloration is shorter than that of the ECD of the comparative example. I understand that.

(Effects of the Invention) As described above, the electrochromic display element of the present invention has excellent display stability because the conductive polymer film and the electrochromic layer are entangled and strongly bonded to each other. At the same time, since the surface of the conductive polymer film swells and the area for carrying out the electron exchange reaction with the electrochromic layer is large, the time required for discoloration can be shortened.

[Brief description of drawings]

The drawing is a schematic cross-sectional view showing an example of the electrochromic display element according to the present invention. 4 ... Electrochromic layer 6 ... Electrolyte solution 7 ... Electrochromic display element 10 ... Conductive polymer film.

Claims (1)

[Claims] 1. An anode, an electrochromic layer formed by electrolytically oxidatively polymerizing a monomer on the anode in an electrolyte solution, a cathode facing the anode, a facing surface of the cathode and the electrochromic layer. In an electrochromic display element comprising an electrolyte solution filled in a space between the layers and performing a display by applying a voltage between the electrodes, the anode forms an electrochromic layer on the anode. An electrochromic display device characterized by being a conductive polymer film formed by mixing conductive fine powder with a high molecular polymer having a property of swelling in an electrolyte solution used in forming .