JPH0820647B2 - Electrochromic display - Google Patents

Description

The present invention relates to a novel electrochromic display device (hereinafter referred to as "electrochemical display device").
The present invention relates to an ECD device, and more specifically to an ECD device that uses a novel organic conductor that exhibits color in an oxidized state and white in a reduced state as a coloring layer.

(Prior art) In recent years, EC has been adopted as a new display device to replace liquid crystal display devices.
The D device is receiving attention. Compared to liquid crystal, ECD device has less visual dependency, sharper display, and memory effect, so it can continue to display without power consumption.

The ECD device utilizes electrochromism in which light absorption characteristics change according to voltage application and current, and materials having such properties can be roughly classified into inorganic materials and organic materials. As inorganic materials, oxides of transfer metals such as tungsten oxide and complexes such as Prussian blue have been mainly studied. In addition to phthalocyanine and viologen complex, conductive polymer materials have been studied as organic materials.

The discoloration mechanism of inorganic materials is generally due to the change in spectral structure due to charge transfer of the transition metal. Therefore, the response speed of color change is faster than that of organic materials, but protons are often involved in the charge transfer reaction, and the deterioration of the electrode is likely to occur. In addition, the color tone is poorer than that of organic materials. Even with organic materials, phthalocyanine and the like are vapor-deposited on the substrate, but there remains a problem with the adhesion to the electrodes. On the other hand, the conductive polymer can obtain a polymerized film adhered to the electrode by electrode oxidation of a solution containing a monomer, and by further immersing the film-coated electrode in an electrolyte solution and applying a voltage,
Ions in the solution can be easily doped and dedoped. Some of these conductive polymers cause a color change by such doping and dedoping, and polyaniline shows a yellow-green color, polythiophene shows a red-blue color, and polypyrrole shows a yellow-brown color change. However, most of these are changes from colored to colored, and few show white changes. The conductive polymer having an isothianaphthene structure gives only a color tone close to colorless (Japanese Patent Laid-Open No. 61-12784). This polymer gives a color tone close to colorless in the oxidized state, and shows a blue color in the reduced state.

(Problem to be Solved by the Invention) An object of the present invention is to provide an electrochromic display device that changes color between white and colored in view of the above-mentioned drawbacks.

(Means for Solving the Problem) The ECD device of the present invention has a structure in which an organic coloring layer and an electrolyte layer are arranged between a working electrode and a counter electrode, and the organic coloring layer is poly (o-dialkoxybenzene). Is the main subject.

Poly (o-dialkoxybenzene) has a structural unit represented by the following general formula.

In the formula, R ¹ and R ² represent an alkyl group such as a methyl group, an ethyl group and a propyl group, R ¹ and R ² may be the same or different, and as o-dialkoxybenzene, Examples thereof include o-dimethoxybenzene, o-diethoxybenzene, o-dipropoxybenzene and the like.

This polymer can be obtained by chemically or electrochemically polymerizing o-dialkoxybenzene. Particularly, in the electrochemical polymerization method, the polymer can be easily obtained by dissolving o-dialkoxybenzene in a solvent together with a supporting electrolyte and then performing electrode oxidation.

As the supporting electrolyte, those generally used in electrolytic polymerization can be used, for example, metal halides such as AlCl ₃ , perchlorates such as LiClO ₄ , and (nC ₄ H ₉ ) ₄ NPF ₆ , ( C ₂
Quaternary ammonium chlorine such as H ₅ ) ₄ NBF ₄ can be used.

Further, as the above-mentioned solvent, any solvent that can dissolve o-dialkoxybenzene, that is, any non-aqueous solvent can be used. Preferred examples include nitromethane, acetonitrile, propylene carbonate and the like.

Furthermore, as the electrode used in the polymerization, any electrode used in ordinary electrolytic polymerization can be used,
This electrode may be used as it is as a working electrode of the ECD device.

As the electrode, a platinum plate or glass, a transparent electrode obtained by vapor-depositing a metal or a metal oxide on a transparent substrate such as polyester can be used.
Examples thereof include indium oxide-tin vapor deposited glass (ITO glass) and tin oxide vapor deposited glass.

The electropolymerization is carried out by applying a voltage to the electrode, which is generally 2 to 10 V, and the polymer is deposited on the electrode to obtain a film.

In the display device of the present invention, the organic coloring layer and the electrolyte layer are arranged between the working electrode and the counter electrode, that is, the coloring layer is in close contact with either the working electrode or the counter electrode, and the electrolyte layer is the other. It is in close contact with the electrodes, and has a structure in which at the interface between the color-developing layer and the electrolyte layer, ions freely move in and out due to charge transfer at the electrode interface. A color change occurs due to the entry and exit of these ions. As the method for adhering the color forming layer to the electrode, any known method such as a physical / chemical adsorption method or a casting method can be adopted, but the simplest method is to carry out electrolytic polymerization on the electrode as described above. .

As the electrolyte layer, a solution prepared by dissolving the above-mentioned supporting electrolyte in an organic solvent or water, a polymer matrix in which the supporting electrolyte is dispersed, or the like is used. It should be noted that a solvent or a polymer matrix that is electrically decomposed or generates a gas depending on an applied voltage is significantly deteriorated by repeated use, which is not preferable for constituting the ECD device of the present invention.

The configuration of the ECD device of the present invention is as described above, and when a voltage is applied between the electrodes, the color forming layer changes its color between white and colored.

(Example) Next, the Example of this invention is described.

Example 1 0.3 mol / l o-dimethoxybenzene and 0.3 mol / l Et
Dissolved oxygen was removed by bubbling an electrolytic solution of ₄ NBF ₄ dissolved in nitromethane for 5 minutes with argon gas. Using ITO as a working electrode and a platinum plate as a counter electrode, Ag / AgCl
When the potential was continuously scanned in the range of 0 to 3 V with respect to the reference electrode at a scanning speed of 100 mV / sec, a thin film in which o-dimethoxybenzene was polymerized was obtained on ITO. This thin film is 1.5V
When applied above, it turned blue and turned white when the potential approached OV.

The polymer film on ITO was left in the above solution at 3V for several seconds, the circuit was opened as it was, the electrode coated with the blue polymer film was taken out and washed with nitromethane, and then 0.3 mol containing no o-dimethoxybenzene was used. When it was immersed in a nitromethane solution containing / l Et ₄ NBF ₄ and an OV (vs. Ag / AgCl) potential was applied, the blue color disappeared and a white color was obtained.

Similarly, after leaving at OV for a few seconds, the circuit is opened to take out the white polymer film-coated electrode, and a potential of 3V is applied in the solution containing no o-dimethoxybenzene.
It turned blue.

Example 2 Electropolymerization was carried out in the same manner as in Example 1 except that a platinum plate was used as the working electrode, and a thin film in which o-dimethoxybenzene was polymerized was obtained on the platinum plate. After applying a potential of 3 V to this working electrode for several seconds, the circuit was opened as it was and the blue polymer film-coated electrode was taken out and washed with nitromethane, and then 0.3 mol / l containing no o-dimethoxybenzene.
Was immersed in a nitromethane solution containing LiClO ₄ and the OV (vs.A
The thin film turned white when an electric potential of g / Agcl) was applied. Similarly, after being left at OV for several seconds, the circuit was opened to take out the white polymer film-coated electrode, and when a potential of 3 V was applied in the above solution containing no o-dimethoxybenzene, the color changed from white to blue.

Example 3 Regarding the conductive film on ITO polymerized in Example 1, o-
0.3 mol / l L as a solution without dimethoxybenzene
The same procedure as in Example 1 was performed except that iClO ₄ dissolved in water was used. The color change was completely the same as in Example 1.

Example 4 When electrolytic polymerization was carried out in the same manner as in Example 1 except that LiClO ₄ was used instead of Et ₄ NBF ₄ , a thin film in which o-dimethoxybenzene was polymerized was obtained on ITO. This thin film turned deep purple when 3 V was applied, and became light gray when OV was applied.

The polymer film on ITO was left in the above solution at 3V for several seconds, then the circuit was opened as it was, the electrode covered with the dark purple polymer film was taken out, washed with nitromethane, and then containing no o-dimethoxybenzene, 0.3. When it was immersed in a nitromethane solution containing mol / l LiClO ₄ and an OV (vs. Ag / AgCl) potential was applied, it turned light gray. Similarly, after leaving at OV for a few seconds, the circuit is opened and the light gray polymer film-coated electrode is taken out and placed in a solution containing no o-dimethoxybenzene.
When a potential of 3 V was applied, the color changed from light gray to dark purple.

(Effect of the Invention) Since the configuration of the electrochromic display device of the present invention is as described above, it is possible to change the color between blue and purple colors and white due to the difference in applied voltage.

Claims (1)

[Claims] 1. An electrochromic display device in which an organic coloring layer and an electrolyte layer are arranged between a working electrode and a counter electrode, wherein the organic coloring layer is mainly composed of poly (o-dialkoxybenzene). Electrochromic display device.