JPH0737611B2 - Electrochromic display element - 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 element used for various displays such as watches, measuring instruments and home appliances.

[0002]

2. Description of the Related Art Compared with liquid crystal, which is one of light receiving displays, electrochromic displays are characterized by having no viewing angle dependence and being bright and vivid in color.
Electrochromic materials are of inorganic type and organic type.
Classified into one. As an inorganic material, transition metal oxides, particularly WO ₃ are well known. Viologen, anthraquinone, pyrazoline and styryl analogues are known as organic pigments. In addition, recently, the use of a complex such as phthalocyan or Prussian blue or a thin film of a conductive polymer has been announced.

[0003]

In WO ₃ , a device is formed by forming a thin film on a transparent electrode by a vapor deposition method or the like and providing an electrolytic solution or a dielectric film between the counter electrodes. A practical problem of WO ₃ is that, in addition to the display life, the color unevenness between the display segments and the coloring color are only one blue type. Further, in connection with the improvement of the display life, there is a problem that the counter electrode material is generally devised to stabilize the counter electrode reaction, and the reflector and the like must be incorporated in the element.

On the other hand, an organic dye has a possibility of diversifying coloring species as compared with an inorganic material, but generally has a problem in display life.

Viologen-based dyes are accompanied by the phenomenon that the dyes are insoluble and soluble in a solvent depending on the coloring and decoloring. However, the reversibility problem greatly affects the display life. In addition, although the decolorization phenomenon occurs due to the redox reaction of the dye, since ions are involved in these reactions, the ions may adversely affect the transparent electrode and the power consumption is high. There's a problem. Other organic dyes and complexes have similar problems.

The characteristics of the current electrochromic display which are inferior to those of the liquid crystal display are the characteristics of display life and response speed.

The present invention solves the above-mentioned conventional problems, and an object thereof is to improve the response speed and display life of an electrochromic display device.

[0008]

The present invention achieves the above object, and is formed between two substrates, at least one of which is transparent, is provided with a display electrode on one side and a counter electrode on the other side. In space, general formula

[0009]

[Chemical 2]

(In the formula, X is a halogen group such as Cl or Br, --H, --NO ₂ , --SO ₂ R, --COOR, --OR.
(Wherein R is a lower alkyl group), or a group such as —CH ₃ , R ₁ and R ₂ are the same or different lower alkyl groups,
A hydroxyalkyl group or an alkoxyalkyl group, R ₃ is hydrogen, or an alkyl group, and R ₄ and R ₅ are the same or different lower alkyl groups. The present invention provides an electrochromic display device characterized by encapsulating a spiropyran dye, a supporting electrolyte, and a non-aqueous organic solvent represented by (4).

[0011]

With this structure, the response speed and display life of the electrochromic display device can be greatly improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the basic structure of an electrochromic display device which is an embodiment of the present invention. Reference numeral 1 is a glass substrate, 2 is a display electrode, 3 is a counter electrode, 4 is a sealing material, 5 is a sealing material, and 6 is a displayable substance. At least one of the glass substrates 1 may be a transparent material. As the electrode material of the display electrode 2 and the counter electrode 3, a transparent electrode such as In ₂ O ₃ or SnO ₂ is used. As for the area, the display electrode 2 is smaller than the counter electrode 3. As the sealing material 4 and the sealing material 5, epoxy resin, low melting point glass, solder or the like is used. The displayable substance 6 includes a dye that is an electrochromic material, a supporting electrolyte, and a solvent that dissolves these.

One of the necessary components for the displayable substance 6
The other electrochromic material is a spiropyran-based organic dye having a general formula as shown in Chemical formula 2.

It is known that spiropyran-based dyes exhibit a phenomenon from decoloring to color development using light irradiation or an acid as a catalyst, and their application to various recording materials has been developed. However, as an electrochromic material, a substance that exhibits so-called photochromism, which exhibits color upon irradiation with sunlight, is not suitable for practical use. In (Chemical formula 2),

[0015]

[Chemical 3]

Instead of, an electron-withdrawing group, --N
Photochromism is well shown when a substance such as O ₂ or —OH group is attached. If an electron donating property (Chemical Formula 3) is applied, it becomes difficult to exhibit photochromism. On the other hand, electrochemically oxidizing the N atom causes the spiropyran ring to be cleaved, resulting in coloring electrochromism.

The dye is dissolved in a solvent and injected into the display element as shown in the figure, but as the solvent, one which is electrochemically stable must be selected. Also, a supporting electrolyte is applied to the solution in order to obtain a good color density and response speed.

Non-aqueous organic solvents are excellent as electrochemically stable solvents. For example, the amide type includes dimethylformamide, N-methylformamide, N-methylacetamide, and N-methylpyrrolidone, the nitrile type includes acetonitrile, propionitrile, and benzonitrile, and the ketone type includes acetone, methylethylketone, and methyl. Examples of ethers such as isobutyl ketone and acetylacetone include tetrahydrofuran, 1,4-dioxane and the like, as well as propylene carbonate, γ-butyrolactone, nitromethane and dichloroethane.

Any supporting electrolyte may be used as long as it can be easily dissolved in a non-aqueous organic solvent. Generally, a quaternary alkylammonium ion is used as a cation, and other alkali metal ions such as Li ⁺ , Na ⁺ and K are used. ^{+ And the} like, and alkylphosphonium ions are used. Methyl, ethyl, propyl and butyl groups are often used as the alkyl group. Examples of the anion Cl ^-, Br ^-, I ^-
Other halogen ions such as NO ₃ ⁻ , ClO ₄ ⁻ various sulfonate ions (for example, P-toluenesulfonate ion), BF ₄ ⁻ and PF ₆ ⁻ are used.

After injecting a solution in which a dye and a supporting electrolyte are dissolved in a solvent into a display device as shown in FIG. 1, the coloring phenomenon occurs due to the oxidation reaction of the dye, and therefore the voltage is positive between the display electrode 2 and the counter electrode 3. When the voltage is applied in the range of 0.5-1.5 V, the coloring occurs. When the voltage sign is reversed, the dye is reduced and the color disappears.

The effect of the display device using such a dye is as follows. (1) The electrochemical redox reaction is reversibly and stably repeated by applying a voltage of 1.5 V or less.

(2) The color can be diversified by changing the structure of the dye. (3) The response speed of coloring and erasing is fast in this type of device.

Next, specific examples of the present invention will be shown. (Specific Example) As the electrochromic material, a spiropyran dye having the following structural formula was used.

[0024]

[Chemical 4]

Tetrabutylammonium perchlorate was used as the supporting electrolyte. Propylene carbonate was used as the solvent, and the dye and the supporting electrolyte were dissolved in the respective concentrations of 0.03 and 0.3 M / l. This solution was injected into the display device as shown in FIG. When the applied voltage was changed with respect to the counter electrode 3, it was observed that a coloring reaction occurred near +1 V and a decoloring reaction occurred near -0.5 V. The optical absorption characteristics show a light yellow color with weak absorption at 450 nm or less in the decolored state, but show large absorption with an absorption peak near 540 nm in the colored state.
The coloring color is magenta.

A display life test was conducted using this display element. Applied voltage of 1.3V for repeated color development
Is alternately applied to the display pole 2 at 5 second intervals.
We were able to confirm the repetition more than ten thousand times. As a continuous color development test, 1.3 V was continuously applied between the display electrode 2 and the counter electrode 3 in a 60 ° C. constant temperature bath. Color density of 80% or more of the initial color is 20
It was confirmed that the product was kept for more than 00 hours. The current consumption during continuous application was 10 μA / cm ² or less. There are few ordinary organic dyes that develop and decolor at a driving voltage of 1.5 V or less, are easily affected by impurities, and are likely to cause side reactions. Therefore, the number of times of repeated coloring and erasing is less than 1,000 times, which is not practical, and when the consumption current is large or the driving voltage is high, the corrosion reaction of the electrodes easily occurs and the display life is shortened. When the above dye is used, the effect is small. As for the response speed, the time required for the color development to reach the saturated density after the voltage application is 5 seconds or less, and the color erasing time is 2-3 seconds. It is easy to obtain a response speed of 1 second or less by controlling the driving method and the color density.

[0027]

In summary, according to the present invention, a display electrode is provided on one of two substrates, at least one of which is transparent, and a counter electrode is provided on the other of the two substrates, and a space formed between the substrates is represented by (Chemical Formula 2). The present invention provides an electrochromic display device characterized by encapsulating a spiropyran-based dye, a supporting electrolyte and a non-aqueous organic solvent, and can significantly improve the response speed and the display life.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the basic structure of an electrochromic display device that is an embodiment of the present invention.

[Explanation of symbols]

 1 glass substrate 2 display electrode 3 counter electrode 4 sealing material 5 sealing material 6 displayable substance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Nakagawa 1-3-2 Shimoishii, Okayama-shi, Okayama Japan Sensitivity Research Institute (72) Inventor Masaaki Hayami 1-2-2 Shimoishii, Okayama-shi, Okayama No. 3 In the Japan Photosensitive Dye Research Institute (72) Inventor Sadaharu Suga 1-2-3 Shimoishii, Okayama City, Okayama Prefecture

Claims (1)

[Claims] 1. A display electrode is provided on one of two substrates, at least one of which is transparent, and a counter electrode is provided on the other of the two substrates, and a general formula: embedded image is provided in a space formed between the substrates. (In the formula, X is a halogen group such as Cl or Br, -H, -N
O ₂ , -SO ₂ R, -COOR, -OR (where R is a lower alkyl group), or a group such as -CH ₃ , R ₁ and R ₂
Are the same or different lower alkyl groups, hydroxyalkyl groups, or alkoxyalkyl groups, R ₃ is hydrogen,
Alternatively, an alkyl group and R ₄ and R ₅ represent the same or different lower alkyl groups. ) A spiropyran-based dye, a supporting electrolyte, and a nonaqueous organic solvent are encapsulated, and an electrochromic display device is characterized.