JP2910172B2 - Electrochromic display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrochromic display device (hereinafter referred to as an ECD) which is applied to a pattern display such as a numeral or character display, an XY matrix display, and a halftone dot display. Write).

[Summary of the Invention]

The present invention relates to an ECD using a specific electrochromic (hereinafter, referred to as EC) liquid, which is composed of an active material N, N'-dibenzyl-4,4'-bipyridinium chloride and an auxiliary oxide. Using an alkali chloride composed of the same alkali ion and chloride ion as the alkali ferrocyanide as the reducing substance and the cation of the auxiliary redox substance, and an aqueous solution containing sodium hypophosphite or potassium hypophosphite, By changing the composition ratio of the auxiliary redox substance, the display color can be continuously selected from magenta to dark blue
ECD.

[Conventional technology]

ECD is a non-light emitting type display device, which has the advantage of less fatigue even after long-time observation because it is a display using reflected light or transmitted light, and has relatively low driving voltage and low power consumption. It has advantages such as small size.

As a liquid-type ECD, a halide of viologen (general name of 4,4'-bipyridine derivatives) as an active material and potassium forocyanate of an auxiliary redox system are introduced, and two pairs of redox comprising viologen halide / potassium ferrocyanide are introduced. There is known a system in which an electron transfer reaction is performed reversibly in a system to form a colored or decolored state.

For example, the present inventor has proposed, as an EC solution, a green ECD using a p-cyanophenyl viologen (hereinafter, referred to as p-CV) halide and an aqueous solution of an alkali ferrocyanide as an EC solution, the ECD having further improved color density and life. It has already been disclosed (JP-A-61-107323).

According to this, a mixed aqueous solution of a p-CV halide and an alkali ferrocyanide, which is an EC solution, is used as a first electrolyte to have the same halogen ion as the p-CV halide anion and the same cation as the alkali ferrocyanide cation. By adding an alkali halide composed of the above-mentioned alkali ions, precipitation due to complex formation of p-CV and ferrocyanide ions can be suppressed, so that a high-concentration EC solution can be prepared.

Using this EC solution, a clear display with a large color density can be obtained. Further, by adding sodium hypophosphite or potassium hypophosphite as the second electrolyte, the display electrode can be repeatedly displayed and erased. Can be prevented, and a long-life ECD can be achieved.

[Problems to be solved by the invention]

As described above, this type of ECD has been improved in terms of display color depth and life, however, it has not been possible to continuously select the display color tone.

An object of the present invention is to continuously select a color tone of a display color.
To provide an ECD.

[Means for solving the problem]

According to the present invention, an EC solution is charged between at least one of the opposed electrodes serving as display electrodes, and the EC solution is a mixed solution in which an active material, an auxiliary redox material, and first and second electrolytes are dissolved in water. Wherein the active material is N, N'-dibenzyl-4,4'-
Bipyridinium (hereinafter referred to as benzyl viologen, BV
), The concentration of which is A, and the auxiliary redox substance is potassium bromide or sodium ferrocyanide, whose concentration is B, A ≧ 0.005M, B
≧ 0.005M and A + B ≦ 0.11M, the first electrolyte is an alkali chloride composed of the same alkali ion and chloride ion as the cation of the auxiliary redox substance, and the concentration thereof is 0.35M or more.
2.0M, and the second electrolyte is sodium hypophosphite or potassium hypophosphite at an ECD concentration of 0.2M to 2.0M.
It is.

In this ECD, the display color can be continuously selected from magenta to dark blue by changing the composition ratio of the active material / auxiliary redox material in the EC solution.

[Action]

The present inventor has found that in a viologen halide / alkali ferrocyanide ECD, when BV chloride is used as a viologen halide, the color tone at the time of coloring can be changed by changing the composition ratio of BV chloride / alkali ferrocyanide. It has been found that it changes continuously in the range from magenta to dark blue. Further, by adding an alkali chloride consisting of the same chloride ion as the anion of the BV chloride and the same alkali ion as the cation of the alkali ferrocyanide, precipitation from the solution is suppressed, and the BV chloride / ferrocyanide is added. As a result of increasing the concentration of BV chloride in the alkali halide solution, the contrast at the time of coloring can be increased.

 The effect of suppressing precipitation is understood as follows.

For example, BV dichloride (BV ⁺⁺
When 2Cl ⁻ ) and potassium ferrocyanide (K ₄ Fe (CN) ₆ ) are used, it is considered that a reaction represented by the following formula (1) occurs in a mixed aqueous solution thereof.

2 [BV ^{+ · ·} 2Cl ^-] _{+ 2K 4 Fe (CN) 6} K [BV _{+ ·] ^{2 [Fe (CN) 6 3-}} ] ↓ + K 3 Fe (CN) 6 + 4KCl ...... (1) chloride in a mixed aqueous solution by addition of potassium (KCl), (1) equation of the equilibrium proceeds to the left, consisting of green crystals precipitate K [BV ^{++] _{2 [Fe (CN) 6 3-}} ] is the one that dissolves again Seem. The second electrolyte, sodium hypophosphite (Na
The addition of H ₂ PO ₂ ) greatly reduces the unerased residue on the electrode when repeated color-decoloring is performed, and prolongs the life of the ECD.

〔Example〕

In the ECD according to the present invention, for example, as shown in FIGS. 1 and 2, two glass substrates 1 and 2 are sealed to face each other via a spacer 3 provided along the periphery thereof. The EC liquid 8 is filled in this cell. Electrodes 4 and 5 are entirely deposited on each inner surface of each of the glass substrates 1 and 2, and insulating layers 6 and 7 are provided on both electrodes 4 and 5, respectively.
For example, a SiO ₂ layer is coated. At least one of the electrodes 4 and 5 is made of a transparent electrode, for example, ITO (composite oxide of In and Sn). The insulating layers 6 and 7 on both the electrodes 4 and 5 have through holes corresponding to the patterns to be displayed, respectively. , "FM" in the example shown
And "AM" through holes 6a and 7a. For example, mutually different side edges 1a and 2a of each of the substrates 1 and 2 are pierced outside so as not to be opposed to the other substrates 2 and 1, and electrodes 4 and 5 are respectively provided on these side edges 1a and 2a. Alternatively, a conductive layer connected to these electrodes 4 and 5 is applied, and the terminal portions 4a and 5a are led out.

Example 1 The EC liquid 8 composed of an aqueous solution having the following composition was filled in the cell between the substrates 1 and 2 described above.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.01M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.01M auxiliary redox compound / composition ratio of the active material (R) = 1.0 a first electrolyte KCl... 1.0 M Second electrolyte; NaH ₂ PO ₂ ... 0.5 M This EC solution was prepared according to the following procedure.

First, a but sufficiently blown distilled water nitrogen gas to remove oxygen dissolved, the distilled water active material BV ⁺⁺ · described above in 2Cl ^- stirred into the auxiliary redox subsequently thereto Potassium ferrocyanide K ₄ [Fe (CN) ₆ ]
And stir. In this case, a precipitate consisting of green crystals is deposited as described above. The first electrolyte potassium chloride KCl is added to redissolve the deposited precipitate.
Thereafter, sodium hypophosphite NaH ₂ PO ₂ is added and stirred for 30 minutes, for example, with a magnetic stirrer. The obtained mixed aqueous solution was used as an EC solution.

The ECD thus obtained is applied to each of the electrodes 4 and 5 by applying a DC voltage and by inverting the polarity of each of the electrodes 4 and 5, each window 6a not covered by the insulating layers 6 and 7 of each electrode 4 and 5. In addition, purple coloring occurred in 7a and 7a, whereby each display, in the above-described example, switching between “FM” and “AM” could be performed.

Next, each characteristic of the EC solution in Example 1 was measured. This measurement was performed by the EC cell 32 shown in FIG. this
The EC cell 32 is formed by immersing a pair of counter electrodes 10 and 11 and a reference electrode 14 in a container 9 containing an EC solution 8. On one electrode 10, an ITO transparent conductive layer 12 having a sheet resistance of 10Ω / □ is deposited on a glass substrate, and an SiO ₂ insulating layer 13 having a 0.95 cm ² window 13a formed thereon is coated thereon. Be done. The other electrode 11 is made of a 4 cm ² platinum plate, and has a reference electrode 14.
Used a silver / silver chloride electrode. The measurement of the voltammogram was performed by combining a Hokuto Denko HA-301 potentiostat with a Hokuto Denko HB-104 function generator. The voltage sweep speed was 30 mV / sec. Electrode 10
The change in transmittance due to coloring and decoloring in the window 13a was performed by using a double beam spectrophotometer (UNIDEC-610C) manufactured by JASCO Corporation with light incident in the direction of the arrow. The cell was driven in the rectangular wave voltage mode shown in FIG. 4, and the spectroscope was swept from the long wavelength side to the short wavelength side at a speed of 40 nm / min.

By this measuring method, the driving voltage to the cell 32 is changed to the fourth voltage.
As shown in the figure, + 0.6V (1.5 seconds), -0.74V (4.5 seconds)
FIG. 5 shows the measurement results of the wavelength-transmittance when.

According to this, a high transmittance is shown in the visible region in the oxidized state, and the transmittance is reduced in the reduced state. The transmittance in the reduced state is relatively large in the blue and red regions. This corresponds to the display color of the ECD of Example 1 being purple.

FIG. 6 is a voltammogram obtained by sweeping at 30 mV / sec. In the portion where the current sharply increases in the negative direction, it is observed that electrons are taken in, that is, a reduction reaction occurs, and the electrode surface is colored. Further, it is observed that electron emission, that is, an oxidation reaction occurs in a portion where the current sharply increases in the positive direction, and the colored substance deposited on the electrode surface is discolored and dissolved.

Example 2 As in Example 1, the cells of the substrates 1 and 2 were filled with an EC solution 8 comprising an aqueous solution having the following composition.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.01M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.005M auxiliary redox compound / composition ratio of the active material (R) = 0.5 a first electrolyte KCl... 1.0 M Second electrolyte; NaH ₂ PO ₂ ... 0.5 M This EC solution was prepared in the same manner as in Example 1. By applying a DC voltage to the thus-obtained ECD in the same manner as in Example 1, red-violet coloring / decoloring could be displayed.

Example 3 As in Example 1, the cells of the substrates 1 and 2 were filled with an EC solution 8 comprising an aqueous solution having the following composition.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.01M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.02M auxiliary redox compound / composition ratio of the active material (R) = 2.0 a first electrolyte KCl... 1.0 M Second electrolyte; NaH ₂ PO ₂ ... 1.0 M This EC solution was prepared in the same manner as in Example 1. By applying a DC voltage to the thus obtained ECD in the same manner as in Example 1, it was possible to display blue-violet coloring / decoloring.

From the results of Examples 1 to 3, it can be seen from the results of Examples 1 to 3 that when R = 1, purple coloring is displayed, when R <1, red tends to increase as R decreases, and when R> 1, blue increases as R increases. Is shown.

Example 4 As in Example 1, the cells of the substrates 1 and 2 were filled with an EC solution 8 composed of an aqueous solution having the following composition.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.01M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.04M auxiliary redox compound / composition ratio of the active material (R) = 4.0 a first electrolyte KCl... 1.5 M Second electrolyte; NaH ₂ PO ₂ ... 1.0 M This EC solution was prepared in the same manner as in Example 1. By applying a DC voltage to the thus obtained ECD in the same manner as in Example 1, it was possible to display dark blue coloring / decoloring. However, the EC liquid is a transparent liquid at first, but when coloring / decoloring is repeated, crystals are deposited and become a devitrified state (mat state). In this case, the ECD is observed from the display electrode side.

Example 5 As in Example 1, the cells of the substrates 1 and 2 were filled with an EC solution 8 composed of an aqueous solution having the following composition.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.005M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.005M auxiliary redox compound / composition ratio of the active material (R) = 1.0 a first electrolyte KCl... 0.5 M Second electrolyte; NaH ₂ PO ₂ ... 0.5 M This EC solution was prepared in the same manner as in Example 1. By applying a DC voltage to the ECD thus obtained in the same manner as in Example 1, the display of purple coloring / decoloring could be performed. The color display is purple with R = 1, which is the same as that of Example 1. However, since the concentration of the active material in the EC solution is low, the color of the color display is lighter than that of Example 1.

Example 6 As in Example 1, the cells of the substrates 1 and 2 were filled with an EC solution 8 comprising an aqueous solution having the following composition.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.05M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.05M auxiliary redox compound / composition ratio of the active material (R) = 1.0 a first electrolyte KCl... 2.0 M Second electrolyte; NaH ₂ PO ₂ ... 2.0 M This EC solution was prepared in the same manner as in Example 1. By applying a DC voltage to the ECD thus obtained in the same manner as in Example 1, the display of purple coloring / decoloring could be performed. The color display was purple in the same R = 1 as in Example 1, but the color display was darker than that in Example 1 because of the high concentration of the active material in the EC solution.

Example 7 As in Example 1, the cells of the substrates 1 and 2 were filled with an EC solution 8 composed of an aqueous solution having the following composition.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.1M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.01M auxiliary redox compound / composition ratio of the active material (R) = 0.1 a first electrolyte KCl... 2.0 M Second electrolyte; NaH ₂ PO ₂ ... 2.0 M This EC solution was prepared in the same manner as in Example 1. By applying a DC voltage to the thus-obtained ECD in the same manner as in Example 1, red-violet coloring / decoloring could be displayed. Although the display is the same magenta color display as in Example 2, the color depth of the color display in Example 1 is high because the concentration of the active material in the EC solution is high.
Than was obtained.

Example 8 In the same manner as in Example 1, the cells of the substrates 1 and 2 were filled with an EC solution 8 composed of an aqueous solution having the following composition.

Active material; BV ⁺⁺ · 2Cl ^- ...... 0.01M auxiliary redox _{substances; K 4 [Fe (CN)} 6] ...... 0.1M auxiliary redox compound / composition ratio of the active material (R) = 0.1 a first electrolyte KCl... 1.5 M Second electrolyte; NaH ₂ PO ₂ ... 1.0 M This EC solution was prepared in the same manner as in Example 1. By applying a DC voltage to the thus obtained ECD in the same manner as in Example 1, it was possible to display dark blue coloring / decoloring. As in Example 4, the EC liquid was initially transparent, or became devitrified by repeated coloring / decoloring. In the above embodiment, potassium ferrocyanide was used as the auxiliary redox substance.
Similar results were obtained by using NaCl as the electrolyte. Similar effects were obtained by using potassium hypophosphite (KH ₂ PO ₂ ) instead of sodium hypophosphite as the second electrolyte.

〔The invention's effect〕

As described above, according to the present invention, in a viologen halide / alkali ferrocyanide ECD, by using BV chloride as a viologen halide, and changing the composition ratio of BV chloride / alkali ferrocyanide, The color tone at the time of coloring can be continuously selected from magenta to dark blue, and the unremoved remaining on the electrode when repeated coloring and erasing is repeated is reduced, thereby providing a long-life ECD.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of the electrochromic display device of the present invention, FIG. 2 is a sectional view taken along the line AA, FIG. 3 is a perspective view of the cell for measuring characteristics, and FIG. 5 is a measurement result of transmittance-wavelength characteristics, and FIG. 6 is a measurement result of voltammogram. In the drawings, 1 and 2 are substrates, 4 and 5 are electrodes, and 8 is an electrochromic liquid.

Claims (1)

(57) [Claims] An electrochromic liquid is filled in contact with at least one of the opposing electrodes serving as display electrodes in contact with these electrodes. The electrochromic liquid comprises an active material, an auxiliary redox material, and first and second electrochromic liquids. The active material is a chloride of N, N'-dibenzyl-4,4'-bipyridinium, the concentration of which is A
When the auxiliary redox substance is potassium ferrocyanide or sodium ferrocyanide and its concentration is B, A ≧ 0.005M, B ≧ 0.005M and A + B ≦ 0.11M, and the first electrolyte is An alkali chloride composed of the same alkali ion and chloride ion as the cation of the reducing substance, the concentration of which is 0.35 M to 2.0 M, and the second electrolyte is sodium hypophosphite or potassium hypophosphite. An electrochromic display device having a concentration of 0.2 M to 2.0 M.