JPS5848031A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To obtain an electrochromic display element improved in response characteristics, durability against repeated actions, contrast, etc., by using a reactive medium containing a styryl-like compd., a specified supporting electrolyte, and a basic solvent. CONSTITUTION:An electrochromic display element is manufactured by arranging between 2 conductive electrodes, at least one of the two being transparent, a reactive medium containing a styryl-like compd. having formulaI, such as formula VI, etc., a supporting electrolyte, such as (C4H9)4N.PF6 or (C4H9)4N. BF4, and a basic solvent, such as dimethylformamide or dimethylacetamide. In formulaI, n is 1 or 2; A is H, lower alkyl, halogen, or alkoxyalkyl, a group of formula II-IV; Z is 2-4C alkylene optionally substituted by alkyl necessary to form a cyclic structure together with a group of formula V; Y is O or S; and R is lower alkyl. In formula VII, R1 is 2-8C alkyl, and X is ClO4, -PF6, -BF4, or -SO3CF3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochromic display element, and improves the basic characteristics of display such as responsiveness, repeated operation life, contrast, etc. by configuring a specific combination of reactive media. With the goal.

Electrochromic display elements are made by enclosing a reactive medium between two electrically conductive electrodes, at least one of which is transparent. In such a structure, information is selectively displayed by dividing the electrodes into appropriate segments and applying a potential between the electrodes to cause coloring in a desired area.

As a result of various studies on the above-mentioned reactive medium, the present inventor found that a reactive medium having a styryl-like compound as shown in Structural Formula (1), a supporting electrolyte as shown in Structural Formula (2), and a basic solvent, It has been found that responsiveness, repeated operation life, and contrast are significantly improved over conventional ones.

ゝ'z-'' Here, n is an integer of 1 or 2, and A is -H2 lower alkyl group, halogen group, alkoxylalkyl group, -80
2CH3, -8o2c2H5, -8o2c4H9, Z has or does not have an argyl substituent necessary to form a cyclic structure with -N-C-Y, or an alkylene group having 2 to 4 carbon atoms, Y is 0 or II-J, S
, R represents a lower alkyl group, respectively.

(R1)4N-x ・・・・・・・・・・・・
...(2) Here, R1 is an alkyl group having 2 to 8 carbon atoms, X is -CI+, 04. -PF6. -BF4. -8
The Vh deviation of o3CF3 is shown respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings, while comparing them with conventional ones.

Pigments of styryl-like compounds are colorless when no voltage is applied, but are oxidized and colored when voltage is applied. 1. In acidic solvents, they will explode just by mixing them. Generally, when moisture is contained, the material develops color or is likely to develop color. This varies depending on the acidity of the solvent. On the other hand, when a basic solvent is used, the dye does not develop color just by being dissolved in the solvent. Therefore, only by applying a voltage can the phenomenon of decoloring and developing occur. Therefore, the contrast between decolorization and decolorization is good, and it looks beautiful because coloration occurs from a colorless state.

Tetraalkylammonium salts exhibit the best properties as supporting electrolytes. Other supporting electrolytes used in non-aqueous solvents, such as LiCl! , 04. CuCpo4 develops color only when mixed with a dye, and the responsiveness of decolorization and development is slow. In order to dissolve well in nonaqueous solvents, the alkyl group needs to have a larger number of carbon atoms than the ethyl group, which has two carbon atoms. As an anion, (404''' is the most common, but BF
There is 4-PF-169 So3CF3-. When halogen ions are used, the electrodes are likely to be corroded and react with dyes, resulting in a shortened repeated operation life. Incidentally, the coloring potential of the dye of the styryl-like compound is +0.8 to +1.6V, and the decoloring potential is -o,es to -1.5V (vs. 5OE).

The responsiveness of decoloring and developing due to voltage application is most easily affected by the viscosity of the solvent. The color density changes over time as shown in the figure. The time t1 from when voltage is applied until the concentration is saturated is, for example, 6 to 10 seconds when using something like propylene carbonate.

It takes 4 to 8 seconds for γ-butyrolactone, 0.5 to 1 second for methyl isobutyl ketone, and 0.5 seconds or less for acetonitrile. dimethylformamide, which is a basic solvent;
For dimethylacetamide, it is 0.6 to 2 seconds.

The coloring density varies depending on the concentration of the dye and supporting electrolyte in the reactive medium, but when compared at the saturation density A1 in the figure,
The color density increases in the order of propylene carbonate, acetonitrile, dimethylformamide, dimethylacetamide, methyl isobutyl ketone, and γ-butyrolactone.

From a practical standpoint as a display device, the most important characteristic is the repeated operation life. As a result of this test, it was confirmed that 2×10 6 times or more were used when a basic solvent was used. When other solvents were used, it was about 6×10 5 .

The dye concentration in the reactive medium is ○, O○ 6M/2 or more, and the supporting electrolyte concentration is 0. ○ Can be used up to saturation concentration at 1M/2 or higher. By the way, since the dye has good solubility in a basic solvent, it is easy to obtain a high color density because a large amount of the dye is dissolved. Therefore, even when the number of electrode segments increases, variations in color density between segments can be reduced.

Decoloring is accomplished by reversing the voltage used to develop color, by short-circuiting the positive pole and one pole, or by simply leaving it as it is. The decoloring time is shorter in this order. When a basic solvent is used, as described above, the dye tends to become decolored, so decoloring can be carried out in a short time without applying voltage. When comparing the cases where propylene carbonate and dimethylformamide are used as solvents, dimethylformamide can erase the color in about 10% of the time. It takes about 4 to 5 minutes.

To obtain a colored state continuously, a DC voltage is continuously applied or a pulse is applied, but in this case, decomposition of the supporting electrolyte becomes a problem. For example, even though it is generally said that there is no problem when the supporting electrolyte is used in the range of -1.6 to +1.6V, there may be differences in the supporting electrolyte when coloring continuously for hundreds to thousands of hours. come. In terms of longevity, NR4Cuo4 and NR45o3CF3<NR4
It becomes like BF4, NR4PF6.

Specific examples will be described below.

<Example 1> The dye used as an electrochromic material was 3,3-dimethyl-5-methylsulfonyl-2-(P-dimethylaminostyryl)indolino[2-1-b] shown by the following structural formula. Oxazoline is 1 cH2-cH2 The supporting electrolyte is tetrabutylammonium perchlorov-
(C4H9)4N-ClO2. Propylene carbonate was used as the solvent, and dimethylphoslumamide was used as the basic solvent. The display properties of the two solvents are shown in Table 1. The distance between the display electrode and the counter electrode of the display element used was 35 μm. The concentrations of dye and supporting electrolyte are each 0.1 mol/
ft,, o, ts mol/2.

Table 1 *■ Color development voltage 1.2V, application time 1 second for dimethylformamide and 7 seconds for propylene carbonate Color development time is tl in the figure, color eradication time is t2°, applied voltage is 1. 2V.

*■ It is shown as the change in optical density (ΔD, D,) at the absorption peak of 570 nn in the colored state of the dye.

<Example 2> The dye used was the same as in Example 1. Supporting electrolyte C (C4H9)4N-ClO4, (C4H9)4N-PF
There are 602 types. The solvent is dimethylformamide.

The concentrations of the dye and supporting electrolyte are each 0.1 mol/2゜0.
．． It is 6 mol/2. Table 2 shows display characteristics when two types of supporting electrolytes are used.

Tests (2), (2), and (2) in Table 2 are the same as in Example 1.

*■ 1. o Continuously apply DC voltage to the initial concentration of 7
The point at which the temperature decreased to 0% or less was defined as the life span.

In addition to the above examples, as the basic solvent, any one of N-methylformamide, N-methylacetamide, and pyri% may be used, or two or more of these including dimethylformamide and dimethylacetamide may be mixed. The same results as in each of the Examples were obtained even when using the same method.

Furthermore, as a supporting electrolyte, (C4H9)4N-BF4
The same results as in each example were obtained using the following.

As described above, the present invention uses a styryl-based analog compound as an electrochromic material, and has improved display characteristics by using a specific combination of a basic solvent and a supporting electrolyte of a tetraalkylammonium salt. In particular, the repeated operation life, which is a practically important property, is improved.

[Brief explanation of drawings]

The drawing shows the change in color density over time when a voltage is applied to an electrochromic display element.

Claims (3)

[Claims] (1) A styryl analog compound represented by structural formula (1);
An electrochromic display element characterized in that a reactive medium containing a supporting electrolyte represented by the structural formula (■) and a basic solvent is disposed between two conductive electrodes, at least one of which is transparent. Here, n is an integer of 1 or 2, A is -H1 lower alkyl group, halogen group, alkoxyalkyl group, -8O
2CH3, -8O2C2H6, -802C4H9, Z has or does not have an alkyl substituent necessary to form a cyclic structure with -N゛C-Y-, or an alkylene group having 2 to 4 carbon atoms. , Y is O or S, R
each represents a lower alkyl group. (R1)4N-X ・・・・・・Salary・・
...(■) R1 is an alkyl group having 2 to 8 carbon atoms, and X is CI! , O-PF-BF4. -8o3CF3(7
) Any 41 6? are shown respectively. (2) Claim 1, wherein the basic solvent contains at least one member from the group consisting of dimethylformamide, N-methylformamide, dimethylacetamide, N-methylacetamide, and pyridine.
The electrochromic display element described in . (3) The supporting electrolyte is (C4H9)4N-PF6 or (
2. The electrochromic display element according to claim 1, wherein the electrochromic display element is made of C4H9)4N-BF4, and the basic solvent is dimethylformamide or dimethylacetamide.