JPS6053078B2 - Electrochemical microscopy device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochemical cell related to electrochemicomism, and more particularly to a cell for applying a coloring phenomenon based on an electrochemical redox reaction.

In general, a reversible coloring phenomenon that is dependent on electrical polarity, in which a certain element develops a color when it is energized, and becomes a rosy color when energized with a polarity opposite to that of the energization, is called an electrochromy phenomenon.

The electrochromy phenomenon is based on the physical electrochromy phenomenon, which is based on the generation of color centers within a substance due to an applied voltage, and the chemical electrochromy phenomenon, which is based on the electrolysis of a substance due to an electric current, that is, the redox of the substance.XΘ-N-
N (TEL-R 上 Y) There are two main types.

The coloring mechanisms of the two are completely different, and the latter in particular is called electrochemicomism to distinguish it from the physical electrochromic phenomenon. The technical object of the present invention is an electrochemical cell related to electrochemicomism. Application of such cells to devices for controlling the amount of light transmission or reflection, such as image display devices and variable filters, has been proposed.

Particularly in image display applications, conventional fluorescent displays such as J
Tube, gas discharge tube, plasma display element, LED, Lf■i
Elements using electrochemical microscopy have various advantages compared to D and the like. In other words, the driving voltage is low, the memory characteristics are good, the contrast is good,
These features include a wide viewing angle, full-screen display, and ease of large-area display. Needless to say, such characteristics are extremely useful for devices such as variable filters and shutters that electrically control the amount of light transmission or reflection. The electroresponsive coloring/decolorizing medium involved in such electrochemicomism is generally composed mainly of a redox-reactive organic substance, an electrolyte, and an inert solvent that dissolves them. Among them,
For redox-reactive organic substances, the following conditions must be met: 1. The non-colored species must have high solubility in the solvent and the colored species must be insoluble, and 2. The colored species must adhere to the electrode without precipitating due to insolubilization. , 3, it is desirable that the oxidation-reduction potential is sufficiently lower than the electrolytic potential of the solvent. Conventionally, 4,4'' dipyridine derivatives such as dihebutyl viologen dibromide and diN-(p-cyanophenyl) viologen dichloride are well known as this type of compound. It is dissolved in water or other suitable solvent together with an electrolyte such as iron, and when an electrode is brought into contact with this electrolyte and a voltage is applied, it is reduced on the cathode side and develops color.

Moreover, this reaction is reversible, and the color can be erased by reversing the polarity of the applied voltage. This type of device is disclosed in U.S. Patent No. 3,652,14, U.S. Pat.
It is described in the specification of No. 54,794. However, in such devices, the problem of device life remains an unresolved issue in the process of practical application. That is, conventionally proposed electrochemochemical devices tend to deteriorate due to repeated writing and erasing operations. Specifically, problems such as coloring species remaining, electrode contamination due to side reactions of yellow precipitates, and generation of bubbles occur, and eventually writing and erasing become impossible. At present, no effective solution to this problem has been proposed. The cause of deterioration is a complex intertwining of several factors, and is not clearly explained.
Particularly, it is presumed that one of the reasons for this is that the difference in redox potential between the first reduced form and the second reduced form of the color-developing and decolorizing substance, and the difference between this potential and the electrolytic potential of the solvent are small. Therefore, in the present invention, the drive operation life, that is, (writing←memory→
The main objective is to provide an electrochemical cell for electrochemical microscopy applications, which has a significant improvement in the repeat life of the erasing cycle.

The present invention, which achieves the above object, is, in short, an electrochemical cell which is equipped with at least a working electrode in a container and which contains an electroresponsive coloring/decolorizing medium in contact with the electrode. In the decolorizing medium, a compound of the general formula (wherein R is an alkylene group having 1 to 10 carbon atoms, an unsaturated alkylene group, or a xylylene group, xθ is an anion, Y is a chlorine atom, a bromine atom, an iodine atom, Indicates an HSO, group, H2PO, group, NO3 group, BF4 group, CIO, group, or CH3COO group.

Further, n is 2 to 12.7. ) is an electrochemical cell characterized by containing a compound represented by:

Devices based on electrochemochemical microscopy include at least a light-transmissive or reflective working electrode, its counter electrode, and its oxidation/reduction state reversibly changed by the passage of electric current. Using a cell containing an electro-responsive color-bleaching medium consisting of an electrochemical color-bleaching substance and an electrolyte, as well as a solvent thereof, capable of producing a detectable change in the appearance of the electrode. It has been known.

These electrodes and the medium are housed in a suitable housing with means for seeing through the working electrode. The electrochemical color-developing materials in such devices can accept or donate electrons, thereby converting them into radical ions with high absorbance, usually in the visible region of the spectrum, and at the same time The radical ions combine with anions present in the medium to form a medium-insoluble colored body on the working electrode. Its general structure is as shown in FIG. 1, in which a working electrode 1 and a counter electrode 2 are arranged in a cell 3 made of glass or the like, and each electrode is connected to a power supply section 4 by conducting wires 5 and 6.

Inside the cell 3, an electroresponsive coloring/decolorizing medium 7 is enclosed. Next, the driving method of such a device is as follows.

That is, first, writing to the working electrode occurs when a DC voltage is applied from the outside so that the working electrode is negative and the counter electrode is positive, and second, the memory effect occurs when the external voltage is turned off and the circuit is opened. (Writing on the working electrode continues.

) Thirdly, the writing on the working electrode is erased by reversing the polarity from the writing and applying an external DC voltage so that the working electrode side is positive and the counter electrode side is negative. There is a driving step. FIG. 2 shows a typical drive pulse application method, in which 8 represents a write step, 9 represents a memory step, and 10 represents an erase step.

The above driving method is the simplest bipolar constant voltage method, but other known methods include a bipolar constant current method and a three-polar constant potential driving method.

The three-electrode constant potential method uses a reference electrode in addition to the working electrode and counter potential to detect fluctuations in the potential of the working electrode and automatically adjust the applied voltage to keep the potential of the working electrode constant. The drive system is The present invention is applicable to any of these drive systems. The present invention is based on the discovery of an organic compound that is particularly excellent as a coloring/discoloring element in an electrochemical cell to which electrocheminomyce as described above is applied.

Here, the constituent elements of the electrochemical cell of the present invention will be explained in detail by giving specific examples.

As described above, the electroresponsive coloring/decolorizing medium housed in the cell in the present invention is generally composed mainly of an electrochemical coloring/decolorizing substance, an electrolyte, and a solvent thereof.

The electrochemical color-developing and fading substance used in the present invention is a compound represented by the following general formula.

However, in the formula, R represents an alkylene group having 1 to 10 carbon atoms, an unsaturated alkylene group, or a xylylene group, and Xe represents an anion.

Further, n is 2 to 12.7. In addition, as Xθ, for example, Cl-, Br-, I-, HSO4-, NO, -, H
Anions such as 2PO, 1, 8, 1, ClO, -, COO, etc. can be used. Or, as Y, a chlorine atom, a bromine atom, an iodine atom, an HSO4 group, a H2PO, group,
It represents a NO3 group, a BF4 group, a ClO4 group, or a COO group. These compounds represented by the above general formula are, for example, “゜1RDC Card NO.12O” published by Nankodo Co., Ltd.
82 (published at 197@) obtained at Shizuoka Pharmaceutical University, and a quaternization reagent with two active groups (e.g., alkyl dihalide, unsaturated alkyl dihalide, xylene halide). ) can be easily synthesized by reacting.Hereinafter, synthesis examples of typical compounds used in the present invention will be shown.

Synthesis Example 1 (Synthesis of the compound used in Example 1 below) 6.1 gr (0.03 mol) of azodipyridyl and 8 gr (0.03 mol) of P-xylylene dibromide were dissolved in 150 gr of dimethyl sulfoxide (reaction solvent), The mixture was placed in a three-necked flask and reacted at 700C for 10 hours.

The reaction solution was added to 500g of ethyl acetate, and the resulting precipitate was washed with 100g of ethanol and dried. The yield of the reaction product was 13.5 gr, and the reaction yield was 90.7%. The raw materials azodipyridyl and P-xylene dibromide were both soluble in ethyl acetate but insoluble in water, whereas the reaction product was well soluble in water but insoluble in ethyl acetate. Therefore, the reaction product is presumed to be the desired quaternized reactant. This reaction product was purified by repeating recrystallization three times with water and ethanol, and then the melting point was measured and elemental analysis was performed.

Furthermore, the molecular weight was measured using an Ostwald viscometer and the average degree of polymerization was calculated.

Measurement Data Compounds described in Examples 2 to 11 below were also synthesized in the same manner.

The melting point and average degree of polymerization are shown below. However, in Example 9, 4
The counter anion coordinated to the class nitrogen was Br- at the time of synthesis, but was converted to HSO4 using an ion exchange resin.
] This is the replacement. The compound represented by the above general formula is preferably contained in the color developing and decoloring medium in a molar concentration ranging from 1.times.10@-5 M to 1 M in order to obtain a practical coloring density.

Other constituent electrolytes include lithium chloride,
Potassium chloride, sodium chloride, potassium bromide, potassium sulfate, potassium acetate, potassium phosphate, ferrous sulfate,
Potassium perchlorate, zinc ammonium sulfate, magnesium ammonium sulfate, etc. can be preferably used.

Preferred solvents include water, nonaqueous solvents such as methyl alcohol, ethyl alcohol, ethylene glycol, propylene carbonate, ethylene glycol monoethyl ether acetate, and dimethyl formamide, and mixed solvents of water and these nonaqueous solvents. In addition to the above, various additives such as surfactants and iminocarboxylic acids may be appropriately added to the color developing/decoloring medium for the purpose of improving the stability of the medium over time. Ru.

In the electrochemical cell of the present invention, when the so-called electrolytic solution in which these components τ components are dissolved is housed in a suitable housing, the dissolved oxygen concentration in the electrolytic solution must be adjusted to 5 ppm or less. is desirable.

By reducing dissolved oxygen in the electrolyte, it is possible to extend the memory time and at the same time have a positive effect on the lifespan.
You can get results. In addition, the constituent materials of the electrode are:
Various low resistance metals, such as copper, aluminum, platinum,
In addition to palladium, gold, etc., metal oxides such as tin oxide or indium oxide, or photoconductive substances can be used.

In the present invention, it is preferable to use relatively chemically stable ones among the above. Selection of these materials, arrangement within the cell, etc. can be made arbitrarily depending on the specifications of the target device. The specific effects of the present invention will be more clearly understood from the following examples.

Example 1 A tin oxide film having a resistance value of 15 Ω/d was used and placed as a working electrode and a counter electrode in a cell as shown in the first figure.

Note that each electrode had a rectangular shape of 2WR×3T1rIt, and the interval between both electrodes was 2W1t. This cell was filled with an electrolytic solution in which A and K were dissolved in water.

The concentration of the former was 0.1M and the concentration of the latter was 0.3M. Furthermore, the electrolyte was deoxidized by passing N2 gas, and the amount of dissolved oxygen was adjusted to 2 PPM. For the sensor obtained above, a voltage of -1 V (1 sec) was applied using a DC power supply.
When the driving operation was continuously performed with a potential cycle of →0V (0.5sec) → +1V (1sec), the cell developed a blackish brown color when -1■ was applied, and then a blackish brown color when it was brought into the α state. Maintain status and get +1
It was found that when V was applied, a decolored state in which the blackish brown color disappeared. In addition, in order to measure the operating life of such a cell, when the cell was repeatedly subjected to potential cycles similar to those described above, it was found that the area of the working electrode used in the cell was approximately 1'10. It was found that the number of cycles (driving operation life) until the color remains unbleached when +1 V is applied is 3×1 CP (cycles). Note that the measurement temperature in the measurement was 24°C. For comparison, the compound used previously was replaced with the known dihebutyl viologen dibromide,
Other than that, when the test was carried out under the same conditions as above, the number of cycles until the problem of remaining cells disappeared was 3 × 1σ.
It was hot.

In addition, after writing -1V to the cell of this example and the comparative cell, we turned off the power, opened the circuit, and measured the time it took for the color to completely disappear. It took 17 minutes, whereas it took 7 minutes for the comparison cell, indicating that the cell of this example has better memory characteristics than the comparison cell.

Examples 2 to 11 Cells were prepared in the same manner as in Example 1, except that electrolytes having the compositions summarized in the table below were used, and each cell was driven in the same manner.

The operating life of each cell was measured in the same manner as in Example 1 above. The results are shown in the table below. Further, the hue of each cell when colored was blackish brown in Examples 2 to 11. 1 The values shown in parentheses in electrolyte composition are concentrations.

The lifetimes of the cells prepared in Examples 2 to 11 were as shown in the table below.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating an example of the configuration of an electrochemical cell to which electrochemicomism is applied, and FIG. 2 is an explanatory diagram illustrating an outline of a driving method of the electrochemical cell. In the figure, 1, 2... electrode, 3... cell, 4... power supply section, 5, 6... conductor,
7...Electro-responsive color developing and fading medium.

Claims (1)

[Claims] 1. An electroresponsive coloring/decolorizing medium obtained by containing a compound represented by the following general formula and an electrolyte in a solvent is placed in a container equipped with a working electrode and a counter electrode. Characteristic electrochemical microscopy device. General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (However, in the formula, R is an alkylene group having 1 to 10 carbon atoms,
unsaturated alkylene group or xylylene group, X is an anion, Y is chlorine atom, bromine atom, iodine atom, HSO_4 group, H_2PO_4 group, NO_3 group, BF_4 group, ClO
Indicates _4 group or CH_3COO group. n is 2 to 12.7. )