JPS5951588B2 - display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrochemically redox display material [C7H
15-N゛〇ON゛(1) [C7H15-N〇ON-(li) The operation is that the biologen compound i, which is initially dissolved in the electrolyte in a colorless state, becomes an electrochemically reduced cation radical. , a purple-colored, water-insoluble salt ii is produced, which is deposited on the surface of the display electrode to provide color display.

On the other hand, since the precipitated salt ii is reversibly oxidized, a display device in which at least two electrodes are brought into contact with an electrolytic solution containing biologinated initial substances by, for example, reversing the polarity of the display electrodes. . Conventionally, display devices that utilize such electrochemical redox reactions are ECD.
(electrochromic display), for example, in the literature (Appl, Phys, Lett, 23, 6
4 (1973).

This device uses heptyl viologen bromide as a display material and erases color display using an electrochemical reaction formula according to equation (1) below. C7H15〕2B
Ding+e2H15] B7・・・・・・・・・・・・・・・・・・
(1) Compound i is regenerated and color disappears.

However, since this color display utilizes a radical state, it is extremely easy to self-extinguish due to dissolved oxygen in the electrolyte, and unless the dissolved oxygen is sufficiently removed, the displayed image will have a memory effect. make things worse. Furthermore, since the reversible reduction potential of the electrochemical reaction for erasing the display is narrow, the life of the display device cannot be extended unless the voltage applied to the display electrode is regulated and the electrochemical reaction proceeds within the reversible potential region. For this reason, it is necessary to provide a reference electrode in addition to the display electrode and counter electrode for regulating the potential of the display electrode as shown in the above-mentioned literature, which makes the drive circuit of this device extremely complicated. There were various drawbacks such as: In order to eliminate the above-mentioned drawbacks, the inventors first developed an iodine ion I
- and heterocyclic compound ion
I.

) is deposited and erased on the top of the display 31-+X+=XI.

+2e・・・・・・(2) Erase color display,
We have proposed a display device that has a longer image storage time and is simpler. The present invention uses a pyridine carboxylic acid ester as a heterocyclic compound ion on the same principle as the previously proposed device, and has an excellent display effect with fast display erasing response speed and high color density. The purpose is to provide a display device.

The display erasing principle of the present invention is that in formula (2), iodine (I.) generated on the display layer by an electrochemical oxidation reaction of iodine ions I, interacts with iodine ions near the electrode and a heterocyclic nitrogen compound. Compounds (XI.
), and since this compound is insoluble in the two aqueous solutions, it stays on the surface of the display electrode, making it possible to display both black and color, and at the same time having a display memory function. On the other hand, by reversing the polarity of the electrode, the precipitated complex is reversibly reduced and the initial iodine ion and heterocyclic nitrogen compound 5
It returns to positive ions, and color erasure becomes possible. Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings. 1 and 2 show an embodiment of the display device of the present invention, FIG. 1 is a plan view thereof, and FIG. 2 is a sectional view taken along the line 11--11 in FIG. 1.

1 is a transparent substrate made of glass or the like, 2 is a counter electrode, and 3 is a mask that allows only the display portion to be seen.

4 is a display electrode made of SnO.

, In. O. , Pt, Au, etc., and consists of display segments (4a to 4g). Each lead portion is covered with an insulating film (SiO., Al.O., etc.). 5
6 is a spacer, and 6 is an electrolyte injection hole, which is sealed after the electrolyte is injected.

The electrolytic solution 8 used here is, for example, an aqueous solution containing a halogenated heterocyclic nitrogen compound and potassium iodide. In this display device, when the display electrode 4 is used as a positive electrode and the counter electrode is used as a negative electrode, and a DC voltage is applied between both electrodes, a colored compound consisting of iodine and a heterocyclic nitrogen compound is formed based on the reaction shown in formula (2). An image is displayed by depositing on the positive electrode, and the displayed image remains in a memorized state even after the applied voltage is removed.

When a reverse voltage is applied between the two electrodes, the compound on the display layer returns to its initial state and the image is erased. Display materials with electrochemically reversible oxidation-reduction functions used in such display devices have a high contrast (rate of change in light transmittance) in image display when a certain amount of electricity is applied. This is indeed preferable, and it is also preferable because the image storage time is long.

Furthermore, it is desired that the response speed when erasing the display be fast. The inventors conducted a comparative test on the properties of the heterocyclic nitrogen compound according to the present invention and the heterocyclic nitrogen compound proposed previously.

The results are shown in Table 1. Here, compounds 1 to 7 are the heterocyclic nitrogen compounds proposed above, and compounds 8 to 13 are the heterocyclic nitrogen compounds according to the present invention.

Each actual response speed value is based on the display response speed, which is the time required to obtain a display state with contrast (1:5), and the erasing response speed, which is the time required to completely return the display state to its original state. And so.

The contrast ratio and storage time ratio are compared on the basis of the characteristic values of N-ethylpyridinium iodide, which is one of the heterocyclic nitrogen compounds proposed earlier, and are compared in terms of ratios of 1 to 1. The electrolyte used here contained 0.1 mol/l (a) of a halogenated heterocyclic nitrogen compound. Those that do not dissolve at 1 mol/l are saturated), KIO. It is an aqueous solution containing 2 mol/l.

1 The contrast ratio shown in Table 1 represents the ratio of the contrast change (light transmittance change ratio) when the same amount of electricity (10 mc/Eml) is applied. In addition, the image storage time ratio shown in Table 1 refers to the same amount of electricity (10mC/CIrl2).
It represents the ratio of the time required for the image to be erased until the light transmittance reaches a certain value after energizing to display an image and then removing the voltage application.

As is clear from Table 1, the heterocyclic nitrogen compound based on the present invention having a pyridine carboxylic acid ester in the basic skeleton of the molecule is superior on average in terms of erasure response speed, contrast, and memory time. It can be seen that it has certain characteristics.

Other embodiments of the present invention are listed in Table 2 A, b, and c.

Regarding these, Tables 1 8 to 13 which are examples of the present invention
The same effect was obtained. Furthermore, as a compound of the present invention, the substituents Rl, R2, and R3 in the formula) can be substituted with substituents other than those exemplified, and X- is C1-, Br-, I-,
DlO4 etc.

In the heterocyclic nitrogen compounds according to the present invention, there was a tendency that the higher the number of carbon atoms, the higher the solubility in the electrolytic solution, and the lower the response speed.

Claims (1)

[Scope of Claims] 1. A display device comprising at least two electrodes in contact with an electrolytic solution containing an electrochemically reversible redox display material, wherein the display material contains iodine ions and a compound of the following formula: ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R_1 represents an alkyl group, while R_2 represents an alkyl group or a phenyl group). . 2. The display device according to claim 1, wherein R_2 in the pyridine carboxylic acid ester derivative ion is an alkyl group having 7 or less carbon atoms.