JPS6087315A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To render a reducing auxiliary electrode unnecessary, to obtain a large display area, and an element small in cell distance, and to reduce electrolysis capacity, by using an electrolytic soln. contg. a reducing substance as an electrolyte. CONSTITUTION:The surface of an upper transparent glass base 1 is coated with a transparent electrode 2, and WO3 is vapor deposited as the first electrochromic layer 3 in a prescribed form. The surface of a lower transparent glass base 1 is also coated with a transparent electrode, and prussian blue 6 is electrodeposited as the second electrochromic layer. The upper base 1 is overlaid on the lower base 1, and bonded with pressure at 130 deg.C to form a vacant cell. An electrolytic soln. 7 dissolving 1mol/l triglyme as an electrolyte is injected into this vacant cell. As a result, an auxiliary electrode to be used for initial reduction is made unnecessary, a large display area and an element small in cell distance can be obtained, and further, labor cost for fixing the auxiliary electrode can be cut off.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrochromic display element, in particular a pair of electrodes, at least one of which is translucent, comprising an electrochromic layer on the surface of one of the electrodes, the other of which is transparent. The present invention relates to an electrochromic display element comprising a redox substance on the surface of the electrode and an electrolyte sealed between the two electrodes.

Conventional technology When a device is manufactured using, for example, Prussian blue (PB) and tungsten oxide (WO8) as an electrochromic layer, both PB and WO2 are in an oxidized state at that point.
In order to develop and fade colors simultaneously, it is necessary to bring one of them into a reduced state. At this time, if there is no substance that causes an oxidation reaction such as an auxiliary electrode, water in the electrolyte decomposes and oxygen is generated.

This oxygen oxidizes the display electrode in a reduced state, significantly impeding memory performance.

In order to solve this drawback, the present applicant filed a patent application in Japanese Patent Application No. 58-329.
In the specification of No. 18, a display element using an auxiliary electrode made of a substance that reversibly performs redox was proposed. This display element has a 6'q structure as shown in FIG. In the electrochromic layer, 7 is a 1-blind substance for 'I, and 8 is an auxiliary electrode.By reducing the oxidized display electrode by this auxiliary electrode, both display electrodes can be colored and erased at the same time. , the above drawbacks can be solved.

However, according to such a conventional reduction method using an auxiliary electrode, (a) it is necessary to produce an auxiliary electrode that does not have the original display and flash.

(b) The display area becomes smaller due to the auxiliary electrode.

(/Sai) When the cell spacing is as small as 101LTnNIIIm, it is difficult to insert an auxiliary electrode.

) An electrode extraction section from the auxiliary electrode must be provided.

(E) It is necessary to prevent short circuit between the display pole and the
There was a problem in that it was necessary to take measures such as etching the nest and inserting an insulating material.

DISCLOSURE OF THE INVENTION The present invention has been made by focusing on the above-mentioned problems of the conventional art, and solves the above-mentioned problems by using an electrolytic solution to which a reducing substance is added as an electrolyte.

That is, the display element of the present invention uses an electrolytic solution to which a reducing substance is added as an electrolyte as described above, and thereby oxidizes and reduces both oxidizing and reducing substance layers at the initial stage when voltage is applied to both electrodes or when memory performance deteriorates. It is characterized by maintaining the balance of the amount of electricity, and the reducing substance to be added meets the following conditions: Gred<Area, Bred<Aox, B
ox<Cox<HoxHowever, AOX, Area? Reaction potential of oxidation and reduction of the first coloring layer, BOX, Bred j Reaction potential of oxidation and reduction of the second coloring layer, Cox, 0red: Reaction potential of oxidation and reduction of the reducing substance to be added, 1(ox: Reaction potential of water It is necessary to add 111 - the decomposition voltage in oxidation (less than -2 V for reduction), and by satisfying this condition, the first or second
The coloring layer, the electrochromic layer, etc. can be reduced. Further, it is preferable that the material be transparent in an oxidized state in an electrolytic solution. Such reducing substances include thiophene, pyrrole, indole, 8-methylthio-7-ene,
Heterocyclic compounds such as 3,4-dimethylthiophene and 2,2'-dithiophene, and their Jf' [forms and 0H8
ether represented by 0(OH,OH,O)nOH8,
Examples include diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme) and cyclopentacycloheptene (azulene), hydroquinone. The redox potentials of these reducing substances are shown in Table 1 below.

The amount is about 2 moles at most, preferably about 1 mole per first surface liquid 11. Here, Q is the electricity ffi required to electrically reduce the electrochromic substance to be reduced, and F is the number of groups to be oxidized per molecule, for example, 3. )
It becomes 4 in regram. The reason for this is that below this range, the electrochromic substance cannot be purchased sufficiently, and increasing it is generally undesirable because ffi[t<t>.

Examples of the invention Hereinafter, the present invention will be explained by way of examples with reference to the drawings.

EXAMPLE An electrotetrachromic device of the example shown in FIG. 2 was prepared according to the following steps.

(1) The surface of the glass transparent substrate 1 for the upper substrate is
) was coated with an electrode (ITO) 2, and WO2 was deposited in a predetermined shape on top of this as a first electrochromic layer 8 (
8X10""mu H9 (Torr), thickness 3,
500 people).

(2) The surface of the glass transparent substrate 1 for the lower substrate is similarly coated with a transparent electrode (TO) 2, and Prussian blue 6 is electrodeposited on top of this in a predetermined shape as the 21st electrochromic layer. did.

(3) Seal material on the upper substrate [epoxy base material LOB30]
4 (El (manufactured by O Company, trade name): Imidazole curing agent 2
PZ (manufactured by Shikoku Kasei, trade name)-25:2)-5 was applied by printing except for the electrolyte injection port.

(4) Five to six glass fibers (diameter 10 μm) were sprinkled on the lower substrate as a spacer material at a ratio of 4-4.

(5) The upper substrate and the lower substrate were stacked and bonded under pressure at 130'C for 1 hour to produce an empty cell.

(6) An electrolytic solution (1 mol Li(3tO4/) lyethylene glycol dimethyl ether) in which 1 mol/l of triglyme was dissolved was injected into the empty cell.

(7) The injection port for the electrolytic solution was sealed with an adhesive (manufactured by Three Bond Co., Ltd., TB20002:TB2108.-100:8).

(8) The lead wires attached to each electrode were connected to a power source to obtain a display element.

For comparison, a display element was produced in the same manner except that a similar solution containing no triglyme was injected as an electrolyte.

Triglyme, PB and WO2 for the above two types of elements
The reaction potential was measured and shown in Figure 3.

The reduction reaction potential of triglyme is much higher than that of PB, and once oxidized, no reduction reaction occurs even during display drive.

Therefore, if a potential difference is applied to both electrodes of the element when both B and vo are in the oxidized state at the initial stage, PB is reduced on the PB side and triglyme is oxidized on the WO2 side, resulting in initial decolorization. A potential difference is applied to the electrodes using a constant current (0.1 to 0.5 mA 7effi'', which is initially applied by the amount of electrodeposited electricity). If the oxidation potential is higher than the second wave of PB, WO8 may be reduced, but it is easier to determine the end point if PB is reduced and discolored.

In addition, if the memory condition worsens over time, that is, if both electrodes are oxidized and the amounts of electricity for oxidation and reduction of PB and WO8 are no longer the same, perform the same operation as the initial reduction as appropriate, and The spirit is no longer the same.

In Fig. 3, curve 1 is the VI curve of WO2, curve 2 is the V-1 curve of PB, and curve 8 is the V-I curve of WO2.
1 mole/! , Triglyme 17/! Curve H4 is a curve showing the reaction potential of water (1 mole of H2O/1-propylene carbonate).

Effects of the Invention As explained above, in this invention, by using an electrolytic solution to which a reducing substance is added as an electrolyte,
Since an auxiliary electrode for initial reduction is not required, a large display area can be obtained, an element with small cell spacing can be obtained, the amount of electrolyte can be reduced, and the number of man-hours required for attaching the auxiliary electrode can be reduced. can get.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional electrochromic display element, Fig. 2 is a cross-sectional view of an electrochromic display element of the present invention, and Fig. 3 is a V-1 curve diagram that does not show the reaction potential of triglyme, PB1W08, and water. be. DESCRIPTION OF SYMBOLS 1... Transparent substrate 2 Transparent m-pole 8... First electrochromic layer or first coloring layer, 4... Insulating film 5... Sealing material 6... Second electrochromic layer or Second coloring layer 7... Electrolyte 8... Auxiliary electrode. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Akatsuki Sugimura Competence Patent Attorney Oki Sugimura Figure 1 Figure 2

Claims (1)

[Claims] L A pair of electrodes, at least one of which is translucent, includes an electrochromic layer on the surface of one electrode, a redox substance layer on the surface of the other electrode, and an electrolyte between the two electrodes. In an electrochromic display element that simultaneously develops and erases color at both electrodes, both oxidizing and reducing substance layers are formed at the initial stage when a voltage is applied to both electrodes or when the memory condition deteriorates using an electrolytic solution containing a reducing substance as the electrolyte. An electrochromic display element characterized by maintaining a balance between the amount of electricity for oxidation and reduction.