JPS63148241A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To improve the repetitive use life of an EC display element by providing a protection layer which prevents an electrochromic coloring layer from swelling and being dissolved in an electrolyte. CONSTITUTION:This electrochromic display element is equipped with a transparent electrode 3 formed on a substrate, the electrochromic coloring layer 4 formed on the transparent electrode 3, an electrolytic polymerization film 5 formed on the coloring layer 4, a counter electrode 7 arranged opposite the transparent electrode 3 at an interval, and the electrolyte put between a display electrode 9A and the counter electrode 7. The electrolytic polymerization film 5 is an electric conductive high polymer film formed on the electrochromic coloring layer 4 by electrolytic polymerization and prevents the electrochromic coloring layer 4 from swelling and being dissolved in the electrolyte 6. Further, ions necessary for the electrochromic oxidation-reduction reaction of the electrochromic coloring layer 4 are transmitted. Consequently, the electrochromic coloring layer 4 never contacts the electrolyte directly and is prevented from swelling and being dissolved in the electrolyte, so that the repetitive use life is improved greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to the structure of an electrochromic display element that utilizes electrochemical coloring/decoloring phenomena.

[Conventional technology]

The electrochromic display element is the so-called ECD (electrochromic display, εIec-troch).
A display that applies the so-called electrochromism phenomenon in which the color and light transmittance change reversibly due to the redox reaction that occurs on or near the electrode surface when a voltage is applied to a substance. It is element.

Displays can be roughly divided into self-luminous types such as light-emitting diodes and non-luminous types such as liquid crystals, and electrochromic display elements belong to the non-luminescent types.

ECDs are visible from any angle and have good display quality, but they consume less power than LCDs (Liquid Crystal Displays, Liquid Crys
-tal Display), the lifetime depends on the number of on-off cycles. Since multiplex drive (time division drive) is difficult, applications such as transportation-related destination information boards, fare displays, hospital counter information, and various measuring instruments are being considered.

Materials that exhibit electrochromism include metal oxides such as WO2, and the mechanism of coloring and fading has also been elucidated.

On the other hand, organic electrochromic materials have also been widely studied, such as rare earth compounds such as sifthalodianine, which have features such as the ability to produce multiple colors and the ability to produce clear images.

An electrochromic display element (hereinafter abbreviated as an EC display element) applies a voltage between a display electrode that performs an electrochromic operation and a counter electrode, and repeats coloring and erasing by controlling the applied voltage. Japanese Patent Application No. 1983-010622, which was previously filed by the present applicant, discloses an ITO formed on a glass substrate 1, as clearly shown in FIG.
(Indium Tin Oxide) An electrochromic coloring layer 4 such as iron phthalocyanine is deposited on the transparent electrode 3, and a display electrode 9B with a predetermined display pattern formed with a resist 8 is formed on the glass substrate 2 with an electrochromic coloring layer 4 such as platinum formed on the glass substrate 2. The counter electrode 7 is disposed oppositely, and a saturated K
A structure in which an electrolytic solution 6 made of a CI aqueous solution is arranged is shown. When iron phthalocyanine is used as the electrochromic coloring layer 4, when the potential of the display electrode 9B is set to -1.IV to -1.2V with respect to the counter electrode, the display electrode exhibits a red color. When set to OV, it turns blue.

[Problem that the invention seeks to solve]

However, in such a conventional EC display element, when the cycle of the applied voltage as described above is repeated, the electrochromic coloring layer 4 of the display electrode 9B comes into direct contact with the electrolyte 6. swells or
There has been a problem that the EC display element has a short cycle life as a result of elution into the electrolytic solution 6.

An object of the present invention is to provide a protective layer that can prevent the electrochromic coloring layer of a display electrode from swelling or eluting into an electrolytic solution, thereby improving the cycle life of an EC display element.

[Means for solving problems]

In order to achieve the above object, according to the present invention, (a)
A transparent electrode 3 formed on a substrate; (b) an electrochromic coloring layer 4 formed on this transparent electrode 3; (c) an electrolytic polymer film 5 formed on this coloring layer;
d) a counter electrode 7 disposed at a distance from the transparent electrode 3; and (e) an electrolytic solution 6 disposed between the display electrode 9A and the counter electrode 7.

[Effect]

The electrolytic polymer film 5 is a conductive polymer film formed on the electrochromic coloring layer 4 by electrolytic oxidative polymerization, and prevents the electrochromic coloring layer 4 from swelling and eluting into the electrolytic solution 6. At the same time, ions necessary for the electrochemical redox reaction of the electrochromic coloring layer 4 are transmitted.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a schematic cross-sectional view of an EC display element according to an embodiment of the present invention. This EC display element is constructed as follows. ITO (Indium T
A transparent electrode 3 (in oxide) is provided, and an electrochromic coloring layer 4 made of iron phthalocyanine (hereinafter abbreviated as FePc) is provided on the transparent electrode 3. Electropolymerized films 5 made of polypyrrole are laminated, and the outermost layer is formed with a resist 8 in a predetermined pattern. On the other hand, a counter electrode 7 made of platinum is provided on the glass substrate 2, which is connected to the display electrode 9A (ITO transparent electrode 3, electrochromic color forming layer 4, electrolytic polymer film 5, and resist 8) via an electrolyte 6. (constituted).

Electrolyte 6 is a saturated solution of KCffi.

Such an EC display element is prepared as follows.

ITO (Indiul) is sputtered onto the glass substrate 1.
TITin Oxide) transparent electrode 3 is formed. The electrochromic coloring layer 4 is produced by charging a predetermined amount of FePc into a deposition source boat, and heating the deposition source heater at a temperature 4 using a resistance heating method.
It is deposited to a thickness of about 1000 mm on the ITO transparent electrode 3 at 50° C. and a vacuum degree of I Xl0-5 torr.

Subsequently, 0.5M pyrrole+0. Using platinum as the counter electrode in the OIM rose bengalum solution, +1.4 with respect to the platinum electrode.
A constant voltage electrolytic oxidation polymerization of V is performed to form a polypyrrole/rose bengal electrolytic polymer film 5 with a thickness of 300 to 500 layers on the FePc thin film. When pyrrole is electrolytically oxidized and polymerized to form a polypyrrole polymer film, the polypyrrole is partially oxidized.7 To neutralize its positive charge, anionic rose bengal is added to the polymer film using an acidic dye. Doped inside. This electrolytic polymer film 5 is electrically conductive.

Next, a resist 8 is formed in a predetermined pattern by photolithography.

Next, a counter electrode 7 is formed on the glass substrate 2 by sputtering, and is made to face the indicator electrode 9A via an electrolyte 6 which is a saturated KCI aqueous solution. Electrolyte 6 is sealed.

Display electrode 9A of the EC display element thus prepared
When electrolytic reduction is performed by applying a voltage of -1,1V to -1,2V between the display electrode 9A and the counter electrode 7 so that the display electrode 9A becomes a negative voltage, the display electrode exhibits a red color. Also, the applied voltage is −0
, 6V to Ov, the color quickly turns blue. This blue color is a unique color of FePc.

Electrolytic polymerization of polypyrrole W! 5 isolates the FePc electrochromic coloring layer 4 from the electrolyte 6.

Therefore, FePc does not swell with the electrolytic solution 6 or dissolve into the electrolytic solution 6.

The red coloration in the electrolytic reduction described above is due to the following reaction (1)
It is estimated that

Since the K ions necessary for this reaction can diffuse into and out of the polypyrrole membrane, the polypyrrole membrane has an EC
The electrochromic coloring layer 4 can be effectively protected without interfering with the operation of the display element.

In order to investigate the effect of the polypyrrole electropolymerized film 5, voltages of OV, -1, and IV were repeatedly applied to the EC display element at a period of 10 seconds to investigate the characteristics. As a result, with the electropolymerized membrane 5, the cycle life is 10 times lower than that without the electrolytic polymerized membrane.
It turned out to be 0x.

The electropolymerized polypyrrole film 5 can be doped with rose bengal as described above, but since this rose bengal is an organic pigment and has an absorption spectrum unique to rose bengal, visible light is absorbed by both FePc and rose bengal. The substance will absorb the spectrum,
The effect of diversifying the coloring states compared to the case of FePc alone can also be obtained.

Further, the electropolymerized membrane can form a homogeneous membrane in a short period of time, and the thickness of the membrane can be controlled by the amount of electricity applied, making it easy to form a protective membrane.

〔Effect of the invention〕

According to this invention, since the electrolytic polymer film is provided as a protective layer on the electrochromic coloring layer, the electrochromic coloring layer does not come into direct contact with the electrolyte, thereby preventing swelling and elution into the electrolyte. As a result, the cycle life is greatly improved. Furthermore, since the electrolytically polymerized membrane can be doped with an organic dye during its oxidative polymerization, the spectral absorption caused by the organic dye can be superimposed on that caused by electrochemical redox, resulting in the effect of diversifying color development.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an EC display element according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a conventional EC display element. 1.2 Substrate, 3 Transparent electrode, 4 Electrochromic coloring layer, 5 Electrolytic polymer film, 6 Electrolyte, 7 Counter electrode, 8 Resist, 9A Display electrode.

Claims (1)

[Claims] 1) (a) a transparent electrode formed on a substrate, (b) an electrochromic coloring layer formed on the transparent electrode, and (c) a transparent electrode formed on the coloring layer. and (d) electropolymerized membrane.
An electrochromic display element comprising: a counter electrode disposed at a distance from the transparent electrode; and (e) an electrolytic solution disposed between the transparent electrode and the counter electrode. 2) An electrochromic display element according to claim 1, wherein the electrochromic coloring layer is a vapor-deposited layer of iron phthalocyanine. 3) An electrochromic display element according to claim 1, wherein the electrolytically polymerized film is a polymer film of polypyrrole.