JPS62186233A - Driving method for electrochromic element - Google Patents

Abstract

PURPOSE:To extend the life and to provide an element having good appearance by impressing a plus voltage to an electrochromic (EC) element in the coloring stage thereof and temporarily short-circuiting between electrodes in the decoloring stage then impressing a decoloring voltage which has the polarity reverse from the polarity of the voltage impressed in the coloring stage and has the absolute value of the crest value lower than in the coloring stage thereto. CONSTITUTION:The plus voltage is impressed to the element in the coloring stage and the electrodes are temporarily short-circuited therebetween in the decoloring stage. The decoloring voltage which has the polarity reverse from the polarity of the voltage impressed in the coloring stage and has the absolute value of the crest value lower than in the coloring stage is thereafter impressed thereto. More specifically, the two terminals of the electrodes are held open and the colored state is maintained by making use of the memory characteristic of the EC layer after the impression of the decoloring voltage +V1 to the element. Both terminals of the element are short-circuited to erase most of the coloration in the stage of decoloring the element. The decoloring voltage -V2 which has the polarity reversed from the polarity of the voltage impressed in the coloring stage and has the absolute value of the crest value lower than in the coloring stage is thereafter impressed thereto.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for driving an electrochromic element using an electrochemical coloring/decoloring phenomenon, that is, an electrochromic phenomenon. It can be applied to Y matrix displays, optical shutters, aperture mechanisms, etc. Such electrochromic devices can be classified into liquid type and all-solid type based on their materials, and the present invention relates to a method for driving an all-solid type electrochromic device, particularly a complementary electrochromic device.

[A Summary of the Disclosure] The present specification and drawings describe a complementary method for driving an electrochromic device in which a positive voltage is applied during coloring, a temporary short-circuit state is created between the electrodes during decolorization, and then polarity is changed during coloring. By applying a decoloring voltage in which the voltage is reversed and the absolute value of the peak value is lower than that during coloring, an element with a long life and good appearance can be obtained.

[Prior Art] Fig. 2 shows an example of the structure of an all-solid-state EC element that utilizes electrochromic (hereinafter referred to as EC) phenomenon. Fig. 2 particularly shows an example of complementary chemistry. A first electrode 2 made of a transparent conductive film is placed on a transparent substrate 1. A first EC layer 3 which is a coloring layer on the anode side, an insulating layer 4 made of a dielectric film, a second EC layer 6 which is a coloring layer on the pole side, and a second electrode 5 made of a dielectric film are sequentially laminated. This is what happens.

In the above structure, the substrate l is generally formed of a glass plate, but it is not limited to a glass plate, and may be any colorless and transparent plate such as a plastic plate or an acrylic plate, and also regarding its position.

It may be provided on the second electrode 5 instead of under the first electrode 2, or may be provided on both sides depending on the purpose (for example, for the purpose of serving as a protective cover). However, depending on these cases, it is necessary to use a transparent conductive film for the 2' center pole 5 or a transparent conductive film for both electrodes. If both electrodes are made of transparent electrodes, it can be used as a transmission type element. can do. The insulating layer 4 may be made of not only a dielectric but also a solid electrolyte or the like.

As the transparent conductor film, ITO film (indium oxide In
2O3 doped with tin oxide 5N02), NESA film, etc. are used. The first EC layer 3, which is the coloring layer on the anode side, has conventionally been formed of chromium trioxide (Cr203), iridium oxide (IrOx), nickel oxide (NiOz), or the like. The insulating layer 4 made of a dielectric film is made of zircon dioxide (Zr(h), tantalum pentoxide (↑a205)
, silicon sulfide (Sin, 5i02), oxides represented by rods, or lithium fluoride (LiF),
It is formed using a fluoride typified by magnesium fluoride (MgFz)i. In addition, the second color forming layer on the cathode side
The EC layer 6 is made of tungsten oxide (WO2, W(h),
It is formed using molybdenum oxide (Mo02, MoO3), vanadium pentoxide (V2O3), etc.

In an all-solid-state electrochromic element having such a structure, an electrochemical reaction occurs by applying a voltage between the first electrode 2 and the second electrode 5, and the element is colored or decolored. This coloring mechanism is generally said to be due to bronze formation by double injection of cations and electrons into the second EC layer 6.For example, as an EC material,
When WO3 is used, an oxidation-reduction reaction represented by the following formula (1) occurs, resulting in coloration.

WO3+ xH・+ xe−: HxW(h (
1) According to formula (1), tungsten bronze HxWO
3 is formed and colored, but if the applied voltage is reversed at this point, it becomes a decolored state. This kind of reaction in equation (1) is.

In an all-solid-state EC element, protons H° are supplied by an insulating layer inside the element and the element is colored.

In the above-mentioned EC element, the first ECPfj3, which is the coloring layer on the anode side, has conventionally been formed from a hydroxide such as iridium oxide (IrOx) by reactive sputtering or anodic oxidation.

[Problem that the invention attempts to solve] A conventional driving method for the above-mentioned phase compensation type EC element is shown in FIG.

In FIG. 3, the vertical axis represents voltage V, and the horizontal axis represents time t. Conventionally, for example, as shown in FIG. 3(a), a positive voltage is applied when coloring, and when decoloring, a positive voltage is applied. Either a method of applying a pulse of opposite polarity or short-circuiting between both electrodes as shown in FIG. 3(b) has been used.

However, both of these driving methods, such as 7cl, have a short service life due to the green-turning drive, and in particular, if only a short circuit is made during erasing, the color cannot be completely erased due to factors such as one remaining color.

The present invention has been made in view of the drawbacks of the conventional example, and aims to provide a method for driving an EC element that has a long life and good appearance.

[Means for Solving the Problems] Figures m1 (a) and (b) are pulse waveforms showing an example of the driving method according to the present invention. The O level in the figure means that both ends of the electrodes of the element are at the same potential (short-circuited state). 1st
In Figure (a), after applying the coloring voltage +v1, both ends of the electrode are in an open state.

When decoloring the 0th order, which maintains the colored state by taking advantage of the memory property of E (J, short both ends of the element to erase most of the coloring.Next, the polarity is opposite to that when coloring, and A decoloring voltage -v2 whose absolute value of the peak value is lower than that during coloring is applied.FIG. 1(b) shows that after applying the decoloring voltage -v2, the circuit is brought into a short-circuit state again.

In any case, it is preferable that the pulse width of the erasing voltage be shorter than that of the coloring voltage.

[Sakukawa] When a decoloring voltage is applied as shown in FIG. 3(a), ions are likely to be generated in the EC layer, resulting in a shortened lifespan.

Therefore, when decoloring the element, by temporarily shorting the element and then applying a slight voltage to the negative side, the color can be easily decolored without applying any extra voltage. Furthermore, if the short circuit is maintained even after decoloring, the decoloring state is always kept stable.

[Example] A specific example of the present invention will be described with reference to FIGS. 1 and 2.

First, a first EC layer on the anode side is formed on a glass substrate l with a transparent electrode on which a first electrode 2 having a predetermined shape and a lead electrode (not shown) are patterned. 2,
It was patterned and formed with a thickness of 200A. Next, Ta205 was formed to a thickness of 3000 Å as the insulating layer 4, and then llIO3 was formed to a thickness of 4000 Å as the second EC layer on the cathode side by vacuum evaporation using an electric T-gun.

Furthermore, using a mask, an ITO film serving as the second electrode 5 was formed using a reactive ion blating method.
Formed.

For the device obtained in this way, FIG. 1(a),
The pulse waveform shown in (b) (peak value of coloring applied voltage + 1.
5V, pulse width 250m5ec, short time +00
m5, peak value of reverse polarity applied voltage -〇, 5V, pulse width 150rms), Δ0. A device with a performance of D = 0.48 was
I was able to drive it over 106 times. This increases the lifetime of the element in the conventional drive α by one order of magnitude.

[Effects of the Invention] As explained above, according to the present invention, a positive voltage is applied when coloring an EC element, a temporary short circuit is created between the electrodes when decoloring, and then the polarity is reversed from that when coloring. , and the absolute value of the peak value is lower than that at the time of coloring) By printing a decoloring voltage that is lower than that during coloring, it is possible to extend the life of the element compared to the conventional method, and to make the element look good without any color residue when decoloring. I can do it.

[Brief explanation of drawings]

FIG. 1 shows a pulse waveform showing an example of the driving method according to the present invention.
FIG. 2 is a sectional view of an all-solid-state EC element according to the present invention, and FIG. 3 is a pulse waveform showing an example of a conventional driving method. l...Substrate, 2...First electrode, 3...E of the "l"
C layer. 4... Insulating layer, 5... Second electrode, 6... Second E
C layer.

Claims (1)

[Claims] 1) In a method of driving a phase-compensated electrochromic element, a positive voltage is applied during coloring, a temporary short circuit is created between the electrodes when decoloring, and then the polarity is reversed from that during coloring, A method for driving an electrochromic element, characterized in that a decoloring voltage is applied, and the absolute value of the peak value is lower than that during coloring. 2) The method for driving an electrochromic element according to claim 1, wherein the electrochromic element is brought into a short-circuited state again after the decoloring voltage is applied.